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
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