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-- 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)
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-- 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
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-- 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
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 4 J/ J/ signal before cuts + - inv. Mass: J/ signal after cuts
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 5 e + e Invariant mass spectrum (| 1 - E/p| < 0.3) No J/ signal …
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 6 beam e+e+ ECAL e+e+ magnetic field Bremsstrahlung recovery
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 7 e e Invariant mass spectrum
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-- 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
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 9 e e Invariant mass spectrum with bremsstrahlung requirement After background subtractionBefore background subtraction
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 10 J/ production Hera-B has large x F (and good p T ) acceptance xFxF xFxF
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 11 p T and x F distribution with e and sample:
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 12 Comparison with other experiments:
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-- 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 -
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 14 Energy dependence of exponent c
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 15 Energy dependence of width p T
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-- 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
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 17 R c = N J/ * NcNc 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/ McMc Ratio of J/ from c : c Production
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 18 M-spectrum: c -signal on top of combinatorial background (J/ -- g )
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 19 ADC shift Dependency of c reconstruction on ECAL miscalibration N c (relative)
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 20 Dependency of R c on upper limit of tracks: J varies, but R c constant. RcRc N vds
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 21 RcRc N clus Dependency of R c on upper limit of Ecal clusters: varies, but R c constant.
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-- 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
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-- 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
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 24 bb-cross section Previous data Factor 7
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-- 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
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 26 Invariant di-muon mass spectrum after detached event selection (incl. likelihood-fit).
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-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 27 DataMonte Carlo Invariant Mass: for downstream and upstream events clear signal of detached J/
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-- 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
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-- 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.
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-- 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 %
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-- 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
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