guoliang tongtau04,nara,septemper 16,20041 searching for lepton flavor violation decays j/ e μ,...
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Guoliang TONG Tau04,Nara,Septemper 16,2004 1
Searching for Lepton Flavor Violation Decays J/ e μ, μ τ , e τ
at BESGuoliang Tong
( BES Collaboration)
IHEP CAS, Beijing ChinaE-mail: [email protected]
8th International Workshop on Tau Lepton Physics
Nara, September 14 – 17, 2004
Guoliang TONG Tau04,Nara,Septemper 16,2004 2
Outline
1.Introduction
2.Search for LFV in
J/ e μ
3.Search for LFV in
J/ μ τ , e τ
4.Summary
Guoliang TONG Tau04,Nara,Septemper 16,2004 3
1. Introduction-In the SM of electroweak theory, the lepton flavor symmetries are conserved
-In many extensions of the SM, such as SUSY,GUT, left-right symmetric models ,lepton flavor symmetries speculated to be violated
-Some theorists predicted LFV decay branching-ratio of vector bosons(,J/,, Z0) in recent years
-Super-Kamiokande and Kamland, SNO experimental results indicate strongly m0, and mix with each others
Guoliang TONG Tau04,Nara,Septemper 16,2004 4
Experimental status
-Experimentally, no evidence for direct LFV has been
reported so far.
-Many research for LFV have been done in μ and τ
decays.
-Direct searches at the Z peak performed by the LEP
experiments yielded 95% C.L. upper limits
BR(Z e μ, e τ ,μ τ) <1.7x10-6, 9.8x10-6 and 1.2x10-5
respectively.
-J/Ψ e μ’s search was reported by BES with 58M J/
sample and U.L. BR(J/Ψ e μ )<1.1x10-6 reached (@
90%C.L.)(PLB 561(2003)49-54)
Guoliang TONG Tau04,Nara,Septemper 16,2004 5
Theoretical limits and predictions for LFVD on BR
Boson Mode
Theoretical limits
(Peccei, Nussinov and
Zhang;
PRD63 ,016003,(2001))
Theoretical Predictions
(Leptoquark model, SUSY model, Huo, Feng, Yue; PRD67,114001,(2003))
J/Ψ(1S)
μ τ
e τ
e μ
< 6x10-7
<6x10-7
<4x10-13
3.0x10-8
3.0x10-8
3.5x10-15
Υ(1S)
μ τ
e τ
e μ
< 10-2
<10-2
<2x10-9
1.3x10-7
1.3x10-7
4.1x10-12
Guoliang TONG Tau04,Nara,Septemper 16,2004 6
The Beijing Electron Positron Collider
L ~ 51030 /cm2s at J/ peak Ecm~2-5 GeV
Guoliang TONG Tau04,Nara,Septemper 16,2004 7
BEPC consists of Linac、 Storage Ring、 Detector(BES) and Synchrotron Facility(BSRF). Ground breaking in 1984, completed in 1988 within budget and according to the schedule. Soon after reached the designed performances.
Guoliang TONG Tau04,Nara,Septemper 16,2004 8
BESII Detector
VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 % = 7.9 mr B field: 0.4 T p/p=1.7%(1+p2) z = 2.3 cm
Guoliang TONG Tau04,Nara,Septemper 16,2004 9
Korea (4)
Korea University Seoul National University
Chonbuk National UniversityGyeongsang Nat. Univ.
Japan (5)
Nikow UniversityTokyo Institute of Technology
Miyazaki UniversityKEK
U. Tokyo
USA (4)
University of HawaiiUniversity of Texas at Dallas
Colorado State University Stanford Linear Accelerator Center
UK (1)Queen Mary University
China (18)IHEP of CAS
Univ. of Sci. and Tech. of ChinaShandong Univ., Zhejiang Univ.
Huazhong Normal Univ. Shanghai Jiaotong Univ.
Peking Univ., CCAST Wuhan Univ., Nankai Univ.
Henan Normal Univ.Hunan Univ., Liaoning Univ.
Tsinghua Univ., Sichuan Univ. Guangxi Univ., Guangxi Normal Univ.
Jiangsu Normal Univ.
Guoliang TONG Tau04,Nara,Septemper 16,2004 10
0
2
4
6
8
10
12
14
MKI MKII MKIII CBAL BESI BESII CLEOc
3.0M
14M
J/
0
10
20
30
40
50
60
MarkI I I DM2 BES I BES I I
(2S)
World J/ and (2S) Samples (×106)
BESII 14M
(2S)
BESII 58M J/
(99.11-01.03) (01.11-02.03)
Guoliang TONG Tau04,Nara,Septemper 16,2004 11
Event selection
For charged tracks:
• mfit=2 or –19 • |cos| < 0.8 • • θ12>178.5°
4,0,2 neuchrg NQN
cmzcmycmx 15,5.1,5.1
the angle between two charged tracks θ12
2. Search for J/ e μ
Guoliang TONG Tau04,Nara,Septemper 16,2004 12
• The invariant mass of two charged tracks
• The momentum of
charge tracks, 1.45<P<1.65GeV/c
2/25.395.2 cGeVM e
the invariant mass of electron and μ and the momenta of electron and μ ( MC)
J/ e (con’t)
Guoliang TONG Tau04,Nara,Septemper 16,2004 13
Cuts for isolated photon are
we need no isolated photon.
MeVEsc 5015c18 E/P of electron and μ (data)
• particle identification - identify e: E/P>0.7, μhit=0 - identify μ: E/P<0.3, μhit pass Pxy cuts , Pxy -transverse momentum.
J/ e (con’t)
BES counter: Iron a bsorber-1st layer: 120 mm (67%, solid angle)-2nd layer: 140 mm (67%)-3rd layer: 140 mm (63%)
Guoliang TONG Tau04,Nara,Septemper 16,2004 14
J/ e (con’t)
E/P of electron and μ (data)
With data sample.
Guoliang TONG Tau04,Nara,Septemper 16,2004 15
J/ e (con’t)
Guoliang TONG Tau04,Nara,Septemper 16,2004 16
Survivals events cuts Survivals events
Nchrg = 2 38045098
Vertical cuts and M_fit=2 or -19
16119944
Qi = 0 158788361.45 < P <1.65GeV/c 4114702
|cos| < 0.8 396314512 > 178.50 1947195
Reject cosmic ray 1843853Niso = 0 1799597
One of two track is identified as
152820
The other is identified as e 4
2.95 < Me < 3.25GeV/c2 4
J/ e (con’t)
Guoliang TONG Tau04,Nara,Septemper 16,2004 17
Result
The upper limit of BR(J/e) with 58 M
J/Ψ sample at BES could
be got:
Background,
candidates and
Upper limit
1.490.79
Total number of backgrounds
2.2
4
The upper limit
(conservatively calculated with 0 background)
1.1 10-6(90% C.L)
/J
KKJ /
eJ /
J/ e (con’t)
PLB 561(2003)49-54
Br < (NOB)/[NTJ/e]
Guoliang TONG Tau04,Nara,Septemper 16,2004 18
Events selection • 2 good charged tracks
• Q(sum) = 0
• |cos| < 0.8
• 1.0<P(e)GeV/c Pe()<1.4GeV/c
• E/P>0.7 for electron
Ebsc<0.3 for μ • Muonhit=3 for μ
Muonhit=0 for electron
3. J/ μ τ , e τ
(a)
(b)
Guoliang TONG Tau04,Nara,Septemper 16,2004 19
J/ e(con’t)
Detector efficiency μ ID efficiency in μ counter
is determined from real μ data. Others are from MC simulation. Efftotal = effMC*eff μ ID. ef
f μ ID= ii here, i is the weig
ht of events, i is the ith efficienc
y from μ real data sample.
Systematic error Systematic error is incorporat
ed when calculating upper limit: Un=Un0(1+En
2 ) where En=
Un0-1
Guoliang TONG Tau04,Nara,Septemper 16,2004 20
J/ e(con’t)
J/ candidate J/ e candidate
2 σ regions from MCBackground event is 0 for J/ to .
Background event is 0.4 for J/ to e . which is from J/ to K*K.
Guoliang TONG Tau04,Nara,Septemper 16,2004 21
J/ e(con’t)
J/
J/ e
Guoliang TONG Tau04,Nara,Septemper 16,2004 22
Upper Limits (@ 90% C.L.)J/ e(con’t)
Paper has been accepted by PLB(hep-ex/0406018)
( ) ( )
PLB 598(2004)172-177
Guoliang TONG Tau04,Nara,Septemper 16,2004 23
The results of three decay modes:
Decay mode
Nsignal Nbackground Upper limit (@90%C.L.)
J/Ψ→e 4 2 1.110-6
J/Ψ→ 0 0 2.010-6
J/Ψ→e 1 0 8.310-6
J/ e μ, μ τ, e τ
Guoliang TONG Tau04,Nara,Septemper 16,2004 24
4.SummaryNo evidence for direct LFV has been found in these searches. These searches reached new upper limits for LFV processes
Br(J/Ψ→e) < 1.110-6 ;
Br(J/Ψ→) < 2.010-6 ;
Br(J/Ψ→e) < 8.310-6
(@ 90%C.L.)
Prospect
BEPCII/BESIII Project is making good progress Nov. 2006: commissioning detector/machine
Guoliang TONG Tau04,Nara,Septemper 16,2004 25
BEPCII/BESIII Project
Two rings
Beam energy 1 – 2.1 GeV
Optimal energy 1.89 GeV
Luminosity 1 x 10 33 cm-2s-1 @ 1.89 GeV
Linac requirements Full energy injection: 1.55 1.89 GeV Positron injection rate > 50 mA/min
Dedicated SR 250 mA @ 2.5 GeV
Guoliang TONG Tau04,Nara,Septemper 16,2004 26
工工
BESIII Detector
system BES III
XY = 130 m
MDT(Drift Chamber)
P/P = 0.5 %(1 GeV)
dE/dx = 6-7 %
EMC(CsI Crystal)
E/√E = 2.5 %(1 GeV) z,= 5-6mm (1 GeV)
TOF T = 90-100 ps Barrel 110 ps endcap
counter(RP
C)
9- 8 layers
Magnet(S.C.)
1.0 tesla
BESIII Main Parameters
Guoliang TONG Tau04,Nara,Septemper 16,2004 27
Sub-system BES III BESII XY (m) = 130 250
MDC P/P (0/0) = 0.5 %(1 GeV)
2.4% (1 GeV)
dE/dx (0/0) = 6-7 % 8.5%
E.M. Calorimeter
E/√E(0/0) = 2.5 %(1 GeV)z,(cm) = 0.6cm/√E
22% (1 GeV) 3 cm /√E
ToF T (ps) = 90-100 ps barrel 110 ps endcap
180 ps barrel350 ps endcap
Counter 9- 10 layers 3 layers
Magnet 1.0 tesla 0.4 tesla
Comparison between BESIII and BESII
Guoliang TONG Tau04,Nara,Septemper 16,2004 28
BESIII Schedule
2-3/2005: endcap muon chamber installation5/2005: magnet installation10/2005: magnetic field mapping2/2006: EMC installation3/2006: MDC/TOF installation7/2006: BESIII debug and commissioning,
Cosmic ray11/2004: supporting structure/yoke installation10/2006: BESIII detector in beam-line11/2006: commissioning detector/machine
Guoliang TONG Tau04,Nara,Septemper 16,2004 29
Physics
Chann
el
C. M. Energy (GeV)
Peak Lumi. (1033cm-2s-
1)
Cross Section
(nb)
Events
per Year
J/ 3.097 0.6 ~3400 10109
3.670 1.0 ~2.4 12106
3.686 1.0 ~640 3.0109
D 3.770 1.0 ~5 25106
Ds 4.030 0.6 ~0.32 1.0106
Ds 4.140 0.6 ~0.67 2.0106
Expected Number of Events in One Year’s Running
With such a data sample, a precise measurements are expected
Guoliang TONG Tau04,Nara,Septemper 16,2004 30
BES III with 1010 J/Ψ events in one year’s running can further improve these measurements with much higher sensitivities, and may reach the level to test the prediction for some theoretical model
Thank you !