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 ~ 45°sin 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 = 3×10 -3 eV 2  cal relative near/far energy calibration  norm relative near/far normalization Scenarios: Reactor I = 12ton×7GW×5yrs Reactor II = 250ton×7GW×5yrs

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; world’s 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 OpérateurEDF ? Chooz, 2x10 tonnes, D1=0.7 km, D2=1.1 km, 3 ans (70 kevts)  sin2(2  13)<0.037 Positive signs from EDF for reusing the former CHOOZ site. Near site  civil engineering 2x11.5 tons, D1= m, D2=1050m. Sensitivity: 3 years  sin 2 (2  13 ) < ~0.03

CHOOZ-Far

CHOOZ-Far detector 7 m 3.5 m Existing CHOOZ tub

CHOOZ-Near new Laboratory ~5- 15 m High-Z material ~10-15 m

U.S. Nuclear Power Plants

Braidwood, Illinois 7.17 GW 24 miles SW of Joliet

Braidwood site

Powerful: Two reactors ( GW E th ) Overburden: Horizontal tunnel could give 800 mwe shielding Infrastructure: Construction roads. Controlled access. Close to wineries. Diablo Canyon Nuclear Power Plant 1500 ft 2 underground detectors

We’ve formed a small collaboration to develop a proposal for a midwest site: Chicago, Columbia, ANL, FNAL, Kansas, Michigan, Oxford, Texas Chicago involvement: Kelby Anderson, Ed Blucher, Juan Collar, Jim Pilcher, Matt Worcester (postdoc), Erin Abouzaid (grad), Abby Kaboth (undergrad), Jennifer Seger (undergrad) Significant effort also underway at LBNL to investigate feasibility of experiment at Diablo Canyon.

Conclusions Extremely exciting time for neutrino physics! The possibility of observing CP violation in the neutrino sector presents a great experimental challenge. Reactor and accelerator experiments are complementary. Reactor experiment has potential to be faster, cheaper, and better for establishing value of  .

Was baryogenesis made possible by leptonic CP violation? Leptogenesis may have been the result of direct CP violation in decays of heavy Majorana particles: This antilepton excess in converted to a baryon excess through nonperturbative Standard Model B-L conserving processes. - Fukugita and Yanagida, Phys. Lett. B174 (1986)