Apr. 4, KEK JHF-SK neutrino workshop 1 e appearance search Yoshihisa OBAYASHI (KEK - IPNS)
Apr. 4, 2001JHF-SK neutrino KEK2 Three Active Neutrino & Mass Degeneration Scenario : m 2 12 << m 2 13 ~ m 2 23 Present Limit: sin 2 2 13 <10 m 2 ~3x10 -3 eV 2 Obtained by CHOOZ (PALO VERDE) experiment Neutrino Beam is Essentially Pure ( : e e appearance search = small 13 search to e oscillation search ~0.5 from SK Atm.
Apr. 4, 2001JHF-SK neutrino KEK3 Appearance Signal e C.C. interaction Single Fussy Ring Cherenkov Angle ~ 42 o e e +- shower
Apr. 4, 2001JHF-SK neutrino KEK4 BG(1): C.C. interaction Sharp Ring Edge Cherenkov Angle < 42 o easy to reject
Apr. 4, 2001JHF-SK neutrino KEK5 →2 : 2 Shower Rings 2 rings overlap A ring is too weak Not Reproduce E BG(2): N.C. 0 production → 2 showers Single Ring
Apr. 4, 2001JHF-SK neutrino KEK6 0 production Sudden raise from E ~500MeV (w/ 0 )/ (total) E (GeV)
Apr. 4, 2001JHF-SK neutrino KEK7 e selection SK Atm official selection (single-ring e-like): Fully Contained (No Anti-counter Activity) Only one ring is reconstructed PID likelihood is e-like (Showering) No Muon Decay Electron Evis > 100MeV OAB 2 o C.C. N.C.Beam e Osc ’ d e Generated ring e-like red. eff.0.1%6.1%23.4%67.5% m 2 =3x10 -3 eV 2, sin 2 2 e=0.05 Too Much!
Apr. 4, 2001JHF-SK neutrino KEK8 Tight e/ 0 separation 0 BG tend to have a forward peak cos e : Large for BG 2 nd ring for the signal is fake E( 2 )/E( 1 + 2 ): Large for BG Likelihood diff. between 1-ring and 2-rings Invariant mass
Apr. 4, 2001JHF-SK neutrino KEK9 e/ 0 separation efficiency OAB 2 o C.C. N.C.Beam e Osc ’ d e Generated ring e-like red. eff.0.1%6.1%23.4%67.5% e/ 0 sep red.eff.0.03%0.6%7.5%50.4% m 2 =3x10 -3 eV 2, sin 2 2 e=0.05
Apr. 4, 2001JHF-SK neutrino KEK10 0 contamination Black: Single-ring e-like ~2% Green: Standard 0 rejection~0.2% Red: More tight 0 rejection~0.1% E (GeV) Eff. Identified as e
Apr. 4, 2001JHF-SK neutrino KEK11 BG(3): C.C. +N e could be a source of BG Energy threshold > 3 GeV Negligibly small
Apr. 4, 2001JHF-SK neutrino KEK12 Expected Signal & BG distribution Reconstruct E as Quasi-Elastic interaction Apply Energy Cut 0.4GeV< E <1.2GeV (OAB2 o ) OAB2 o 5year
Apr. 4, 2001JHF-SK neutrino KEK13 Sensitivity for Mixing Angle sin 2 2 e sensitivity
Apr. 4, 2001JHF-SK neutrino KEK14 Sensitivities Sensitive down to sin 2 2 e >3x10 m 2 =3x10 -3 eV 2 By tuning E, sensitive down to sin 2 2 e >5x10 -3 in all allowed m 2 atm sin 2 2 13 >1x10 -2
Apr. 4, 2001JHF-SK neutrino KEK15 Sensitivities (2)
Apr. 4, 2001JHF-SK neutrino KEK16 Comparison to Other Projects MINOS: Too high E CC→ →e may be a serious BG OPERA(,ICARUS) Target physics is different ( app.) Much more high E Small Far Detector
Apr. 4, 2001JHF-SK neutrino KEK17 Summary ~1 GeV neutrino beam + SK(Water Cherenkov) seems to be a best solution to search: 0.01 < sin 2 2 13 < m 2 atm. Expected sensitivity: sin 2 2 13 ~ 90%C.L. JHFnu-SK has much higher sensitivity for e appearance search than MINOS and OPERA.