May 30, 2001 Yoshihisa OBAYASHI 1

e appearance search

Yoshihisa OBAYASHI(KEK - IPNS)

May 30, 2001 Yoshihisa OBAYASHI 2

Three Active Neutrino & Mass Degeneration Scenario (m2

12<<m213~m2

23)

Present Limit: sin2213>10-1@m2~3x10-3eV2

Obtained by CHOOZ (PALO VERDE) experimentNeutrino Beam is Essentially Pure

(: e~100:0.2@peak)Optimum neutrino energy: below 1GeV

1322

222

2sin5.02sin

)27.1(sin)2(sin)(

e

ee ELmP

to e oscillation search

May 30, 2001 Yoshihisa OBAYASHI 3

Appearance SignalQ.E.e C.C. interaction

No hadronNo recoiled proton ringSingle electron shower

Single Fussy RingCherenkov Angle ~ 42o

E can be reconstructed

ee+- shower

May 30, 2001 Yoshihisa OBAYASHI 4

BG(1): C.C. interactionSharp Ring EdgeCherenkov Angle < 42o

Good PID (atm. study)

Easy to reject

May 30, 2001 Yoshihisa OBAYASHI 5

→2If 2 rings overlap or

A ring is too weak

single ring likeNot Reproduce E

BG(2): N.C. 0 production

→

2 showers

May 30, 2001 Yoshihisa OBAYASHI 6

e selectionSK Atm official selection (single-ring e-like):

Fully Contained (No Anti-counter Activity)Only one ring is reconstructedPID likelihood is e-like (Showering)Evis > 100MeVNo Muon Decay Electron

C.C. N.C. Beam e Osc’d e

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%

m2=3x10-3eV2,

sin22e=0.05

We need to reject more!

Number of events for JHF(0.77MW) 5yr exposure to Super-Kamiokande(22.5kt)

May 30, 2001 Yoshihisa OBAYASHI 7

Tight e/0 separationShower direction w.r.t. beam

cose: from 0 tend to have a forward peakForce to find 2nd ring and…

E(2)/E(1+2): Large for BGLikelihood diff. between 1-ring and 2-ringsInvariant mass: Small for e

May 30, 2001 Yoshihisa OBAYASHI 8

Expected Backgrounds & Signal

C.C. N.C. Beam e Osc’d e

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/0 sep. 3.5 23.0 21.9 152.2

red.eff. 0.03% 0.6% 7.5% 50.4%

.4<E<1.2 1.8 9.3 11.1 123.2

red.eff. 0.02% 0.2% 3.8% 40.8%

m2=3x10-3eV2,

sin22e=0.05

Number of events for JHF(0.77MW) 5yr exposure to Super-Kamiokande(22.5kt)

May 30, 2001 Yoshihisa OBAYASHI 9

Expected Signal & BG distributionReconstruct E as Quasi-Elastic interactionApply Energy Cut

0.4GeV< E <1.2GeV (OAB2o)

OAB2o 5year

May 30, 2001 Yoshihisa OBAYASHI 10

Sensitivity for Mixing Anglesi

n2 2

e sen

sitiv

ity

May 30, 2001 Yoshihisa OBAYASHI 11

Sensitivities Sensitive down to sin22e~3x10-3

@m2=3x10-

3eV2

By tuning E, sensitive down to sin22e~5x10-3 in all allowed m2

atm

sin2213~1x10-2 @90% C.L.

May 30, 2001 Yoshihisa OBAYASHI 12

Comparison to Other ProjectsMINOS:

High ECC→ →e may be a serious BG

OPERA(,ICARUS)Tuned to find appearanceMore high ESmall Far Detector

JHF neutrino has highest sensitivity in e appearance search

May 30, 2001 Yoshihisa OBAYASHI 13

Summary ~1 GeV neutrino beam + SK(Water Cherenkov) is a good solution to search:

0.01 < sin2213 < 0.1 @ m2atm.

Expected sensitivity: sin2213~ 0.01 @ 90%C.L.

e appearance sensitivity of JHFnu+SK is higher than MINOS, OPERA.