1. Apr. 4, 2001 @ KEK JHF-SK neutrino workshop 1 e appearance search Yoshihisa OBAYASHI (KEK - IPNS)

2. Apr. 4, 2001JHF-SK neutrino workshop @ KEK2 Three Active Neutrino & Mass Degeneration Scenario :  m 2 12 <<  m 2 13 ~  m 2 23 Present Limit: sin 2 2  13 <10 -1 @  m 2 ~3x10 -3 eV 2 Obtained by CHOOZ (PALO VERDE) experiment Neutrino Beam is Essentially Pure  (  : e ~100:0.2@peak) e appearance search = small  13 search  to e oscillation search  ~0.5 from SK Atm.

3. Apr. 4, 2001JHF-SK neutrino workshop @ KEK3 Appearance Signal e C.C. interaction Single Fussy Ring Cherenkov Angle ~ 42 o e e +- shower

4. Apr. 4, 2001JHF-SK neutrino workshop @ KEK4 BG(1):  C.C. interaction Sharp Ring Edge Cherenkov Angle < 42 o    easy to reject

5. Apr. 4, 2001JHF-SK neutrino workshop @ 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

6. Apr. 4, 2001JHF-SK neutrino workshop @ KEK6  0 production Sudden raise from E ~500MeV  (w/  0 )/  (total) E (GeV)

7. Apr. 4, 2001JHF-SK neutrino workshop @ 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 Generated10713.64080.3292.1301.6 1ring e-like14.3247.168.4203.7 red. eff.0.1%6.1%23.4%67.5%  m 2 =3x10 -3 eV 2, sin 2 2  e=0.05  Too Much!

8. Apr. 4, 2001JHF-SK neutrino workshop @ 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

9. Apr. 4, 2001JHF-SK neutrino workshop @ KEK9 e/  0 separation efficiency OAB 2 o  C.C.  N.C.Beam e Osc ’ d e Generated10713.64080.3292.1301.6 1ring e-like14.3247.168.4203.7 red. eff.0.1%6.1%23.4%67.5% e/  0 sep. 3.523.021.9152.2 red.eff.0.03%0.6%7.5%50.4%  m 2 =3x10 -3 eV 2, sin 2 2  e=0.05

10. Apr. 4, 2001JHF-SK neutrino workshop @ 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

11. Apr. 4, 2001JHF-SK neutrino workshop @ KEK11 BG(3):  C.C.   +N  e could be a source of BG Energy threshold > 3 GeV  Negligibly small

12. Apr. 4, 2001JHF-SK neutrino workshop @ KEK12 Expected Signal & BG distribution Reconstruct E as Quasi-Elastic interaction Apply Energy Cut 0.4GeV< E <1.2GeV (OAB2 o ) OAB2 o 5year

13. Apr. 4, 2001JHF-SK neutrino workshop @ KEK13 Sensitivity for Mixing Angle sin 2 2   e sensitivity

14. Apr. 4, 2001JHF-SK neutrino workshop @ KEK14 Sensitivities Sensitive down to sin 2 2   e >3x10 -3 @  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

15. Apr. 4, 2001JHF-SK neutrino workshop @ KEK15 Sensitivities (2)

16. Apr. 4, 2001JHF-SK neutrino workshop @ 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

17. Apr. 4, 2001JHF-SK neutrino workshop @ KEK17 Summary ~1 GeV neutrino beam + SK(Water Cherenkov) seems to be a best solution to search: 0.01 < sin 2 2  13 < 0.1 @  m 2 atm. Expected sensitivity: sin 2 2  13 ~ 0.01 @ 90%C.L. JHFnu-SK has much higher sensitivity for e appearance search than MINOS and OPERA.