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Searching for Lepton Flavor Violation Decays J/ e μ, μ τ , e τ at BES Guoliang Tong ( BES Collaboration) IHEP CAS, Beijing China E-mail: tonggl@mail.ihep.ac.cn 8th International Workshop on Tau Lepton Physics Nara, September 14 – 17, 2004. Outline. Introduction.
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Searching for Lepton Flavor Violation Decays J/ e μ, μ τ , e τ at BES Guoliang Tong ( BES Collaboration) IHEP CAS, Beijing ChinaE-mail: tonggl@mail.ihep.ac.cn • 8th International Workshop on Tau Lepton Physics • Nara, September 14 – 17, 2004 Tau04,Nara,Septemper 16,2004
Outline Tau04,Nara,Septemper 16,2004
Introduction Tau04,Nara,Septemper 16,2004
Experimental status Tau04,Nara,Septemper 16,2004
Theoretical limits and predictions for LFVD on BR Tau04,Nara,Septemper 16,2004
The Beijing Electron Positron Collider L ~ 51030 /cm2s at J/ peak Ecm~2-5 GeV Tau04,Nara,Septemper 16,2004
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. Tau04,Nara,Septemper 16,2004
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 Tau04,Nara,Septemper 16,2004
The BES Collaboration Korea (4) Korea University Seoul National University Chonbuk National University Gyeongsang Nat. Univ. USA (4) University of Hawaii University 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 China Shandong 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. Japan (5) Nikow University Tokyo Institute of Technology Miyazaki University KEK U. Tokyo Tau04,Nara,Septemper 16,2004
World J/ and (2S) Samples (×106) (99.11-01.03) J/ (2S) (01.11-02.03) BESII 58M J/ BESII 14M (2S) 14M 3.0M Tau04,Nara,Septemper 16,2004
2. Search for J/ e μ Event selection • For charged tracks: • mfit=2 or –19 •|cos| < 0.8 • •θ12>178.5° the angle between two charged tracks θ12 Tau04,Nara,Septemper 16,2004
J/ e m (con’t) the invariant mass of electron and μ and the momenta of electron and μ ( MC) • The invariant mass of two charged tracks • The momentum of charge tracks, 1.45<P<1.65GeV/c Tau04,Nara,Septemper 16,2004
J/ e m (con’t) BES m counter: Iron a bsorber -1st layer: 120 mm (67%, solid angle) -2nd layer: 140 mm (67%) -3rd layer: 140 mm (63%) Cuts for isolated photon are we need no isolated photon. • particle identification - identify e: E/P>0.7, μhit=0 - identify μ: E/P<0.3, μhit pass Pxy cuts , Pxy -transverse momentum. E/P of electron and μ(data) Tau04,Nara,Septemper 16,2004
J/ e m (con’t) With data sample. E/P of electron and μ(data) Tau04,Nara,Septemper 16,2004
J/ e m (con’t) Tau04,Nara,Septemper 16,2004
J/ e m (con’t) Survivals events Tau04,Nara,Septemper 16,2004
J/ e m (con’t) Result • The upper limit of BR(J/e) with 58 M J/Ψ sample at BES could be got: Br < (NOB)/[NTJ/e] PLB 561(2003)49-54 Tau04,Nara,Septemper 16,2004
3. J/μ τ , e τ • Events selection • 2 good charged tracks • Q(sum) = 0 • |cos| < 0.8 • 1.0<Pm(e)<1.08GeV/c Pe(m)<1.4GeV/c • E/P>0.7 for electron Ebsc<0.3 for μ • Muonhit=3 for μ Muonhit=0 for electron (a) (b) Tau04,Nara,Septemper 16,2004
J/ mt,et (con’t) Detector efficiency μ ID efficiency in μcounter is determined from real μdata. Others are from MC simulation. Efftotal = effMC*effμID. effμID= ii here, iis the weight of events, i is the ith efficiency from μ real data sample. Systematic error Systematic error is incorporated when calculating upper limit:Un=Un0(1+En2) where En= Un0-1 Tau04,Nara,Septemper 16,2004
2 σ regions from MC J/ mt candidate J/ et candidate J/ mt,et (con’t) • Background event is0forJ/tomt . • Background event is0.4forJ/toet . which is fromJ/to K*K. Tau04,Nara,Septemper 16,2004
J/ mt,et (con’t) J/ mt J/et Tau04,Nara,Septemper 16,2004
J/ mt,et (con’t) ( ) ( ) Upper Limits (@ 90% C.L.) Paper has been accepted by PLB(hep-ex/0406018) PLB 598(2004)172-177 Tau04,Nara,Septemper 16,2004
J/ e μ, μ τ, e τ • The results of three decay modes: Tau04,Nara,Septemper 16,2004
4.Summary • No 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 Tau04,Nara,Septemper 16,2004
BEPCII/BESIII Project Two rings Tau04,Nara,Septemper 16,2004
BESIII Detector BESIII Main Parameters 工 Tau04,Nara,Septemper 16,2004
Comparison between BESIII and BESII Tau04,Nara,Septemper 16,2004
BESIII Schedule • 2-3/2005: endcap muon chamber installation • 5/2005: magnet installation • 10/2005: magnetic field mapping • 2/2006: EMC installation • 3/2006: MDC/TOF installation • 7/2006: BESIII debug and commissioning, Cosmic ray • 11/2004: supporting structure/yoke installation • 10/2006: BESIII detector in beam-line • 11/2006: commissioning detector/machine Tau04,Nara,Septemper 16,2004
Expected Number of Events in One Year’s Running With such a data sample, a precise measurements are expected Tau04,Nara,Septemper 16,2004
BES III with 1010J/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 ! Tau04,Nara,Septemper 16,2004