Neutrino at Daya Bay, 28 Nov 2003 KamLAND: Disappearance of Reactor Anti-neutrinos Kam-Biu Luk University of California, Berkeley and Lawrence Berkeley National Laboratory

Neutrino at Daya Bay, 28 Nov 2003 Determination of  m 12 2 and  12 LMA is favoured This region can be explored with reactor with a baseline of ~100 km ~ 100 km

Neutrino at Daya Bay, 28 Nov 2003 The KamLAND Experiment

Neutrino at Daya Bay, 28 Nov 2003 Nuclear Reactors in Japan ~80GW ~ 180 km 86% of events from ~180 km

Neutrino at Daya Bay, 28 Nov 2003 Thermal Flux from Japanese Reactors

Neutrino at Daya Bay, 28 Nov 2003    Present analysis The KamLAND Detector ~22% (3.2 kton)

Neutrino at Daya Bay, 28 Nov 2003 Detecting Reactor e in Liquid Scintillator

Neutrino at Daya Bay, 28 Nov Ge : MeV (  +  ) 65 Zn : MeV (  ) 60 Co : MeV (  +  ) AmBe : 2.20, 4.40, 7.6 MeV  -5m5m Reconstructing Position Position resolution ~ 25 cm

Neutrino at Daya Bay, 28 Nov 2003 Energy Determination  E/E ~ 7.5% /√E, Light Yield ~ 300 p.e./MeV Energy scale stable to 0.6% through out the period  E syst = 1.91% at 2.6 MeV  2.13% for e

Neutrino at Daya Bay, 28 Nov 2003 Prompt E ~ 3.2 MeV  t ~ 110  sec Delayed E ~ 2.22 MeV  R ~ 0.35 m An Anti-neutrino Candidate  time charge

Neutrino at Daya Bay, 28 Nov B 12 N  L < 3m  -Induced Neutrons & Spallation- 12 B/ 12 N

Neutrino at Daya Bay, 28 Nov 2003  V/V = 4.06 %  V fid /V fid = 4.6 % Neutron R = 5m R 3 Vertex Distributions of Neutrons & 12 B/ 12 N

Neutrino at Daya Bay, 28 Nov 2003 Radioactivity inside Liquid Scintillator

Neutrino at Daya Bay, 28 Nov 2003 Energy Spectrum of Radioactivity inside Liquid Scintillator × × ×    Requirements for reactor e detection: 238 U 232 Th ~ g/g 40 K ~ g/g

Neutrino at Daya Bay, 28 Nov 2003 Estimated Systematic Uncertainties For E prompt > 2.6 MeV 4.60 % Total LS mass2.13 Fiducial mass ratio4.06 Energy threshold2.13 Tagging efficiency2.06 Live time0.07 Reactor power2.05 Fuel composition 1.00 Time lag0.28 e spectra2.48 Cross section0.2 Total Uncertainty6.42 %

Neutrino at Daya Bay, 28 Nov 2003 Data Sample Mar. 4 – Oct. 6, tonyr (145.1 days)  Fiducial cut: R < 5m Mass = 408 ton, yielding 3.46 x free protons  Inverse  -decay selection: no OD signals E prompt > 2.6 MeV 1.8 < E delay < 2.6 MeV  R < 1.6m, 0.5 <  T < 660  sec Using AmBe & LED,  tag = (78.3  1.6)%  Software cut on Spallation event:  T  < 2sec  E  > 3 GeV or  R  < 3m e Event Selection E prompt > 2.6 MeV x 2 + y 2 (m 2 ) Z (m)

Neutrino at Daya Bay, 28 Nov 2003 Correlation Between Prompt and Delayed Energies  from n 12 C

Neutrino at Daya Bay, 28 Nov 2003 Based on 162 tonyr, with E prompt > 2.6 MeV Final sample, N obs 54 events Expected, N no 86.8  5.6(sys) events Background, N bg 0.95  0.99 event Accidental  event 9 Li/ 8 He ( , n)0.94  0.85 event fast neutron< 0.5 event Evidence for Reactor e Disappearance First Results From KamLAND =  (stat)  (sys) N obs - N bg N no

Neutrino at Daya Bay, 28 Nov 2003 Perspective of Observed Rate Deficit LMA:  m 12 2 = 5.5x10 -5 eV 2 sin 2 2   = G.Fogli et al., PR D66, , (2002) LMA flux prediction at 95% C.L. N obs /N no_osc

Neutrino at Daya Bay, 28 Nov 2003 Implication of Observed Rate Deficit Before KamLAND

Neutrino at Daya Bay, 28 Nov 2003 Energy Spectrum (E prompt > 2.6 MeV)

Neutrino at Daya Bay, 28 Nov 2003 Impact of KamLAND Results on  m 12 2 and  12 Best fit :  m 12 2 = 6.9 x eV 2 sin 2 2    = % C.L.

Neutrino at Daya Bay, 28 Nov 2003 Spring 2003 : Inspection Operation of Reactors Useful for distinguishing LMA-I from LMA-II Reduce rate by 50% but good for studying backgrounds

Neutrino at Daya Bay, 28 Nov 2003 Future Prospects With 5 years of running 95 % C.L.

Neutrino at Daya Bay, 28 Nov 2003 Based on 162 tonyr of data, KamLAND observed a deficit in the number of e events. Interpreting this observation as evidence of neutrino oscillation, it implies the LMA solution as the most viable explanation of the solar-neutrino problem. With higher statistics, we will look for spectral distortion, and measure neutrino mixing parameters with better precision. Conclusions

Neutrino at Daya Bay, 28 Nov 2003 G.A.Horton-Smith, R.D.McKeown, J.Ritter, B.Tipton, P.Vogel California Institute of Technology C.E.Lane, T.Miletic Drexel University Y-F.Wang IHEP, Beijing T.Taniguchi KEK B.E.Berger, Y-D.Chan, M.P.Decowski, D.A.Dwyer, S.J.Freedman, Y.Fu, B.K.Fujikawa, J.Goldman, K.M. Heeger, K.T.Lesko, K-B.Luk, H.Murayama, D.R.Nygren, C.E.Okada, A.W.Poon, H.M.Steiner, L.A.Winslow UC Berkeley/LBNL S.Dazeley, S.Hatakeyama, R.C.Svoboda Louisiana State University J.Detwiler, G.Gratta, N.Tolich, Y.Uchida Stanford University K.Eguchi, S.Enomoto, K.Furuno, Y.Gando, H.Ikeda, K.Ikeda, K.Inoue, K.Ishihara, T.Iwamoto, T.Kawashima, Y.Kishimoto, M.Koga, Y.Koseki, T.Maeda, T.Mitsui, M.Motoki, K.Nakajima, H.Ogawa, K.Oki, K.Owada, I.Shimizu, J.Shirai, F.Suekane, A.Suzuki, K.Tada, O.Tajima, K.Tamae, H.Watanabe Tohoku University L.DeBraeckeleer, C.Gould, H.Karwowski, D.Markoff, J.Messimore, K.Nakamura, R.Rohm, W.Tornow, A.Young TUNL J.Busenitz, Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke, E.Yakushev University of Alabama P.Gorham, J.Learned, J.Maricic, S.Matsuno, S.Pakvasa University of Hawaii B.D.Dieterle University of New Mexico M.Batygov, W.Bugg, H.Cohn, Y.Efremenko, Y.Kamyshkov, Y.Nakamura University of Tennessee The KamLAND Collaboration

Neutrino at Daya Bay, 28 Nov 2003 If neutrinos have mass, it is possible that the weak eigenstates are not the same as the mass eigenstates: PMNS (Pontecorvo-Maki-Nakagawa-Sakata) matrix Neutrino Mixing The time evolution of the flavour eigenstate is then given by:

Neutrino at Daya Bay, 28 Nov 2003 Evidence of Neutrino Oscillation Accelerator (LSND) Solar (SNO) Atmospheric (SuperK)

Neutrino at Daya Bay, 28 Nov 2003 Parametrize the mixing matrix as: The probability of e  e is: Probability of Neutrino Mixing atmospheric reactor short baseline  solar at large L/E.