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Searching for Lepton Flavor Violation Decays J/   e μ, μ τ , e τ at BES Guoliang Tong

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

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  1. 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

  2. Outline Tau04,Nara,Septemper 16,2004

  3. Introduction Tau04,Nara,Septemper 16,2004

  4. Experimental status Tau04,Nara,Septemper 16,2004

  5. Theoretical limits and predictions for LFVD on BR Tau04,Nara,Septemper 16,2004

  6. The Beijing Electron Positron Collider L ~ 51030 /cm2s at J/ peak Ecm~2-5 GeV 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. 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 Tau04,Nara,Septemper 16,2004

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. J/ e m (con’t) With data sample. E/P of electron and μ(data) Tau04,Nara,Septemper 16,2004

  15. J/ e m (con’t) Tau04,Nara,Septemper 16,2004

  16. J/ e m (con’t) Survivals events Tau04,Nara,Septemper 16,2004

  17. 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)/[NTJ/e] PLB 561(2003)49-54 Tau04,Nara,Septemper 16,2004

  18. 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

  19. 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= ii 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+En2) where En= Un0-1 Tau04,Nara,Septemper 16,2004

  20. 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

  21. J/ mt,et (con’t) J/ mt J/et Tau04,Nara,Septemper 16,2004

  22. 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

  23. J/ e μ, μ τ, e τ • The results of three decay modes: Tau04,Nara,Septemper 16,2004

  24. 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) < 1.110-6 ; Br(J/Ψ→) < 2.010-6 ; Br(J/Ψ→e) < 8.310-6 (@ 90%C.L.) • Prospect BEPCII/BESIII Project is making good progress Nov. 2006: commissioning detector/machine Tau04,Nara,Septemper 16,2004

  25. BEPCII/BESIII Project Two rings Tau04,Nara,Septemper 16,2004

  26. BESIII Detector BESIII Main Parameters 工 Tau04,Nara,Septemper 16,2004

  27. Comparison between BESIII and BESII Tau04,Nara,Septemper 16,2004

  28. 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

  29. Expected Number of Events in One Year’s Running With such a data sample, a precise measurements are expected Tau04,Nara,Septemper 16,2004

  30. 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

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