1. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 1 Hera-B Physics results 1.Data of the year 2000 limited statistics 2.Commissioning: trigger and detector not yet fully available (limited acceptance in x F ) 3.Targets: C and Ti (partially simultaneously)

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

3. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 3 Hera-B detector and trigger layout geared towards J/  : 1.Based on J/  e + e - and J/   +  - ; 2.Good vertexing through Si-  strips; 3.e + and e - in ECAL; 4.  + and  - in Muon  detector; 5.Magnetic field for charge determination. ECAL is also fine-grain photon detector. Not used in this part of analysis: 1.Rich 2.Inner Tracker 3.Trans. Rad. Detector

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

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

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

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

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

9. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 9 e   e   Invariant mass spectrum with bremsstrahlung requirement After background subtractionBefore background subtraction

10. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 10 J/  production Hera-B has large x F (and good p T ) acceptance xFxF xFxF

11. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 11 p T and x F distribution with e and  sample:

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

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

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

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

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

17. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 17 R  c = N J/  *   NcNc Identification of  c through :  M = M( l + l -  ) - M ( l + l - ) uncertainty in J/  mass essentially cancels: M  c = (M J/  2 + 2E  E J/  – 2p  p J/  )  M  c =  M J/  = 0.877  M J/   (M  c - M J/  ) = -0.123  M J/  M J/  McMc Ratio of J/  from  c :  c Production

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

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

20. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 20 Dependency of R  c on upper limit of tracks:  J    varies, but R  c constant. RcRc N vds

21. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 21 RcRc N clus Dependency of R  c on upper limit of Ecal clusters:   varies, but R  c constant.

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

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

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

25. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 25 Method:  B = 10 -12 s B only long lived decay into J/  at 920 GeV:  ~ 1 cm look for detached J/  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

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

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

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

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

30. -- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 30 Final result:  (bb) = 32 +15 + 8 syst 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 -  1 %  +  - background shape20 %  +  - background fluct.23 % e + e - background shape14 % e + e - background fluct11 % Total24 % – 33 %

31. -- 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 negative large acceptance in - negative - x F ; full event capability: PID, g, … Improved detector (trigger) in 2002: high statistics expected