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  • richardmitnick 5:05 pm on February 23, 2015 Permalink | Reply
    Tags: , , Neutrinos,   

    From Scientific American: “Higgs Boson Could Explain Matter’s Dominance over Antimatter” 

    Scientific American

    Scientific American

    February 20, 2015
    Clara Moskowitz

    1
    Computer simulation of particle tracks from an LHC collision that produced a Higgs boson.
    CERN

    The stars, the planets and you and I could just as easily be made of antimatter as matter, but we are not. Something happened early in the universe’s history to give matter the upper hand, leaving a world of things built from atoms and little trace of the antimatter that was once as plentiful but is rare today. A new theory published February 11 in Physical Review Letters suggests the recently discovered Higgs boson particle may be responsible—more particularly, the Higgs field that is associated with the particle.

    The Higgs field is thought to pervade all of space and imbue particles that pass through it with mass, akin to the way liquid dye gives Easter eggs color when they are dunked in. If the Higgs field started off with a very high value in the early universe and decreased to its current lower value over time, it might have briefly differentiated the masses of particles from their antiparticles along the way—an anomaly, because antimatter today is characterized by having the same mass but opposite charge as its matter counterpart. This difference in mass, in turn, could have made matter particles more likely to form than antimatter in the cosmos’ early days, producing the excess of matter we see today. “It is a nice idea that deserves further study,” says physicist Kari Enqvist of the University of Helsinki, who was not involved in the new study but who has also researched the possibility that the Higgs field lowered over time. “There is a very high probability for the Higgs field to have a high initial value after inflation.”

    The inflation of the universe

    Inflation is a theorized early epoch of the universe in which spacetime rapidly ballooned. “Inflation has a very peculiar property; it allows fields to jump around,” says study leader Alexander Kusenko of the University of California, Los Angeles. During inflation, which radically altered the universe in a span much less than a second, the Higgs field might have hopped from one value to another due to quantum fluctuations and could have gotten stuck at a very high value when inflation ended. From there it would have settled down into its lower “equilibrium” value, but while it was changing its constantly varying value could have given matter particles different masses than their antimatter counterparts. Because lighter particles require less energy to form they arise more often. Thus, if matter was lighter, it could have quickly become more plentiful.

    The reason the Higgs field would have had such an easy time of jumping around during inflation is that the measured mass of the Higgs boson, the particle associated with the field, is relatively low. The boson appeared in 2012 inside the Large Hadron Collider (LHC) in Switzerland, revealing its mass to be about 126 GeV (giga-electron volts), or roughly 118 times the mass of the proton.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    That is somewhat lighter than it could have been, according to various theories. Think of the Higgs field as a valley between two cliffs. The value of the field is akin to the elevation of the valley, and the mass of the boson determines the slope of the cliff walls. “If you have a very curved valley then you probably have very steep sides,” Kusenko says. “That’s what we discovered. This value tells us that the walls are not very steep—that means the Higgs field could jump around and go very far” to other valleys at higher elevations. Enqvist agrees that the Higgs could very well have started off much higher than it is today. Whether or not this caused the matter to split from antimatter is “somewhat more speculative,” he says.

    A new particle

    Such splitting would depend on the presence of a theorized particle that has gone undetected so far: a so-called heavy Majorana neutrino. Neutrinos are fundamental particles that come in three flavors (electron, muon and tau). A fourth neutrino might also exist, however, that is expected to be much heavier than the others and thus more difficult to detect (because the heavier a particle is, the more energy a collider must produce to create it). This particle would have the strange virtue of being its own antimatter partner. Instead of a matter and antimatter version of the particle, the matter and antimatter Majorana neutrinos would be one and the same.

    This two-faced quality would have made neutrinos into a bridge that allowed matter particles to cross over into antimatter particles and vice versa in the early universe. Quantum laws allow particles to transform into other particles for brief moments of time. Normally they are forbidden from converting between matter and antimatter. But if an antimatter particle, say, an antielectron neutrino turned into a Majorana neutrino, it would cease to know whether it was matter or antimatter and could then just as easily convert to a regular electron neutrino as turn back into its original antielectron neutrino self. And if the neutrino happened to be lighter than the antineutrino back then, because of the varying Higgs field, then the neutrino would have been a more likely outcome—potentially giving matter a leg up on antimatter.

    “If true, this would solve a big mystery in particle physics,” says physicist Don Lincoln of the Fermi National Accelerator Laboratory in Illinois, who was not involved in the study. Yet the Majorana neutrino “is entirely speculative and has eluded discovery, even though the LHC experiments have a vigorous research program looking for it. Researchers will certainly keep this idea in mind as they dig through the new data the LHC will begin generating in the early summer this year.”

    Kusenko and his colleagues also have another hope for finding additional support for their theory. The Higgs field process they envision could have created magnetic fields with particular properties that would still inhabit the universe today—and if so, they might be detectable. If found, the existence of such fields would provide evidence that the Higgs field really did decrease in value long ago. The scientists are trying to calculate just what the magnetic field properties would be and whether experiments have a plausible hope of seeing them, but the option raises the tantalizing hope that their theory could have testable consequences—and maybe a chance to solve the antimatter mystery after all.

    See the full article here.

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  • richardmitnick 1:25 pm on February 3, 2015 Permalink | Reply
    Tags: , , Neutrinos   

    From FNAL: “Director’s Corner – Electron neutrinos from supernovae” 

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

    1
    Fermilab Director Nigel Lockyer wrote this column

    Neutrino research has the potential to lead to discoveries that rival the observation of the Higgs boson. And just as with the successful search for the Higgs, the question of the nature of neutrinos is being investigated by different teams using different methods.

    Here at Fermilab we are very familiar with one method — the study of neutrinos created from high-power particle accelerators. But at last month’s ELBNF collaboration meeting, Duke University Professor Kate Scholberg gave a fascinating introduction to the future use of a large, deep underground liquid-argon detector (currently referred to as ELBNF) to study neutrinos from supernovae in our galaxy. In Scholberg’s words:

    “When massive stars run out of nuclear fuel, they collapse in on themselves, forming ultradense neutron stars and, in some cases, even black holes. Just as gravitational potential energy turns to kinetic energy when you drop an object, the vast energy of the star’s infall must be released somehow. Some will be released in an enormous supernova explosion, but 100 times more is released in the form of neutrinos, particles famous for their feeble interactions with matter. Because neutrinos interact so weakly, they escape the supernova with nearly all of the collapse energy within only tens of seconds, creating an intense burst of all three flavors of neutrinos and antineutrinos with energies of a few tens of MeV.

    Sanford Underground Research Facility Interior
    Sanford Underground Research Facility

    “Neutrinos are also known for their ability to transform from one flavor to another. The time, energy and flavor evolution of the burst not only tells the story of the star’s destruction and the creation of its exotic compact progeny, but will also give us insight into the properties of neutrinos themselves. The different flavors tell different stories. The electron flavor neutrinos have a particularly interesting story to tell — they are emitted in an initial flash (tens of milliseconds) as protons and electrons are squeezed together to make neutrons and are more likely to bear the signatures of explosion processes and flavor oscillations.

    “On Earth we have a chance to witness the unfolding of a Milky Way core-collapse supernova by observing the neutrino burst in large underground neutrino detectors. About four explosions per century are expected. Observing the different flavor components of the burst is a bit like making a movie in different colors.

    “Different kinds of detectors are sensitive to different neutrino flavors. Existing large water and scintillator detectors (such as Super-K, IceCube, KamLAND, LVD Daya Bay and Borexino) are primarily sensitive to electron antineutrinos, which interact with free protons. Argon, in contrast, has unique sensitivity to electron neutrinos. A large underground liquid-argon detector like ELBNF would enable us to clearly record the birth of the neutron star and will bring new understanding of neutrino flavor transformation.”

    Super-Kamiokande experiment Japan
    Super-Kamioka

    ICECUBE neutrino detector
    IceCube

    KamLAND
    KamLAND

    Daya Bay
    Daya Bay

    Borexino Solar Neutrino detector
    Borexino

    See the full article here.

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  • richardmitnick 12:30 pm on January 27, 2015 Permalink | Reply
    Tags: , FNAL ELBNF, Neutrinos   

    From FNAL: “From the Deputy Director ELBNF is born” 

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

    Tuesday, Jan. 27, 2015
    Joe Lykken

    At approximately 6:15 p.m. CST on January 22, 2015, the largest and most ambitious experimental collaboration for neutrino science was born.

    It was inspired by a confluence of scientific mysteries and technological advances, engendered by the P5 report and the European Strategy update, and midwifed by firm tugs from Fermilab, CERN and Brookhaven Lab. Going by the placeholder name ELBNF (Experiment at the Long Baseline Neutrino Facility), the newborn had the impressive heft of 145 institutions from 23 countries.

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    The new Institutional Board (IB), convened by interim chair Sergio Bertolucci, unanimously approved a Memorandum of Collaboration that launches the election of spokespeople and a process to develop bylaws. The IB also endorsed an international governance plan for oversight of ELBNF detector projects, in concert with the construction of the LBNF facility hosted by Fermilab.

    The goal of this international collaboration is crystal clear: a 40-kiloton modular liquid argon detector deep underground at the Sanford Underground Research Facility, exposed to a megawatt-class neutrino beam from Fermilab, with the first 10 kilotons in place by 2021. This goal will enable a comprehensive investigation of neutrino oscillations that can establish the presence of CP violation for leptons, unequivocally determine the neutrino mass ordering and strongly test our current neutrino paradigm. A high-resolution near detector on the Fermilab site will have its own rich physics program, and the underground far detector will open exciting windows on nucleon decay, atmospheric neutrinos, and neutrino bursts from supernova detonations.

    Unlike most births, this one took place at an international meeting hosted by Fermilab; there was room for nearly all the friends and family of accelerator-based neutrino experiments. One of the critical items flagged at this meeting is to find a better name for the new collaboration. Here are a few of my unsolicited attempts:

    nuLAND = neutrino Liquid ArgoN Detector

    GOLDEN = Giant OsciLlation Detector Experiment for Neutrinos

    Think you can do better? Go ahead. My older son, a high-priced management consultant, offered another one pro bono: NEutrino Research DetectorS.

    I am too young to have been in the room when ATLAS and CMS (or for that matter CDF and D0) came into being, but last week I had the thrill of being part of something that had the solid vibe of history being made. The meeting website is here.

    See the full article here.

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    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.

     
  • richardmitnick 2:30 pm on January 9, 2015 Permalink | Reply
    Tags: , , Neutrinos   

    From FNAL “Frontier Science Result: MINERvA Who let the pions out (of the nucleus)?” 

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

    Friday, Jan. 9, 2015
    Steve Dytman, University of Pittsburgh

    Neutrinos are odd particles: They rarely interact in matter and can change character back and forth over time in a process called oscillation. When neutrinos do interact with matter, however, they do so in ways that are similar to how other high-energy particles produced by Fermilab accelerators interact: by making still more particles. So even though neutrinos themselves contain no quarks, they are still able to produce pions, quark-antiquark pairs that can be either charged or neutral. At today’s Joint Experimental-Theoretical Physics Seminar, MINERvA will release its new result on how neutral pions are produced in a beam of antineutrinos from Fermilab’s NuMI beamline.

    4
    This plot shows what a neutral pion looks like in the MINERvA detector when produced with a muon. Colors correspond to energy deposited in each triangular scintillator bar.

    A previous MINERvA result described how charged, rather than neutral, pions are made from neutrinos. At least “on paper,” that result is similar to today’s new result. Both of these interactions are predicted to happen and even to have similar probabilities.

    However, they leave very different footprints in detectors and so present different challenges. In fact the neutral pion’s footprint is a worry for oscillation experiments because it can look like something it’s not. So oscillation experiments need good measurements of how many neutral pions are made in neutrino and antineutrino beams.

    Measuring both charged- and neutral-pion production at similar neutrino energies also helps us better understand the nucleus with which a neutrino interacts, since the two different kinds of pions see the nucleus differently as they exit it. Before the research that led to today’s result, though, only a few dozen neutral pion-antineutrino events have ever been seen in a single experiment.

    Neutral pions are harder to see than charged pions because they decay very rapidly and must be detected through their decay products — two neutral photons, which interact on average about a foot away from where the neutral pion decayed in the first place. For today’s result, the neutral pion is produced at the same time as a muon, which is a heavier version of an electron.

    This new measurement adds more than 400 new events to the world’s collection for this novel interaction and tells us much more about how neutrinos and pions are both affected by the nucleus.

    There has been a lot of interest in pion production because the best theories are unable to describe previous MiniBooNE measurements of charged pions. Although the best calculation was also unable to reproduce the MINERvA charged-pion data, it failed in a different way, extending the controversy. Experimenters don’t stop, though. They just keep trying to find another way to measure what’s happening inside the nucleus until they understand it. Now MINERvA’s new result, which sees better agreement between the best calculation and the prediction (see figure below), paints a new picture of the nucleus.

    2
    This plot shows the cross section (likelihood per proton or neutron) of a neutral pion and an antimuon being made from an antineutrino as a function of the pion momentum. The two different models represent turning on and off the effects of the nucleus where the neutrino interacted. The effects of the nucleus were clearly “turned on” in the data. The inner error bars are statistical and the outer error bars are the total uncertainties.

    t
    Trung Le of Rutgers University will present MINERvA’s latest results at today’s wine and cheese seminar at 4 p.m. in One West.

    See the full article here.

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  • richardmitnick 4:18 pm on January 7, 2015 Permalink | Reply
    Tags: , Indian Neutrino Observatory, Neutrinos   

    From physicsworld: “Indian Neutrino Observatory set for construction” 

    physicsworld
    physicsworld.com

    Jan 7, 2015
    T V Padma

    The Indian government has given the go-ahead for a huge underground observatory that researchers hope will provide crucial insights into neutrino physics. Construction will now begin on the Rs15bn ($236m) Indian Neutrino Observatory (INO) at Pottipuram, which lies 110 km from the temple city of Madurai in the southern Indian state of Tamil Nadu. Madurai will also host a new Inter Institutional Centre for High Energy Physics that will be used to train scientists and carry out R&D for the new lab.

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    Getting ready for construction

    Originally planned to be complete by 2012, the INO has been in limbo for a number of years. In 2010 ecologists and conservationists raised objections to the INO’s initial proposed site at Singara in Tamil Nadu, which was near an elephant corridor and a tiger reserve. Researchers then had to find a new location, with the environment ministry only approving the Pottipuram site in 2011. Funding from the government arrived three years later.

    The INO will be built some 1.3 km underground, accessible via a 2 km-long tunnel. The lab will comprise three caverns, the largest being 132 m long, 26 m wide and 30 m high, which will house a 50,000 tonne Iron Calorimeter (ICAL) neutrino detector. The detector will consist of alternate layers of some 30,000 “resistive plate chambers” and iron plates.

    The INO team hopes to use the detector to address the “neutrino-mass hierarchy”. Scientists know that there are three neutrino-mass states, but do not yet know which is the most massive and which is the lightest. “Understanding this will help scientists to pick the correct theory beyond the Standard Model and, along with other accelerator-based experiments worldwide, address the problem of matter–antimatter asymmetry in the universe,” says INO project director Naba Mondal, who is based at the Tata Institute of Fundamental Research in Mumbai (TIFR).

    t
    TIFR

    As well as housing other experiments such as those searching for dark matter and neutrino-less double-beta decay, scientists are also hopeful that the INO will provide opportunities for young students to work on all aspects of particle-physics research, such as detector development and data analysis. “Science students across the country will have the opportunity to participate in building sophisticated particle detectors and electronic data-acquisition systems from scratch,” says Mondal.

    Indeed, Krishnaswamy Vijayraghavan, secretary of the Department of Science and Technology, which oversees funding for many science projects, says that the INO could “allow India to train experimental physicists and high-end engineers on a large scale” in “extremely important and competitive high-energy physics”. “INO will be the agent of transforming physics of this kind in India and will make a global impact,” he adds. “The outcome of this investment will be extraordinary and long term.”

    Taking centre stage

    Researchers also hope that the INO could help India to reclaim its leading position in neutrino physics and in constructing underground labs. The country led the way in the 1960s when physicists used a gold mine at Kolar in the southern state of Karnataka to create what was then the world’s deepest underground lab. Known as the Kolar Gold Field Lab, in 1965 it enabled researchers to detect neutrinos that are created when cosmic rays smash into the atmosphere. The lab later studied proton decay and was only shut down in 1992 when gold mining at the site became uneconomical.

    “With the closure of the mines, we lost a unique facility for carrying out research in the field of non-accelerator-based particle physics,” rues Mondal. “With the approval of the INO facility, we are now back on the centre stage of particle-physics research.”

    See the full article here.

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  • richardmitnick 3:46 pm on January 7, 2015 Permalink | Reply
    Tags: , FNAL PIP-II, Neutrinos   

    From FNAL: Proton Improvement Plan-II (PIP-II) 

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

    12/18/2014
    No Writer Credit

    Proton Improvement Plan-II (PIP-II) is Fermilab’s plan for providing powerful, high-intensity proton beams to the laboratory’s experiments. The increased beam power will position Fermilab as the leading laboratory in the world for accelerator-based neutrino experiments. PIP-II will also provide a flexible platform for further enhancement of the Fermilab accelerator complex to extend this leadership to the full range of particle physics research based on intense beams in the decades to come.

    The heart of PIP-II is a 800-MeV superconducting linear accelerator, which capitalizes on the lab’s expertise in superconducting radio-frequency technologies. Along with modest improvements to Fermilab’s existing Main Injector and Recycler accelerators, the superconducting linac, called SCL, will provide the megawatt proton beam that is needed for the Long-Baseline Neutrino Facility.

    PIP-II is planned to deliver beam in the early part of the next decade.

    p

    How PIP-II Works

    Fermilab’s Proton Improvement Plan II, or PIP-II, will enable the world’s most intense neutrino beam and help scientists search for rare particle physics processes. These investigations will require intense beams of protons, which will produce gushers of other neutrinos that scientists can then study in greater detail.

    Scheme

    The raw material for experiments at PIP-II is protons, lots of them, which are used to generate other types of particles for multiple experiments.

    Protons are first emitted from a source and formed into a beam. The proton beam then speeds down a 250-meter superconducting linear accelerator, or linac, to an energy of 800 million electronvolts (or 800 megaelectronvolts, MeV). The PIP-II linac is situated on the infield of the (decommissioned) Tevatron accelerator on the Fermilab site. This siting takes advantage of existing cryogenic, electrical and water infrastructure. Once it exits the 800-MeV linac, the proton beam is steered towards the existing Booster accelerator, where it is accelerated to 8 billion electronvolts (or gigaelectronvolts, GeV).

    Some of the protons exiting the Booster will head directly toward a variety of targets, striking them. These will initiate strings of newly produced particles, of which some fraction eventually decay into muons. The muons will be captured within the MC-1 Building, right on the Fermilab site. There they will enter a detector, where scientists can make measurements of this short-lived particle.

    The other protons exiting the Booster will take a different path, continuing down the accelerator chain. They will be transferred and accelerated within the existing Main Injector-Recycler complex — a set of 3.3-kilometer-circumference rings that will produce a beam of protons at an energy of 120 billion electronvolts (or 120 gigaelectronvolts, GeV). These protons then strike a target, eventually producing neutrinos. The neutrinos will then fly through the Earth at nearly light speed. Under the PIP-II scheme, they will be directed to the Long-Baseline Neutrino Facility experimental area, planned to be built at Homestake, South Dakota, 1,300 kilometers away. The LBNF detectors will help researchers better understand the behavior of neutrinos, which are notoriously difficult to observe because of their flighty nature.

    Read the PIP-II white paper.

    Superconducting radio-frequency technology

    At the heart of the PIP-II accelerator is a technology that provides for a highly efficient way to accelerate particle beams. Superconducting radio-frequency (SRF) cavities make it possible to accelerate intense proton beams to higher energies in relatively short distances.

    PIP-II SRF cavities come in a number of shapes and sizes, but the engineering principle of particle acceleration is the same for all of them.

    Cavities are highly polished, perfectly shaped niobium structures whose task is to generate electric fields that propel the particle beam forward. As a superconducting metal, niobium can generate these electric fields without creating wasted heat, as would be generated if one were to use a normal-conducting metal such as copper. So long as the niobium’s temperature is kept to a few kelvin —a few degrees above absolute zero – it can accelerate particles with supreme efficiency.

    c

    A string comprising several of these cavities nestles in a vessel called a cryomodule, which bathes them in liquid helium and keeps them at the ultracold temperature that is key to their operation and efficiency.

    Cavities are constructed from one or more cells, compartments that enclose one cycle of an oscillating electric field. Cells can be strung together to form cavities. Their number and shape depend on acceleration requirements.

    The electric field runs down the center of the single-cell and multicell cavities. It oscillates between positive and negative, swelling to a peak and sinking to a valley within the space of a single cell; it is as if each cell rapidly switches between a positive and negative charge.

    The cycles are timed to kick charged particles riding the wave from cell to cell. Each time a positively charged proton enters a cell, the cell’s charge changes to negative, which attracts the proton. As the proton leaves the cell, the cell’s charge changes to positive and pushes the proton forward. Traversing the next cell, the proton is propelled in the same fashion. This process continues until the particle has shot all the way through the accelerator.

    PIP -II Collaboration

    Argonne National Laboratory
    Bhaba Atomic Research Center, Mumbai
    Brookhaven National Laboratory
    Cornell University
    Fermi National Accelerator Laboratory
    International Linear Collider
    Inter University Accelerator Center, Delhi
    Lawrence Berkeley National Laboratory
    Michigan State University
    North Carolina State University
    Oak Ridge National Laboratory/SNS
    Pacific Northwest National Laboratory
    Raja Ramanna Center of Advanced Technology, Indore
    SLAC National Accelerator Laboratory
    Thomas Jefferson National Accelerator Facility
    Variable Energy Cyclotron Center, Kolkota

    See the full article here.

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  • richardmitnick 5:28 am on December 31, 2014 Permalink | Reply
    Tags: , , Neutrinos,   

    From U Rochester: “Researchers show neutrinos can deliver not only full-on hits but also ‘glancing blows’” 

    U Rochester bloc

    University of Rochester

    December 30, 2014
    Leonor Sierra and Peter Iglinski
    585-276-6264
    lsierra@ur.rochester.edu
    @leonor_sierra

    In what they call a “weird little corner” of the already weird world of neutrinos, physicists have found evidence that these tiny particles might be involved in a surprising reaction.

    Neutrinos are famous for almost never interacting. As an example, ten trillion neutrinos pass through your hand every second, and fewer than one actually interacts with any of the atoms that make up your hand. However, when neutrinos do interact with another particle, it happens at very close distances and involves a high-momentum transfer.

    And yet a new paper, published in Physical Review Letters this week, shows that neutrinos sometimes can also interact with a nucleus but leave it basically untouched – inflicting no more than a “glancing blow” – resulting in a particle being created out of a vacuum.

    Professor Kevin McFarland is a scientific co-spokesperson with the international MINERvA collaboration, which carries out neutrino scattering experiments at Fermilab. McFarland, who also heads up the Rochester team that was primarily responsible for the analysis of the results, compares neutrino interactions to the firing of a bullet at a bubble, only to find the bubble was left intact.

    f
    from Fermilab Today: This MINERvA event display shows a coherent pion production candidate interaction. The neutrino enters the detector from the left and interacts with a nucleus, producing a muon and a pion. The colors indicate the amount of energy deposited at that point.

    “The bubble – a carbon nucleus in the experiment – deflects the neutrino ‘bullet’ by creating a particle from the vacuum,” McFarland explains. “This effectively shields the bubble from getting blasted apart and instead the bullet only delivers a gentle bump to the bubble.”

    Producing an entirely new particle – in this case a charged pion – requires much more energy than it would take to blast the nucleus apart – which is why the physicists are always surprised that the reaction happens as often as it does. McFarland adds that even painstakingly detailed theoretical calculations for this reaction “have been all over the map.”

    “The production of pions from this reaction had not been observed consistently in other experiments,” McFarland said. By using a new technique, they were able to measure how much momentum and energy were transferred to the carbon nucleus – showing that it remained undisturbed – and the distribution of the pions that were created.

    “After analyzing the results, we now have overwhelming evidence for the process,” McFarland says.

    The two members of the collaboration who were primarily responsible for analyzing the results were Aaron Higuera, at the time a postdoc at Rochester and now at the University of Houston, and Aaron Mislivec, one of McFarland’s doctoral students.

    Working with Higuera, Mislivec wrote the computer code that allowed them to sift through the results and get a picture of the reaction. “Our detector gave us access to the full information of exactly what was happening in this reaction,” Mislivec explains. “Our data was consistent with the unique fingerprint of this reaction and determined how these interactions happen and how often.” The key to identifying the reaction was finding undisturbed carbon nuclei and then studying the two resulting particles – the pion, which is responsible for shielding the nucleus, and the muon.

    Understanding this reaction, McFarland states, “is not going to make a better mousetrap, but it is exciting to learn that this weird reaction really does take place.”

    Researchers in the MINERvA collaboration measure low energy neutrino interactions both to support neutrino oscillation experiments and study the strong dynamics of the nucleon and nucleus that affect the interactions.

    The work is funded by the Department of Energy, the National Science Foundation, and partnering scientific agencies in Brazil, Chile, Mexico, Switzerland, Peru and Russia.

    See the full article here.

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    The University of Rochester is one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

     
  • richardmitnick 3:28 pm on December 22, 2014 Permalink | Reply
    Tags: , , , , , Neutrinos,   

    From IceCube: “Gamma-ray bursts are not main contributors to the astrophysical neutrino flux in IceCube” 

    icecube
    IceCube South Pole Neutrino Observatory

    22 Dec 2014
    Silvia Bravo

    Gamma-ray bursts (GRBs) were once the most promising candidate source of ultra-high-energy cosmic rays (UHECRs). They release extremely large amounts of energy in short periods of time, so if they could accelerate protons as they do electrons, then GRBs could account for most of the observed UHECRs.

    But along comes IceCube, the first gigaton neutrino detector ever built, ready to dig into the origin of UHECRs using neutrinos. There’s a whole universe in which to look for a signal but, to test GRBs as possible sources, they started with a search for neutrinos in coincidence with observed GBRs. Previous results, published by the IceCube Collaboration in 2012 in Nature, found no such coincidence. This cast doubt on GRBs as the main source of UHECRs. In a follow-up study submitted today to the Astrophysical Journal Letters, the collaboration shows that the contribution of GRBs to the observed astrophysical neutrino flux cannot be larger than about 1%.

    The study also sets the most stringent limits yet on GRB neutrino production, excluding much of the parameter space for the most popular models. The collaboration is now also providing a tool to set limits on other GRB models using IceCube data.

    grb
    The jet from a gamma-ray burst emerging at nearly light speed. Image credit: NASA / Swift / Cruz deWilde.

    NASA SWIFT Telescope
    NASA/Swift

    One may wonder how observing neutrinos in Antarctic ice tells us anything about cosmic rays and GRBs. The answer is simple, if you ask a physicist: neutrinos are an unambiguous signature of proton acceleration. And cosmic rays are, in their vast majority, very high energy protons.

    That cosmic rays exist at energies up to 10^20 eV is a fact; we have observed them with all sort of detectors since their discovery by Victor [Francis] Hess back in 1912. Physicists have developed several models that could explain how and where cosmic rays can be accelerated to such extreme energies. All of these models also tell us that any cosmic proton accelerator that we can imagine would also be a very high energy neutrino generator. While cosmic rays are scrambled by intergalactic magnetic fields, neutrinos travel in straight paths, potentially allowing us to identify their sources. For this reason, the search for the sources of cosmic rays has also become the search for very high energy neutrinos.

    IceCube, the first detector to measure a very high energy neutrino flux, is now squeezing every bit of information out of its data, to learn more about the origins of those neutrinos and thus of cosmic rays. In the current research, IceCube has looked for a neutrino signature in coincidence with over 500 GRBs observed during the data-taking period from April 2008 to May 2012. A single low-significance neutrino was found, confirming previous results by the collaboration. However, this data sample was much larger, including the first data from the completed detector and allowing still more stringent limits on GRB neutrino production.

    GRBs were once very promising candidates for the source of UHECRs. Corresponding author Michael Richman from University of Maryland notes that “using data taken from one year of operation of the completed detector, IceCube has already cast doubt on that hypothesis.” IceCube’s recent observation of an astrophysical neutrino flux marks a new era of neutrino astronomy. This flux is compatible with the expectation from cosmic ray production. While GRBs are excluded as dominant sources of either UHECRs or the diffuse astrophysical neutrinos, ongoing analyses will shed new light on these mysterious signals.

    + Info Search for Prompt Neutrino Emission from Gamma-Ray Bursts with IceCube, IceCube Collaboration: M.G. Aartsen et al. Submitted to Astrophysical Journal Letters, arxiv.org/abs/1412.6510

    See the full article here.

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    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 8:51 pm on December 17, 2014 Permalink | Reply
    Tags: , , Neutrinos   

    From IceCube: “Designing the future of the IceCube Neutrino Observatory” 

    icecube
    IceCube South Pole Neutrino Observatory

    17 Dec 2014
    Sílvia Bravo

    The IceCube Neutrino Observatory is a successful and large scientific facility located near the Amundsen-Scott South Pole station in Antarctica. This observatory hosts IceCube, a cubic-kilometer deep-ice particle detector that is, so far, the largest ever built – and on the surface, IceTop, an extended air shower array.

    Completed in 2010, IceCube has recently discovered astrophysical neutrinos, revealing their potential to explore our universe at energies at the PeV scale and above, where most of the universe is opaque to high-energy photons. But the big questions remain unsolved: where do these neutrinos come from? How does nature accelerate particles to such extreme energies?

    Prof. Olga Botner, IceCube spokesperson and a physics professor at the University of Uppsala, and Prof. Francis Halzen, IceCube principal investigator and a professor at the University of Wisconsin–Madison, tell us about the plans for an upgrade to the IceCube Neutrino Observatory. As an extension of the current detector, it can be built in a few years and within an affordable budget, thanks to expertise acquired with IceCube.

    a
    Artistic view of the Antarctic surface around the South Pole station, showing the position of the 86 strings of sensors in IceCube and the possible grid of the next-generation detector. Image: J.Yang/IceCube Collaboration

    Q: What has IceCube accomplished so far?

    Olga Botner (O): IceCube is the world’s foremost neutrino observatory, which, after just two years of running in its final configuration, discovered neutrinos from outer space that have energies a billion times larger than those of neutrinos produced by our Sun and a thousand times larger than any produced on Earth with man-made accelerators. The discovery of this high-energy neutrino flux is a turning point for neutrino astronomy: a dream of 50 years ago on the verge of becoming reality.

    Francis Halzen (F): The high level of the observed neutrino flux implies that a significant fraction of the energy in the non-thermal universe, powered by the gravitational energy of compact objects from neutron stars to supermassive black holes, is generated in hadronic accelerators. This tells us that we are approaching exciting times when high-energy neutrinos will reveal new sources or provide new insight on the energy generation in known sources.

    But IceCube has also been a successful detector with respect to its technical development. We developed highly successful designs for transforming natural ice into a particle detector. The optimized methods for deploying and commissioning large volume detectors in ice can be used for a next-generation detector; minimal modifications will target improvements focused on modernization, efficiency, and cost savings.

    O: This is a very important point. The detector was built within the expected time frame, within budget, and with a performance at least a factor of two better than anticipated.

    Going back to physics, I should also add that IceCube has yielded many interesting results beyond neutrino astronomy. We are studying cosmic rays, looking for signatures of the annihilations of dark matter particles into neutrinos, and investigating the properties of the neutrinos themselves. We have published competitive results in all these areas.

    Q: Why do we need a next-generation IceCube detector?

    F: We all agree on the observed spectrum of neutrinos, there’s no doubt about the discovery, but independent analyses of IceCube data have produced only on the order of 100 astrophysical neutrino events in several years. These modest numbers of cosmic neutrinos limit the ability of IceCube to be an efficient tool for neutrino astronomy over the next decade. A next-generation detector will provide an unprecedented view of the high-energy universe, taking neutrino astronomy to new levels of discovery. It is likely to resolve the question of the origin of the cosmic neutrinos recently discovered.

    O: That’s right! IceCube’s discovery of extraterrestrial neutrinos has shown us that even a cubic-kilometer detector is not enough. To fully exploit the potential for neutrino astronomy, a much larger observatory is needed. We are already working on its design. The new detector has been named IceCube-Gen2.

    Q: Is it feasible and cost-effective to build an even bigger detector at the Pole?

    O: It sure is. The good news is that the successful deployment and running of IceCube demonstrates that we have mastered the technologies to construct and operate a detector in the deep ice. The drilling systems and the optical modules for the next-generation detector will closely follow the designs that have been proven to work well—with certain modifications to improve the overall performance. This makes us confident that a next-generation detector is not only feasible but can be built in a cost-effective manner, just like IceCube.

    F: We didn’t know this before IceCube, but now we have measured the extremely long photon absorption lengths in ice. This will allow the spacing between strings of light sensors to exceed 250 m in a future IceCube extension; i.e., the instrumented volume can rapidly grow without increasing the costs much. In fact, we can build a ten-cubic-kilometer IceCube-Gen2 telescope by roughly doubling the instrumentation already deployed. Thus, a tenfold increase in astrophysical neutrino detection rates could be achieved with a cost comparable to the current IceCube detector.

    Q: And what about the time scale of this project? Will we need to wait a long time to see new results?

    O: We are aiming at an expanded array instrumenting a volume of 10 km3 for the detection of high-energy neutrinos—but also at improving the low-energy performance through deployment of a densely instrumented infill detector, PINGU, targeting neutrino mass hierarchy as its prime goal. We believe that this new IceCube-Gen2 observatory can be built within seven years of obtaining funding.

    Q: Sounds like a plan. Who is leading this next-generation IceCube?

    F: The present plan is to build IceCube following a management strategy that was successful in delivering IceCube on time and on budget. The collaboration is rapidly expanding, both in the US and in Europe and Canada. We expect that a larger fraction of the cost will be carried by significant contributions from our foreign collaborators.

    O: Exactly. The high-energy array and PINGU are both envisioned as parts of an IceCube-Gen2 observatory. A new collaboration, including IceCube members and additional institutions, is now being formed. This IceCube-Gen2 collaboration will work to develop proposals in the US and abroad to secure funding. We hope that IceCube-Gen2 will become a flagship scientific project for NSF as well as for funding agencies abroad.

    o
    This image shows a simulated high-energy event of about 60 PeV in the proposed IceCube Gen2 detector. Image: IceCube Collaboration

    Q: Can other current or in-design experiments do better than IceCube-Gen2?

    F: Well, we have strong competitors. Early efforts for cubic-kilometer neutrino detectors focused on deep-water-based detectors, including DUMAND, Lake Baikal, and ANTARES. So far, there is no cubic-kilometer neutrino detector in deep water, but these experiments have paved the way toward the proposed construction of KM3NeT in the Mediterranean Sea and GVD in Lake Baikal.

    O: These new projects, GVD in Lake Baikal and KM3NeT in the Mediterranean, are presently in the prototyping or early construction phase. They will eventually provide a complementary view of the sky to that of an Antarctic observatory.

    Q: Should we expect IceCube-Gen2 to be as successful as IceCube? That may be the desire, but are there objective reasons to think so?

    O: The main one is that we already have established the existence of a flux of high-energy neutrinos. What we now need are substantial number of events to further characterize this flux in terms of energy spectrum, a possible energy cut-off, flavor composition, and provenance. We just need a larger detector to do this in a reasonable time. The higher event rates in a larger array will also improve the chances of correlating our neutrino events with observations by the new generation of high-energy gamma-ray telescopes and gravitational wave detectors, together charting the non-thermal universe.

    F: The larger samples of high-energy neutrinos with improved angular resolution and energy measurement will give us a detailed understanding of the source distribution. This sample will reveal an unobstructed view of the universe at energies at PeV and above. Those are unexplored wavelengths where most of the universe is opaque to high-energy photons. As Olga was mentioning, the operation of IceCube-Gen2 in coincidence with other telescopes and detectors will present totally novel opportunities for multimessenger astronomy and multiwavelength follow-up campaigns to obtain a truly complete picture of astrophysical sources.

    + Info IceCube-Gen2: A Vision for the Future of Neutrino Astronomy in Antarctica, IceCube Collaboration: M.G. Aartsen et al. arxiv.org/abs/1412.5106

    This white paper presents early studies toward a next-generation IceCube detector with the aim of instrumenting a 10 km3 volume of clear glacial ice at the South Pole and delivering an order of magnitude increase in astrophysical neutrino samples of all flavors.

    Read also a short description of IceCube-Gen2 on the IceCube w

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ICECUBE neutrino detector
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 1:16 pm on December 17, 2014 Permalink | Reply
    Tags: , , Neutrinos,   

    From FNAL: “Gaining support for new long-baseline neutrino experiment at Fermilab” 

    FNAL Home


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

    Wednesday, Dec. 17, 2014
    Rob Roser

    i
    Jim Strait, project director for Fermilab’s proposed long-baseline neutrino experiment, answers a question at the Dec. 12 meeting to form a new collaboration at Fermilab. Photo: Reidar Hahn

    On Dec. 5 and 12, many of the world’s neutrino scientists gathered at CERN and Fermilab, respectively, to learn about the newly proposed next-generation long-baseline neutrino oscillation experiment. These meetings were established to discuss a new letter of intent (LOI) for the experiment.

    m
    More than 150 people attended the collaboration-forming meeting at Fermilab on Dec. 12. Photo: Reidar Hahn

    The LOI, which is currently signed by more than 350 scientists from more than 100 institutions around the world, leverages the Fermilab neutrino facility to undertake an experiment at Sanford Underground Research Facility in South Dakota.

    Sanford Underground Research Facility Interior
    Sanford

    The two meetings were designed to be identical in content. Fermilab Director Nigel Lockyer kicked off both meetings with a historical overview as well as a high-level plan forward. Jim Strait, project director for the proposed long-baseline neutrino experiment, discussed the Fermilab facility and what is being offered. ICFA Neutrino Panel Chair Ken Long and I presented the LOI in our role to bring the world’s long-baseline neutrino community together, and Fermilab Deputy Director Joe Lykken summarized the current discussions on the international governance process. Lively panel discussions followed, giving attendees a chance to interact with the LOI authors and learn more about the proposal. Copies of the talks are online.

    People can find the current draft of the LOI and sign it from the website. The deadline to sign it prior to its presentation to the PAC[?] is Jan. 11, 2015.

    The next step in the formation of this new international collaboration is its first meeting, to be held at Fermilab from Jan. 22-23. It is open to anyone who is interested in joining this new scientific endeavor. Sergio Bertolucci, CERN director of research and the interim Institutional Board chair for the collaboration, has called the meeting and will announce the agenda in the coming weeks.

    See the full article here.

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    STEM Icon

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    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.

     
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