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  • richardmitnick 9:10 am on April 27, 2017 Permalink | Reply
    Tags: , , , , , , , Particle Physics, SCOAP3   

    From CERN: “CERN and the American Physical Society sign an open access agreement for SCOAP3” 

    Cern New Bloc

    Cern New Particle Event

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    CERN

    Geneva, 27 April 2017. The European Organization for Nuclear Research (CERN) and the American Physical Society (APS) signed an agreement today for SCOAP3 – the Sponsoring Consortium for Open Access Publishing in Particle Physics. Under this agreement, high-energy physics articles published in three leading journals of the APS will be open access as from January 2018.

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    All authors worldwide will be able to publish their high-energy physics articles in Physical Review C, Physical Review D and Physical Review Letters at no direct cost. This will allow free and unrestricted exchange of scientific information within the global scientific community and beyond, for the advancement of science.

    “Open access reflects values and goals that have been enshrined in CERN’s Convention for more than sixty years, such as the widest dissemination of scientific results. We are very pleased that the APS is joining SCOAP3 and we look forward to welcoming more partners for the long-term success of this initiative”, said Fabiola Gianotti, CERN’s Director General.

    APS CEO Kate Kirby commented that, “APS has long supported the principles of open access to the benefit of the scientific enterprise. As a non-profit society publisher and the largest international publisher of high-energy physics content, APS has chosen to participate in the SCOAP3 initiative in support of this community.”

    With this new agreement between CERN and the APS, SCOAP3 will cover about 90 percent of the journal literature in the field of high-energy physics.

    Convened and managed by CERN, SCOAP3 is the largest scale global open access initiative ever built. It involves a global consortium of 3,000 libraries and research institutes from 44 countries, with the additional support of eight research funding agencies. Since its launch in 2014, it has made 15 000 articles by about 20 000 scientists from 100 countries accessible to anyone.
    The initiative is possible through funds made available from the redirection of former subscription monies. Publishers reduce subscription prices for journals participating in the initiative, and those savings are pooled by SCOAP3 partners to pay for the open access costs, for the wider benefit of the community.

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  • richardmitnick 3:15 pm on April 25, 2017 Permalink | Reply
    Tags: Archaeology meets particle physics, , Cosmic-ray muons research, Particle Physics,   

    From Symmetry: “Archaeology meets particle physics” 

    Symmetry Mag

    Symmetry

    04/25/17
    Jameson O’Reilly

    Undergraduates search for hidden tombs in Turkey using cosmic-ray muons.

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    Lycian rock-cut tombs in Hellenistic style – Dalyan, Turkey

    While the human eye is an amazing feat of evolution, it has its limitations. What we can see tells only a sliver of the whole story. Often, it is what is on the inside that counts.

    To see a broken femur, we pass X-rays through a leg and create an image on a metal film. Archaeologists can use a similar technique to look for ancient cities buried in hillsides. Instead of using X-rays, they use muons, particles that are constantly raining down on us from the upper atmosphere.

    Muons are heavy cousins of the electron and are produced when single-atom meteorites called cosmic rays collide with the Earth’s atmosphere. Hold your hand up and a few muons will pass through it every second.

    Physics undergraduates at Texas Tech University, led by Professors Nural Akchurin and Shuichi Kunori, are currently developing detectors that will act like an X-ray film and record the patterns left behind by muons as they pass through hillsides in Turkey. Archaeologists will use these detectors to map the internal structure of hills and look for promising places to dig for buried archaeological sites.

    Like X-rays, muons are readily absorbed by thick, dense materials but can traverse through lighter materials. So they can be stopped by rock but move easily through the air in a buried cavern.

    The detector under development at Texas Tech will measure the amount of cosmic-ray muons that make it through the hill. An unexpected excess could mean that there’s a hollow subterranean structure facilitating the muon’s passage.

    “We’re looking for a void, or a tomb, that the archaeologists can investigate to learn more about the history of the people that were buried there,” says Hunter Cymes, one of the students working on the project.

    The technique of using cosmic muons to probe for subterranean structures was developed almost half a century ago. Luis Alvarez, a Nobel Laureate in Physics, first used this technique to look inside the Second Pyramid of Chephren, one of the three great pyramids of Egypt. Since then, it has been used for many different applications, including searching for hidden cavities in other pyramids and estimating the lava content of volcanoes.

    According to Jason Peirce, another undergraduate student working on this project, those previous applications had resolutions of about 10 meters. “We’re trying to make that smaller, somewhere in the range of 2 to 5 meters, to find a smaller room than what’s previously been done.”

    They hope to accomplish this by using an array of scintillators, a type of plastic that can be used to detect particles. “When a muon passes through it, it absorbs some of that energy and creates light,” says student Hunter Cymes. That light can then be detected and measured and the data stored for later analysis.

    Unfortunately, muons with enough energy to travel through a hill and reach the detector are relatively rare, meaning that the students will need to develop robust detectors which can collect data over a long period of time. Just like it’s hard to see in dim light, it’s difficult to reconstruct the internal structure of a hill with only a handful of muons.

    Aashish Gupta, another undergraduate working on this project, is currently developing a simulation of cosmic-ray muons, the hill, and the detector prototype. The group hopes to use the simulation to guide their design process by predicting how well different designs will work and much data they will need to take.

    As Peirce describes it, they are “getting some real, hands-on experience putting this together while also keeping in mind that we need to have some more of these results from the simulation to put together the final design.”

    They hope to finish building the prototype detector within the next few months and are optimistic about having a final design by next fall.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 1:25 pm on April 24, 2017 Permalink | Reply
    Tags: , , , New ALICE results show novel phenomena in proton collisions, , Particle Physics, , Strange quark   

    From ALICE at CERN: “New ALICE results show novel phenomena in proton collisions” 

    CERN
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    CERN ALICE Icon HUGE

    24 Apr 2017.
    Harriet Kim Jarlett

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    As the number of particles produced in proton collisions (the blue lines) increase, the more of these so-called strange hadrons are measured (as shown by the orange to red squares in the graph) (Image: ALICE/CERN)

    In a paper published today in Nature Physics , the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behaviour was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma, a very hot and dense state of matter that existed just a few millionths of a second after the Big Bang, and is commonly created in collisions of heavy nuclei. But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. This result is likely to challenge existing theoretical models that do not predict an increase of strange particles in these events.

    “We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”

    The study of the quark-gluon plasma provides a way to investigate the properties of strong interaction, one of the four known fundamental forces, while enhanced strangeness production is a manifestation of this state of matter. The quark-gluon plasma is produced at sufficiently high temperature and energy density, when ordinary matter undergoes a transition to a phase in which quarks and gluons become ‘free’ and are thus no longer confined within hadrons. These conditions can be obtained at the Large Hadron Collider by colliding heavy nuclei at high energy. Strange quarks are heavier than the quarks composing normal matter, and typically harder to produce. But this changes in presence of the high energy density of the quark-gluon plasma, which rebalances the creation of strange quarks relative to non-strange ones. This phenomenon may now have been observed within proton collisions as well.

    In particular, the new results show that the production rate of these strange hadrons increases with the ‘multiplicity’ – the number of particles produced in a given collision – faster than that of other particles generated in the same collision. While the structure of the proton does not include strange quarks, data also show that the higher the number of strange quarks contained in the induced hadron, the stronger is the increase of its production rate. No dependence on the collision energy or the mass of the generated particles is observed, demonstrating that the observed phenomenon is related to the strange quark content of the particles produced. Strangeness production is in practice determined by counting the number of strange particles produced in a given collision, and calculating the ratio of strange to non-strange particles.

    Enhanced strangeness production had been suggested as a possible consequence of quark-gluon plasma formation since the early eighties, and discovered in collisions of nuclei in the nineties by experiments at CERN’s Super Proton Synchrotron.

    CERN Super Proton Synchrotron

    Another possible consequence of the quark gluon plasma formation is a spatial correlation of the final state particles, causing a distinct preferential alignment with the shape of a ridge. Following its detection in heavy-nuclei collisions, the ridge has also been seen in high-multiplicity proton collisions at the Large Hadron Collider, giving the first indication that proton collisions could present heavy-nuclei-like properties. Studying these processes more precisely will be key to better understand the microscopic mechanisms of the quark-gluon plasma and the collective behaviour of particles in small systems.

    The ALICE experiment has been designed to study collisions of heavy nuclei. It also studies proton-proton collisions, which primarily provide reference data for the heavy-nuclei collisions. The reported measurements have been performed with 7 TeV proton collision data from LHC run 1.

    See the full article here .

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  • richardmitnick 9:14 am on April 23, 2017 Permalink | Reply
    Tags: , Doppel, Fotini Markopoulou, Particle Physics,   

    From Nautilus: “This Physics Pioneer Walked Away from It All” 

    Nautilus

    Nautilus

    July 28, 2016
    Sally Davies
    Illustrations by Ping Zhu
    Photography by Tom Jamieson

    Inside the South London offices of Doppel, a wearable technology start-up, sandwiched into a single room on a floor between a Swedish coffee shop and a wig-making studio, CEO and quantum physicist Fotini Markopoulou is debating the best way to describe an off-switch.

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    Doppel: the wearable heartbeat that works with your body

    Markopoulou and her three co-founders have gathered in convivial discomfort around a cluttered formica table and lean-to blackboard. They’re redesigning the features of their eponymous first device, which is due to be released in October. It’s a kind of elegant watch that sits on the inside of your wrist and delivers a regular, vibrating pulse. By mimicking a heartbeat, the Doppel helps regulate a person’s emotions and mental focus.

    Swiveling in a chair, Markopoulou says she likes a “smothering” gesture—placing a palm over the face of the Doppel to turn it off—because it is intuitive and simple, and the term suggests the device is “alive.” “You could always murder it,” deadpans commercial director Jack Hooper. Head of technology Andreas Bilicki chimes in. “Why not ‘choke’ or ‘asphyxiate’?” The team throws around alternatives: “throttle”; “go to sleep, to sleep”; “turn your Doppel off, just like putting a blanket over a parrot’s cage.”

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    A NEW BEAT: Fotini Markopoulou at work at Doppel, the wearable technology startup she co-founded, after saying goodbye to theoretical physics.

    Markopoulou, 45, observes the banter with a half-smile. She is fine-featured and striking. Her heavy-lidded eyes anchor a gaze that seems wary of its own powers, as if her promiscuous intelligence must hold itself back from latching on to your every word. She wears her hair in a tousled pixie-cut, and on this spring day, a green knit sweater and blue scarf with a pattern of fish-like scales. There are no airs about her, nor any indication that she’s 20 years older than the rest of the team. Markopoulou lives in Oxford but sleeps on design director Nell Bennett’s couch whenever she comes down to London.

    After the meeting, Markopoulou and I walk downstairs to get a coffee. With the zeal of the reborn, she tells me how much she relishes the pleasures of making a product that people will use and pay for. “There is a very 
practical satisfaction to getting stuff done, whether it’s making something or selling something,” she says. “I do enjoy solving practical problems, like how to convince people Doppel’s a good idea, or how to get the right deal from an accountant.”

    It’s hard to see how these tasks could fully absorb Markopoulou. She is one of the most radical and fiercely creative theoretical physicists alive today, and a founding faculty member of the Perimeter Institute for Theoretical Physics in Waterloo, Canada, where she was at the vanguard of quantum gravity.

    Perimeter Institute in Waterloo, Canada

    This is the branch of physics striving to unify the two most fundamental theories of the universe: general relativity, proposed by Einstein, and quantum mechanics.

    Quantum theory describes the rowdy interactions of fundamental particles that govern many of the forces in the known universe—except gravity. Gravity is rendered beautifully predictable by general relativity, which envisions it as an effect of how the four dimensions of space and time curve in response to matter, like a piece of tarpaulin bending under a bowling ball. Quantum theory’s ability to predict the behavior of an electron in a magnetic field has been described as the most precisely tested phenomenon in the history of science. But putting it together with gravity has so far produced absurd mathematical results. It’s as if a soccer player and a tennis player were managing to carry on a game despite being ignorant of the opponent’s rules.

    After years of single-minded study, Markopoulou co-created a novel potential solution known as “quantum graphity.” This model of the universe operates at a scale that is tiny even by subatomic standards—as tiny in relation to a speck of dust as a speck of dust is to the entire universe. It suggests that space itself and its attendant laws and features could evolve out of interconnected dots to create the dimensions we experience as space, like a soufflé rising from a pan.

    “Fotini is extremely original, original to a fault,” says Lee Smolin, a fellow founder of Perimeter who used to be married to Markopoulou. “Most scientists pick up on ideas which are dominant, which come from living figures, and develop them incrementally. She doesn’t do that—she works solely on her own ideas.”

    Between sips of a latte, Markopoulou describes how theoretical physics consumed her. “It’s a lot like being in a monastery, like no normal human needs should make you waver from the cause of understanding where the universe came from,” she says. “In my previous eyes, just leaving is a moral failure, more than anything else. It’s a devotion thing—your devotion has just gone.” She pauses to shape her next thought. “It’s also not really a loss of faith; I changed.”

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    GOT RHYTHM?: Markopoulou oversaw the design and engineering of the Doppel, which sends a mood-affecting pulse to a wearer’s wrist, from prototype to product.

    Five years after walking away from physics, Markopoulou is still trying to explain that change to herself. She was forced to re-examine her position when Perimeter’s new director, Neil Turok, who joined in 2008, deemed her work too speculative and squeezed her out of the Institute. But her unease had deeper roots.

    Working in a field where the air of reality was so thin, Markopoulou started to lose touch with her own life. “I have so many friends in their late 40s, and they still don’t have an actual home or a family or anything. As long as they have a place where they can go and think they’re happy.” She casts a wry smile. “I failed that test, obviously. For a lot of people that makes sense, and even for me that makes sense 80 percent. It’s that other 20 percent that causes problems.”

    Doppel embodies many of the qualities that Markopoulou came to miss in her work as a physicist. The company is grounded in psychophysiology, a field which considers the mind to be deeply rooted in the body and its environment. But embracing the fact that the self is interwoven with the world, and at its mercy, is a frightening thought, Markopoulou says. Escaping that fear, and trying to pin down the interconnection between humans and the natural systems that make us what we are, is what drew her to physics in the first place.

    “I did appreciate, for a long time, the way science detaches you from that scariness, because you ignore it,” Markopoulou says. “Between the truth of the physical world and a physics theory, there’s humans. Of course, nothing happens there, because removing the person is the whole point of training as a scientist.” A pause. “But this may or may not be possible.”

    As a teenager growing up in Athens, Greece, Markopoulou looked like an ordinary kid: permed hair, heavy ribbed sweaters, a penchant for Clint Eastwood Westerns. But she was already attracted to the study of transcendent truths. On her way home from school, she would sometimes drop in at Greek orthodox churches to lie on her back in the pews, and contemplate the elaborate scenes of stars and angels painted into the interior domes. One summer, when she was 15, she happened across a book in the library of the British Council with the title Starseekers, a quasi-mystical account of the history of cosmology, by English writer Colin Wilson. “I got totally obsessed with that book,” Markopoulou says. She convinced her mother, Maria, to buy her an Atari computer, and spent hours trying to translate Starseekers into Greek on a word processor.

    Markopoulou lived with her mother in a cramped two-story studio in Athens, where Maria worked as a figurative sculptor. She was a magnetic, troubled figure, unafraid to set her own moral compass but riven with internal conflicts. She’d fallen pregnant one summer to a Greek sculptor she had known in Florence, where she trained as an artist against the wishes of her parents, and decided to raise the baby as a single mother in Athens. She was 33. “Her lovely way of putting this was, ‘Jesus was also 33 when he was put on the cross,’ ” Markopoulou says. “But it was also very clear that I was the best thing that had ever happened to her.” (Markopoulou has never met and knows little about her father, who died in 1997.)

    Markopoulou loved accompanying Maria to exhibitions and openings, but struggled to disentangle her sense of self from her mother’s strong and particular judgments. “My mother’s relation with reality, it would be wrong to say that it wasn’t solid, but it was just different,” Markopoulou says. Maria hated to sleep and refused to have a bed: “My mother clearly thought that sleeping was like dying, and that she might not wake up if she did, and something like a bed might as well have been a tombstone. I did realize as I was growing up that you couldn’t rely on her description of something.”

    The subjectivity of aesthetic merit troubled Markopoulou. “One of the things I hated about the art-world is that decision-making is quite arbitrary,” she says. “People could say Picasso is shit just because they felt like saying it. I found that very frustrating, and very political; they’re gatekeepers, and then your life and self-perception is a function of those gatekeepers.”

    Markopoulou’s education in Greece was “a complete disaster,” she says, with teachers whose instruction consisted of reading the newspaper at the front of the classroom. In her final year of high school, Markopoulou went in search of private evening classes; by mistake, she walked through the door of an institution that offered A-levels, the exams for students entering the British university system. She hadn’t considered studying in the United Kingdom, but ended up enrolling. “The usual story about people in quantum gravity is, ‘I read about Einstein when I was 8,’ ” she says. That was not her. The pendulum for her imaginary career had swung between being an astronaut and an archeologist. She only selected theoretical physics under the pressure of her university application, and chose the course on the casual advice of a tutor at the school, a former NASA scientist, who said it would be a good balance for her aptitude in physics and mathematics.

    Markopoulou failed her A-levels—“the first time I walked into the lab was for the exam, and half the questions I answered in Greek”—but, as part of the clearing process between teachers and universities, her tutor secured her a place at Queen Mary’s University in London, her first choice. The department had several excellent particle physicists investigating the top quark, but the place retained the welcoming atmosphere of institutions unburdened by hallowed reputations.

    Money was tight, so Markopoulou didn’t have much of a social life. She planned birthday parties at McDonald’s for a bit of extra cash, while her mother, who was living with her in London to get the rent from her studio in Athens, repaired antiques. (They would continue to live together until the last year of Markopoulou’s Ph.D.) But Markopoulou loved it all the same. She and a clutch of the other undergraduates would relax in the chapel café between lectures, and occasionally head out in the evenings to hear one of their professors play amateur hard rock. At the same time, in her classes, she got wind of the fact that “there was some forbidden place”—that when it came to certain subjects, such as why time moves in one direction, it was better not to ask. She was not content with what the rules were; she wanted to know how they came to be.

    Toward the end of her undergraduate degree, a friend suggested Markopoulou attend a lecture on quantum gravity by Chris Isham, a rigorously mathematical physicist at Imperial College. He was also a Jungian analyst and devout Christian, with the air of a mystic and a fondness for peppering his lectures with passages from T.S. Eliot and Heidegger. “You can’t take out of the world the fact we see it,” Isham tells me. “What is the reality we hang onto? Well, it’s us, but who are we that sit inside this space which is relative to us?”

    Isham was the first person Markopoulou encountered who could relate the technical dimensions of science to humans’ wider search for meaning. “Sometimes doing physics can be a bit like doing plumbing—you have your equations and tools and you go around and fix stuff, and if you do it in a smart way, people respect you,” she says. “Because you are a professional physicist, you get used to the idea that there are difficult questions that you do not do for a living. But these are what drove most of us to join the ranks.”

    Markopoulou was developing her own clear vision of what she wanted to achieve as a physicist. “I am not going to devote my life to something because it’s beautiful—it’s this quest for the truth,” she says. “Science is not philosophy—there is not a lot of value in thinking about questions if you cannot come up with answers. But I’ve always been attracted to what is the furthest away you can get such that you can still come back with an answer. You’re trying to find the end of the coil to unfold it.”

    Under Isham’s influence, Markopoulou started to grapple with quantum gravity. Her assigned Ph.D. project was based on a previous paper that examined the movement of dust particles to develop a new approach to splitting time away from the three dimensions of space. This sounds like a solution in search of a problem—surely time is a different thing from space?—until you remember Einstein’s counterintuitive insight that time is intimately interwoven with the fabric of space, and can be similarly twisted and bent by matter and movement. Time is dynamic, and defined by its relationship to what’s happening around it. It follows that there is no absolute time that the whole universe obeys—and more troublingly, when you push the equations far enough, time has a tendency to disappear entirely. “The relativity view of the world is that space and time is out there and it’s more or less a static thing—time is just another dimension,” the distinguished physicist Roger Penrose explains to me.

    However, Einstein’s account of time doesn’t make sense in quantum theory. The quantum realm is host to all sorts of phenomena—particles existing in two places at once, or becoming entangled, as if they’re able to communicate their properties instantly and seemingly telepathically, whether separated by a lab-bench or a light-year. It adopts a version of time that’s far more conventional, like a metronome ticking away in the background, distinct from the bizarre behavior of quantum theory’s zoo of quarks, bosons, and fermions.

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    DESIGN NOTES: When she worked on quantum gravity, Markopoulou gave many presentations with graphics. Likewise at Doppel, she and her colleagues post notes to visualize and solve problems.

    It began to dawn on Markopoulou that you might be able to reconcile these two accounts of time by looking more closely at how they viewed space. After her first paper on dust modeling, she turned to spin networks. These are geometric models which help physicists describe quantum interactions in space, and fit more readily with the mathematics of general relativity. Markopoulou had the idea of combining spin networks with a “causal set,” which allows time to be captured as a history of discrete events rather than a continuous flow. Showing how histories could be represented spatially let her bring a more substantive version of time into general relativity—one that wasn’t rigid (as in some accounts of quantum theory) nor completely flexible (as in general relativistic spacetime).

    Her work caught the eye of Smolin, an American theoretical physicist who at the time was visiting Imperial from Penn State University. He’d made a name for himself as a joint inventor of loop quantum gravity theory—a competitor to string theory in the quantum gravity sweepstakes—which was building on spin networks to develop a more sophisticated picture of quantum spacetime. Smolin worked with Markopoulou on a paper on causal sets, and invited her back to Penn State for three months while she was finishing her dissertation. They would marry in 1999.

    At the time, Penn State was a premier institution for non-string quantum gravity, and Markopoulou was surrounded by a number of other brilliant young scientists. “A bunch of different ideas were coming together; there was this sense that you might actually do something faster than the person in the next room, which is very unusual in quantum gravity,” she says. String theory had never appealed to Markopoulou, who saw it as cutthroat and conformist. “String theory has a very strong pecking order,” she says. “It comes with a strong machismo: What complicated stuff can you do? They’re very good at maintaining that.”

    Some of Markopoulou’s contemporaries saw the equations pointing to the conclusion that time is an illusion at the fundamental level, and that what we experience as the progression of events emerges as a byproduct of fluctuations in space. But Markopoulou tended to attack the problem from the other direction—looking at time as the most important thing, and space as something that grows out of it, or is left as a trace, like a logbook of what has taken place in time. “I’m a bit extreme in that I would actually like to keep a fairly old-style time,” Markopoulou says. “I’m not wrong in my views. They come with challenges, but they also come with opportunities.”

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    IN HER ELEMENT: At the Perimeter Institute for Theoretical Physics, where she was a founding member, Markopoulou, seen here in 2002, was known as a persuasive, though not forceful, leader. Derek Shapton

    In early 2000, whispers went around the theoretical physics community that somebody wanted to donate $100 million for an institute dedicated to foundational physics. Markopoulou and Smolin were approached by Howard Burton, a Canadian with a Ph.D. in theoretical physics from the University of Waterloo, who was the emissary for this Gatsby-like figure. “I genuinely thought the guy was a sociologist studying the reactions of physicists to that statement—the amount of money is crazy for foundational physics,” Markopoulou says. By now she was doing a postdoctoral fellowship at the Max Planck Institute for Gravitational Physics in Berlin. She and Smolin were flown in secrecy to Canada and only informed that the donor was Mike Lazaridis, the founder of Blackberry, on the drive from the airport: “We spent the night at Mike’s house, where he made us French toast and talked us into coming to Waterloo.”

    By the time Perimeter was set up, she and Smolin had separated, but remained friends—which was just as well. To lay the scientific groundwork for the institute, the three founding faculty huddled together in a former restaurant, along with several postdoctoral students and Burton, whom Lazaridis had appointed as the director. They inherited the coffee machine and learned to make top-notch barista cappuccinos. The institute aspired to a flat management structure hospitable to free-thinkers, without tenured jobs or the ordinary hierarchies of a university physics department, in the hope that this would foster more interesting research.

    While Markopoulou was not a forceful leader, she was a persuasive one, says Seth Lloyd, a physicist and professor at the Massachusetts Institute of Technology, and a longtime collaborator of Markopoulou’s. He recalls trekking with her and some postdocs in the Sangre de Cristo Mountains, when she was on a fellowship at the Santa Fe Institute in New Mexico. “At each stage of the hike, there were different suggestions about where to go, and we always ended up doing what Fotini thought was a good thing,” he says. “We had a great time, none of us ever thought Fotini was imposing her will—just that what Fotini seemed to want to do was the right thing to do.”

    At Perimeter, Markopoulou was at her best when the learning and experimentation were the quickest. Invariably her work became playful and synthetic. “At some point I thought we should just reduce the whole thing to the basic property of space, which is here and there,” she says. Physicists were willing to toy with the nature of time and “hack” general relativity to create a quantum gravity theory, she says. But they seldom played with the nature of space or “hacked” quantum theory. With Simone Severini, an Italian computer scientist, and graduate student Tomasz Konopka, Markopoulou drew on quantum information theory to develop the notion of quantum graphity. “Fotini thought it was fun—this cute idea, that the universe is a big network, like the London Underground, that changes over time,” Severini says.

    Markopoulou was partly inspired by the principle of emergence, where complexity can emerge from simplicity, or, more to her point, simplicity from complexity, such as wiggling water molecules forming ice crystals or waves. Paramount in her model was the ability to create images that explained “geometrogenesis,” her and her colleagues’ term for the emergence of the structure of spacetime during a critical phase in the birth of the universe. “Once it starts being hard to visualize, I’m not happy, I get uncomfortable,” she says. “I also think you can have an extreme richness while staying with very few building blocks.”

    She was tickled by an aperçu from Ludwig Boltzmann, the 19th-century Austrian physicist, who looked at the physical properties of atoms and said, “Every Tom, Dick, and Harry felt himself called upon to devise his own special combination of atoms and vortices, and fancied in having done so that he had pried out the ultimate secrets of the Creator.” Markopoulou chuckles. “It felt to me, when we were arguing ‘Is it my model? Is it your model?’ we were totally every Tom, Dick, and Harry.”

    In quantum graphity, space evolves out of dots that are either “on” or “off ”—connected or disconnected to the next dot. It doesn’t matter exactly what the dots are; they represent coordinates in a network of relationships, the fundamental constituents of the universe. The idea, Markopoulou explains, comes from a branch of mathematics known as category theory, in which “what something is, is the sum of how it behaves, rather than how it is.” At the highest possible energy, at the beginning of the universe, all the dots in the graph are joined, and no notion of space exists. But as the system cools and loses energy, the points start detaching, which creates the dimensions and laws of space. In this model, space becomes like a crystal that forms out of a liquid as it cools. “The value of this is in trying to give, however primitive it might be, some language to talk about space not being there,” she says.

    “It was very courageous of Fotini to start working on this,” says Sabine Hossenfelder, a research fellow at the Frankfurt Institute for Advanced Studies, a think tank devoted to theoretical physics, who from 2006 to 2009 did postdoc work at Perimeter. “It’s the kind of thing you think has been done long ago, but surprisingly it wasn’t.” It would have been much easier, Hossenfelder says, for Markopoulou to find a niche for herself within an existing theory, like loop quantum gravity. “But quantum graphity of course is much more exciting. It’s a new idea, one that could have done a good job bridging the gap between theory and experiment.”

    6
    No image caption. No image credit.

    As Markopoulou’s reputation grew, she was often called upon to represent Perimeter to the public. She was a young, accomplished woman in physics—a rarity. She enjoyed and tended to accept speaking invitations, partly to help change perceptions of female scientists. “For previous generations, the question was ‘Are there women in science?’ Now there are, but girls want to know, ‘Are they normal?’ When you seem to be happy, and you seem to be a woman they’d be happy to be, that’s a fairly big thing.” Her world revolved around quantum gravity. Shortly after separating from Smolin, she had fallen into a relationship with a German postdoctoral fellow at the institute, Olaf Dreyer, whom she married after four years. They lived and breathed their discipline. “It’s nice to share these things with somebody closely,” she says.

    But Markopoulou found her more radical theories were sometimes greeted with the sly criticism that they were “creative.” “The fact that you don’t look like the standard makes it hard for them; they will take longer to form judgments, which means you stay in the doubt area for longer,” she says. It was made worse by the pervasive attitude among physicists that you should gather your laurels by doing sensible calculations throughout your career, and only cook up new theories of quantum gravity in your old age.

    Markopoulou refused to play that game, and a sense of discontent began to build. Every problem she solved created a quagmire of fresh ones; and, daughter of sculptors, she was tiring of academic papers as the only tangible thing she could “make.” After a while, even her public-facing activities began to grate. “There is a part of me that felt like a kind of clown, telling people magical things about the universe,” she says. “Something you take very seriously and you’ve devoted your life to, and you’ve made your own sacrifices for, is, for other people, at best entertainment.” She consoled herself with something Isham once told her, counsel he’d received in turn from the physicist John Archibald Wheeler. When it comes to quantum gravity, he says, you’re bound to fail. “What’s important is not the fact you fail, but how you fail.” Markopoulou was determined to fail better, to borrow Samuel Beckett’s phrase.

    In 2008, the South African physicist Turok was appointed director of Perimeter. Turok, who describes himself as “very demanding,” pulled back from the more outré flavors of foundational physics and expanded into other areas, including particle physics, cosmology, and quantum computing. He didn’t want the institute, he says, “to be center for alternative physicists who were doing unusual things in speculative directions.”

    By 2009, Markopoulou’s personal life was undergoing its own quantum transitions. At a conference in Waterloo about physics and the financial crisis, organized by Smolin, Markopoulou met systems theorist and physicist Doyne Farmer. The pair was instantly dazzled by one another, and within five days decided to upend their lives to be together. Markopoulou separated from Dreyer and Farmer from his wife. Not long after, she got pregnant on a road trip from San Francisco to Santa Fe in Farmer’s 1967 Datsun convertible. Their son, Maris, was born in 2010; a year later, Markopoulou’s mother Maria passed away.

    Markopoulou was still attracted to deep inquiry, but the further down she went, the less objective she found her colleagues’ judgments about the value of her work. “If you’re in a place where everything is certain, that’s a very boring place,” she says. “But if you jump out with no parachute, it’s either a sociological exercise or a folly.” She’d been striving to position her research at the metaphorical “edge of chaos,” the point at which order emerges from complexity. But she’d started to get the creeping suspicion she was back with the artists in her mothers’ studio, competing for recognition and influence without any clear standards.

    “In the absence of any kind of experimental confirmation or the ability to falsify your theories, quantum gravity has ended up being dominated by a few influential tastemakers,” says Lloyd. “Fotini fell foul of that because she had her own strong sense of what is a good thing to do; her tastes were different.”

    As the institute continued to grow, Turok faced the challenges of needing to formalize its processes and manage larger numbers of physicists. Perimeter had already begun the process of implementing tenure for its faculty, which Turok inherited. Markopoulou prepared to apply. By this time she was back in Berlin again, on a fellowship at the Max Planck Institute. She put together a dossier of her accomplishments for Turok, which was also to be reviewed by a tenure committee and quantum gravity experts.

    Turok says he respected Markopoulou, but doubted her work would lead anywhere. He denied her tenure. “Fotini had pursued a very independent line of inquiry that was really very different and hardly acknowledged by leading researchers in the field,” Turok says. “I applauded her for her bravery for pursuing her own line, but that inevitably brings risks with it. She is a very fundamental thinker; she had original ideas. But at the end of the day you had to decide if those ideas are going to pan out.”

    Markopoulou says she was disappointed that Perimeter had “shifted from a flat hierarchy of scientists to an all-powerful director.” Turok emailed her out of the blue, she says, to stop the review process and deny her tenure. “As a result of my case, an independent consultant was appointed because I had been the only woman faculty for nine years, I had a strong academic record, and Neil stopped the tenure process just as I had a baby,” Markopoulou says. (“I respectfully beg to differ,” Turok responds. “A tenure review process was never initiated.”) The matter is subject to an out-of-court settlement.

    In the autumn of 2011, Markopoulou walked out of Perimeter for good.

    One sunny morning in March, I visit Markopoulou at her home outside Oxford, perched on a hill and encircled by stands of oak, ash, and silvery birch. Nancy, the wife of the poet and classicist Robert Graves, used to run a grocery store on the site before the poet John Masefield knocked it down to build a theater in 1924. The top rooms sit snug under the original proscenium arch. Markopoulou loves theater—a legacy of being Greek, she says. It allows you to “step out of your normal shoes, to shift reality a bit, and to actively participate by forcing you to suspend your belief.” Not unlike science at its highest levels.

    In the living room, Markopoulou bundles herself up into a burgundy armchair with the cheerful self-possession of a family cat. A Persian rug sprawls across the wood floor, monopolized by a Lego space station. One of her mother’s bronze busts broods from a windowsill, a beautiful, dauby figure of a woman with braids parted down the middle. “You were asking me the other day what made me change,” she says. “One big thing was my mother died and opened up a space for me.” Markopoulou wouldn’t have touched art while her mother was alive, but recognizes now that a similar desire to make, to craft and to create, is part of who she is.

    “In many ways, physics and what I did are almost ideally positioned to my experience with my mother,” she says. “I probably did come out of that wanting a much more firm grasp of what is what, and objective decision-making. Now I don’t feel I need that much any more, but growing up that was a big deal. Also, it was far away from her, it was my own space, but at the same time there were many ways in which the deeper challenges are the same.” Sculpture is a lot like creating a physics theory, she says, because you have to turn it around and make sure it works from every angle. “You have to understand the essence of what you’re doing before you start, because only then do you have a chance that it’s going to work from all sides.”

    Did she believe this philosophy could help her solve quantum gravity? “I never really wanted to single-handedly solve it. But I never went in thinking that we can’t. I always assumed it was possible.” Does she still think it is? “Not soon, but I don’t know. If I knew, I would be doing it,” she quips.

    During her unsteady transition out of physics, Farmer was a pillar of support for Markopoulou. “I’m very much what I do, so going through a transition is a time when I don’t know who I am,” she says. “I was lucky to have the context where that was perfectly possible.”

    Farmer is a distinguished and idiosyncratic physicist in his own right. While still in grad school at the University of California, Santa Cruz, studying physical cosmology, he and fellow physicist, Norman Packard, created one of the world’s first wearable computers. Released in the 1970s, it was a toe-operated device embedded in the tip of a shoe, which allowed the wearer and an accomplice to track the progress of a roulette ball and achieve a 20 percent advantage over the house. He and Packard later decided to found one of the first predictive stock trading companies, which was ultimately sold to UBS, a financial services company, in 2006. Farmer’s interests now lie in “econophysics,” a field which he founded and which applies the mathematics of natural systems to gather insights about the economy.

    When Farmer landed a post at Oxford University in 2011, Markopoulou was faced with “the usual two body problem in academia” of trying to find a job nearby. But when she started looking, she realized her heart wasn’t in it. She had been toying with industrial design, and asked the advice of the musician Brian Eno, a physics follower and a friend. He advised her to look into the master’s program in Innovation Design Engineering run by the Royal College of Arts and Imperial College in London, and wrote her a letter of reference.

    She sailed through the admissions process, which included an exercise where prospective students had to explain how they would evade a pack of zombies chasing them toward the lip of a cliff. She enjoyed the classwork but found the mental shift hard at first. “It just felt silly because you go from, ‘This is how the universe started’ to, ‘This mattress has these bubbles.’ ”

    But she loved making things, and also made the personal connections that evolved into Doppel. A sailing trip to Greece, in which the Doppel crew nearly scuppered Markopoulou’s and Farmer’s large-bottomed boat on the rocks off the island of Cephalonia, cemented the team’s conviction that they could withstand the trials of doing a start-up.

    The kernel for Doppel came from a piece in New Scientist about interoception—the way humans can discern the internal states of the body and conceive of it as “their own.” The idea is that our sense of self is not merely a mental process that somehow envelops the body, but somehow arises from the two-way conversation between the brain and other organs. As Manos Tsakiris, the softly spoken psychologist and neuroscientist who advises Doppel, tells me, “You cannot cut off cognition from the rest of the body, and you cannot cut off the body from the rest of the world in which you interact.” By harvesting your natural response to rhythm, Doppel runs counter to the notion that the self resides in the mind alone—that the human is a creature of the will, a maker of rational decisions, a sovereign mind bossing around dumb matter.

    With hindsight, Markopoulou sees her work at Doppel as a “natural evolution” from what she did before. Isham had inspired her to pursue physics as a quest to understand reality from within, when scientists can’t stand apart from what they’re trying to analyze. But now, instead of the universe as the ultimate system, she has the human body. “If you think about physics, it’s a human creation. The equations represent stuff we come up with because of our senses. So shouldn’t our senses be part of what goes into physics?” Markopoulou says.

    Markopoulou thinks that many disputes in science come down to competing metaphysical commitments. She recognizes that her own belief in the fundamental nature of time, and her dislike of timelessness, is a moral preference as much as anything else. “Most of the physics where time does not exist comes with determinism as well. There is something about thinking that time is real and being responsible for your actions,” she tells me.

    This belief in the inexorable movement of time is what seems to have allowed Markopoulou to reinvent herself—to turn away from years spent building a career as a physicist and to start from scratch as a designer and entrepreneur. “This is the nice thing about me, but it’s also a little bit weird: When I do something, I just do it. So when I switched, I switched,” she says. “Our mind can live in the past, the future, or any fantasy place it wants, but our body only processes the now.”

    Doppel is unlikely to be the end of Markopoulou’s journey. “Whatever it is that you do, it has to have a context. Academia is one context, business is another context. I can’t really tell you if it’s better or worse, it’s a different set of rules—and right now I have come to no conclusions as to what I think about those rules. I’m still exploring.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 2:16 pm on April 22, 2017 Permalink | Reply
    Tags: , , , , Particle Physics, Videos   

    From CMS at CERN: Fantastic Videos 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    These incredible videos are presented in no particular order.,


    An introduction to the CMS Experiment at CERN


    Welcome to LHC season 2: new frontiers in physics at #13TeV


    LHC animation: The path of the protons


    The Large Hadron Collider Returns in the Hunt for New Physics


    Physics Run 2016


    Back to the Big Bang: Inside the Large Hadron Collider – From the World Science Festival


    Higgs boson: what’s next? #13TeV

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    CernCourier
    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 11:56 am on April 20, 2017 Permalink | Reply
    Tags: , , , , New LHC Results Hint At New Physics... But Are We Crying Wolf?, , Particle Physics   

    From Ethan Siegel: “New LHC Results Hint At New Physics… But Are We Crying Wolf?” 

    Ethan Siegel
    Apr 20, 2017

    1
    The LHCb collaboration is far less famous than CMS or ATLAS, but the bottom-quark-containing particles they produce holds new physics hints that the other detectors cannot probe. CERN / LHCb Collaboration

    Over at the Large Hadron Collider at CERN, particles are accelerated to the greatest energies they’ve ever reached in history. In the CMS and ATLAS detectors, new fundamental particles are continuously being searched for, although only the Higgs boson has come through. But in a much lesser-known detector — LHCb — particles containing bottom quarks are produced in tremendous numbers. One class of these particles, quark-antiquark pairs where one is a bottom quark, have recently been observed to decay in a way that runs counter to the Standard Model’s predictions. Even though the evidence isn’t very good, it’s the biggest hint for new physics we’ve had from accelerators in years.

    2
    A decaying B-meson, as shown here, may decay more frequently to one type of lepton pair than the other, contradicting Standard Model expectations. KEK / BELLE collaboration

    KEK Belle detector, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan

    There are two ways, throughout history, that we’ve made extraordinary advances in fundamental physics. One is when an unexplained, robust phenomenon pops up, and we’re compelled to rethink our conception of the Universe. The other is when multiple, competing, but heretofore indistinguishable explanations of the same set of observations are subject to a critical test, where only one explanation emerges as a valid one. Particle physics is at a crossroads right now, because even though there are fundamentally unsolved questions, the energy scales that we can probe with experiments all give results that are perfectly in line with the Standard Model.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    3
    The discovery of the Higgs Boson in the di-photon (γγ) channel at CMS. That ‘bump’ in the data is an unambiguous new particle: the Higgs.

    CERN CMS Higgs Event

    CERN/CMS Detector

    The Higgs boson, discovered earlier this decade, was created over and over at the LHC, with its decays measured in excruciating detail. If there were any hints of departures from the Standard Model — if it decayed into one type of particle more-or-less frequently than predicted — it could be an extraordinary hint of new physics. Similarly, physicists searches exhaustively for new “bumps” where there shouldn’t be any in the data: a signal of a potential new particle. Although they showed up periodically, with some mild significance, they always went away entirely with more and better data.

    4
    The observed Higgs decay channels vs. the Standard Model agreement, with the latest data from ATLAS and CMS included. The agreement is astounding, but there are outliers (which is expected) when the error-bars are larger.

    CERN ATLAS Higgs Event

    CERN/ATLAS detector

    Statistically, this is about what you’d expect. If you had a fair coin and tossed it 10 times, you might expect that you’d get 5 heads and 5 tails. Although that’s reasonable, sometimes you’ll get 6 and 4, sometimes you’ll get 8 and 2, and sometimes you’ll get 10 and 0, respectively. If you got 10 heads and 0 tails, you might begin to suspect that the coin isn’t fair, but the odds aren’t that bad: about 0.2% of the time, you’ll have all ten flips give the same result. And if you have 1000 people each flipping a coin ten times, it’s very likely (86%) that at least one of them will get the same result all ten times.

    The Standard Model makes predictions for lots of different quantities — particle production rates, scattering amplitudes, decay probabilities, branching ratios, etc. — for every single particle (both fundamental and composite) that can be created. Literally, there are hundreds of such composite particles that have been created in such numbers, and thousands of quantities like that we can measure. Since we look at all of them, we demand an extremely high level of statistical significance before we’re willing to claim a discovery. In particle physics, the odds of a fluke need to be less than one-in-three-million to get there.

    6
    The standard model calculated predictions (the four colored points) and the LHCb results (black, with error bars) for the electron/positron to muon/antimuon ratios at two different energies. LHCb Collaboration / Tommaso Dorigo

    Earlier this week, the LHCb collaboration announced their greatest departure yet observed from the Standard Model: a difference in the rate of decay of bottom-quark-containing mesons into strange-quark-containing mesons with either a muon-antimuon pair or an electron-positron pairs. In the Standard Model, the ratios should be 1.0 (once mass differences of muons and electrons are taken into account), but they observed a ratio of 0.6. That sure sounds like a big deal, and like it might be a hint of physics beyond the Standard Model!

    7
    The known particles and antiparticles of the Standard Model all have been discovered. All told, they make explicit predictions. Any violation of those predictions would be a sign of new physics, which we’re desperately seeking. E. Siegel

    The case gets even stronger when you consider that the BELLE collaboration, last decade, discovered these decays and began to notice a slight discrepancy themselves. But a closer inspection of the latest data shows that the statistical significance is only about 2.4 and 2.5 sigma, respectively, at the two energies measured. This is about a 1.5% chance of a fluke individually, or about 3.7-sigma significance (0.023% chance of a fluke) combined. Now, 3.7-sigma is a lot more exciting than 2.5-sigma, but it’s still not exciting enough. Given that there were thousands of things these experiments looked at, these results barely even register as “suggestive” of new physics, much less as compelling evidence.

    7
    The ATLAS and CMS diphoton bumps from 2015, displayed together, clearly correlating at ~750 GeV. This suggestive result was significant at more than 3-sigma, but went away entirely with more data. CERN, CMS/ATLAS collaborations; Matt Strassler

    Yet already, just on Wednesday, there were six new papers out (with more surely coming) attempting to use beyond-the-Standard-Model physics to explain this not-even-promising result.

    Why?

    Because, quite frankly, we don’t have any good ideas in place. Supersymmetry, grand unification, string theory, technicolor, and extra dimensions, among others, were the leading extensions to the Standard Model, and colliders like the LHC have yielded absolutely no evidence for any of them. Signals from direct experiments for physics beyond the Standard Model have all yielded results completely consistent with the Standard Model alone. What we’re seeing now is rightly called ambulance-chasing, but it’s even worse than that.

    8
    The Standard Model particles and their supersymmetric counterparts. Non-white-male-American scientists have been instrumental in the development of the Standard Model and its extensions. Claire David

    We know that results like this have a history of not holding up at all; we expect there to be fluctuations like this in the data, and this one isn’t even as significant as the others that have gone away with more and better data. You expect a 2-sigma discrepancy in one out of every 20 measurements you make, and these two are little better than that. Even combined, they’re hardly impressive, and the other things you’d seek to measure about this decay line up with the Standard Model perfectly. In short, the Standard Model is much more likely than not to hold up once more and better data arrives.

    9
    The string landscape might be a fascinating idea that’s full of theoretical potential, but it doesn’t predict anything that we can observe in our Universe. University of Cambridge

    What we’re seeing right now is a response from the community is what we’d expect to an alarm that’s crying “Wolf!” There might be something fantastic and impressive out there, and so, of course we have to look. But we know that, more than 99% of the time, an alarm like this is merely the result of which way the wind blew. Physicists are so bored and so out of good, testable ideas to extend the Standard Model — which is to say, the Standard Model is so maddeningly successful — that even a paltry result like this is enough to shift the theoretical direction of the field.

    A few weeks ago, famed physicist (and supersymmetry-advocate) John Ellis asked the question, Where is Particle Physics going? Unless experiments can generate new, unexpected results, the answer is likely to be “nowhere new; nowhere good” for the indefinite future.

    See the full article here .

    Please help promote STEM in your local schools.

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 11:05 am on April 19, 2017 Permalink | Reply
    Tags: , , Particle Physics, ,   

    From Ethan Siegel: “Why Does The Proton Spin? Physics Holds A Surprising Answer” 

    Ethan Siegel
    Apr 19, 2017

    1
    The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. APS/Alan Stonebraker

    You can take any particle in the Universe and isolate it from everything else, yet there are some properties that can never be taken away. These are intrinsic, physical properties of the particle itself — properties like mass, charge, or angular momentum — and will always be the same for any single particle. Some particles are fundamental, like electrons, and their mass, charge and angular momentum are fundamental, too. But other particles are composite particles, like the proton. While the proton’s charge (of +1) is due to the sum of the three quarks that make it up (two up quarks of +2/3 and one down quark of -1/3), the story of its angular momentum is much more complicated. Even though it’s a spin = 1/2 particle, just like the electron, simply adding the spins of the three quarks that make it up together isn’t enough.

    2
    The three valence quarks in the proton, two up and one down, were initially thought to constitute its spin of 1/2. But that simple idea didn’t conform to experiments. Arpad Horvath.

    There are two things that contribute to angular momentum: spin, which is the intrinsic angular momentum inherent to any fundamental particle, and orbital angular momentum, which is what you get from two or more fundamental particles that make up a composite particle. (Don’t be fooled: no particles are actually, physically spinning, but “spin” is the name we give to this property of intrinsic angular momentum.) A proton has two up quarks and one down quark, and they’re held together by gluons: massless, color-charged particles which mutually bind the three quarks together. Each quark has a spin of 1/2, so you might simply think that so long as one spins in the opposite direction of the other two, you’d get the proton’s spin. Up until the 1980s, that’s exactly how the standard reasoning went.

    3
    The proton’s structure, modeled along with its attendant fields, show that the three valence quarks alone cannot account for the proton’s spin, and instead account only for a fraction of it. Brookhaven National Laboratory

    With two up quarks — two identical particles — in the ground state, you’d expect that the Pauli exclusion principle would prevent these two identical particles from occupying the same state, and so one would have to be +1/2 while the other was -1/2. Therefore, you’d reason, that third quark (the down quark) would give you a total spin of 1/2. But then the experiments came, and there was quite a surprise at play: when you smashed high-energy particles into the proton, the three quarks inside (up, up, and down) only contributed about 30% to the proton’s spin.

    4
    The internal structure of a proton, with quarks, gluons, and quark spin shown. Brookhaven National Laboratory

    There are three good reasons that these three components might not add up so simply.

    The quarks aren’t free, but are bound together inside a small structure: the proton. Confining an object can shift its spin, and all three quarks are very much confined.
    There are gluons inside, and gluons spin, too. The gluon spin can effectively “screen” the quark spin over the span of the proton, reducing its effects.
    And finally, there are quantum effects that delocalize the quarks, preventing them from being in exactly one place like particles and requiring a more wave-like analysis. These effects can also reduce or alter the proton’s overall spin.

    In other words, that missing 70% is real.

    4
    As better experiments and theoretical calculations have come about, our understanding of the proton has gotten more sophisticated, with gluons, sea quarks, and orbital interactions coming into play. Brookhaven National Laboratory

    Maybe, you’d think, that those were just the three valence quarks, and that quantum mechanics, from the gluon field, could spontaneously create quark/antiquark pairs. That part is true, and makes important contributions to the proton’s mass. But as far as the proton’s angular momentum goes, these “sea quarks” are negligible.

    5
    The fermions (quarks and gluons), antifermions (antiquarks and antileptons), all spin = 1/2, and the bosons (of integer spin) of the standard model, all shown together. E. Siegel

    Maybe, then, the gluons would be an important contributor? After all, the standard model of elementary particles is full of fermions (quarks and leptons) which are all spin = 1/2, and bosons like the photon, the W-and-Z, and the gluons, all of which are spin = 1. (Also, there’s the Higgs, of spin = 0, and if quantum gravity is real, the graviton, of spin = 2.) Given all the gluons inside the proton, perhaps they matter, too?

    6
    By colliding particles together at high energies inside a sophisticated detector, like Brookhaven’s PHENIX detector at RHIC, have led the way in measuring the spin contributions of gluons. Brookhaven National Laboratory

    There are two ways to test that: experimentally and theoretically. From an experimental point of view, you can collide particles deep inside the proton, and measure how the gluons react. The gluons that contribute the most to the proton’s overall momentum are seen to contribute substantially to the proton’s angular momentum: about 40%, with an uncertainty of ±10%. With better experimental setups (which would require a new electron/ion collider), we could probe down to lower-momentum gluons, achieving even greater accuracies.

    7
    When two protons collide, it isn’t just the quarks making them up that can collide, but the sea quarks, gluons, and beyond that, field interactions. All can provide insights into the spin of the individual components. CERN / CMS Collaboration

    But the theoretical calculations matter, too! A calculational technique known as Lattice QCD has been steadily improving over the past few decades, as the power of supercomputers has increased exponentially. Lattice QCD has now reached the point where it can predict that the gluon contribution to the proton’s spin is 50%, again with a few percent uncertainty. What’s most remarkable is that the calculations show that — with this contribution — the gluon screening of the quark spin is ineffective; the quarks must be screened from a different effect.

    8
    As computational power and Lattice QCD techniques have improved over time, so has the accuracy to which various quantities about the proton, such as its component spin contribtuions, can be computed. Laboratoire de Physique de Clermont / ETM Collaboration

    The remaining 20% must come from orbital angular momentum, where gluons and even virtual pions surround the three quarks, since the “sea quarks” have a negligible contribution, both experimentally and theoretically.

    9
    A proton, more fully, is made up of spinning valence quarks, sea quarks and antiquarks, spinning gluons, all of which mutually orbit one another. That is where their spins come from. Zhong-Bo Kang, 2012, RIKEN, Japan

    It’s remarkable and fascinating that both theory and experiment agree, but most incredible of all is the fact that the simplest explanation for the proton’s spin — simply adding up the three quarks — gives you the right answer for the wrong reason! With 70% of the proton’s spin coming from gluons and orbital interactions, and with experiments and Lattice QCD calculations improving hand-in-hand, we’re finally closing in on exactly why the proton “spins” with the exact value that it has.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 1:56 pm on April 18, 2017 Permalink | Reply
    Tags: , , , , , LHCb Finds New Hints of Possible Deviations from the Standard Model, , Particle Physics   

    From Astro Watch: “LHCb Finds New Hints of Possible Deviations from the Standard Model” 

    Astro Watch bloc

    Astro Watch

    April 18, 2017
    CERN

    1
    CERN LHCb

    The LHCb experiment finds intriguing anomalies in the way some particles decay. If confirmed, these would be a sign of new physics phenomena not predicted by the Standard Model of particle physics. The observed signal is still of limited statistical significance, but strengthens similar indications from earlier studies. Forthcoming data and follow-up analyses will establish whether these hints are indeed cracks in the Standard Model or a statistical fluctuation.

    Today, in a seminar at CERN, the LHCb collaboration presented new long-awaited results on a particular decay of B0 mesons produced in collisions at the Large Hadron Collider. The Standard Model of particle physics predicts the probability of the many possible decay modes of B0 mesons, and possible discrepancies with the data would signal new physics.

    In this study, the LHCb collaboration looked at the decays of B0 mesons to an excited kaon and a pair of electrons or muons. The muon is 200 times heavier than the electron, but in the Standard Model its interactions are otherwise identical to those of the electron, a property known as lepton universality. Lepton universality predicts that, up to a small and calculable effect due to the mass difference, electron and muons should be produced with the same probability in this specific B0 decay. LHCb finds instead that the decays involving muons occur less often.

    While potentially exciting, the discrepancy with the Standard Model occurs at the level of 2.2 to 2.5 sigma, which is not yet sufficient to draw a firm conclusion. However, the result is intriguing because a recent measurement by LHCb involving a related decay exhibited similar behavior.

    While of great interest, these hints are not enough to come to a conclusive statement. Although of a different nature, there have been many previous measurements supporting the symmetry between electrons and muons. More data and more observations of similar decays are needed in order to clarify whether these hints are just a statistical fluctuation or the first signs for new particles that would extend and complete the Standard Model of particles physics. The measurements discussed were obtained using the entire data sample of the first period of exploitation of the Large Hadron Collider (Run 1). If the new measurements indeed point to physics beyond the Standard Model, the larger data sample collected in Run 2 will be sufficient to confirm these effects.

    See the full article here .

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  • richardmitnick 1:45 pm on April 18, 2017 Permalink | Reply
    Tags: , , , Gabriella Carini, How do you catch femtosecond light?, Particle Physics, , , , ,   

    From SLAC: “How do you catch femtosecond light?” 


    SLAC Lab

    1
    Gabriella Carini
    Staff Scientist
    Joined SLAC: 2011
    Specialty: Developing detectors that capture light from X-ray sources
    Interviewed by: Amanda Solliday

    Gabriella Carini enjoys those little moments—after hours and hours of testing in clean rooms, labs and at X-ray beamlines—when she first sees an instrument work.

    She earned her PhD in electronic engineering at the University of Palermo in Italy and now heads the detectors department at the Linac Coherent Light Source (LCLS), the X-ray free-electron laser at SLAC.

    SLAC/LCLS

    Scientists from around the world use the laser to probe natural processes that occur in tiny slivers of time. To see on this timescale, they need a way to collect the light and convert it into data that can be examined and interpreted.

    It’s Carini’s job to make sure LCLS has the right detector equipment at hand to catch the “precious”, very intense laser pulses, which may last only a few femtoseconds.

    When the research heads in new directions, as it constantly does, this requires her to look for fresh technology and turn these ideas into reality.

    When did you begin working with detectors?

    I moved to the United States as a doctoral student. My professor at the time suggested I join a collaboration at Brookhaven National Laboratory, where I started developing gamma ray detectors to catch radioactive materials.

    Radioactive materials give off gamma rays as they decay, and gamma rays are the most energetic photons, or particles of light. The detectors I worked on were made from cadmium zinc telluride, which has very good stopping power for highly energetic photons. These detectors can identify radioactive isotopes for security—such as the movement of nuclear materials—and contamination control, but also gamma rays for medical and astrophysical observations.

    We had some medical projects going on at the time, too, with detectors that scan for radioactive tracers used to map tissues and organs with positron emission tomography.

    From gamma ray detectors, I then moved to X-rays, and I began working on the earliest detectors for LCLS.

    How do you explain your job to someone outside the X-ray science community?

    I say, “There are three ingredients for an experiment—the source, the sample and the detector.”

    You need a source of light that illuminates your sample, which is the problem you want to solve or investigate. To understand what is happening, you have to be able to see the signal produced by the light as it interacts with the sample. That’s where the detector comes in. For us, the detector is like the “eyes” of the experimental set-up.

    What do you like most about your work?

    2

    There’s always a way we can help researchers optimize their experiments, tweak some settings, do more analysis and correction.

    This is important because scientists are going to encounter a lot of different types of detectors if they work at various X-ray facilities.

    I like to have input from people who are running the experiments. Because I did experiments myself as a graduate student, I’m very sensitive to whether a system is user-friendly. If you don’t make something that researchers can take the best advantage of, then you didn’t do your job fully.

    And detectors are never perfect, no matter which one you buy or build.

    There are a lot of people who have to come together to make a detector system. It’s not one person’s work. It’s many, many people with lots of different expertise. You need to have lots of good interpersonal skills.

    What are some of the challenges of creating detectors for femtosecond science?

    In more traditional X-ray sources the photons arrive distributed over time, one after the other, but when you work with ultrafast laser pulses like the ones from LCLS, all your information about a sample arrives in a few femtoseconds. Your detector has to digest this entire signal at once, process the information and send it out before another pulse comes. This requires deep understanding of the detector physics and needs careful engineering. You need to optimize the whole signal chain from the sensor to the readout electronics to the data transmission.

    We also have mechanical challenges because we have to operate in very unusual conditions: intense optical lasers, injectors with gas and liquids, etc. In many cases we need to use special filters to protect the detectors from these sources of contamination.

    4
    And often, you work in vacuum. With “soft” or low-energy X-rays, they are absorbed very quickly in air. Your entire system has to be vacuum-compatible. With many of our substantial electronics, this requires some care.

    So there are lots of things to take into account. Those are just a few examples. It’s very complicated and can vary quite a bit from experiment to experiment.

    Is there a new project you are really excited about?

    All of LCLS-II—this fills my life! We’re coming up with new ideas and new technologies for SLAC’s next X-ray laser, which will have a higher firing rate—up to a million pulses per second. For me, this is a multidimensional puzzle. Every science case and every instrument has its own needs and we have to find a route through the many options and often-competing parameters to achieve our goals.

    X-ray free-electron lasers are a big driver for detector development. Ten years ago, no one would have talked about X-ray cameras delivering 10,000 pictures per second. The new X-ray lasers are really a game-changer in developing detectors for photon science, because they require detectors that are just not readily available.

    LCLS-II will be challenging, but it’s exciting. For me, it’s thinking about what we can do now for the very first day of operation. And while doing that, we need to keep pushing the limits of what we have to do next to take full advantage of our new machine.

    6

    SLAC LCLS-II

    See the full article here .

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    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 12:59 pm on April 17, 2017 Permalink | Reply
    Tags: , , Particle Physics, Why is the Weak Force weak?   

    From Don Lincoln at FNAL: “Why is the Weak Force weak?” Video. 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Apr 14, 2017

    FNAL Don Lincoln


    Don Lincoln

    The subatomic world is governed by three known forces, each with vastly different energy. In this video, Fermilab’s Dr. Don Lincoln takes on the weak nuclear force and shows why it is so much weaker than the other known forces.

    Watch, enjoy, learn.

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    See the full article here .

    Please help promote STEM in your local schools.

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    FNAL Icon
    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
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