Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 1

Decay Angular Measurement in the MEG

Experiment

Shuei YAMADAInternational Center for Elementary Particle

PhysicsUniversity of Tokyo

On behalf of the MEG collaboration

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 2

MEG Experiment towards SUSY GUT

LXe scintillation detector

Drift Chamber

Timing Counter

Compensation

CoilCOBRA Magnet

262cm

252cm

Surface beam～ 0.25x108 /sec

4 Countries, ～ 50 CollaboratorsUnder construction at PSI Start engineering run in 2005, physics run from 2006

Paul Scherrer Institut

Aim for observation of Lepton Flavor Violation: +e+with x102 ～ 3 improved sensitivity

See T.Mori’s talk for the detail:June 20, 9:30-9:55“Search for lepton flavor violation with muons”

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 3

Contents

Physics motivations+ beam MEG detector+e+signature Decay angular measurementSummary

Is MEG experiment sensitive to SUSY-GUT by measuring +e+ decay angular?

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 4

Physics Motivation

J.Hisano et al.,Phys.Lett.B391 (1997) 341

1st Phase : +e+search with sensitivity down to 4.5x10-14

Y.Kuno et al.,Phys.Rev.Lett. 77 (1996) 434

2nd Phase : angular distribution measurement to reach SUSY-GUT using polarized + beam

SU(5) SUSY-GUT

SO(10) SUSY-GUT

MSSM with R

e+ angular distribution

This talk

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 5

Muons from “Surface” of + production target + decay at rest near the surface

100% polarized + beam by nature

Surface Muon Beam

Primary Proton

+ stop

+

p29.8MeV/c100% polarized

Pspin

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 6

+ Beamline

+/e+

separator

MEGdetector

PrimaryProton

Quadruplemagnets Beam Transport

Solenoid

Bendingmagnets

Degrader

E5 area@PSI

+ Beamline

target

1st phase : 0.25x108/sec (optimal for discovery sensitivity)Capable up to 1x108/sec transport

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 7

MEG DetectorAcceptance

|cos|<0.35 ||<65deg

Liquid Xe scintillator for detector Fast & High resolution EM calorimeter

Gradient magnetic filed e+ spectrometerSee T.Mori’s talk for the detail:June 20, 9:30-9:55“Search for lepton flavor violation with muons”

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 8

+e+signature Back to Back Ee=E=52.8MeV

Backgrounds Accidental overlap

e+from Michel decayfrom radiative decay,

e+-annihilation in flight

　　　 Down to ～ 10-14

Radiative + decay　　 Down to <10-14

Signal and Background

e

e

e

?

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 9

Decay Angular Measurement

Able to reach SUSY-GUT by using + non-depolarization target such as Be, graphite

My Assumptions: + beam intensity : 1.0x108/sec beam time : 5.2x107sec (2 years) P=97% (from MEGA)

+ depolarization during transport under investigation

Measurement of depolarization needed

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 10

SUSY Model and Asymmetry

SU(5) SUSY-GUT A = +1 (AL0, AR=0)

SO(10) SUSY-GUT A 0 (ALAR)

MSSM with R A = -1 (AL=0, AR0)

Detector acceptanceY.Kuno et al.,Phys.Rev.Lett. 77 (1996) 434

dN(+e+) / dcose Ｂ (+e+)x(1+APcose)/2 A = (|AL|2-|AR|2)/(|AL|2+|AR|2)

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 11

BKG Angular Distribution

Radiative + decay N(+e+)

∝ (1+Pcose)

Detector acceptance

Y.Kuno et al.,Phys.Rev.Lett. 77 (1996) 434

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 12

e+ from Michel decay ∝ (1+Pcose)

from radiative decay ∝ (1+Pcos)

Back to back : =e- ⇒ 　 Accidental BKG ∝ (1-P

cos2e)

～ 11% suppression @ P=97%, cose=0.35

Accidental BKG suppression

Y.Kuno et al.,Phys.Rev.D 55 (1997) 2517

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 13

Angular DistributionA=+1B (+e+) =10-12

Signal

Backgrounds

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 14

2 testPoisson-distributed

2= [2(Nobs-Nexp)+Nobsloge(Nobs/Nexp)]

A=+1B(+e+) = 10-12

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 15

Sensitive region for A=+1Excluded region for each B(+e+) @ A=+1

68.3%90.0%95.4%

excluded

Allowed

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 16

Able to distinguish A=-1, 0 or +1 by 68% C.L. for B(+e+)>10-12.5

A=-1 A=+1

A=0

68% C.L. Sensitive Regions

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 17

Allowed region for A=1,B=10-12

68.3%90.0%95.4%

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 18

Summary

the MEG experiment is able to reach SUSY-GUT by measuring decay angular distribution A=-1, 0 or +1 are distinguishable for B(+e+)>10-12.5 with 2 years of full intensity beam

New experiment to search for +e+ at Paul Scherrer Insitut

Start engineering run in 2005, physics run from 2006

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 19

End of Slides

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 20

68% C.L. Sensitive Regions

Able to distinguish A=-1, 0 or +1 by 68% C.L. for B(+e+)>10-12.5

A=-1 A=+1A=0

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 21

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 22

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 23

Shuei YAMADA, ICEPP, University of Tokyo @ SUSY2004 Tsukuba, June 17-23, 2004 24

Sensitivity 4.5x10-14

N=0.25x108/sec, t=2.6x107 sec /4=0.09, e=0.90, =0.6 and sel=0.7

Ee 0.8%E 4.5 ～ 5.0%e 19mradte 230ps

FWMH resolution