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Searching for Lepton Flavor Violation and Other Rare Decays at BES Guoliang Tong

Searching for Lepton Flavor Violation and Other Rare Decays at BES Guoliang Tong ( BES Collaboration) IHEP CAS, Beijing China E-mail: tonggl@mail.ihep.ac.cn 32rd International Conference on High Energy Physics Beijing, August 16 – 22, 2004. Outline. Introduction. Experimental status.

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Searching for Lepton Flavor Violation and Other Rare Decays at BES Guoliang Tong

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  1. Searching for Lepton Flavor Violation and Other Rare Decays at BES Guoliang Tong ( BES Collaboration) IHEP CAS, Beijing ChinaE-mail: tonggl@mail.ihep.ac.cn • 32rd International Conference on High Energy Physics • Beijing, August 16 – 22, 2004 ICHEP04,Beijing,August 17,2004

  2. Outline ICHEP04,Beijing,August 17,2004

  3. Introduction ICHEP04,Beijing,August 17,2004

  4. Experimental status ICHEP04,Beijing,August 17,2004

  5. Theoretical limits and predictions for LFVD on BR ICHEP04,Beijing,August 17,2004

  6. The Beijing Electron Positron Collider L ~ 51030 /cm2s at J/ peak Ecm~2-5 GeV ICHEP04,Beijing,August 17,2004

  7. 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 ICHEP04,Beijing,August 17,2004

  8. World J/ and (2S) Samples (×106) J/ (2S) BESII 58M J/ BESII 14M (2S) 14M 3.0M ICHEP04,Beijing,August 17,2004

  9. 2. Search for J/ e μ, μ τ , e τ Event selection 2.1 J/ e m • For charged tracks: • mfit=2 or –19 •|cos| < 0.8 • •θ12>178.5° the angle between two charged tracks θ12 ICHEP04,Beijing,August 17,2004

  10. J/ e m 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 ICHEP04,Beijing,August 17,2004

  11. J/ e m • particle identification - identify e: E/P>0.7, μhit=0 - identify μ: E/P<0.3, μhit pass Pxy cuts , Pxy -transverse momentum. Cuts for isolated photon are we need no isolated photon. E/P of electron and μ(data) ICHEP04,Beijing,August 17,2004

  12. J/ e m Survivals events ICHEP04,Beijing,August 17,2004

  13. J/ e m 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 ICHEP04,Beijing,August 17,2004

  14. 2.2 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) ICHEP04,Beijing,August 17,2004

  15. J/ mt,et 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 ICHEP04,Beijing,August 17,2004

  16. 2 σ regions from MC J/ mt candidate J/ et candidate J/ mt,et • Background event is0forJ/tomt . • Background event is0.4forJ/toet . which is fromJ/to K*K. ICHEP04,Beijing,August 17,2004

  17. J/ mt,et ( ) ( ) Upper Limits (@ 90% C.L.) Paper has been accepted by PLB(hep-ex/0406018) ICHEP04,Beijing,August 17,2004

  18. J/ e μ, e τ , μ τ • The results of three decay modes: ICHEP04,Beijing,August 17,2004

  19. 3. Search for’, J/ KS KS • Events selection • 4 good charged tracks • Q(sum) = 0 • |cos| < 0.8 • KS decay length Lxy > 3 mm • |M - MKS| < 2 σM • CP violating process • Test EPR paradox • (Einstein-Podolsky-Rosen) • MarkIII: 2.7M J/ • B(J/ KS KS)< 5.210-6 • (@90% C.L.) • BESII: 58M J/ • 14M ’ ICHEP04,Beijing,August 17,2004

  20. ’, J/ KS KS 2 circles – 1 σ & 2 σ regions from MC 1 evt in 2 σ region 1 evt in 2 σ region bkg=0.7 ± 0.3 eff=20% bkg=1.0 ± 0.4 eff=21% J/ KS KS candidate ’  KS KS candidate ICHEP04,Beijing,August 17,2004

  21. ’, J/ KS KS Upper Limits (@95% C.L.) • 1st upper limit for B(’  KS KS ). • Higher sensitivity for B(J/ KS KS) upper limit. • Sensitivity insufficient for testing EPR paradox and CP violation. The expectations on the CP violation in KS KS is at 10-9 level for both J/ and ’ , and that for EPR is at 10-8 level by some theories. ICHEP04,Beijing,August 17,2004 PLB 589, 7 (2004)

  22. J/ KS KS Most like ’ Most like J/ and with an isolated photon(126MeV)  KS KS And • Event Display Ecm=3.097GeV Ecm=3.686GeV ’ KS KS ICHEP04,Beijing,August 17,2004

  23. 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.) • CP Violation search:the upper limit for Br( KS KS ) < 1.0 10-6 and B(’ KS KS ) < 4.6 10-6 (@ 95%C.L.) ICHEP04,Beijing,August 17,2004

  24. Prospect BES III with 1010J/Ψ events and 3109Ψ(2S) 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. 谢谢！ Thank you ! ICHEP04,Beijing,August 17,2004

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