6 January 2004EFI Faculty Lunch Future Neutrino Oscillation Experiments Neutrino oscillations, CP violation, and importance of 13 Accelerator vs. reactor experiments Future reactor experiments to measure sin 2 2 13 Ed Blucher Neutrino Oscillations During last few years, oscillations among different flavors of neutrinos have been established; physics beyond the S.M. Mass eigenstates and flavor eigenstates are not the same (similar to quarks): mass eigenstates flavor eigenstates Raises many interesting questions including possibility of CP violation in neutrino oscillations. CP violation in neutrino sector could be responsible for the matter-antimatter asymmetry. MNSP matrix Quark and Neutrino Mixing Matrices 2 Flavor Neutrino Mixing The time evolution of the flavor states is: For a beam that is pure at t=0, 12 ~ 30 23 ~ 45sin 2 2 13 < 0.2 at 90% CL MNSP Matrix What is e component of 3 mass eigenstate? Minakata and Nunokawa, hep-ph/ CP Violation in Neutrino Oscillations Methods to measure sin 2 2 13 Appearance e (Accelerator Exp) Use fairly pure, accelerator produced beam with a detector at long distance (300 km km) from the source Look for the appearance of e events Use near detector to measure background e s (beam and misid) Disappearance (Reactor Exp) Use a set of reactors as a source of e 's with a detector at few km Look for a non- 1/r 2 behavior of the e rate Use near detector to measure the unoscillated flux Diablo Canyon, CA 150m 1500m overburden Accelerator and reactor measurements of 13 Accelerator experiments measure: Reactor measurement of 13 is independent of matter effects and CP violation: Reactor Measurements of Neutrino Oscillations Reactors are copious sources of per second. Detection of antineutrino by followed by or for Gd-loaded scintillator Long history of neutrino experiments at reactors Current interest is focused mainly on possibility of measuring 20 m KamLAND 6 m CHOOZ Reactor Measurements of Future: Search for small oscillations at 1-2 km distance (corresponding to Reactor experiments allow direct measurement of sin 2 2 : no matter effects, no CP violation, almost no correlation with other parameters. Sensitivity goal: sin 2 2 ~0.01. Level at which long-baseline superbeams can be used to measure mass hierarchy, CPV; ~ sensitivity goal of proposed accel. expts. Distance to reactor (m) P ee Previous Reactor Experiments CHOOZ and Palo Verde Experiments Single detector experiments Detectors used liquid scintillator with gadolinium and buffer zones for background reduction Shielding: CHOOZ: 300 mwe Palo Verde: 32 mwe Fiducial mass: CHOOZ: 5 1km, 5.7 GW ~2.2 evts/day/ton with bkg evts/day/ton ~3600 events Palo Verde: km, 11.6 GW ~7 evts/day/ton with 2.0 bkg evts/day/ton ~26000 events CHOOZ Systematic Errors CHOOZ Target: 5 ton Gd-doped scintillator Is it possible to improve the Chooz experiment by order of magnitude (i.e., sensitive to sin 2 2 ~ 0.01)? Add second detector; bigger detectors; better control of systematics. ~200 m~1500 m What systematic error is attainable? Efficiency and energy calibration strategy (movable detectors?) Backgrounds Multiple reactor cores Site / depth Choice of scintillator (stability of Gd-loaded scintillator) Size, distance of detectors Counting Experiment Compare number of events in near and far detector Energy Shape Experiment Compare energy spectrum in near and far detector Normalization and spectral information E (MeV) Predicted spectrum 13 =0 Observed spectrum sin 2 2 13 =0.04 Analysis Using Counting and Energy Spectrum (Huber et al. hep-ph/ ) Counting exp. region Spectrum & Rate region (12 ton det.)(250 ton det.) 90%CL at m 2 = 310 -3 eV 2 cal relative near/far energy calibration norm relative near/far normalization Scenarios: Reactor I = 12ton7GW5yrs Reactor II = 250ton7GW5yrs Worldwide interest in two-detector reactor experiment Workshops: Alabama, June 2003 Munich, October 2003 Niigata, Japan, March 2004 Based on early workshops, a whitepaper describing physics possibilities of reactor experiment has been written. Sites under discussion: Kraznoyarsk (Russia) Chooz (France) Kashiwazaki (Japan) Diablo Canyon (California) Braidwood, Byron (Illinois) Wolf Creek (Kansas) Brazil Taiwan China Ref: Marteyamov et al, hep-ex/ Reactor Detector locations constrained by existing infrastructure Features - underground reactor - existing infrastructure ~20000 ev/year ~1.5 x 10 6 ev/year Kr2Det: Reactor 13 Experiment at Krasnoyarsk Kashiwazaki - 7 nuclear power stations; worlds most powerful reactors - requires construction of underground shaft for detectors near far Kashiwazaki-Kariwa Nuclear Power Station Proposal for Reactor 13 Experiment in Japan near far 70 m m 6 m shaft, m depth Kashiwazaki: Proposal for Reactor 13 Experiment in Japan The Chooz site, Ardennes, France Double-CH 13 13 Z The Chooz site Near site: D~ m [severall options under study] Far site: D~1.1 km, overburden 300 mwe [former experimental hall] TypePWR Cores2 Power8.4 GW th Couplage1996/1997 (%, in to 2000) 66, 57 ConstructeurFramatome OprateurEDF ? Chooz, 2x10 tonnes, D1=0.7 km, D2=1.1 km, 3 ans (70 kevts) sin2(2 13)