Using Reactor Neutrinos to Study Neutrino Oscillations Jonathan Link Columbia University

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Using Reactor Neutrinos to Study Neutrino Oscillations Jonathan Link Columbia University Heavy Quarks and Leptons 2004 June 1, 2004. Doing Physics With Reactors Neutrinos - PowerPoint PPT Presentation

Transcript of Using Reactor Neutrinos to Study Neutrino Oscillations Jonathan Link Columbia University

  • Using Reactor Neutrinos to Study Neutrino Oscillations

    Jonathan LinkColumbia University

    Heavy Quarks and Leptons 2004 June 1, 2004

  • Doing Physics With Reactors NeutrinosThe original Neutrino discovery experiment, by Reines and Cowan, used reactor neutrinosReines and Cowan at the Savannah River Reactoractually anti-neutrinos. The e interacts with a free proton via inverse -decay:Later the neutron captures giving a coincidence signal. Reines and Cowan used cadmium to capture the neutrons.The first successful neutrino detector

  • Minimum energy for the primary signal is 1.022 MeV from e+e annihilation at process threshold. Two part coincidence signal is crucial for background reduction.Nuclear Reactors as a Neutrino SourceArbitraryFlux Cross SectionObservable n Spectrum The observable ne spectrum is the product of the flux and the cross section. The spectrum peaks around ~3.6 MeV. Visible positron energy implies energy

    From Bemporad, Gratta and Vogel Nuclear reactors are a very intense sources of e deriving from the b-decay of the neutron-rich fission fragments. A typical commercial reactor, with 3 GW thermal power, produces 61020 ne/sE = Ee + 0.8 MeV ( =mn-mp+me-1.022)

  • Uses of Reactor Neutrinos Measure cross sections or observe new processes (e.g. neutral current nuclear coherent scattering) Search for anomalous neutrino electric dipole moment Measure the weak mixing angle, sin2W Monitor reactor core (non-proliferation application) Measure neutrino oscillation parameters (m2s and mixing angles)

  • Observations of Neutrino Oscillationsm23 to 310-2 eV2??m22.510-3 eV223 & 13m27.510-5 eV212Short Baseline: 10 to 100 meters Bugey, Gosgen & Krasnoyarsk

    Medium Baseline: 1 to 2 km Chooz, Palo Verde & futureLong Baseline: 100+ km KamLANDReactor neutrinos can probe oscillations in all three observed m2 regions.Oscillations are observed as a deficit of e with respect to expectation.

  • Short Baseline Oscillation SearchesReactorExcludedExperiments like Bugey rule out the low m2, large mixing angle region of the LSND signal.Bugey looked for evidence of oscillations between 15 & 45 meters. Gosgen was closer and Krasnoyarsk farther away.Neutrons capture on LithiumThe Bugey Detector

  • Observations of Neutrino Oscillationsm23 to 310-2 eV2??m22.510-3 eV223 & 13m27.510-5 eV212Short Baseline: 10 to 100 meters Bugey, Gosgen & Krasnoyarsk

    Medium Baseline: 1 to 2 km Chooz, Palo Verde & futureLong Baseline: 100+ km KamLANDReactor neutrinos can probe oscillations in all three observed m2 regions.Oscillations are observed as a deficit of e with respect to expectation.

  • Medium Baseline Oscillation SearchesChooz Nuclear Reactors, FranceExperiments like Chooz looked for oscillations in the atmospheric m2. At the time they ran the atmospheric parameters were determined by Kamiokande, not Super-K (larger m2). Gadolinium loaded liquid scintillating target.1050 m baseline

  • sin22q13< 0.18 at 90% CL (at Dm2=2.010-3) Future experiments should try to improve on these limits by at least an order of magnitude.Down to sin22q13 0.01In other words, a measurement to better than 1% is needed! No evidence found for ne oscillation. This null result eliminated nmne as the primary mechanism for the Super-K atmospheric deficit.Medium Baseline Oscillation Searches

  • Observations of Neutrino Oscillationsm23 to 310-2 eV2??m22.510-3 eV223 & 13m27.510-5 eV212Short Baseline: 10 to 100 meters Bugey, Gosgen & Krasnoyarsk

    Medium Baseline: 1 to 2 km Chooz, Palo Verde & futureLong Baseline: 100+ km KamLANDReactor neutrinos can probe oscillations in all three observed m2 regions.Oscillations are observed as a deficit of e with respect to expectation.

  • Long Baseline OscillationsThe KamLAND experiment uses neutrinos from 69 reactors to measure the solar mixing angle (12) at an average baseline of 180 km.Neutron Capture on Hydrogen results in a 2.2 MeV gammaScatter plot of energies for the prompt and delayed signalsIn 145 days of running they saw 54 events where 86.85.6 events where expected.The fit energy confirms the oscillation hypothesis.

  • Long Baseline OscillationsEliminates all but the large mixing angle (LMA) solution. The best fit sin2212= 0.91The best fit m2 = 6.910-5 eV2KamLAND ResultsThe m2 sensitivity comes primarily from the solar measurements

  • Future Experiments to Search for a Non-zero Value of sin2213

    Subject of a lot of interest because of it relevance to lepton CP violation and neutrino mass hierarchy.See Whitepaper: hep-ex/0402041

  • DistanceProbability e1.0E 8 MeV 1200 to 1800 metersSin2213 Reactor Experiment BasicsUnoscillated flux observed hereWell understood, isotropic source of electron anti-neutrinosOscillations observed as a deficit of eSurvival Probability

  • Proposed Sites Around the WorldStatus

    SitePower(GWthermal)BaselineNear/Far (m)ShieldingNear/Far (mwe)Sensitivity90% CLKrasnoyarsk, Russia1.6115/1000600/6000.03Kashiwazaki, Japan24300/1300150/2500.02Double Chooz, France8.9150/105030/3000.03Diablo Canyon, CA6.7400/170050/7000.01Angra, Brazil5.9500/135050/5000.02Braidwood, IL7.2200/1700450/4500.01Daya Bay, China11.5250/2100250/11000.01

    Krasnoyarsk, Russia1.6115/1000600/6000.03

    Kashiwazaki, Japan24300/1300150/2500.02

    Double Chooz, France8.9150/105030/3000.03

    Diablo Canyon, CA6.7400/170050/7000.01

    Angra, Brazil5.9500/135050/5000.02

    Braidwood, IL7.2200/1700450/4500.01

    Daya Bay, China11.5250/2100250/11000.01

  • The combination of these two plus a complex analysis gives you the anti-neutrino fluxWhat is the Right Way to Design the Experiment?Start with the dominate systematic errors from previous experiments and work backwardsCHOOZ Systematic Errors, NormalizationNear DetectorCHOOZ Background Error BG rate 0.9% Statistics may also be a limiting factor in the sensitivity.Identical Near and Far DetectorsMovable Detectors, Source Calibrations, etc.Muon Veto and Neutron Shield (MVNS)

  • BackgroundsThere are two types of background Uncorrelated Two random events that occur close together in space and time and mimic the parts of the coincidence. This BG rate can be estimated by measuring the singles rates, or by switching the order of the coincidence events. Correlated One event that mimics both parts of the coincidence signal. These may be caused fast neutrons (from cosmic ms) that strike a proton in the scintillator. The recoiling proton mimics the e+ and the neutron captures. Or they may be cause by muon produced isotopes like 9Li and 8He which sometimes decay to +n.Estimating the correlated rate is much more difficult!

  • Go as deep at you can (300 mwe 0.2 BG/ton/day at CHOOZ)Reducing BackgroundVeto ms and shield neutrons (Big effective depth)Measure the recoil proton energy and extrapolate into the signal region. (Understand the BG that gets through and subtract it)6 metersShielding

  • Isotope Production by MuonsA second veto after every muon that deposits more that 2 GeV in the detector should eliminate 70 to 80% of all correlated decays.The vetoed sample can be used to make a background subtraction of in a fit to the energy spectrum.

    Source300 mwe (/ton/day)450 mwe (/ton/day)Comments:9Li+8He0.17 0.030.075 0.014E 13.6 MeV, = 0.12 to 0.18 s16% to 50% correlated +n 8Li0.28 0.110.13 0.05E 16 MeV, = 0.84 s 6He1.1 0.20.50 0.07E 3.5 MeV, = 0.81 s11C63 928 4E 0.96 MeV, = 20 m10C8.0 1.53.6 0.6E 1.98 MeV, = 19 s9C0.34 0.110.15 0.05E 16 MeV, = 0.13 s8B0.50 0.120.22 0.05E 13.7 MeV, = 0.77 s7Be16.0 2.67.2 1.1E 478 keV, = 0.53 d12B113E 13.4 MeV, = 0.02 s

  • Movable Detector ScenarioThe far detector spends about 10% of the run at the near site where the relative normalization of the two detectors is measured head-to-head. Build in all the calibration tools needed for a fixed detector system and verify them against the head-to-head calibration.1500 to 1800 meters

  • Reactor Sensitivity Sensitivity to sin2213 0.01 at 90% CL is achievable. Combining with off-axis some of the CP phase, , range can be ruled out. Unexpected results are possible & might break the standard model.

  • Is the mixing angle 23 is not exactly 45 then sin223 has a two-fold degeneracy.Combining reactor results with off-axis breaks this degeneracy.With the 0.03 precision of the Double Chooz experiment the degeneracy is not broken.Reactor Sensitivity

  • 20032004200520062007200820092010Run2011Aggressive Experiment TimelineConstructionYears1 year 2 years 2 years 3 years (initially)Site Selection: Currently underway.The early work on a proposal is currently underway.With movable detectors, the detectors are constructed in parallel with the civil constructionRun Phase: Initially planned as a three year run. Results or events may motivate a longer run.Site SelectionProposal

  • Conclusions and Prospects Reactor neutrinos are relevant to oscillations in all observed m2 regions. The KamLAND experiment has been crucial to resolving the oscillation parameters in the solar m2 region. There are many ideas for reactor 13 experiments around the world and it is likely that more than one will go forward. Controlling the systematic errors is the key to making this measurement. With a 3+ year run, the sensitivity in sin22q13 should reach 0.01 (90% CL) at Dm2 = 2.010-3. Reactor sensitivities are similar off-axis and the two methods are complementary. The physics of reactor neutrinos is interesting and important.

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