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Hera-B Physics results Data of the year 2000 limited statistics 2. Commissioning:

Hera-B Physics results Data of the year 2000 limited statistics 2. Commissioning: trigger and detector not yet fully available (limited acceptance in x F ) Targets: C and Ti (partially simultaneously). General view of Hera-B. Rich. Trans. rad. det. vertex detector. ECAL. p.

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Hera-B Physics results Data of the year 2000 limited statistics 2. Commissioning:

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  1. Hera-B Physics results • Data of the year 2000 • limited statistics • 2. Commissioning: • trigger and detector not yet fully available • (limited acceptance in xF) • Targets: • Cand Ti • (partially simultaneously) -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  2. General view of Hera-B Rich Trans. rad. det. vertex detector ECAL p e target magnet (2 Tm) muon chambers (/h) inner tracker outer tracker hi-Pt tracker 20 m -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  3. Hera-B detector and trigger layout geared towards J/ : • Based on J/ e+ e- and J/ + - ; • Good vertexing through Si- m strips; • e+ ande- in ECAL; • + and- in Muondetector; • Magnetic field for charge determination. • ECAL is also fine-grain photon detector. • Not used in this part of analysis: • Rich • Inner Tracker • Trans. Rad. Detector -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  4. m+m- inv. Mass: J/ signal before cuts J/ J/ signal after cuts -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  5. e+ e-Invariant mass spectrum (| 1 - E/p| < 0.3) No J/ signal … -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  6. Bremsstrahlung recovery e+ beam e+ magnetic field ECAL -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  7. e+e-Invariant mass spectrum -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  8. e+e-Invariant mass spectrum (012) BR (12) BR (2) BR before background subtraction after background subtraction -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  9. e+e-Invariant mass spectrum with bremsstrahlung requirement Before background subtraction After background subtraction -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  10. J/ production Hera-B has large xF (and good pT ) acceptance xF xF -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  11. pT and xF distribution with e and m sample: -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  12. Comparison with other experiments: -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  13. d N(J/) Fit ansatz: = a * (1 - |xF | )c d xF c = 6.2 + 0.6 - -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  14. Energy dependence of exponent c -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  15. Energy dependence of width pT -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  16. Nuclear effects: Hera-B uses up to 8 different target wires simultaneously (in 2000: C and Ti). Most uncertainties cancel out: can easily measure nuclear exponent a as function of xF or other parameters. Important: goodaccep-tance in negative xF. (use W and C targets…) 2000 2002 -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 16a

  17. cProduction Identification of c through : D M = M(l +l -g ) - M (l +l -) uncertainty in J/ mass essentially cancels: Mc = (MJ/2 + 2Eg EJ/ – 2pgpJ/ ) dMc = dMJ/ = 0.877 dMJ/ d(Mc - MJ/ ) = -0.123 dMJ/ MJ/ Mc Nc Ratio ofJ/fromc : Rc = NJ/ * eg -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  18. DM-spectrum: cc-signal on top of combinatorial background (J/ -- g) -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  19. Nc (relative) Dependency of c reconstruction on ECAL miscalibration ADC shift -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  20. Rc Dependency of Rc on upper limit of tracks: eJ/ varies, but Rc constant. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 Nvds

  21. Rc Dependency of Rc on upper limit of Ecal clusters: eg varies, but Rc constant. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 Nclus

  22. Final result : Rc = 0.321 + 0.064stat+ 0.035syst Comparison ofwith previous experiments -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  23. Rcas function of energy CSM p p CEM NRQCD p-A p p-A p Hera-B -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  24. bb-cross section Previous data Factor 7 -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  25. Method: • tB = 10-12 s • B only long lived decay • intoJ/ • at 920 GeV: lB ~ 1 cm • look for detachedJ/ • normalize using known • cross section and • measured number of J/ • and BR B J/ • no efficiency/trigger/… • knowledge required • (well, “almost not required”…) Monte Carlo -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  26. Invariant di-muon mass spectrum after detached event selection (incl. likelihood-fit). -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  27. Data Monte Carlo Invariant Mass: for downstream and upstream events clear signal of detachedJ/ -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  28. Decay length fit lsignal = 1.0 +/- 0.3 (lMC = 0.83 +/- 0.03) lbackgr. = 0.39 +/- 0.11 -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  29. Single cut optimization on downstream bkgr. Simult. cut optimization on upstream bkgr. Simult. cut optimization on downstream bkgr. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  30. Final result: s(bb) = 32 +15+ 8syst nb/nucleon -12 stat - Uncertainties: Reference J/ cross sect. 11 % Trigger simulation: 5 % prompt J/ product. models 2.5 % b prod. and decay model 8 % A-dep. ignored 1.7 % prompt J/ counting 5 % b lifetime error 1 % J/  e+e-g 1 % m+m- background shape 20 % m+m- background fluct. 23 % e+e- background shape 14 % e+e- background fluct 11 % Total 24 % – 33 % -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

  31. Conclusion • Results of 2000 limited in statistics • (though competitive: s(bb), Rc ) • Hera-B offers good possibilities: • Simultaneous different targets • small relative uncertainties • large acceptance in - negative - xF; • full event capability: PID, g, … • Improved detector (trigger) in 2002: • high statistics expected -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002

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