Apr. 4, 2001 @ KEK

JHF-SK neutrino workshop

1

e appearance search

Yoshihisa OBAYASHI

(KEK - IPNS)

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 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) experiment

Neutrino Beam is Essentially Pure (: e~100:0.2@peak)

e appearance search = small 13 search

232

1322

22

232

132

sin2sin2sin

)27.1

(sinsin2sin)(

e

e E

LmP

to e oscillation search

~0.5 from SK Atm.

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 3

Appearance Signal

e C.C. interaction

Single Fussy Ring

Cherenkov Angle ~ 42o

e

e+- shower

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

BG(1): C.C. interactionSharp Ring Edge

Cherenkov Angle < 42o

easy to reject

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

→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, 2001 JHF-SK neutrino workshop @ KEK 6

0 productionSudden raise from E~500MeV

(w

/0 )

/(t

otal

)

E(GeV)

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 7

e selectionSK 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 > 100MeVOAB 2o 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

Too Much!

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

Tight e/0 separation0 BG tend to have a forward peak

cose: Large for BG

2nd ring for the signal is fakeE(2)/E(1+2): Large for BG

Likelihood diff. between 1-ring and 2-rings

Invariant mass

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 9

e/0 separation efficiency

OAB 2o 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%

m2=3x10-3eV2,

sin22e=0.05

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

0 contaminationBlack: Single-ring e-like ~2%

Green: Standard 0 rejection ~0.2%

Red: More tight 0 rejection ~0.1%

E(GeV)

Eff.

Iden

tifie

d as

e

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 11

BG(3): C.C. +N e could be a source of BG

Energy threshold > 3 GeV

Negligibly small

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 12

Expected Signal & BG distributionReconstruct E as Quasi-Elastic interaction

Apply Energy Cut0.4GeV< E <1.2GeV (OAB2o)

OAB2o 5year

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 13

Sensitivity for Mixing Anglesi

n22

e s

en

sitiv

ity

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 14

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

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 15

Sensitivities (2)

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

Comparison to Other ProjectsMINOS:

Too high ECC→→e may be a serious BG

OPERA(,ICARUS)Target physics is different ( app.)

Much more high ESmall Far Detector

Apr. 4, 2001 JHF-SK neutrino workshop @ KEK 17

Summary ~1 GeV neutrino beam + SK(Water Cherenkov) seems to be a best solution to search:

0.01 < sin2213 < 0.1 @ m2atm.

Expected sensitivity:

sin2213~ 0.01 @ 90%C.L.

JHFnu-SK has much higher sensitivity for e appearance search than MINOS and OPERA.