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MicroBooNE Takes a Big Step Forward

      On June 23rd, the MicroBooNE neutrino detector was lowered into position at the U.S. Department of Energy's Fermi National Accelerator Laboratory. The detector consists of a 32-foot long "time projection chamber" that is readout by 3 layers of wires. Once the detector is filled with 170 tons of liquid argon, a sophisticated computer processing program will be able to create a 3-D image of neutrinos interacting with the liquid argon. The MicroBooNE team, which includes CNP's Camillo Mariani and his research group, hopes the data can be used to learn more about how neutrinos change from one flavor to another, and to help narrow the search for a possible fourth neutrino flavor, known as the sterile neutrino. The Virginia Tech group is responsible for the online monitoring of the system to ensure safe operation, and a muon veto system, according to Prof. Mariani.

The MicroBooNE time projection chamber is loaded into a tank which will be filled with 170 tons of liquid argon.

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Virginia Tech Hosts the International Neutrino Summer School

      The Center for Neutrino Physics, the Department of Physics and the College of Science hosted the International Neutrino Summer School from July 10th through July 21st, 2012. The two week school was attended by more than 70 postdoctoral and graduate students from 14 different countries. Students attended lectures given by top researches from around the world. The lectures included topics such as neutrino oscillations, neutrino mass, leptogenesis (a theory in which neutrinos may be responsible for the matter-antimatter asymmetry in the universe), neutrinos in cosmology and astrophysics, neutrino interactions, the physics of neutrino detection, and experiments with neutrinos from the upper atmosphere, accelerators, nuclear reactors and the Sun. In addition to attending lectures students worked in groups to solve problems such as designing experiments to measure critical neutrino properties.
Portrait of INSS Participants

      The International Neutrino Summer School was sponsored by the Virginia Tech College of Science, the VT Physics Department, the Center for Neutrino Physics, Fermi National Accelerator Laboratory, the US Department of Energy, the National Science Foundation, The Sanford Underground Research Facility, Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory.

Daya Bay Measures the Neutrino Mixing Parameter sin213

      In a letter submitted to the Physical Review (arXiv:1203.1669[hep-ex]), the Daya Bay Collaboration, including mebers of Virginia Tech's Center for Neutrino Physics, announces the first observation and measurement on the neutrino mixing parameter sin213. The mixing angle θ13 governs the rate of electron neutrino conversion to muon and tau neutrinos at baselines consistent with atmospheric oscillations. The hunt for theta;13 is currently the focus of several major experiments world wide, who are using either electron antineutrinos from nuclear reactors or beams of muon neutrios/anitneutrinos produced at accelerators.

      In reactor neutrino experiments such as Daya Bay, the oscillation is observed as an electron antineutrino disappearance at a distance of about 2 km from the reactor. The effect can only be measured with confidence in the comparison of detectors placed near the reactor cores – which measure the neutrino flux before significant oscillation has occured – to detectors placed farther away – at a location close to the oscillation maximum. In this way uncertainties associated with antineutrino production in the reactor, the interaction cross section in the detector, and to a lessor degree detector efficiency will cancel in the near/far detector comparison. Daya Bay Collaboration is the first to apply this technique and report results, finding:

sin213=0.092±0.016(stat.)±0.005(syst.).

The measured vs. expected signal in each detector, assuming no oscillation. Reactor and survey data are used to compute the weighted average baselines. The oscillation survival probability at the best fit value is given by the smooth curve.

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Borexino Sees First Evidence of Neutrinos from the Rare pep Solar Fusion Process

      In a recently published article (Phys.Rev.Lett. 108, 051302) the Borexino Collaboration, including members of the Virginia Tech group lead by Prof. Bruce Vogelaar, announced a first ever observation of neutrinos from the sun consistent with the rare fusion process in which two light hydrogen nuclei, or protons, combine with an electron to make a heavy hydrogen nucleus, known as a duteron, and an electron neutrino. This process know as pep fusion is about 500 times less likely than the primary pp process in which a two protons combine to to make a duteron, and electron and an electron neutrino. While neutrinos from the pp fusion process are much more common, neutrinos from the pep process have higher energies, which makes it possible for them to be seen in the Borexino detector.

      The Borexino observation is consistant with the Standard Solar Model prediction for flux of neutrinos from the pep fusion combined with the best fit model of neutrino oscillations.
See the Article in APS Spotlight

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News & Events


Camillo Mariani, of the Center for Neutrino Physics, has been named as the recipient of a prestigious CAREER Award from the National Science Foundation.
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CNP members Bruce Vogelaar and Leo Piilonen were elected fellows of the American Physical Society.
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