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  • richardmitnick 5:12 pm on February 4, 2019 Permalink | Reply
    Tags: , , MINERvA neutrino experiment at Fermilab,   

    From Fermi National Accelerator Lab: “CSI: Neutrinos cast no shadows” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

    February 4, 2019
    Xianguo Lu

    Scientists solve neutrino mysteries by watching them interact with detectors — specifically, with the atomic nuclei in the detector material. Most of the time, a neutrino does not even shake hands with a nucleus. But when it does, the lightweight, neutral particle can transform into a charged particle and knock things out of the nucleus as it escapes — leaving a crime scene behind. It is the job of scientists at Fermilab’s MINERvA [see below] experiment to reconstruct the crime scene and figure out what has happened during the interaction.

    The impact

    Neutrinos are lightweight particles that rarely interact with matter. Their reluctance to interact makes them difficult to study, but they’re also the very particles that could answer longstanding questions about the creation of the cosmos, so they’re worth the pursuit. And it’s a tough one, since the neutrino can’t be studied directly. Rather, scientists must study the traces it leaves behind. The more information they can gather about the meaning of those traces, the better their neutrino measurements — not just at MINERvA, but at other neutrino experiments as well.

    Summary

    Neutrinos are lightweight, neutral particles, and they usually sail through matter without bumping into it. But once in a while, it does shake hands with a nucleus, and sometimes the handshake takes a destructive turn: A charged lepton (an electron or muon, sometimes called a “heavy electron”) is produced, while the constituents of the nucleus are knocked out. The traces of the charged lepton and the knock-out are collected by a particle detector.

    MINERvA scientists study the resultant particles’ traces to reconstruct the interaction between the neutrinos and the nuclei. So far, this has not been an easy task: Nuclear effects have obscured much of the evidence of the intruding neutrinos, leaving researchers with complex and seemingly irrelevant information. Not all neutrinos misbehave but, unfortunately, the neutrinos we care about – those with energy comparable to the mass of the constituents of the nuclei and could possibly tell us about the creation of the cosmos – all have this modus operandi.

    1
    The transverse boosting angle δαT represents the direction of the net transverse motion of the charged lepton and the knock-out.

    To reconstruct the resulting crime scene, scientists need a complete understanding of how the nuclear effects work.

    Both the charged lepton and the knock-out retain partial fingerprints from the original neutrino, and those partial fingerprints lie ambiguously on top of the nuclear effect background.

    Researchers have found that the fingerprints can be lifted via a novel neutrino CSI technique known as “final-state correlations.” Just as the sun’s corona is visible only during a solar eclipse, the fine details of the nuclear effects become clear only when other effects are removed.

    To get a sense of the “final-state correlations” technique, let’s take a step back and look at the events leading to the crime scene: A neutrino bumps into a nucleus. The interaction produces other particles. Those new particles — charged lepton and knock-out — fly off in opposite directions, leaving traces of themselves in the detector.

    In the absence of nuclear effects, the charged lepton and the knock-out would fly off in separate, roughly back-to-back paths, away from the incoming neutrino path. Picture a neutrino entering through, say, the south entrance of some tiny, subatomic building. It bumps into a nucleus. The resulting charged lepton flees through an east exit, and the knock-out particle flees through some west exit.

    With no nuclear effects, the charged lepton heads east with as much determination as the knock-out particle heads west. That is, the charge lepton’s east-pointing momentum matches the knock-out particle’s west-pointing momentum.

    But in reality, there are nuclear effects, and that means that the charged lepton’s eastward motion does not match the knock-out particle’s westward motion. These subtle momentum differences are clues; they reflect everything that happens inside the nucleus, like a shadow of the crime scene cast by the flashlight carried by the neutrino. Thus, neutrinos cast no shadows – only nuclear effects do.

    The final-state correlations technique matches the nuclear effects with the postinteraction particles’ departures from the paths of equal east-west momenta.

    In a recent MINERvA neutrino investigation, researchers used the new technique. They laid out a detailed reconstruction of the nuclear effects. The underlying phenomena – such as the initial state of the nucleus, additional knock-out mechanism, and final-state interactions between the knock-out and the rest of the nucleus – are now separated. New insights on the workings of nuclear effects have been reported in Phys. Rev. Lett. 121, 022504. Those interested are much encouraged to review MINERvA’s findings.

    Xianguo Lu is a physicist at the University of Oxford.

    See the full article here .


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    FNAL Icon

    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.

    FNAL MINERvA front face Photo Reidar Hahn

    FNAL DAMIC

    FNAL Muon g-2 studio

    FNAL Short-Baseline Near Detector under construction

    FNAL Mu2e solenoid

    Dark Energy Camera [DECam], built at FNAL

    FNAL DUNE Argon tank at SURF

    FNAL/MicrobooNE

    FNAL Don Lincoln

    FNAL/MINOS

    FNAL Cryomodule Testing Facility

    FNAL Minos Far Detector

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    FNAL/NOvA experiment map

    FNAL NOvA Near Detector

    FNAL ICARUS

    FNAL Holometer

     
  • richardmitnick 4:51 pm on June 18, 2018 Permalink | Reply
    Tags: , , MINERvA neutrino experiment at Fermilab, ,   

    From Fermilab: “The secret to measuring the energy of an antineutrino” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

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

    June 18, 2018
    No writer credit found

    Scientists study tiny particles called neutrinos to learn about how our universe evolved. These particles, well-known for being tough to detect, could tell the story of how matter won out over antimatter a fraction of a second after the Big Bang and, consequently, why we’re here at all.

    Getting to the bottom of that split-second history means uncovering the differences, if any, between the neutrino and its antimatter counterpart, the antineutrino.

    The MINERvA neutrino experiment at Fermilab recently added some detail to the behavior profiles of neutrinos and antineutrinos: Scientists measured the likelihood that these famously fleeting particles would stop in the MINERvA detector. In particular, they looked at cases in which an antineutrino interacting in the detector produced another particle, a neutron — that familiar particle that, along with the proton, makes up an atom’s nucleus.

    MINERvA’s studies of such cases benefit other neutrino experiments, which can use the results to refine their own measurements of similar interactions.

    It’s typical to study the particles produced by the interaction of a neutrino (or antineutrino) to get a bead on the neutrino’s behavior. Neutrinos are effortless escape artists, and their Houdini-like nature makes it difficult to measure their energies directly. They sail unimpeded through everything — even lead. Scientists are tipped off to the rare neutrino interaction by the production of other, more easily detected particles. They measure and sum the energies of these exiting particles and thus indirectly measure the energy of the neutrino that kicked everything off.

    This particular MINERvA study — antineutrino enters, neutron leaves — is a difficult case. Most postinteraction particles deposit their energies in the particle detector, leaving tracks that scientists can trace back to the original antineutrino (or neutrino, as the case may be).

    But in this experiment, the neutron doesn’t. It holds on to its energy, leaving almost none in the detector. The result is a practically untraceable, unaccounted energy that can’t easily be entered in the energy books. And unfortunately, antineutrinos are good at producing energy-absconding neutrons.

    Researchers make the best of missing-energy situations. They predict, based on other studies, how much energy is lost and correct for it.

    To give the scientific community a data-based, predictive tool for missing-energy moments, MINERvA collected data from the worst-case situation: An antineutrino strikes a nucleus in the detector and knocks out the untraceable neutron so nearly all of the energy bestowed to the nucleus goes “poof.” (These interactions also produce positively charged particles called muons which signal the antineutrino interaction.) By studying this particular disappearing act, scientists could directly measure the effects of the missing energy.

    FNAL/MINERvA

    Scientists at Fermilab use the MINERvA to make measurements of neutrino interactions that can support the work of other neutrino experiments. Photo Reidar Hahn

    Other researchers can now look for these effects, applying the lessons learned to similar cases. For example, researchers on Fermilab’s largest operating neutrino experiment, NOvA, and the Japanese T2K experiment will use this technique in their antineutrino measurements.

    FNAL/NOvA experiment map

    FNAL Near Detector

    NOvA Far detector 15 metric-kiloton far detector in Minnesota just south of the U.S.-Canada border schematic


    NOvA Far Detector Block

    T2K Experiment, Tokai to Kamioka, Japan


    T2K map, T2K Experiment, Tokai to Kamioka, Japan

    And the Fermilab-hosted international Deep Underground Neutrino Experiment, centerpiece of a world-leading neutrino program, will also benefit from this once it begins collecting data in the 2020s.

    SURF DUNE LBNF Caverns at Sanford Lab


    FNAL DUNE Argon tank at SURF


    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    The neutron production case is just one type of missing-energy interaction, one of many. So the model that comes out of this MINERvA study is an admittedly imperfect one. There can’t be a one-size-fits-all-missing-energy-scenarios model. But it still provides a useful tool for piecing together a neutrino’s energy — and that’s a tough task no matter what particles come out of the interaction.

    “This analysis is a great testament to both the detector’s ability to measure neutrino interactions and to the collaboration’s ability to develop new strategies,” said Fermilab scientist and MINERvA co-spokesperson Deborah Harris. “When we started MINERvA, this analysis was not even a gleam in anyone’s eye.”

    There’s a bonus to this recent study, too, one that bolsters an investigation conducted last year.

    For the earlier investigation, MINERvA focused on neutrino (instead of antineutrino) interactions that knocked out proton-neutron pairs (instead of lone neutrons or protons). In a detector such as MINERvA, a proton’s energy is much easier to measure than a neutron’s, so the earlier study presumably yielded more precise measurements than the recent antineutrino study.

    How good were these measurements? MINERvA scientists plugged the values of the earlier neutrino study into a model of this recent antineutrino study to see what would pop out. Lo and behold, the adjustment to the antineutrino model improved its ability to predict the data.

    The combination of the two studies gives the neutrino physics community new information about how well models do and where they fall short. Searches for the phenomenon known as CP violation — the thing that makes matter special compared to antimatter and enabled it to conquer in the post-Big Bang battle — depend on comparing neutrino and antineutrino samples and looking for small differences. Large, unknown differences between neutrino and antineutrino reaction products would hide the presence or absence of CP signatures.

    “We are no longer worried about large differences, and our neutrino program can work with small adjustments to known differences,” said University of Minnesota–Duluth physicist Rik Gran, lead author on this result.

    MINERvA is homing in on models that, with each new test, better describe both neutrino and antineutrino data — and thus the story of how the universe came to be.

    These results appeared on June 1, 2018, in Physical Review Letters.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    FNAL Icon

    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.


    FNAL/MINERvA

    FNAL DAMIC

    FNAL Muon g-2 studio

    FNAL Short-Baseline Near Detector under construction

    FNAL Mu2e solenoid

    Dark Energy Camera [DECam], built at FNAL

    FNAL DUNE Argon tank at SURF

    FNAL/MicrobooNE

    FNAL Don Lincoln

    FNAL/MINOS

    FNAL Cryomodule Testing Facility

    FNAL Minos Far Detector

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    FNAL/NOvA experiment map

    FNAL NOvA Near Detector

    FNAL ICARUS

    FNAL Holometer

     
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