ne appearance search

1
ne appearance search

• Yoshihisa OBAYASHI
• (KEK - IPNS)

2
nm to ne oscillation search

• Three Active Neutrino Mass Degeneration
  Scenario (Dm212ltltDm213Dm223)
• Present Limit sin22q13gt10-1_at_Dm23x10-3eV2
• Obtained by CHOOZ (PALO VERDE) experiment
• Neutrino Beam is Essentially Pure nm
• (nm ne1000.2_at_peak)
• Optimum neutrino energy below 1GeV

3
Appearance Signal

• 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
4
BG(1) nm C.C. interaction

• Sharp Ring Edge
• Cherenkov Angle lt 42o
• Good PID (atm. n study)
• Easy to reject

nm
m
5
BG(2) N.C. p0 production

• p0?2g
• If 2 rings overlap or A ring is too weak
• single ring like
• Not Reproduce En

n
n
p0?2g
2 showers
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 gt 100MeV
• No Muon Decay Electron

Dm23x10-3eV2, sin22qme0.05
Number of events for JHF(0.77MW) 5yr exposure to
Super-Kamiokande(22.5kt)
nmC.C. nmN.C. Beam ne Oscd ne
Generated 10713.6 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!

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(g1g2) Large for BG
• Likelihood diff. between 1-ring and 2-rings
• Invariant mass Small for ne

8
Expected Backgrounds Signal
Dm23x10-3eV2, sin22qme0.05
Number of events for JHF(0.77MW) 5yr exposure to
Super-Kamiokande(22.5kt)
nmC.C. nmN.C. Beam ne Oscd ne
Generated 10713.6 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
.4ltEnlt1.2 1.8 9.3 11.1 123.2
red.eff. 0.02 0.2 3.8 40.8
9
Expected Signal BG distribution

• Reconstruct En as Quasi-Elastic interaction
• Apply Energy Cut
• 0.4GeVlt E lt1.2GeV (OAB2o)

OAB2o 5year
10
Sensitivity for Mixing Angle
sin22qme sensitivity
11
Sensitivities

• Sensitive down to sin22qme3x10-3
  _at_Dm23x10-3eV2
• By tuning En, sensitive down to sin22qme5x10-3
  in all allowed Dm2atm
• sin22q131x10-2 _at_90 C.L.

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

13
Summary

• 1 GeV neutrino beam SK(Water Cherenkov) is a
  good solution to search
• 0.01 lt sin22q13 lt 0.1 _at_ Dm2atm.
• Expected sensitivity
• sin22q13 0.01 _at_ 90C.L.
• ne appearance sensitivity of JHFnuSK is higher
  than MINOS, OPERA.