Tagged: FNAL MINOS Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:02 pm on September 25, 2018 Permalink | Reply
    Tags: , , , , FNAL MINOS, , , LSND, , , ,   

    From Symmetry: “How not to be fooled in physics” 

    Symmetry Mag
    From Symmetry

    Laura Dattaro

    Illustration by Sandbox Studio, Chicago with Ana Kova

    Particle physicists and astrophysicists employ a variety of tools to avoid erroneous results.

    In the 1990s, an experiment conducted in Los Alamos, about 35 miles northwest of the capital of New Mexico, appeared to find something odd.

    Scientists designed the Liquid Scintillator Neutrino Detector experiment at the US Department of Energy’s Los Alamos National Laboratory to count neutrinos, ghostly particles that come in three types and rarely interact with other matter.

    LSND experiment at Los Alamos National Laboratory and Virginia Tech

    LSND was looking for evidence of neutrino oscillation, or neutrinos changing from one type to another.

    Several previous experiments had seen indications of such oscillations, which show that neutrinos have small masses not incorporated into the Standard Model, the ruling theory of particle physics. LSND scientists wanted to double-check these earlier measurements.

    By studying a nearly pure source of one type of neutrinos—muon neutrinos—LSND did find evidence of oscillation to a different type of neutrinos, electron neutrinos. However, they found many more electron neutrinos in their detector than predicted, creating a new puzzle.

    This excess could have been a sign that neutrinos oscillate between not three but four different types, suggesting the existence of a possible new type of neutrino, called a sterile neutrino, which theorists had suggested as a possible way to incorporate tiny neutrino masses into the Standard Model.

    Or there could be another explanation. The question is: What? And how can scientists guard against being fooled in physics?

    Brand new thing

    Many physicists are looking for results that go beyond the Standard Model. They come up with experiments to test its predictions; if what they find doesn’t match up, they have potentially discovered something new.

    “Do we see what we expected from the calculations if all we have there is the Standard Model?” says Paris Sphicas, a researcher at CERN.

    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

    “If the answer is yes, then it means we have nothing new. If the answer is no, then you have the next question, which is, ‘Is this within the uncertainties of our estimates? Could this be a result of a mistake in our estimates?’ And so on and so on.”

    A long list of possible factors can trick scientists into thinking they’ve made a discovery. A big part of scientific research is identifying them and finding ways to test what’s really going on.

    “The community standard for discovery is a high bar, and it ought to be,” says Yale University neutrino physicist Bonnie Fleming. “It takes time to really convince ourselves we’ve really found something.”

    In the case of the LSND anomaly, scientists wonder whether unaccounted-for background events tipped the scales or if some sort of mechanical problem caused an error in the measurement.

    Scientists have designed follow-up experiments to see if they can reproduce the result. An experiment called MiniBooNE, hosted by Fermi National Accelerator Laboratory, recently reported seeing signs of a similar excess. Other experiments, such as the MINOS experiment, also at Fermilab, have not seen it, complicating the search.


    FNAL Minos map


    FNAL MINOS Far Detector in the Soudan Mine in northern Minnesota

    “[LSND and MiniBooNE] are clearly measuring an excess of events over what they expect,” says MINOS co-spokesperson Jenny Thomas, a physicist at University College London. “Are those important signal events, or are they a background they haven’t estimated properly? That’s what they are up against.”

    Managing expectations

    Much of the work in understanding a signal involves preparatory work before one is even seen.

    In designing an experiment, researchers need to understand what physics processes can produce or mimic the signal being sought, events that are often referred to as “background.”

    Physicists can predict backgrounds through simulations of experiments. Some types of detector backgrounds can be identified through “null tests,” such as pointing a telescope at a blank wall. Other backgrounds can be identified through tests with the data itself, such as so-called “jack-knife tests,” which involve splitting data into subsets—say, data from Monday and data from Tuesday—which by design must produce the same results. Any inconsistencies would warn scientists about a signal that appears in just one subset.

    Researchers looking at a specific signal work to develop a deep understanding of what other physics processes could produce the same signature in their detector. MiniBooNE, for example, studies a beam primarily made of muon neutrinos to measure how often those neutrinos oscillate to other flavors. But it will occasionally pick up stray electron neutrinos, which look like muon neutrinos that have transformed. Beyond that, other physics processes can mimic the signal of an electron neutrino event.

    “We know we’re going to be faked by those, so we have to do the best job to estimate how many of them there are,” Fleming says. “Whatever excess we find has to be in addition to those.”

    Even more variable than a particle beam: human beings. While science strives to be an objective measurement of facts, the process itself is conducted by a collection of people whose actions can be colored by biases, personal stories and emotion. A preconceived notion that an experiment will (or won’t) produce a certain result, for example, could influence a researcher’s work in subtle ways.

    “I think there’s a stereotype that scientists are somehow dispassionate, cold, calculating observers of reality,” says Brian Keating, an astrophysicist at University of California San Diego and author of the book Losing the Nobel Prize, which chronicles how the desire to make a prize-winning discovery can steer a scientist away from best practices. “In reality, the truth is we actually participate in it, and there are sociological elements at work that influence a human being. Scientists, despite the stereotypes, are very much human beings.”

    Staying cognizant of this fact and incorporating methods for removing bias are especially important if a particular claim upends long-standing knowledge—such as, for example, our understanding of neutrinos. In these cases, scientists know to adhere to the adage: Extraordinary claims require extraordinary evidence.

    “If you’re walking outside your house and you see a car, you probably think, ‘That’s a car,’” says Jonah Kanner, a research scientist at Caltech. “But if you see a dragon, you might think, ‘Is that really a dragon? Am I sure that’s a dragon?’ You’d want a higher level of evidence.”

    Dragon or discovery?

    Physicists have been burned by dragons before. In 1969, for example, a scientist named Joe Weber announced that he had detected gravitational waves: ripples in the fabric of space-time first predicted by Albert Einstein in 1916. Such a detection, which many had thought was impossible to make, would have proved a key tenet of relativity. Weber rocketed to momentary fame, until other physicists found they could not replicate his results.

    The false discovery rocked the gravitational wave community, which, over the decades, became increasingly cautious about making such announcements.

    So in 2009, as the Laser Interferometer Gravitational Wave Observatory, or LIGO, came online for its next science run, the scientific collaboration came up with a way to make sure collaboration members stayed skeptical of their results. They developed a method of adding a false or simulated signal into the detector data stream without alerting the majority of the 800 or so researchers on the team. They called it a blind injection. The rest of the members knew an injection was possible, but not guaranteed.

    “We’d been not detecting signals for 30 years,” Kanner, a member of the LIGO collaboration, says. “How clear or obvious would the signature have to be for everyone to believe it?… It forced us to push our algorithms and our statistics and our procedures, but also to test the sociology and see if we could get a group of people to agree on this.”

    In late 2010, the team got the alert they had been waiting for: The computers detected a signal. For six months, hundreds of scientists analyzed the results, eventually concluding that the signal looked like gravitational waves. They wrote a paper detailing the evidence, and more than 400 team members voted on its approval. Then a senior member told them it had all been faked.

    Picking out and spending so much time examining such an artificial signal may seem like a waste of time, but the test worked just as intended. The exercise forced the scientists to work through all of the ways they would need to scrutinize a real result before one ever came through. It forced the collaboration to develop new tests and approaches to demonstrating the consistency of a possible signal in advance of a real event.

    “It was designed to keep us honest in a sense,” Kanner says. “Everyone to some extent goes in with some guess or expectation about what’s going to come out of that experiment. Part of the idea of the blind injection was to try and tip the scales on that bias, where our beliefs about whether we thought nature should produce an event would be less important.”

    All of the hard work paid off: In September 2015, when an authentic signal hit the LIGO detectors, scientists knew what to do. In 2016, the collaboration announced the first confirmed direct detection of gravitational waves. One year later, the discovery won the Nobel Prize.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger

    ESA/eLISA the future of gravitational wave research

    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    No easy answers

    While blind injections worked for the gravitational waves community, each area of physics presents its own unique challenges.

    Neutrino physicists have an extremely small sample size with which to work, because their particles interact so rarely. That’s why experiments such as the NOvA experiment and the upcoming Deep Underground Neutrino experiment use such enormous detectors.

    FNAL/NOvA experiment map

    FNAL NOvA detector in northern Minnesota

    FNAL NOvA Near Detector

    Astronomers have even fewer samples: They have just one universe to study, and no way to conduct controlled experiments. That’s why they conduct decades-long surveys, to collect as much data as possible.

    Researchers working at the Large Hadron Collider have no shortage of interactions to study—an estimated 600 million events are detected every second.


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    But due to the enormous size, cost and complexity of the technology, scientists have built only one LHC. That’s why inside the collider sit multiple different detectors, which can check one another’s work by measuring the same things in a variety of ways with detectors of different designs.


    CERN/CMS Detector

    CERN ALICE detector

    CERN LHCb chamber, LHC

    While there are many central tenets to checking a result—knowing your experiment and background well, running simulations and checking that they agree with your data, testing alternative explanations of a suspected result—there’s no comprehensive checklist that every physicist performs. Strategies vary from experiment to experiment, among fields and over time.

    Scientists must do everything they can to test a result, because in the end, it will need to stand up to the scrutiny of their peers. Fellow physicists will question the new result, subject it to their own analyses, try out alternative interpretations, and, ultimately, try to repeat the measurement in a different way. Especially if they’re dealing with dragons.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 2:12 pm on May 27, 2017 Permalink | Reply
    Tags: , , , FNAL MINOS, , ,   

    From FNAL: “50 years of discoveries and innovations: MINOS and NOvA observe neutrino oscillations” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    May 27, 2017
    Troy Rummler

    Scientists know relatively little about neutrinos, the most abundant matter particle in the universe. But Fermilab’s MINOS and NOvA experiments have made incredible strides in understanding how and why the fickle particles change their fundamental properties as they travel. MINOS began recording data about the oscillation phenomenon in 2005, and the longer-distance NOvA experiment began in 2015.


    FNAL/NOvA experiment map

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

  • richardmitnick 8:19 am on July 13, 2016 Permalink | Reply
    Tags: , , FNAL MINOS,   

    From AAAS: “Massive neutrino experiment undermines our sense of reality” 



    Jul. 12, 2016
    Adrian Cho

    The test of fundamental quantum theory comes as an unexpected bonus from data collected with the massive Main Injector Neutrino Oscillation Search neutrino detector. R. Hahn/Fermilab

    Data from a massive neutrino experiment show that the elusive subatomic particles must literally be of two mutually exclusive types at once—poking a hole in our intuitive sense of reality. The result is bedrock quantum mechanics. But it’s the sort of thing typically shown with highly controlled quantum optics experiments and not with nearly undetectable neutrinos.

    “If you had told me 10 years ago that we would use neutrinos to study quantum foundations, I would have said that you’d been smoking something very exciting,” says Andrew White, a physicist at the University of Queensland, St. Lucia, in Brisbane, Australia, who was not involved in the work. “The result is utterly unsurprising and yet utterly attractive because it tells us that there’s a new system for testing quantum foundations.”

    According to quantum theory, minuscule things behave nothing like everyday objects. Unlike an apple, a subatomic particle can be in two places or of two different types at once. Those two-way “superposition” states are fragile, however. Measure, say, a particle of light or photon that is simultaneously polarized both horizontally and vertically and it will randomly “collapse” one way or the other.

    Still, according to quantum theory, the photon’s polarization doesn’t exist until it’s measured. Albert Einstein disdained that idea, arguing that a physical property of an object has to be “an element of reality” that exists independently of measurement. To salvage “realism,” some physicists argued that the result of such a measurement is predetermined by some “hidden variable” within the photon.

    In 1964, U.K. theorist John Bell devised a way to test that notion. In quantum theory, two photons in two-way states can be “entangled” so that a measurement on one instantly determines not only its polarization but that of the other photon as well, even if it’s light-years away. That quantum connection produces correlations between the particles that are stronger than hidden variables allow, Bell showed. Last year, physicists in the Netherlands and the United States performed the best demonstrations yet of those correlations, nixing such hidden variables.

    The test with neutrinos involves correlations between measurements separated not in space, but in time. In 1985, theorists Anupam Garg, now at Northwestern University, Evanston, in Illinois, and Anthony Leggett of the University of Illinois, Urbana-Champaign, considered repeated measurements of a single quantum system: a ring of superconductor in which an unquenchable current flows one way or the other. The ring mimics a coin, which can be heads or tails, except that current can also flow both ways at once.

    According to quantum theory, the current will oscillate between the two directions. So a measurement will reveal it flowing, say, clockwise, with a probability that depends on the time. Leggett and Garg found that certain correlations among three or more measurements would be stronger than classical physics allows—if the current has no direction until it’s measured.

    Experimenters have approximated the Leggett and Garg test. In 2011, White and colleagues demonstrated the extrastrong correlations in quantum optics, although in an average way and not with a single photon. Now, Joseph Formaggio, a neutrino physicist at the Massachusetts Institute of Technology in Cambridge, and colleagues provide a demonstration using data from the Main Injector Neutrino Oscillation Search (MINOS) experiment at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, which fires neutrinos at near-light-speed 735 kilometers to a 5.4-kiloton detector in the Soudan Mine in Minnesota.

    FNAL Minos Far Detector

    Neutrinos come in three flavors that morph into one another. Those fired from Fermilab start as so-called muon neutrinos and “oscillate” mainly to electron neutrinos in a process that resembles the one analyzed by Leggett and Garg. MINOS experimenters didn’t repeatedly measure individual neutrinos, as detecting a neutrino destroys it. However, each neutrino starts in the same state whose evolution depends only on the time since it left Fermilab. So measuring many neutrinos was equivalent to measuring the same one repeatedly.

    The MINOS physicists also didn’t measure the neutrinos at different distances from Fermilab, so Formaggio and colleagues couldn’t directly compare measurements made after different flight times. However, the rate at which neutrinos oscillate varies with their energy, with the clock ticking faster for more energetic neutrinos. So instead of looking for correlations between neutrinos measured at different times, Formaggio and colleagues looked for equivalent correlations in the number of muon neutrinos arriving in Minnesota with different energies.

    The researchers observed the strong correlations predicted by Leggett and Garg, as they report in a paper in press at Physical Review Letters. “As we expected, it’s a very obvious effect,” Formaggio says. The data underscore that the neutrino has no flavor until it’s actually measured, he says.

    The result is not surprising, Garg says, as neutrino oscillations are inherently quantum mechanical. Still, he says, it “probes the conflict between the quantum and classical worlds in a new regime.”

    Next would be to see whether neutrinos can test quantum mechanics in other ways, Formaggio and White say. Garg says he still hopes somebody will push the test he and Leggett devised as originally intended: to test whether realism holds for a truly macroscopic object. If it fails, our sense of reality really would go out the window.

    See the full article here .

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

    Please help promote STEM in your local schools.
    STEM Icon
    Stem Education Coalition

  • richardmitnick 9:15 am on May 15, 2015 Permalink | Reply
    Tags: , FNAL MINOS,   

    From FNAL: “Summer, winter and muons” 

    FNAL Home

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

    May 15, 2015
    Maury Goodman, Argonne National Laboratory

    These tracks show a six-muon event in the MINOS far detector.

    The MINOS detectors at Fermilab and in Soudan, Minnesota, were built to study neutrino oscillations over a vast distance. But it turns out that they are also powerful cosmic ray muon detectors.

    FNAL Minos Far Detector.

    When a cosmic ray strikes an atom in the Earth’s atmosphere, it sets off a cascade of particle decay, creating kaons or pions, which in turn decay into muons.

    MINOS previously made the first deep measurement of the ratio of positive to negative muons arising from cosmic ray showers, and that number is related to the ratio of positive to negative cosmic shower kaons. That, in turn, has implications for the predicted rates of neutrino detection in neutrino telescopes such as IceCube.

    MINOS also measured how the cosmic ray muon rate changed with the seasons of the year. It is well known that this rate fluctuates a few percent, being higher in summer when the higher temperatures lower the atmospheric density, which allows for more pion and kaon decay. MINOS was able to correlate this with temperature and demonstrate sensitivity to the ratio of pions to kaons. This ratio happens to be important for calculations of neutrino rates from targets in beams, such as for MINOS itself.

    Now MINOS has made a new measurement of the seasonal variations of underground multiple-muon events. These events come from cosmic ray showers in which two or more muons penetrate the Earth and appear as parallel tracks in the detector.

    The answer was unexpected. Instead of being higher in the summer, the seasonal variation of multiple muons differed. In the near detector, about 300 feet below the surface, the rate was at a maximum in the winter. See the figure below showing the rate of multiple muons throughout the year (top) and single muons (bottom). (Day zero is Jan. 1.)

    In the far detector, about a half mile below the surface, the multiple muons that were within about 13 feet of each other had a maximum rate in the winter, while the events in which muons were separated by 20 or more feet had a summer maximum.

    The difference in depth between the near and far detectors affects the minimum muon energy needed to penetrate the rock and reach the detector. Sophisticated simulations of cosmic ray air showers exist but do not currently include seasonal effects.

    The understanding of this unexpected result will require new simulations or new data. It would be a wonderful coincidence if, once again, the reason turned out to be useful for the neutrino community.

    Multiple-muon events — events in which two or more muons simultaneously penetrate the Earth — seen by the MINOS near detector take a dip in the summer (top). By contrast, single-muon events detected by the MINOS near detector rise in the summer (bottom).

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

  • richardmitnick 1:38 pm on May 15, 2014 Permalink | Reply
    Tags: , FNAL MINOS,   

    From Symmetry: “Long-distance neutrino search” 


    May 15, 2014
    Amanda Solliday

    Physicist Ruth Toner sits facing five computer screens and a TV monitor in a room in Medford, Massachusetts. She’s watching an experiment in action: Tiny particles fly through a pair of detectors hundreds of miles away, one at a laboratory in Illinois and the other in a former iron ore mine near the Canadian border of Minnesota.

    “Nothing’s turned red yet, so it’s going okay,” Toner says as she glances at the largest screen, which glows green.

    Toner, a postdoc at Harvard University, has been taking shifts here in the new control room at Tufts University since January 20, when she was the first to try it out independently. The room allows particle physicists at the two Boston-area schools to observe detectors of the Main Injector Neutrino Oscillation Search, or MINOS, experiment at Fermilab in Illinois and in Soudan Underground Laboratory in Minnesota. The MINOS experiment is on its second iteration, called MINOS+ (pronounced Mee-nohs-plus).

    The experiment studies a beam of neutrinos produced at Fermilab and propelled toward the detectors. Neutrinos interact so rarely with other matter that they are able to travel straight through the earth.

    Posters from previous experiments hang on the control room wall, along with images overlaid with mnemonic devices for the MINOS+ detectors’ component names. There’s also a webcam that connects the room to the distant detectors. It’s switched off, but as Toner watches the other screens display data, she discusses what she sees with a coordinator onsite at Fermilab through the MINOS+ electronic logbook.

    “Fermilab neutrino experiments are bringing far-flung people together to do some really exciting science,” Toner says. “Neutrino physics is a very fast-moving field right now, with the potential for some really interesting future discoveries.”


    Scientists on the MINOS+ experiment aim to learn more about how the perplexing particles oscillate, or change form, and also hunt for new particles such as sterile neutrinos.

    The Boston-area researchers learned how to construct and run the control room from physicists at the University of Rochester, who set up a similar remote operations center for another Fermilab neutrino experiment called MINERνA. Academic institutions in the United States and abroad, including The College of William and Mary and the University of Warsaw, have developed similar centers.

    Patricia Vahle, a physics professor at The College of William and Mary, sees a local control room as a tool with trade-offs.

    “A remote control room definitely saves money, removes travel hassles and also creates a simpler way to expose students to particle physics research,” she says. “But you do lose something. Coming to Fermilab for shifts gives you a chance to connect face-to-face with your colleagues.”

    The Tufts crew has been involved with MINOS since the project was first proposed in the mid-1990s. Tony Mann, a physics professor at Tufts University and co-leader of MINOS+, manages a group currently working on three Fermilab neutrino experiments: MINOS+, MINERνA and the latest addition, NOνA.

    “There’s no way we could participate in all three experiments without local control room capabilities,” Mann says. “I think remote control rooms are a positive development for the particle physics community.”

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

    ScienceSprings is powered by MAINGEAR computers

  • richardmitnick 9:17 am on May 2, 2014 Permalink | Reply
    Tags: , , FNAL MINOS, ,   

    From Fermilab: “Physics in a Nutshell – The twin paradox” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.
    Friday, May 2, 2014

    Fermilab Don Lincoln
    This column was written by Dr. Don Lincoln

    In my last column, I discussed the fact that time passes slower for clocks that are moving at high velocity, and I showed that the Fermilab MINOS beamline proves that the predictions of relativity are right.

    Fermilab NuMI Tunnel
    Fermilab NuMI Tunnel

    The twin paradox is a classic seeming conundrum of Einstein’s theory of special relativity. Today’s column explains why it is important that the word “seeming” is added. In reality, there is no paradox.

    However, one must be very careful. The “relativity” in the theory’s name comes from the absolute core premise of [Albert] Einstein’s idea, which is that nothing is absolute. If you are standing on a train platform and a train whizzes by, you would say that a person on the train is moving. On the other hand, a person sitting on the train would say that he is stationary and that you are moving. Relativity says that both of you are right. Who is moving and who is stationary is just a matter of perspective, and the laws of physics must work equally well for both people.

    But this raises a conundrum when applied to the question of moving clocks. How can moving clocks tick more slowly than stationary ones if the question of who is moving is a matter of opinion? If I can say you are moving and your clock is slow, and if you can say I am moving and my clock is slow, something is inconsistent.

    This longstanding question about special relativity is called the twin paradox. Suppose one in a set of twins sets off in a spaceship, travels to a distant star and then returns. On both legs of the trip, he accelerates to high velocity and then coasts for most of the journey. According to the “moving clocks tick slower” premise, the twin who stays on Earth will have experienced one duration, while the traveling twin will have experienced another, slower duration. The spacefaring twin will return to Earth younger than his homebody brother.

    “But wait,” says the traveling twin, “according to my definition, I was just sitting there on my stationary spaceship while the Earth zoomed away from me and then zoomed back. By all rights, Earth twin should be younger!”

    The solution to this seeming paradox has to do with the idea of a reference frame, which is central to special relativity. “Reference frame” is just a fancy term that means “the world according to me,” putting each person at the center of his or her universe. All “inertial” observers — those who don’t experience any acceleration — will agree that the homebody never changed his reference frame. He just sat there. Similarly, all observers will agree that the traveler lived in two reference frames, one moving away from Earth and one returning. Any third observer coasting through space will see that the homebody’s velocity doesn’t change while the traveler’s velocity does.

    The law of relativity takes the traveler’s two reference frames into account. Thus the so-called paradox isn’t really a paradox. While the question of who is moving is a matter of opinion, the question of who has experienced two reference frames is not.

    Some readers, probably including some of my doctoral-holding colleagues at Fermilab, will claim that the difference between the two twins is that one of the two has experienced an acceleration. (After all, that’s how he slowed down and reversed direction.) However, the relativistic equations don’t include that acceleration phase; they include just the coasting time at high velocity. For the professional (or the brave), I work out the predictions of relativity. That one twin inhabits two frames is the only thing that matters.

    The twin paradox is one of those mind-bending questions you encounter as you first begin to explore the predictions of relativity, but don’t be fooled: It really isn’t a paradox at all. Keep that in mind as you explore other explanations that may resonate with you — the well-known ones posted by physicist John Baez, a video by Neil deGrasse Tyson, the idea of acceleration, or my own description here of one twin being in one frame.

    Embracing the twin paradox is an important first step as you dip your toe into the nonintuitive world of special relativity. If you dig a little deeper into the links given here (and show a little determination), hopefully you’ll begin to be more comfortable that Einstein really was right.

    See the full article here.

    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.

    ScienceSprings is powered by MAINGEAR computers

    • Lubos Motl 9:37 am on May 2, 2014 Permalink | Reply

      ““Reference frame” is just a fancy term that means “the world according to me,” putting each person at the center of his or her universe.

      We’re lucky that my blog is called “The Reference Frame” including the article, “The”, which means that mine is the only true and objectively correct center of *the* Universe. 😉


    • Richard Mitnick 11:20 am on May 2, 2014 Permalink | Reply

      Thanks for reading.


  • richardmitnick 12:23 pm on April 18, 2014 Permalink | Reply
    Tags: , , , FNAL MINOS, , , ,   

    From Fermilab: “Proving special relativity: episode 3” 

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

    Friday, April 18, 2014
    This column was written by Dr. Don Lincoln
    Fermilab Don Lincoln

    “Time waits for no man” goes the saying, and it appears to be true. Inexorably the moments of our lives tick away until we have none left and slip away into the darkness. However, as painful as that truth is, we have some comfort in the fact that time marches on equally for all of us — pauper and prince. Time plays no favorites.

    [Albert] Einstein turned this comforting truism on its head in 1905 when he published his theory of special relativity. In one of the most nonintuitive consequences of his theory, time does not march at the same pace for us all — it depends on a person’s velocity. Slow-moving objects age more quickly than their speedy brethren.

    One of the most nonintuitive consequences of Einstein’s theory of special relativity is the idea that different people will experience time at different rates. This has no analog in classical theory, and yet it is easy to observe at laboratories such as Fermilab and CERN.

    That just didn’t seem even possible.

    Luckily, at particle accelerator laboratories, it is pretty easy to increase the velocity of subatomic particles and put Einstein’s idea to a strict test. Let me immediately get to the punch line: As bizarre as it seems, Einstein is right.

    There are a ton of examples I can give from every particle accelerator laboratory on the planet, and they all confirm the theory of special relativity beyond a shadow of a doubt. Let’s use one to illustrate the point: the Fermilab MINOS beamline, which shoots neutrinos in the direction of Minnesota.


    Fermilab makes neutrinos by slamming high-energy protons into a target, creating a spray of particles. The most common are pions, which then decay into muons and neutrinos. Since the pions come flying out of the collision, they move while they are decaying.

    To see the effect of relativity, we need to see just how long of a tunnel is needed to let them decay. To do that, we need to know the pions’ velocity and how long they live. In the same way that you can combine the speed of a car and the time it travels to determine the distance of its trip, you can figure out how far a pion will travel before it can decay.

    We know very well how long stationary pions live. Because pion decay is essentially a form of radioactive decay, individual pions don’t have a fixed lifetime any more than people do — some live longer and some shorter. But we can certainly say 95 percent of pions decay in 80 billionths of a second.

    Let’s say the pions have an energy of 14 GeV, traveling at 99.995 percent the speed of light (186,000 miles per second). Combining velocity and time, we would predict that the NuMI/MINOS decay tunnel would need to be about 76 feet long to contain all of the pion’s decay. Yet the actual tunnel is 2,320 feet long — almost half a mile. You know that Fermilab wouldn’t dig a much-longer-than-needed tunnel just for fun. There had to be a reason for its length, and that reason is Einstein’s theory of special relativity.

    One of the predictions of relativity is that moving clocks tick more slowly than stationary ones. There are many forms of clocks, from an old-style grandfather clock to the beat of a human heart. The steady decay of particles such as pions forms its own clock, and because of the effects of relativity, the moving-pion clock is slower than the stationary-pion clock, which means Fermilab scientists had to design the NuMI/MINOS tunnel to be long enough to accommodate the longer lifetime of the moving, decaying pion.

    Using the velocities and lifetimes described here, classical physics says that every pion would have decayed in the 2,320-foot-long tunnel — after all, it really only needed 76 feet anyway. Yet Fermilab physicists know that only about 40 percent of the pions will decay before they smash into the end of the tunnel about half a mile away. This is exactly what is predicted by relativity.

    While the fact that clocks tick more slowly if they are moving is not at all intuitive, every time we shoot a beam of neutrinos at Minnesota, we conclusively prove that the universe can be nonintuitive. Relativity works.

    See the full article here.

    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.

    ScienceSprings is powered by MAINGEAR computers

  • richardmitnick 2:05 pm on February 19, 2014 Permalink | Reply
    Tags: , , FNAL MINOS, , ,   

    From Fermilab: “Slip stacked beam sent to NuMI in accelerator complex’s new operational mode” 

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

    Wednesday, Feb. 19, 2014
    No Writer Credit

    On Friday, Feb. 14, the reconfigured Recycler successfully sent 12 batches of slip stacked beam to the NuMI target.

    The Accelerator Division reached a new milestone in the ramp-up of operations at Fermilab’s accelerator complex.

    This is the first time the Accelerator Division carried out all the acceleration steps — from the beginning of the accelerator chain to the NuMI target — in the accelerator complex’s high-power operation mode.

    Starting in the Booster, the 12 batches of beam were injected into and slip stacked in the Recycler, transferred to the Main Injector, accelerated to 120 GeV and delivered to the NuMI target.

    The Accelerator Division will continue to work on gradually increasing the slip-stacked-beam intensity in the Recycler. The goal is to have the reconfigured Recycler fully integrated into the rest of the accelerator complex in May. In the new configuration, the accelerator complex will be able to produce more neutrinos.

    See the full article here.

    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.

    ScienceSprings is powered by MAINGEAR computers

  • richardmitnick 3:25 pm on January 15, 2014 Permalink | Reply
    Tags: , FNAL MINOS, ,   

    From Fermilab: “Final block of NOvA near detector in place” 

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

    Wednesday, Jan. 15, 2014
    No Writer Credit

    Since June, crews have been assembling the massive NOvA near detector in the Minos cavern, located 350 feet underground at Fermilab. On Friday, Jan. 10, the final 21,000-pound plastic block of that detector was put into place, signaling a significant milestone in what will be one of the largest and most sophisticated neutrino experiments in the world.

    Members of the NOvA crew put the final NOvA near-detector block into place in the Minos cavern. Photo: Cindy Arnold

    Construction of the near detector began in June, after the excavation of the NOvA cavern was completed in May. The detector consists of a muon catcher and eight PVC blocks standing 15 feet high and wide and about 6 feet deep. Each block was assembled at the CDF assembly building, driven to Minos on a truck and then carefully lowered down an open shaft to the cavern floor, where workers wheeled it into place.

    In the coming months, the near detector will be filled with liquid scintillator and wired with the sensors needed to take neutrino data. It will weigh about 300 tons. Meanwhile, in northern Minnesota, construction is nearly complete on the 14,000-ton far detector, and the NOvA experiment is already receiving a beam of neutrinos from Fermilab’s Main Injector.

    See the full article here.

    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.

    ScienceSprings is powered by MAINGEAR computers

  • richardmitnick 2:12 pm on December 16, 2013 Permalink | Reply
    Tags: , FNAL MINOS, , ,   

    From Fermilab: “MINOS+ adds to the book on neutrinos” 

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

    Monday, Dec. 16, 2013
    Leah Hesla

    Fermilab’s MINOS neutrino experiment entered a new stage this year, marked by a new name: MINOS+.


    Using a higher-energy and higher-power neutrino beam than its predecessor, the experiment’s second stage explores new territory in neutrino interactions. It also coaxes many times the number of interactions from neutrinos as they pass through the MINOS detector than could the original setup. With MINOS+, scientists hope to uncover new behavior not visible in MINOS’ first phase, which lasted from 2005 to 2012.

    Since 2001, when scientists first confirmed the phenomenon of neutrino oscillation, researchers have been studying precisely how neutrinos change from one of their three types into another. A neutrino of one type at point A may have transformed into another type by the time it reaches point B. The way a neutrino oscillates depends on the ratio of the distance it travels to its energy — or L/E (L over E) in physicist parlance.

    In MINOS+, while the distance the neutrinos travel is the same as it was for MINOS — 734 kilometers — the neutrino energy is significantly higher. This takes scientists’ search for a better understanding of neutrinos into a new L/E region, one where fewer neutrinos “disappear” by the time they reach the detector, having oscillated into a neutrino flavor the detector can’t easily see.

    At the same time, the increased energy and more powerful beam causes the neutrinos to interact more often in the MINOS detector, reducing measurement uncertainties and providing even more opportunities to catch neutrinos doing something out of the ordinary.

    Thus in the new L/E region, scientists can both paint a high-definition picture of neutrino oscillations and look for physics that departs from the standard expectation.

    To date, MINOS provides the best measurement of a key property of neutrino oscillation, the difference in the square of the masses between two of the three mass states. MINOS+ will continue to beat on the precision of this measurement. Neutrino masses themselves — parameters of standard neutrino oscillations — are too small to measure by conventional means.

    Scientists will also look for one or more hypothesized sterile neutrinos, as well as any effects that depart from the Standard Model of particle physics. They may even be able to spot hints of extra dimensions.

    Standard Model of Particle Physics
    Standard Model of Particle Physics

    With the more intense neutrino beam delivered by Fermilab’s revamped accelerator complex, scientists will fill in gaps in the book on neutrinos with more precise details on this subtle and puzzling particle.

    See the full article here.

    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.

    ScienceSprings is powered by MAINGEAR computers

    • Alex Autin 11:09 am on December 17, 2013 Permalink | Reply

      …my head just exploded. 😉


    • richardmitnick 12:55 pm on December 17, 2013 Permalink | Reply

      It is a far far reach; but neutrinos, which are 1/2 spin, and affected by gravity and the weak force could turn out to be dark matter. No one is saying this yet, but…


Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: