From CERN: “LHC accelerates its first ‘atoms'”

From CERN

27 July 2018
Sarah Charley
Posted by Kate Kahle

During a special one-day run, LHC operators injected lead “atoms” containing a single electron into the machine (Image: Maximilien Brice/Julien Ordan/CERN)

Protons might be the Large Hadron Collider’s bread and butter, but that doesn’t mean it can’t crave more exotic tastes from time to time.

LHC

CERN map

CERN LHC Tunnel

CERN LHC particles

On Wednesday, 25 July, for the very first time, operators injected not just atomic nuclei but lead “atoms” containing a single electron into the LHC. This was one of the first proof-of-principle tests for a new idea called the Gamma Factory, part of CERN’s Physics Beyond Colliders project.

“We’re investigating new ideas of how we could broaden the present CERN research programme and infrastructure,” says Michaela Schaumann, an LHC Engineer in Charge. “Finding out what’s possible is the first step.”

During normal operation, the LHC produces a steady stream of proton–proton collisions, then smashes together atomic nuclei for about four weeks just before the annual winter shutdown. But for a handful of days a year, accelerator physicists get to try something completely new during periods of machine development. Previously, they accelerated xenon nuclei in the LHC and tested other kinds of partially stripped lead ions in the SPS accelerator.

“This special LHC run was really the last step in a series of tests,” says physicist Witold Krasny, who is coordinating a study group of about 50 scientists to develop new ways to produce high-energy gamma rays.

Accelerating lead nuclei with one remaining electron can be challenging because of how delicate these atoms are. “It’s really easy to accidentally strip off the electron,” explains Schaumann. “When that happens, the nucleus crashes into the wall of the beam pipe because its charge is no longer synchronised with the LHC’s magnetic field.”

During the first run, operators injected 24 bunches of “atoms” and achieved a low-energy stable beam inside the LHC for about an hour. They then ramped the LHC up to its full power and maintained the beam for about two minutes before it was ejected into the beam dump. “If too many particles go off course, the LHC automatically dumps the beam,” states Schaumann. “Our main priority is to protect the LHC and its magnets.”

After running the magnets through the restart cycle, Schaumann and her colleagues tried again, this time with only six bunches. They kept the beam circulating for two hours before intentionally dumping it.

“We predicted that the lifetime of this special kind of beam inside the LHC would be at least 15 hours,” says Krasny. “We were surprised to learn the lifetime could be as much as about 40 hours. Now the question is whether we can preserve the same beam lifetime at a higher intensity by optimising the collimator settings, which were still set-up for protons during this special run.”

Physicists are doing these tests to see if the LHC could one day operate as a gamma-ray factory. In this scenario, scientists would shoot the circulating “atoms” with a laser, causing the electron to jump into a higher energy level. As the electron falls back down, it spits out a particle of light. In normal circumstances, this particle of light would not be very energetic, but because the “atom” is already moving at close to the speed of light, the energy of the emitted photon is boosted and its wavelength is squeezed (due to the Doppler effect).

These gamma rays would have sufficient energy to produce normal “matter” particles, such as quarks, electrons and even muons. Because matter and energy are two sides of the same coin, these high-energy gamma rays would transform into massive particles and could even morph into new kinds of matter, such as dark matter. They could also be the source for new types of particle beams, such as a muon beam.

Even though this is still a long way off, the tests this week were an important first step in seeing what is possible.

See the full article here.

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Meet CERN in a variety of places:

Quantum Diaries

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THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

ALICE

CMS

LHCb

LHC

CERN map

OTHER PROJECTS AT CERN

CERN AEGIS

CERN ALPHA

CERN ALPHA

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CERN ACACUSA

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CERN AWAKE

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CERN CLOUD

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CERN COMPASS

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CERN DIRAC

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From LHC at CERN and University of Wisconsin Madison via WIRED and Quanta: Women in STEM “Meet the Woman Who Rocked Particle Physics—Three Times” Sau Lan Wu

CERN

via

WIRED

originated at

Quanta Magazine

7.22.18
Joshua Roebke

Sau Lan Wu at CERN, the laboratory near Geneva that houses the Large Hadron Collider. The mural depicts the detector she and her collaborators used to discover the Higgs boson. Thi My Lien Nguyen/Quanta Magazine

In 1963, Maria Goeppert Mayer won the Nobel Prize in physics for describing the layered, shell-like structures of atomic nuclei. No woman has won since.

One of the many women who, in a different world, might have won the physics prize in the intervening 55 years is Sau Lan Wu. Wu is the Enrico Fermi Distinguished Professor of Physics at the University of Wisconsin, Madison, and an experimentalist at CERN, the laboratory near Geneva that houses the Large Hadron Collider.

LHC

CERN map

CERN LHC Tunnel

CERN LHC particles

Wu’s name appears on more than 1,000 papers in high-energy physics, and she has contributed to a half-dozen of the most important experiments in her field over the past 50 years. She has even realized the improbable goal she set for herself as a young researcher: to make at least three major discoveries.

Wu was an integral member of one of the two groups that observed the J/psi particle, which heralded the existence of a fourth kind of quark, now called the charm. The discovery, in 1974, was known as the November Revolution, a coup that led to the establishment of the Standard Model of particle physics.

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.

Standard Model of Particle Physics from Symmetry Magazine

Later in the 1970s, Wu did much of the math and analysis to discern the three “jets” of energy flying away from particle collisions that signaled the existence of gluons—particles that mediate the strong force holding protons and neutrons together. This was the first observation of particles that communicate a force since scientists recognized photons of light as the carriers of electromagnetism. Wu later became one of the group leaders for the ATLAS experiment, one of the two collaborations at the Large Hadron Collider that discovered the Higgs boson in 2012, filling in the final piece of the Standard Model.

CERN ATLAS Higgs Event

CERN/ATLAS detector

She continues to search for new particles that would transcend the Standard Model and push physics forward.

Sau Lan Wu was born in occupied Hong Kong during World War II. Her mother was the sixth concubine to a wealthy businessman who abandoned them and her younger brother when Wu was a child. She grew up in abject poverty, sleeping alone in a space behind a rice shop. Her mother was illiterate, but she urged her daughter to pursue an education and become independent of volatile men.

Wu graduated from a government school in Hong Kong and applied to 50 universities in the United States. She received a scholarship to attend Vassar College and arrived with $40 to her name.

Although she originally intended to become an artist, she was inspired to study physics after reading a biography of Marie Curie. She worked on experiments during consecutive summers at Brookhaven National Laboratory on Long Island, and she attended graduate school at Harvard University. She was the only woman in her cohort and was barred from entering the male dormitories to join the study groups that met there. She has labored since then to make a space for everyone in physics, mentoring more than 60 men and women through their doctorates.

Quanta Magazine joined Sau Lan Wu on a gray couch in sunny Cleveland in early June. She had just delivered an invited lecture about the discovery of gluons at a symposium to honor the 50th birthday of the Standard Model. The interview has been condensed and edited for clarity.

Wu’s office at CERN is decorated with mementos and photos, including one of her and her husband, Tai Tsun Wu, a professor of theoretical physics at Harvard.
Thi My Lien Nguyen/Quanta Magazine

You work on the largest experiments in the world, mentor dozens of students, and travel back and forth between Madison and Geneva. What is a normal day like for you?

Very tiring! In principle, I am full-time at CERN, but I do go to Madison fairly often. So I do travel a lot.

How do you manage it all?

Well, I think the key is that I am totally devoted. My husband, Tai Tsun Wu, is also a professor, in theoretical physics at Harvard. Right now, he’s working even harder than me, which is hard to imagine. He’s doing a calculation about the Higgs boson decay that is very difficult. But I encourage him to work hard, because it’s good for your mental state when you are older. That’s why I work so hard, too.

Of all the discoveries you were involved in, do you have a favorite?

Discovering the gluon was a fantastic time. I was just a second- or third-year assistant professor. And I was so happy. That’s because I was the baby, the youngest of all the key members of the collaboration.

The gluon was the first force-carrying particle discovered since the photon. The W and Z bosons, which carry the weak force, were discovered a few years later, and the researchers who found them won a Nobel Prize. Why was no prize awarded for the discovery of the gluon?

Well, you are going to have to ask the Nobel committee that. [Laughs.] I can tell you what I think, though. Only three people can win a Nobel Prize. And there were three other physicists on the experiment with me who were more senior than I was. They treated me very well. But I pushed the idea of searching for the gluon right away, and I did the calculations. I didn’t even talk to theorists. Although I married a theorist, I never really paid attention to what the theorists told me to do.

How did you wind up being the one to do those calculations?

If you want to be successful, you have to be fast. But you also have to be first. So I did the calculations to make sure that as soon as a new collider at at DESY [the German Electron Synchrotron] turned on in Hamburg we could see the gluon and recognize its signal of three jets of particles.

DESY Helmholtz Centres & Networks: DESY’s synchrotron radiation source: the PETRA III storage ring (in orange) with the three experimental halls (in blue) in 2015.

We were not so sure in those days that the signal for the gluon would be clear-cut, because the concept of jets had only been introduced a couple of years earlier, but this seemed to be the only way to discover gluons.

You were also involved in discovering the Higgs boson, the particle in the Standard Model that gives many other particles their masses. How was that experiment different from the others that you were part of?

I worked a lot more and a lot longer to discover the Higgs than I have on anything else. I worked for over 30 years, doing one experiment after another. I think I contributed a lot to that discovery. But the ATLAS collaboration at CERN is so large that you can’t even talk about your individual contribution. There are 3,000 people who built and worked on our experiment [including 600 scientists at Brookhaven National Lab, NY, USA]. How can anyone claim anything? In the old days, life was easier.

Has it gotten any easier to be a woman in physics than when you started?

Not for me. But for younger women, yes. There is a trend among funding agencies and institutions to encourage younger women, which I think is great. But for someone like me it is harder. I went through a very difficult time. And now that I am established others say: Why should we treat you any differently?

Who were some of your mentors when you were a young researcher?

Bjørn Wiik really helped me when I was looking for the gluon at DESY.

How so?

Well, when I started at the University of Wisconsin, I was looking for a new project. I was interested in doing electron-positron collisions, which could give the clearest indication of a gluon. So I went to talk to another professor at Wisconsin who did these kinds of experiments at SLAC, the lab at Stanford. But he was not interested in working with me.

So I tried to join a project at the new electron-positron collider at DESY. I wanted to join the JADE experiment [abbreviated from the nations that developed the detector: Japan, Germany (Deutschland) and England]. I had some friends working there, so I went to Germany and I was all set to join them. But then I heard that no one had told a big professor in the group about me, so I called him up. He said, “I am not sure if I can take you, and I am going on vacation for a month. I’ll phone you when I get back.” I was really sad because I was already in Germany at DESY.

But then I ran into Bjørn Wiik, who led a different experiment called TASSO, and he said, “What are you doing here?” I said, “I tried to join JADE, but they turned me down.” He said, “Come and talk to me.” He accepted me the very next day.

TASSO detector at PETRA at DESY

And the thing is, JADE later broke their chamber, and they could not have observed the three-jet signal for gluons when we observed it first at TASSO. So I have learned that if something does not work out for you in life, something else will.

Wu and Bjørn Wiik in 1978, in the electronic control room of the TASSO experiment at the German Electron Synchrotron in Hamburg, Germany. Dr. Ulrich Kötz

You certainly turned that negative into a positive.

Yes. The same thing happened when I left Hong Kong to attend college in the US. I applied to 50 universities after I went through a catalog at the American consulate. I wrote in every application, “I need a full scholarship and room and board,” because I had no money. Four universities replied. Three of them turned me down. Vassar was the only American college that accepted me. And it turns out, it was the best college of all the ones I applied to.

If you persist, something good is bound to happen. My philosophy is that you have to work hard and have good judgment. But you also have to have luck.

I know this is an unfair question, because no one ever asks men, even though we should, but how can society inspire more women to study physics or consider it as a career?

Well, I can only say something about my field, experimental high-energy physics. I think my field is very hard for women. I think partially it’s the problem of family.

My husband and I did not live together for 10 years, except during the summers. And I gave up having children. When I was considering having children, it was around the time when I was up for tenure and a grant. I feared I would lose both if I got pregnant. I was less worried about actually having children than I was about walking into my department or a meeting while pregnant. So it’s very, very hard for families.

I think it still can be.

Yeah, but for the younger generation it’s different. Nowadays, a department looks good if it supports women. I don’t mean that departments are deliberately doing that only to look better, but they no longer actively fight against women. It’s still hard, though. Especially in experimental high-energy physics. I think there is so much traveling that it makes having a family or a life difficult. Theory is much easier.

You have done so much to help establish the Standard Model of particle physics. What do you like about it? What do you not like?

It’s just amazing that the Standard Model works as well as it does. I like that every time we try to search for something that is not accounted for in the Standard Model, we do not find it, because the Standard Model says we shouldn’t.

But back in my day, there was so much that we had yet to discover and establish. The problem now is that everything fits together so beautifully and the Model is so well confirmed. That’s why I miss the time of the J/psi discovery. Nobody expected that, and nobody really had a clue what it was.

But maybe those days of surprise aren’t over.

We know that the Standard Model is an incomplete description of nature. It doesn’t account for gravity, the masses of neutrinos, or dark matter—the invisible substance that seems to make up six-sevenths of the universe’s mass. Do you have a favorite idea for what lies beyond the Standard Model?

Well, right now I am searching for the particles that make up dark matter. The only thing is, I am committed to working at the Large Hadron Collider at CERN. But a collider may or may not be the best place to look for dark matter. It’s out there in the galaxies, but we don’t see it here on Earth.

Still, I am going to try. If dark matter has any interactions with the known particles, it can be produced via collisions at the LHC. But weakly interacting dark matter would not leave a visible signature in our detector at ATLAS, so we have to intuit its existence from what we actually see. Right now, I am concentrating on finding hints of dark matter in the form of missing energy and momentum in a collision that produces a single Higgs boson.

What else have you been working on?What else have you been working on?

Our most important task is to understand the properties of the Higgs boson, which is a completely new kind of particle. The Higgs is more symmetric than any other particle we know about; it’s the first particle that we have discovered without any spin. My group and I were major contributors to the very recent measurement of Higgs bosons interacting with top quarks. That observation was extremely challenging. We examined five years of collision data, and my team worked intensively on advanced machine-learning techniques and statistics.

In addition to studying the Higgs and searching for dark matter, my group and I also contributed to the silicon pixel detector, to the trigger system [that identifies potentially interesting collisions], and to the computing system in the ATLAS detector. We are now improving these during the shutdown and upgrade of the LHC. We are also very excited about the near future, because we plan to start using quantum computing to do our data analysis.

Wu at CERN. Thi My Lien Nguyen/Quanta Magazine

Do you have any advice for young physicists just starting their careers?

Some of the young experimentalists today are a bit too conservative. In other words, they are afraid to do something that is not in the mainstream. They fear doing something risky and not getting a result. I don’t blame them. It’s the way the culture is. My advice to them is to figure out what the most important experiments are and then be persistent. Good experiments always take time.

But not everyone gets to take that time.

Right. Young students don’t always have the freedom to be very innovative, unless they can do it in a very short amount of time and be successful. They don’t always get to be patient and just explore. They need to be recognized by their collaborators. They need people to write them letters of recommendation.

The only thing that you can do is work hard. But I also tell my students, “Communicate. Don’t close yourselves off. Try to come up with good ideas on your own but also in groups. Try to innovate. Nothing will be easy. But it is all worth it to discover something new.”

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

From TRIUMF: “Canada to lead ‘coldbox’ technology for High-Luminosity LHC upgrade with $10M from Government of Canada”

From TRIUMF

25 June 2018

Lisa Lambert
Head, Strategic Communications
TRIUMF
lisa@triumf.ca
1.604.222.7356

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN), the most massive and complex science experiment in human history, is a prime example of global achievement through collaboration.

LHC

CERN map

CERN LHC Tunnel

CERN LHC particles

Driven by a multinational community of researchers, engineers, and technicians from over 100 countries, the LHC has enabled us to push the boundaries of scientific knowledge. Now, the machine is in the process of a major upgrade to boost performance – and Canada is playing a key role.

The Honourable Kirsty Duncan, Minister of Science and Minister of Sport and Persons with Disabilities, today announced a $10 million contribution to mission-critical components in support of the High-Luminosity Large Hadron Collider (HL-LHC), a major overhaul to significantly improve the performance of the LHC and, as a result, enhance the probability of discovering new physics. Working with the Canadian research community and industry, experts at TRIUMF, Canada’s particle accelerator centre, will lead the production of the Canadian components with a $2 million in-kind contribution for a total project value of $12 million.

The Canadian community is applying its world-leading expertise to tackle a mission-critical challenge for the upgrade: building five new particle accelerator components called crab cavity cryogenic modules. These are super-sophisticated ‘coldboxes’ that will house the crab cavities.

No image caption or credit.

CERN crab cavities that will be used in the HL-LHC

FNAL Crab cavities for the HL-LHC

The crab cavities will rotate bunches of subatomic particles before they smash together, significantly increasing the number of collisions, or luminosity, of the LHC. To operate effectively, the crab cavities require a highly regulated, constant ultra-low temperature environment, which is a daunting challenge due to the harsh conditions in the operating LHC – the world’s largest and most powerful particle accelerator.

Canada is a world-leader in the cryomodule technology that will surround the cavities and will leverage both TRIUMF’s unique network of expertise and the capacity of Canadian industry to design, fabricate, and deliver the crucial upgrade components over the next five years. With a history of providing mission-critical cavity technology to international science collaborations and successfully transferring these technologies to industry, the Canadian community is uniquely positioned to provide a high-impact, lasting contribution for the benefit of international science and society.

“Great science knows no borders. Great scientists know that success lies in strong collaboration. Today, I am pleased to announce support for Canada’s outstanding researchers, engineers and technicians, whose combined efforts will further our reputation as a global leader in particle physics. Their hard work will take us one step closer to understanding the fundamental nature of matter while delivering new technologies, training and job opportunities for the next generation.”

– The Honourable Kirsty Duncan, Minister of Science and Minister of Sport and Persons with Disabilities

“We are very pleased with Canada’s contribution to the HL-LHC project, which is another important milestone in a long-standing, fruitful collaboration with CERN. The technology and expertise of TRIUMF and Canadian industries, working with the strong particle physics community in the country, will be crucial for the realisation of very ambitious accelerator components for the next major project at CERN.”

– Dr. Fabiola Gianotti, Director-General of CERN

“This major upgrade to the LHC will lead to a significant increase in its already high impact on our understanding of the most fundamental workings of nature. Throughout the coming years of this exciting High Luminosity LHC era, Canadians will continue to be significant contributors and leaders in the international LHC scientific and technological enterprise.”

– Dr, Michael Roney, Director of Canada’s Institute of Particle Physics and University of Victoria Professor of Professor of Physics & Astronomy

“By contributing to the High-Luminosity Large Hadron Collider, Canada will secure its place in what will be one of the largest and most important physics projects in coming decades. From illuminating dark matter to discovering new particles and forces, Canadians will work alongside scientists from many nations. Through this work, Canada will increase its capacity for innovation and economic growth. And TRIUMF is happy to help.”

– Dr. Jonathan Bagger, Director of TRIUMF

To complete the cryomodule project, TRIUMF will call on expertise from its diverse member university base, including contributions from the University of Alberta, University of British Columbia, University of Calgary, Carleton University, McGill University, Université de Montréal, Simon Fraser University, the University of Toronto, the University of Victoria, and York University.

In total, there are over 250 researchers, graduate students, and technical staff from leading Canadian universities and TRIUMF involved in the CERN programme. Canadian subatomic and accelerator researchers, engineers, and technicians have longstanding collaborations with CERN in many other areas, including experimental particle physics (ATLAS), rare isotope physics (ISOLDE), low-energy anti-proton and anti-hydrogen (ALPHA and ALPHA-g) including the accelerator aspects (ELENA), accelerator R&D (including AWAKE and HL-LHC developments), rare kaon decays (NA62), and strong synergy in theoretical physics work.

CERN/ATLAS detector

CERN ISOLDE

CERN ALPHA

CERN ALPHA Antimatter Factory

CERN ELENA

CERN AWAKE schematic

CERN AWAKE

CERN NA62

See the full article here .

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Please help promote STEM in your local schools.

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Triumf Campus
World Class Science at Triumf Lab, British Columbia, Canada
Canada’s national laboratory for particle and nuclear physics
Member Universities:
University of Alberta, University of British Columbia, Carleton University, University of Guelph, University of Manitoba, Université de Montréal, Simon Fraser University,
Queen’s University, University of Toronto, University of Victoria, York University. Not too shabby, eh?

Associate Members:
University of Calgary, McMaster University, University of Northern British Columbia, University of Regina, Saint Mary’s University, University of Winnipeg, How bad is that !!

From Brookhaven Lab: “Upgrades to ATLAS and LHC Magnets for Run 2 and Beyond”

From Brookhaven Lab

6.22.18

Peter Genzer,
genzer@bnl.gov
(631) 344-3174

The following news release was issued by CERN, the European Organization for Nuclear Research, home to the Large Hadron Collider (LHC). Scientists from the U.S. Department of Energy’s Brookhaven National Laboratory play multiple roles in the research at the LHC and are making major contributions to the high-luminosity upgrade described in this news release, including the development of new niobium tin superconducting magnets that will enable significantly higher collision rates; new particle tracking and signal readout systems for the ATLAS experiment that will allow scientists to capture and analyze the most significant details from vastly larger data sets; and increases in computing capacity devoted to analyzing and sharing that data with scientists around the world. Brookhaven Lab also hosts the Project Office for the U.S. contribution to the HL-LHC detector upgrades of the ATLAS experiment. For more information about Brookhaven’s roles in the high-luminosity upgrade or to speak with a Brookhaven/LHC scientist, contact Karen McNulty Walsh, (631) 344-8350, kmcnulty@bnl.gov.

Brookhaven physicists play critical roles in LHC restart and plans for the future of particle physics.

The ATLAS detector at the Large Hadron Collider, an experiment with large involvement from physicists at Brookhaven National Laboratory. Image credit: CERN

July 6, 2015

At the beginning of June, the Large Hadron Collider at CERN, the European research facility, began smashing together protons once again. The high-energy particle collisions taking place deep underground along the border between Switzerland and France are intended to allow physicists to probe the furthest edges of our knowledge of the universe and its tiniest building blocks.

The Large Hadron Collider returns to operations after a two-year offline period, Long Shutdown 1, which allowed thousands of physicists worldwide to undertake crucial upgrades to the already cutting-edge particle accelerator. The LHC now begins its second multi-year operating period, Run 2, which will take the collider through 2018 with collision energies nearly double those of Run 1. In other words, Run 2 will nearly double the energies that allowed researchers to detect the long-sought Higgs Boson in 2012.

CERN CMS Higgs Event

CERN ATLAS Higgs Event

The U.S. Department of Energy’s Brookhaven National Laboratory is a crucial player in the physics program at the Large Hadron Collider, in particular as the U.S. host laboratory for the pivotal ATLAS experiment, one of the two large experiments that discovered the Higgs. Physicists at Brookhaven were busy throughout Long Shutdown 1, undertaking projects designed to maximize the LHC’s chances of detecting rare new physics as the collider reaches into a previous unexplored subatomic frontier.

While the technology needed to produce a new particle is a marvel on its own terms, equally remarkable is everything the team at ATLAS and other experiments must do to detect these potentially world-changing discoveries. Because the production of such particles is a rare phenomenon, it isn’t enough to just be able to smash one proton into another. The LHC needs to be able to collide proton bunches, each bunch consisting of hundreds of billions of particles, every 50 nanoseconds—eventually rising to every 25 nanoseconds in Run 2—and be ready to sort through the colossal amounts of data that all those collisions produce.

It is with those interwoven challenges—maximizing the number of collisions within the LHC, capturing the details of potentially noteworthy collisions, and then managing the gargantuan amount of data those collisions produce—that scientists at Brookhaven National Laboratory are making their mark on the Large Hadron Collider and its search for new physics—and not just for the current Run 2, but looking forward to the long-term future operation of the collider.

Restarting the Large Hadron Collider

LHC

CERN map

CERN LHC Tunnel

CERN LHC particles

THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

ALICE

CMS

LHCb

Brookhaven physicist Srini Rajagopalan, operation program manager for U.S. ATLAS, works to keep manageable the colossal amounts of data that are generated by the Large Hadron Collider and sent to Brookhaven’s RHIC and ATLAS Computing Facility.

The Large Hadron Collider is the largest single machine in the world, so it’s tempting to think of its scale just in terms of its immense size. The twin beamlines of the particle accelerator sit about 300 to 600 feet underground in a circular tunnel more than 17 miles around. Over 1,600 magnets, each weighing more than 25 tons, are required to keep the beams of protons focused and on the correct paths, and nearly 100 tons of liquid helium is necessary to keep the magnets operating at temperatures barely above absolute zero. Then there are the detectors, each of which stand several stories high.

But the scale of the LHC extends not just in space, but in time as well. A machine of this size and complexity doesn’t just switch on or off with the push of a button, and even relatively simple maintenance can require weeks, if not months, to perform. That’s why the LHC recently completed Long Shutdown 1, a two-year offline period in which physicists undertook the necessary repairs and upgrades to get the collider ready for the next three years of near-continuous operation. As the U.S. host laboratory for the ATLAS experiment, Brookhaven National Laboratory was pivotal in upgrading and improving one of the cornerstones of the LHC apparatus.

“After having run for three years, the detector needs to be serviced much like your car,” said Brookhaven physicist Srini Rajagopalan, operation program manager for U.S. ATLAS. “Gas leaks crop up that need to be fixed. Power supplies, electronic boards and several other components need to be repaired or replaced. Hence a significant amount of detector consolidation work occurs during the shutdown to ensure an optimal working detector when beam returns.”

Beyond these vital repairs, the major goal of the upgrade work during Long Shutdown 1 was to increase the LHC’s center of mass energies from the previous 8 trillion electron volts (TeV) to 13 TeV, near the operational maximum of 14 TeV.

“Upgrading the energy means you’re able to probe much higher mass ranges, and you have access to new particles that might be substantially heavier,” said Rajagopalan. “If you have a very heavy particle that cannot be produced, it doesn’t matter how much data you collect, you just cannot reach that. That’s why it was very important to go from 8 to 13 TeV. Doubling the energy allows us to access the new physics much more easily.”

As the LHC probes higher and higher energies, the phenomena that the researchers hope to observe will happen more and more rarely, meaning the particle beams need to create many more collisions than they did before. Beyond this increase in collision rates, or luminosity, however, the entire infrastructure of data collection and management has to evolve to deal with the vastly increased volume of information the LHC can now produce.

“Much of the software had to be evolved or rewritten,” said Rajagopalan, “from patches and fixes that are more or less routine software maintenance to implementing new algorithms and installing new complex data management systems capable of handling the higher luminosity and collision rates.”

Making More Powerful Magnets

Brookhaven physicist Peter Wanderer, head of the laboratory’s Superconducting Magnet Division, stands in front of the oven in which niobium tin is made into a superconductor.

The Large Hadron Collider works by accelerating twin beams of protons to speeds close to that of light. The two beams, traveling in opposite directions along the path of the collider, both contain many bunches of protons, with each bunch containing about 100 billion protons. When the bunches of protons meet, not all of the protons inside of them are going to interact and only a tiny fraction of the colliding bunches are likely to yield potentially interesting physics. As such, it’s absolutely vital to control those beams to maximize the chances of useful collisions occurring.

The best way to achieve that and the desired increase in luminosity—both during the current Run 2, and looking ahead to the long-term future of the LHC—is to tighten the focus of the beam. The more tightly packed protons are, the more likely they’ll smash into each other. This means working with the main tool that controls the beam inside the accelerator: the magnets.

FNAL magnets such as this one, which is mounted on a test stand at Fermilab, for the High-Luminosity LHC Photo Reidar Hahn

“Most of the length of the circumference along a circular machine like the LHC is taken up with a regular sequence of magnets,” said Peter Wanderer, head of Brookhaven Lab’s Superconducting Magnet Division, which made some of the magnets for the current LHC configuration and is working on new designs for future upgrades. “The job of these magnets is to bend the proton beams around to the next point or region where you can do something useful with them, like produce collisions, without letting the beam get larger.”

A beam of protons is a bunch of positively charged particles that all repel one another, so they want to move apart, he explained. So physicists use the magnetic fields to keep the particles from being able to move away from the desired path.

“You insert different kinds of magnets, different sequences of magnets, in order to make the beams as small as possible, to get the most collisions possible when the beams collide,” Wanderer said.

The magnets currently in use in the LHC are made of the superconducting material niobium titanium (NbTi). When the electromagnets are cooled in liquid helium to temperatures of about 4 Kelvin (-452.5 degrees Fahrenheit), they lose all electric resistance and are able to achieve a much higher current density compared with a conventional conductor like copper. A magnetic field gets stronger as its current is more densely packed, meaning a superconductor can produce a much stronger field over a smaller radius than copper.

But there’s an upper limit to how high a field the present niobium titanium superconductors can reach. So Wanderer and his team at Brookhaven have been part of a decade-long project to refine the next generation of superconducting magnets for a future upgrade to the LHC. These new magnets will be made from niobium tin (Nb3Sn).

“Niobium tin can go to higher fields than niobium titanium, which will give us even stronger focusing,” Wanderer said. “That will allow us to get a smaller beam, and even more collisions.” Niobium tin can also function at a slightly higher temperature, so the new magnets will be easier to cool than those currently in use.

There are a few catches. For one, niobium tin, unlike niobium titanium, isn’t initially superconducting. The team at Brookhaven has to first heat the material for two days at 650 degrees Celsius (1200 degrees Fahrenheit) before beginning the process of turning the raw materials into the wires and cables that make up an electromagnet.

“And when niobium tin becomes a superconductor, then it’s very brittle, which makes it really challenging,” said Wanderer. “You need tooling that can withstand the heat for two days. It needs to be very precise, to within thousandths of an inch, and when you take it out of the tooling and want to put it into a magnet, and wrap it with iron, you have to handle it very carefully. All that adds a lot to the cost. So one of the things we’ve worked out over 10 years is how to do it right the first time, almost always.”

Fortunately, there’s still time to work out any remaining kinks. The new niobium tin magnets aren’t set to be installed at the LHC until around 2022, when the changeover from niobium titanium to niobium tin will be a crucial part of converting the Large Hadron Collider into the High-Luminosity Large Hadron Collider (HL-LHC).

Managing Data at Higher Luminosity

As the luminosity of the LHC increases in Run 2 and beyond, perhaps the biggest challenge facing the ATLAS team at Brookhaven lies in recognizing a potentially interesting physics event when it occurs. That selectivity is crucial, because even CERN’s worldwide computing grid—which includes about 170 global sites, and of which Brookhaven’s RHIC and ATLAS Computing Facility is a major center—can only record the tiniest fraction of over 100 million collisions that occur each second. That means it’s just as important to quickly recognize the millions of events that don’t need to be recorded as it is to recognize the handful that do.

“What you have to do is, on the fly, analyze each event and decide whether you want to save it to disk for later use or not,” said Rajagopalan. “And you have to be careful you don’t throw away good physics events. So you’re looking for signatures. If it’s a good signature, you say, ‘Save it!’ Otherwise, you junk it. That’s how you bring the data rate down to a manageable amount you can write to disk.”

Physicists screen out unwanted data using what’s known as a trigger system. The principle is simple: as the data from each collision comes in, it’s analyzed for a preset signature pattern, or trigger, that would mark it as potentially interesting.

“We can change the trigger, or make the trigger more sophisticated to be more selective,” said Brookhaven’s Howard Gordon, a leader in the ATLAS physics program. “If we don’t select the right events, they are gone forever.”

The current trigger system can handle the luminosities of Run 2, but with future upgrades it will no longer be able to screen out and reject enough collisions to keep the number of recorded events manageable. So the next generation of ATLAS triggers will have to be even more sophisticated in terms of what they can instantly detect—and reject.

A more difficult problem comes with the few dozen events in each bunch of protons that look like they might be interesting, but aren’t.

“Not all protons in a bunch interact, but it’s not necessarily going to be only one proton in a bunch that interacts with a proton from the opposite bunch,” said Rajagopalan. “You could have 50 of them interact. So now you have 50 events on top of each other. Imagine the software challenge when just one of those is the real, new physics we’re interested in discovering, but you have all these 49 others—junk!—sitting on top of it.”

“We call it pileup!” Gordon quipped.

Finding one good result among 50 is tricky enough, but in 10 years that number will be closer to 1 in 150 or 200, with all those additional extraneous results interacting with each other and adding exponentially to the complexity of the task. Being able to recognize instantly as many characteristics of the desired particles as possible will go a long way to keeping the data manageable.

Further upgrades are planned over the next decade to cope with the ever-increasing luminosity and collision rates. For example, the Brookhaven team and collaborators will be working to develop an all-new silicon tracking system and a full replacement of the readout electronics with state-of-the-art technology that will allow physicists to collect and analyze ten times more data for LHC Run 4, scheduled for 2026.

The physicists at CERN, Brookhaven, and elsewhere have strong motivation for meeting these challenges. Doing so will not only offer the best chance of detecting rare physics events and expanding the frontiers of physics, but would allow the physicists to do it within a reasonable timespan.

As Rajagopalan put it, “We are ready for the challenge. The next few years are going to be an exciting time as we push forward to explore a new unchartered energy frontier.”

Brookhaven’s role in the LHC is supported by the DOE Office of Science.

See the full article here .

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BNL RHIC Campus

BNL/RHIC Star Detector

BNL RHIC PHENIX

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

From Symmetry: “Inside the Large Hadron Collider”

From Symmetry

By Sarah Charley
05/15/18

If two protons collide at 99.9999991 percent the speed of light, do they make a sound?

What is it like inside the LHC? Symmetry tackles some unconventional questions about the world’s highest energy particle accelerator.

LHC

CERN/LHC Map

CERN LHC Tunnel

CERN LHC particles

Q. The LHC accelerates beams of particles, usually protons, around and around a 17-mile ring until they reach 99.9999991 percent the speed of light. If you could watch this happening, what would you see?

A: The LHC ring is actually made up of both straight and curved sections. If you were watching protons fly through one of the straight sections, it would be totally dark. But as the protons pass through the LHC’s curved sections, the particles emit synchrotron radiation in the form of photons.

Q. At low energies, the photons are generally in the infrared, but at a couple of particular points in the ring, special magnets called undulators cause visible light to be emitted.

During the acceleration process (the so-called ramp), the energy of protons increases, and the energy of the photons they emit also increases. Once the protons reach their maximum energy, most of the photons are in the ultraviolet range. If you looked in the beam pipe at that point, you wouldn’t be able to see anything, but you would get a pretty good sunburn.

Q. What are space and time like for an LHC proton traveling at 99.9999991 percent the speed of light?
A: Two strange but well-known effects of moving at speeds that are a signification fraction of the speed of light are time dilation (moving clocks tick slowly) and length contraction.

Time dilation tells us that the time experienced by a moving observer is shorter than time experienced by a stationary observer. Length contraction tells us that a stationary observer will observe a moving object to be shorter in length than it would be if it were at rest.

To a proton travelling very close to the speed of light, time would appear to be passing normally. Proton time would seem strange only to an observer outside the LHC, for whom 1 second for the proton would appear to last about 2 hours.

What would seem strange from the proton’s point of view would be length. To the proton screaming around the LHC, the 17-mile circumference of the accelerator would appear to take up just about 13 feet.

Q. Speaking of screaming, do the particles going around the LHC generate any sound? If you stuck your ear up against the beam pipe and listened to the protons colliding, what would you hear?

A: The particles in the LHC are travelling in a very good vacuum, and there’s no sound in a vacuum. But there is a recording of the proton beam smashing into the graphite core of the beam dump, where particles are sent when scientists want to stop circulating them in the accelerator, and they do land with a bang.

Q. How powerful are the collisions in the LHC?

A: The LHC collides two beams of protons at a combined energy of 13 TeV, or 13 trillion electronvolts. An electronvolt is a unit of energy, like a calorie or a joule. Electronvolts are used when to talk about the energy of motion of really small things such as particles and atoms.

One photon of infrared light has about 1 electronvolt of energy. A flying mosquito has about 4 trillion electronvolts of energy.

Knowing that, you might think 13 trillion electronvolts isn’t much. But what’s impressive is not so much the energy as the energy density: The energy of about 3 flying mosquitos is crammed into a space about 1 trillion times smaller across than one annoying insect. Nowhere else on Earth can we concentrate energy that much.

Q: What if, instead of colliding protons at 13 TeV, you could collide apples at the same speed?

A.If you could do that, you’d get some real specialty apple juice—and a huge amount of energy: close to 1 x 1020Joules. That’s about the same order of magnitude as the energy that was released when a meteor hit Canada 39 million years ago. The impact of that collision resulted in the Haughton Crater, which is about 14 miles (23 kilometers) across.

The LHC can’t accelerate an apple, though. Right now, it can accelerate about 600 trillion protons at a time. That may sound like a lot, but altogether, it adds up to about 1 nanogram of matter—roughly the same mass as a single human cell.

See the full article here .

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Symmetry is a joint Fermilab/SLAC publication.

From Nature: “Particle physicists turn to AI to cope with CERN’s collision deluge”

Nature

04 May 2018
No writer credit found

The pixel detector at CERN’s CMS experiment records particles that emerge from collisions.Credit: CERN

LHC

CERN/LHC Map

CERN LHC Tunnel

CERN LHC particles

Physicists at the world’s leading atom smasher are calling for help. In the next decade, they plan to produce up to 20 times more particle collisions in the Large Hadron Collider (LHC) than they do now, but current detector systems aren’t fit for the coming deluge. So this week, a group of LHC physicists has teamed up with computer scientists to launch a competition to spur the development of artificial-intelligence techniques that can quickly sort through the debris of these collisions. Researchers hope these will help the experiment’s ultimate goal of revealing fundamental insights into the laws of nature.

At the LHC at CERN, Europe’s particle-physics laboratory near Geneva, two bunches of protons collide head-on inside each of the machine’s detectors 40 million times a second. Every proton collision can produce thousands of new particles, which radiate from a collision point at the centre of each cathedral-sized detector. Millions of silicon sensors are arranged in onion-like layers and light up each time a particle crosses them, producing one pixel of information every time. Collisions are recorded only when they produce potentially interesting by-products. When they are, the detector takes a snapshot that might include hundreds of thousands of pixels from the piled-up debris of up to 20 different pairs of protons. (Because particles move at or close to the speed of light, a detector cannot record a full movie of their motion.)

From this mess, the LHC’s computers reconstruct tens of thousands of tracks in real time, before moving on to the next snapshot. “The name of the game is connecting the dots,” says Jean-Roch Vlimant, a physicist at the California Institute of Technology in Pasadena who is a member of the collaboration that operates the CMS detector at the LHC.

The yellow lines depict reconstructed particle trajectories from collisions recorded by CERN’s CMS detector.Credit: CERN

CERN CMS Higgs Event

After future planned upgrades, each snapshot is expected to include particle debris from 200 proton collisions. Physicists currently use pattern-recognition algorithms to reconstruct the particles’ tracks. Although these techniques would be able to work out the paths even after the upgrades, “the problem is, they are too slow”, says Cécile Germain, a computer scientist at the University of Paris South in Orsay. Without major investment in new detector technologies, LHC physicists estimate that the collision rates will exceed the current capabilities by at least a factor of 10.

Researchers suspect that machine-learning algorithms could reconstruct the tracks much more quickly. To help find the best solution, Vlimant and other LHC physicists teamed up with computer scientists including Germain to launch the TrackML challenge. For the next three months, data scientists will be able to download 400 gigabytes of simulated particle-collision data — the pixels produced by an idealized detector — and train their algorithms to reconstruct the tracks.

Participants will be evaluated on the accuracy with which they do this. The top three performers of this phase hosted by Google-owned company Kaggle, will receive cash prizes of US$12,000, $8,000 and $5,000. A second competition will then evaluate algorithms on the basis of speed as well as accuracy, Vlimant says.

Prize appeal

Such competitions have a long tradition in data science, and many young researchers take part to build up their CVs. “Getting well ranked in challenges is extremely important,” says Germain. Perhaps the most famous of these contests was the 2009 Netflix Prize. The entertainment company offered US$1 million to whoever worked out the best way to predict what films its users would like to watch, going on their previous ratings. TrackML isn’t the first challenge in particle physics, either: in 2014, teams competed to ‘discover’ the Higgs boson in a set of simulated data (the LHC discovered the Higgs, long predicted by theory, in 2012). Other science-themed challenges have involved data on anything from plankton to galaxies.

From the computer-science point of view, the Higgs challenge was an ordinary classification problem, says Tim Salimans, one of the top performers in that race (after the challenge, Salimans went on to get a job at the non-profit effort OpenAI in San Francisco, California). But the fact that it was about LHC physics added to its lustre, he says. That may help to explain the challenge’s popularity: nearly 1,800 teams took part, and many researchers credit the contest for having dramatically increased the interaction between the physics and computer-science communities.

TrackML is “incomparably more difficult”, says Germain. In the Higgs case, the reconstructed tracks were part of the input, and contestants had to do another layer of analysis to ‘find’ the particle. In the new problem, she says, you have to find in the 100,000 points something like 10,000 arcs of ellipse. She thinks the winning technique might end up resembling those used by the program AlphaGo, which made history in 2016 when it beat a human champion at the complex game of Go. In particular, they might use reinforcement learning, in which an algorithm learns by trial and error on the basis of ‘rewards’ that it receives after each attempt.

Vlimant and other physicists are also beginning to consider more untested technologies, such as neuromorphic computing and quantum computing. “It’s not clear where we’re going,” says Vlimant, “but it looks like we have a good path.”

See the full article here .

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Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public.

From CERN: “The 2018 data-taking run at the LHC has begun”

CERN

30 Apr 2018
Achintya Rao

A collision event recorded by LHCb on 28 April, following the formal start of this year’s data taking (Image: LHCb/CERN)

On Saturday, 28 April 2018, the operators of the Large Hadron Collider (LHC) successfully injected 1200 bunches of protons into the machine and collided them. This formally marks the beginning of the LHC’s 2018 physics season. The start of the physics run comes a few days ahead of schedule, continuing the LHC’s impressive re-awakening since the end of its annual winter hibernation just over a month ago. In early April, a small number of bunches were injected into the ring to deliver test collisions inside the four large LHC experiments. These experiments – ALICE, ATLAS, CMS and LHCb – have now begun their data collection in earnest, which they will use to continue measuring the properties of the Standard Model of particle physics and search for any chinks in its armour.

The Standard Model provides the best explanation of the properties of all known particles and three forces that govern them: the electromagnetic force, the weak force and the strong force.

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.

Standard Model of Particle Physics from Symmetry Magazine

But we know that this model does not give us the complete picture of our universe. For one, it only addresses 5% of the contents of the universe: the remaining 95% is thought to be made of dark matter and dark energy, and the Standard Model has no answers for these mysteries. It also does not provide any way of integrating gravity with the three other forces.

Particle physicists working on the LHC experiments seek explanations to fill this gap in two principle ways. Firstly, they do so by taking a close look at various phenomena predicted by the Standard Model and looking for subtle differences between prediction and measurement. In addition, they search for previously unobserved phenomena and particles. Both types of searches for physics beyond the Standard Model require huge quantities of data in order to filter a potential signal from the expected background processes. The LHC experiments will therefore hope that the LHC continues its annual tradition of outdoing its previous year’s data volume.

An event recorded by ATLAS earlier in April, from some of the first collisions of the year with three proton bunches circulating in the LHC (Image: ATLAS/CERN)

ATLAS and CMS, the two “general-purpose” detectors, will continue to probe the properties of the Higgs boson that they discovered in July 2012. This particle is the newest tool in the utility belt used by particle physicists to explore the properties of nature. Since its discovery, physicists have studied its behaviour and interactions with other particles, which have so far shown good agreement with the Standard Model. Searches will also continue for supersymmetric partners of the familiar bosons and fermions that are predicted to exist by a family of theories known as supersymmetry, which might provide us with a candidate for a dark-matter particle. ATLAS, CMS and LHCb are also searching for hints of dark matter through other means, and will add the forthcoming trove of data to their stockpiles as they advance their explorations.

An event recorded by CMS earlier in April, from some of the first collisions of the year with three proton bunches circulating in the LHC (Image: CMS/CERN)

Among other searches, LHCb will continue to seek a solution to the problem of matter-antimatter asymmetry, as the Standard Model cannot adequately explain the observed abundance of matter in the universe. When matter was formed in the Big Bang, there should have been an equal amount of antimatter accompanying it; each matter-antimatter pair should then have annihilated upon contact, leaving us with a universe without stars or human beings to observe them.

ALICE, the LHC’s heavy-ion specialist, focuses on collisions of lead nuclei in order to study the strong interaction and the quark-gluon plasma, a state of matter that is believed to have prevailed in the very early universe. However, ALICE will also record proton-proton collisions to continue its investigation of the properties of collision events that contain a large number of particles produced at the same time and to serve as a baseline with which to compare lead-lead collisions.

An event recorded by ALICE earlier in April, from some of the first collisions of the year with three proton bunches circulating in the LHC (Image: ALICE/CERN)

The LHC operators will keep ramping up the number of bunches, aiming to hit 2556 bunches in total. This will help them achieve their target of 60 inverse femtobarns (fb^-1) of proton-proton collisions this year delivered to both ATLAS and CMS, 20% more than the 50 fb^-1 achieved in 2017. In simple terms, each inverse femtobarn can correspond to up to 100 million million (10^14) individual collisions between protons. The proton-proton run will be followed by the first heavy-ion run since 2016; the LHC will inject and collide lead nuclei at the end of the year.

This is the last year with collisions before the LHC enters a period of hibernation until spring 2021, known as Long Shutdown 2, during which the machine and the experiments will be upgraded. All four experiments will therefore hope to maximise their data-collection efficiency to keep themselves occupied with many analyses and new results over the two-year shutdown, using high-quality data collected this year.

See the full article here.

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Meet CERN in a variety of places:

Quantum Diaries

Cern Courier

THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

ALICE

CMS

LHCb

LHC

OTHER PROJECTS AT CERN

CERN AEGIS

CERN ALPHA

CERN ALPHA

CERN AMS

CERN ACACUSA

CERN ASACUSA

CERN ATRAP

CERN ATRAP

CERN AWAKE

CERN AWAKE

CERN CAST

CERN CAST Axion Solar Telescope

CERN CLOUD

CERN CLOUD

CERN COMPASS

CERN COMPASS

CERN DIRAC

CERN DIRAC

CERN ISOLDE

CERN ISOLDE

CERN LHCf

CERN LHCf

CERN NA62

CERN NA62

CERN NTOF

CERN TOTEM

CERN UA9

From Symmetry: “How to make a Higgs boson”

Symmetry

04/10/18
Sarah Charley

CERN CMS Higgs Event

CERN ATLAS Higgs Event

It doesn’t seem like collisions of particles with no mass should be able to produce the “mass-giving” boson, the Higgs. But every other second at the LHC, they do.

Einstein’s most famous theory, often written as E=mc2, tells us that energy and matter are two sides of the same coin.

The Large Hadron Collider uses this principle to convert the energy contained within ordinary particles into new particles that are difficult to find in nature—particles like the Higgs boson, which is so massive that it almost immediately decays into pairs of lighter, more stable particles.

LHC

CERN/LHC Map

CERN LHC Tunnel

CERN LHC particles

But not just any collision can create a Higgs boson.

“The Higgs is not just created from a ‘poof’ of energy,” says Laura Dodd, a researcher at the University of Wisconsin, Madison. “Particles follow a strict set of laws that dictate how they can form, decay and interact.”

One of these laws states that Higgs bosons can be produced only by particles that interact with the Higgs field—in other words, particles with mass.

The Higgs field is like an invisible spider’s web that permeates all of space. As particles travel through it, some get tangled in the sticky tendrils, a process that makes them gain mass and slow down. But for other particles—such as photons and gluons—this web is completely transparent, and they glide through unhindered.

Given enough energy, the particles wrapped in the Higgs field can transfer their energy into it and kick out a Higgs boson. Because massless particles do not interact with the Higgs field, it would make sense to say that they can’t create a Higgs. But scientists at the LHC would beg to differ.

The LHC accelerates protons around its 17-mile circumference to just under the speed of light and then brings them into head-on collisions at four intersections along its ring. Protons are not fundamental particles, particles that cannot be broken down into any smaller constituent pieces. Rather they are made up of gluons and quarks.

As two pepped-up protons pass through each other, it’s usually pairs of massless gluons that infuse invisible fields with their combined energy and excite other particles into existence—and that includes Higgs bosons.

__________________________________________________________

We know that particles follow strict rules about who can talk to whom.
__________________________________________________________

How? Gluons have found a way to cheat.

“It would be impossible to generate Higgs bosons with gluons if the collisions in the LHC were a simple, one-step processes,” says Richard Ruiz, a theorist at Durham University’s Institute for Particle Physics Phenomenology.

Luckily, they aren’t.

Gluons can momentarily “launder” their energy to a virtual particle, which converts the gluon’s energy into mass. If two gluons produce a pair of virtual top quarks, the tops can recombine and annihilate into a Higgs boson.

To be clear, virtual particles are not stable particles at all, but rather irregular disturbances in quantum mechanical fields that exist in a half-baked state for an incredibly short period of time. If a real particle were a thriving business, then a virtual particle would be a shell company.

Theorists predict that about 90 percent of Higgs bosons are created through gluon fusion. The probability of two gluons colliding, creating a top quark-antitop pair and propitiously producing a Higgs is roughly one in 2 billion. However, because the LHC generates 10 million proton collisions every second, the odds are in scientists’ favor and the production rate for Higgs bosons is roughly one every two seconds.

Shortly after the Higgs discovery, scientists were mostly focused on what happens to Higgs bosons after they decay, according to Dodd.

“But now that we have more data and a better understanding of the Higgs, we’re starting to look closer at the collision byproducts to better understand how frequently the Higgs is produced through the different mechanisms,” she says.

The Standard Model of particle physics predicts that almost all Higgs bosons are produced through one of four possible processes.

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.

Standard Model of Particle Physics from Symmetry Magazine

What scientists would love to see are Higgs bosons being created in a way that the Standard Model of particle physics does not predict, such as in the decay of a new particle. Breaking the known rules would show that there is more going on than physicists previously understood.

“We know that particles follow strict rules about who can talk to whom because we’ve seen this time and time again during our experiments,” Ruiz says. “So now the question is, what if there is a whole sector of undiscovered particles that cannot communicate with our standard particles but can interact with the Higgs boson?”

Scientists are keeping an eye out for anything unexpected, such as an excess of certain particles radiating from a collision or decay paths that occur more or less frequently than scientists predicted. These indicators could point to undiscovered heavy particles morphing into Higgs bosons.

At the same time, to find hints of unexpected ingredients in the chain reactions that sometimes make Higgs bosons, scientists must know very precisely what they should expect.

“We have fantastic mathematical models that predict all this, and we know what both sides of the equations are,” Ruiz says. “Now we need to experimentally test these predictions to see if everything adds up, and if not, figure out what those extra missing variables might be.”

See the full article here .

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Symmetry is a joint Fermilab/SLAC publication.

From BBC via Back Reaction: “Particle Physicists begin to invent reasons to build next larger Particle Collider”

BBC

Back Reaction

April 04, 2018

Sabine Hossenfelder

Nigel Lockyer, the director of Fermilab [FNAL], recently spoke to BBC about the benefits of building a next larger particle collider, one that reaches energies higher than the Large Hadron Collider (LHC).

Nigel Lockyer

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Such a new collider could measure more precisely the properties of the Higgs-boson. But that’s not all, at least according to Lockyer. He claims he knows there is something new to discover too:

“Everybody believes there’s something there, but what we’re now starting to question is the scale of the new physics. At what energy does this new physics show up,” said Dr Lockyer. “From a simple calculation of the Higgs’ mass, there has to be new science. We just can’t give up on everything we know as an excuse for where we are now.”

First, let me note that “everybody believes” is an argument ad populum. It isn’t only non-scientific, it is also wrong because I don’t believe it, qed. But more importantly, the argument for why there has to be new science is wrong.

To begin with, we can’t calculate the Higgs mass; it’s a free parameter that is determined by measurement. Same with the Higgs mass as with the masses of all other elementary particles. But that’s a matter of imprecise phrasing, and I only bring it up because I’m an ass.

The argument Lockyer is referring to are calculations of quantum corrections to the Higgs-mass. I.e., he is making the good, old, argument from naturalness.

If that argument were right, we should have seen supersymmetric particles already. We didn’t. That’s why Giudice, head of the CERN theory division, has recently rung in the post-naturalness era. Even New Scientist took note of that. But maybe the news hasn’t yet arrived in the USA.

Naturalness arguments never had a solid mathematical basis. But so far you could have gotten away saying they are handy guides for theory development. Now, however, seeing that these guides were bad guides in that their predictions turned out incorrect, using arguments from naturalness is no longer scientifically justified. If it ever was. This means we have no reason to expect new science, not in the not-yet analyzed LHC data and not at a next larger collider.

Of course there could be something new. I am all in favor of building a larger collider and just see what happens. But please let’s stick to the facts: There is no reason to think a new discovery is around the corner.

I don’t think Lockyer deliberately lied to BBC. He’s an experimentalist and probably actually believes what the theorists tell him. He has all reasons for wanting to believe it. But really he should know better.

Much more worrisome than Lockyer’s false claim is that literally no one from the community tried to correct it. Heck, it’s like the head of NASA just told BBC we know there’s life on Mars! If that happened, astrophysicists would collectively vomit on social media. But particle physicists? They all keep their mouth shut if one of theirs spreads falsehoods. And you wonder why I say you can’t trust them?

Meanwhile Gordon Kane, a US-Particle physicist known for his unswerving support of super-symmetry, has made an interesting move: he discarded of naturalness arguments altogether.

You find this in a paper which appeared on the arXiv today. It seems to be a promotional piece that Kane wrote together with Stephen Hawking some months ago to advocate the Chinese Super Proton Proton Collider (SPPC) [So far, the Chinese physics community thinks this is a waste of money.].

Kane has claimed for 15 years or so that the LHC would have to see supersymmetric particles because of naturalness. Now that this didn’t work out, he has come up with a new reason for why a next larger collider should see something:

“Some people have said that the absence of superpartners or other phenomena at LHC so far makes discovery of superpartners unlikely. But history suggests otherwise. Once the [bottom] quark was found, in 1979, people argued that “naturally” the top quark would only be a few times heavier. In fact the top quark did exist, but was forty-one times heavier than the [bottom] quark, and was only found nearly twenty years later. If superpartners were forty-one times heavier than Z-bosons they would be too heavy to detect at LHC and its upgrades, but could be detected at SPPC.”

Indeed, nothing forbids superpartners to be forty-one times heavier than Z-bosons. Neither is there anything that forbids them to be four-thousand times heavier, or four billion times heavier. Indeed, they don’t even have to be there at all. Isn’t it beautiful?

Leaving aside that just because we can’t calculate the masses doesn’t mean they have to be near the discovery-threshold, the historical analogy doesn’t work for several reasons.

Most importantly, quarks come in pairs that are SU(2) doublets. This means once you have the bottom quark, you know it needs to have a partner. If there wouldn’t be one, you’d have to discontinue the symmetry of the standard model which was established with the lighter quarks.

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.

Standard Model of Particle Physics from Symmetry Magazine

Supersymmetry, on contrast, has no evidence among the already known particles speaking in its favor.

Standard model of Supersymmetry DESY

Physicists also knew since the early 1970s that the weak nuclear force violates CP-invariance, which requires (at least) three generations of quarks. Because of this, the existence of both the bottom and top quark were already predicted in 1973.

Finally, for anomaly cancellation to work you need equally many leptons as quarks, and the tau and tau-neutrino (third generation of leptons) had been measured already in 1975 and 1977, respectively. (We also know the top quark mass can’t be too far away from the bottom quark mass, and the Higgs mass has to be close by the top quark mass, but this calculation wasn’t available in the 1970s.)

In brief this means if the top quark had not been found, the whole standard model wouldn’t have worked. The standard model, however, works just fine without supersymmetric particles.

Of course Gordon Kane knows all this. But desperate times call for desperate measures I guess.

In the Kane-Hawking pamphlet we also read:

“In addition, a supersymmetric theory has the remarkable property that it can relate physics at our scale, where colliders take data, with the Planck scale, the natural scale for a fundamental physics theory, which may help in the efforts to find a deeper underlying theory.”

I don’t disagree with this. But it’s a funny statement because for 30 years or so we have been told that supersymmetry has the virtue of removing the sensitivity to Planck scale effects. So, actually the absence of naturalness holds much more promise to make that connection to higher energy. In other words, I say, the way out is through.

I wish I could say I’m surprised to see such wrong claims boldly being made in public. But then I only just wrote two weeks ago that the lobbying campaign is likely to start soon. And, lo and behold, here we go.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

From Harvard via Science Alert: “A Second ‘Big Bang’ Could End Our Universe in an Instant, Thanks to The Higgs Boson”

Harvard University

Science Alert

Well, that’s just great.

A Black Hole Artist Concept. (NASA/JPL-Caltech)

5 APR 2018
JEREMY BERKE, BUSINESS INSIDER

Our universe may end the same way it was created: with a big, sudden bang. That’s according to new research from a group of Harvard physicists, who found that the destabilization of the Higgs boson – a tiny quantum particle that gives other particles mass – could lead to an explosion of energy that would consume everything in the known universe and upend the laws of physics and chemistry.

As part of their study, published last month in the journal Physical Review D, the researchers calculated when our universe could end.

It’s nothing to worry about just yet. They settled on a date 10139 years from now, or 10 million trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion years in the future. And they’re at least 95 percent sure – a statistical measure of certainty – that the universe will last at least another 1058 years.

The Higgs boson, discovered in 2012 by researchers smashing subatomic protons together at the Large Hadron Collider, has a specific mass.

LHC

CERN/LHC Map

CERN LHC Tunnel

CERN LHC particles

CERN CMS Higgs Event

CERN ATLAS Higgs Event

If the researchers are correct, that mass could change, turning physics on its head and tearing apart the elements that make life possible, according to the New York Post.

And rather than burning slowly over trillions of years, an unstable Higgs boson could create an instantaneous bang, like the Big Bang that created our universe.

The researchers say a collapse could be driven by the curvature of space-time around a black hole, somewhere deep in the universe. When space-time curves around super-dense objects, like a black hole, it throws the laws of physics out of whack and causes particles to interact in all sorts of strange ways.

The researchers say the collapse may have already begun – but we have no way of knowing, as the Higgs boson particle may be far away from where we can analyse it, within our seemingly infinite universe. “It turns out we’re right on the edge between a stable universe and an unstable universe,” Joseph Lykken, a physicist from the Fermi National Accelerator Laboratory who was not involved in the study, told the Post.

He added: “We’re sort of right on the edge where the universe can last for a long time, but eventually, it should go ‘boom.'”

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Harvard is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.