1. Yoshihisa OBAYASHI (KEK - IPNS)
ne appearance search
Yoshihisa OBAYASHI
(KEK - IPNS)
May 30, 2001
Yoshihisa OBAYASHI

2. nm to ne oscillation search
Three Active Neutrino & Mass Degeneration Scenario (Dm212<<Dm213~Dm223)
Present Limit:
Obtained by CHOOZ (PALO VERDE) experiment
Neutrino Beam is Essentially Pure nm
(nm :
Optimum neutrino energy: below 1GeV
May 30, 2001
Yoshihisa OBAYASHI

3. Appearance Signal ne Q.E.ne C.C. interaction No hadron
No recoiled proton ring
Single electron shower
Single Fussy Ring
Cherenkov Angle ~ 42o
En can be reconstructed
e+- shower ne
May 30, 2001
Yoshihisa OBAYASHI

4. BG(1): nm C.C. interaction
Sharp Ring Edge
Cherenkov Angle < 42o
Good PID (atm. n study)
Easy to reject nm m
May 30, 2001
Yoshihisa OBAYASHI

5. n n p0→2g BG(2): N.C. p0 production 2 showers p0→2g Not Reproduce En
If 2 rings overlap or A ring is too weak
single ring like
Not Reproduce En n n
p0→2g
2 showers
May 30, 2001
Yoshihisa OBAYASHI

6. ne selection SK Atmn official selection (single-ring e-like):
Fully Contained (No Anti-counter Activity)
Only one ring is reconstructed
PID likelihood is e-like (Showering)
Evis > 100MeV
No Muon Decay Electron
Dm2=3x10-3eV2,
sin22qme=0.05
Number of events for JHF(0.77MW) 5yr exposure to Super-Kamiokande(22.5kt)
nmC.C.
nmN.C.
Beam ne
Osc’d ne
Generated
4080.3
292.1
301.6
1ring e-like
14.3
247.1
68.4
203.7
red. eff.
0.1%
6.1%
23.4%
67.5%
We need to reject more!
May 30, 2001
Yoshihisa OBAYASHI

7. Tight e/p0 separation Shower direction w.r.t. beam
cosqne: g from p0 tend to have a forward peak
Force to find 2nd ring and…
E(g2)/E(g1+g2): Large for BG
Likelihood diff. between 1-ring and 2-rings
Invariant mass: Small for ne
May 30, 2001
Yoshihisa OBAYASHI

8. Expected Backgrounds & Signal
Dm2=3x10-3eV2,
sin22qme=0.05
Number of events for JHF(0.77MW) 5yr exposure to Super-Kamiokande(22.5kt)
nmC.C.
nmN.C.
Beam ne
Osc’d ne
Generated
4080.3
292.1
301.6
1ring e-like
14.3
247.1
68.4
203.7
red. eff.
0.1%
6.1%
23.4%
67.5%
e/p0 sep.
3.5
23.0
21.9
152.2
red.eff.
0.03%
0.6%
7.5%
50.4%
.4<En<1.2
1.8
9.3
11.1
123.2
0.02%
0.2%
3.8%
40.8%
May 30, 2001
Yoshihisa OBAYASHI

9. Expected Signal & BG distribution
Reconstruct En as Quasi-Elastic interaction
Apply Energy Cut
0.4GeV< E <1.2GeV (OAB2o)
OAB2o 5year
May 30, 2001
Yoshihisa OBAYASHI

10. Sensitivity for Mixing Angle
sin22qme sensitivity
May 30, 2001
Yoshihisa OBAYASHI

11. Sensitivities Sensitive down to sin22qme~3x10-3 @Dm2=3x10-3eV2
By tuning En, sensitive down to sin22qme~5x10-3 in all allowed Dm2atm
C.L.
May 30, 2001
Yoshihisa OBAYASHI

12. Comparison to Other Projects
MINOS:
High En
ntCC→t→e may be a serious BG
OPERA(,ICARUS)
Tuned to find nt appearance
More high En
Small Far Detector
JHF neutrino has highest sensitivity in ne appearance search
May 30, 2001
Yoshihisa OBAYASHI

13. Summary
~1 GeV neutrino beam + SK(Water Cherenkov) is a good solution to search:
0.01 < sin22q13 < 0.1 @ Dm2atm.
Expected sensitivity:
sin22q13~ 90%C.L.
ne appearance sensitivity of JHFnu+SK is higher than MINOS, OPERA.
May 30, 2001
Yoshihisa OBAYASHI