Status of b Scan Jianchun Wang Syracuse University Representing L b scanners CLEO Meeting 05/11/02.
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Status of b Scan Jianchun Wang Syracuse University Representing L b scanners CLEO Meeting 05/11/02
Jianchun (JC) Wang2 Introduction Goal: Scan the region around b b threshold to find largest cross-section of b b pair production. Tools for the scan: Number of L c reconstructed in pK p, pK S, Lp, and other modes. Number of proton/lepton reconstructed. References: MC at 5.635 GeV for b signal, On and off-resonance data around (4S) (dataset 8+10+11) for continuum and BB background.
05/11/02Jianchun (JC) Wang3 Luminosity Fast turn out, thanks to David Kreinick
05/11/02Jianchun (JC) Wang4 Hadron Event Cross-section No significant structure found
05/11/02Jianchun (JC) Wang5 Quality of Data: dE/dX Calibration of dE/dX is not included in fast pass2. We run on PDS files after pass2 with correct dE/dX parameters. Thanks to Guangpei and Roy.
05/11/02Jianchun (JC) Wang6 Quality of Data: L c Resolution Fast pass2 is used. The resolution is about 6 MeV. Expect 3-4 MeV. No XP or R2 cut in this plot.
05/11/02Jianchun (JC) Wang7 L c Cross-section Number of Reconstructed L c Integrated Luminosity Only pK p mode shown here Estimation of BB and continuum contribution
05/11/02Jianchun (JC) Wang8 Estimated Cross-section This measurement ( average of all points ): s = (0.99 0.10) pb. Continuum and BB background are estimated using data set 8, 10 and 11, assuming BB cross-section above 4S is 250pb. Continuum (non-b): s (continuum) = ( 0.35 0.05 ) pb. BB meson: s (BB) = ( 0.21 0.02 ) pb. Sum of the two: s (continuum) + s (BB) = ( 0.56 0.04 ) pb. Signal is estimated using MC: s ( L b ) = 1.68 pb assuming: b b production cross-section is 50 pb. Br( L b L c X) Br( L c pK p) = 100% 5% = 5%. The excess is (0.43 0.11) pb, equivalent to b b production cross- section of (12.8 3.3) pb. ( Preliminary !!! )
05/11/02Jianchun (JC) Wang9 Further Check The efficiency could be different due to different beam energy. We simulated BB event and continuum event at 10.58 and 11.27 GeV. The efficiency shows no difference. Based on continuum MC simulation, and 3 nb hadronic cross-section at 10.58 GeV we estimate that s = 0.40 pb in comparison with (0.35 0.05 ) pb from 4S data estimation. PDG gives Br( B L c X) Br( L c pK p) = (6.4 1.1)% (5.0 1.3)%. Based on this we estimate that contribution from BB is s = 0.53 pb, more than double of (0.21 0.02 ) pb estimated from 4S data. John Yelton’s CBX: Br( B L c X) Br( L c pK p) = (2.15 0.08) 10 -3 Using this value and MC efficiency, we get s = (0.35 0.01) pb. Both estimations from 4S data and MC may not be good enough. We need MC using current detector condition.
05/11/02Jianchun (JC) Wang10 Proton Cross-section With at least on lepton in the event. Proton + Antiproton Antiproton Only
05/11/02Jianchun (JC) Wang11 Estimated Cross-section This measurement (average of all points): s = (14.83 0.19) pb. Continuum and BB background are estimated using data set 8, 10 and 11, assuming BB cross-section above 4S is 250pb. Continuum (non-b): s (continuum) = ( 7.08 0.09 ) pb. BB meson: s (BB) = ( 3.32 0.03 ) pb. Sum of the two: s (continuum) + s (BB) = ( 10.40 0.09 ) pb After correction ( 11.54 0.10 ) pb. Signal is estimated using MC: s ( L b ) = (8.61 0.15) pb for 50 pb b b production cross-section is. The excess is (3.29 0.21) pb, equivalent to b b production cross- section of (17.1 1.3) pb. Using only antiproton, the excess is equivalent to b b production cross-section of (18.2 1.7) pb. ( Preliminary !!! )
05/11/02Jianchun (JC) Wang12 Estimated Cross-section We thought that the muon efficiency would be higher at 11.27GeV. MC of selected event did not show significant difference. In proton/lepton events, the ratio of muon to electron are 0.504 for BB and 0.657 for continuum estimated from 4S data, while current data shows 0.780. This could be due to detector inefficiency. In rough estimation we increase the muon contribution to background by 29%. The QQ decay table was tuned by Steve Blusk, we still have problem with pass2 using the new table.
05/11/02Jianchun (JC) Wang13 Proton Momentum Spectrum The excess could come from L b, or due to other reasons
05/11/02Jianchun (JC) Wang15 Need to Be Considered The beam energy issue (see Dan’s talk). The absolute value of integrated luminosity. The BB cross-section in this region, contribution from other b-mesons. The detector efficiency. We need to have realistic MC.
05/11/02Jianchun (JC) Wang16 Summary The L b scan is still going on. Preliminary quick results show that there are excess in both L c, and proton/lepton methods, which might come from L b. The nature of such excess is yet to be determined. We are going to run at even lower point.
05/11/02Jianchun (JC) Wang17 c Decay Modes 0.0870.053 0.639 0.27 0.8 3 0.0883.3 1.3 8 0.1030.057 0.639 0.27 0.8 0.26 0.0363.6 1.3 7 0.0900.200 0.639 0.27 0.8 0.1400.9 0.3 6 0.1450.085 0.26 0.8 3 0.1303.4 1.0pK 5 0.0660.051 0.5 0.686 0.39 0.8 3 0.0682.6 0.7pK 4 0.0440.027 0.5 0.686 0.8 0.39 0.26 0.0283.3 1.0pK 3 0.1380.120 0.5 0.686 0.8 0.39 0.1102.3 0.6pK 2 ( 0.02 )0.400 0.8 3 0.5105.0 1.3pK 1 Br Br(pK ) Measured Eff ( ) Estimated Efficiency Br (%)Modes Not all modes will be used in scan, But most of them can be used in further study
05/11/02Jianchun (JC) Wang18 Decay Mode pK Scaled to 12 pb . Sum of three sources: b b pair, BB pair, and udsc continuum. About 20 c from b can be seen. M pK (GeV) Number of Entries / 2 MeV
05/11/02Jianchun (JC) Wang19 Sum of Three Modes S/ S+N 3 0.31.50.00.10.51.8 Background C signal 33.27.824.2Sum 0.51.40.00.20.72.8pK S 7.522.214.171.124.019.6 PK Budsc bb B bb
05/11/02Jianchun (JC) Wang20 Proton Lepton Event Require at least one muon or electron in the event. With R2 < 0.2 cut. The efficiency for b b event is 17%. With 12 pb , reconstruct: 103.3 from b b events. 80.3 from udsc continuum. 30.1 from BB events. S/ S+N = 7.1. XP p Number of Entries / 0.01
05/11/02Jianchun (JC) Wang21 Proton Lepton Event Number of Entries / 0.01
05/11/02Jianchun (JC) Wang22 Track Selection Criteria Dedx information valid, and 3 consistence. Grand LL: LL(K)-LL(pi)+Nsig(K)**2 – Nsig(pi)**2 RICH valid, P(K)>0.5 Gev, P(p)> 1GeV: Grand LL < - 4 Others: (no RICH), Grand LL < -4 Number of expected hits > 0, and number of hits > half of the expected. Number of expected hits in fit > 0, track fitted, fit not abort. Fit helix valid, track quality valid, track fit, not abort, degreesOfFreedom > 0, D0 < 0.6cm (0.35), Z0 < 5cm.
05/11/02Jianchun (JC) Wang23 Brief Selection Criteria Good tracks. P/K/ : Dedx, Grand LL (combine Dedx, RICH info). Electron: Dedx, X925, E/P, Grand LL. Muon: Dedx, Mudepth. : X925, Barrel, no track matching, cos CM. K S : Fit quality(prob>0.01), Distance(r- ) > 2mm. : Fit quality(prob>0.01), Distance(r- ) > 1mm.
05/11/02Jianchun (JC) Wang30 RICH Sequencer Issue: Number of Photon Electrons from two L b runs. Average number of photon per track increases from 11.8 to 13.0.
05/11/02Jianchun (JC) Wang31 RICH Sequencer Issue: Event Scan After fixing the sequencer code Before fixing the sequencer code
05/11/02Jianchun (JC) Wang32 RICH Sequencer Issue: D Reconstruction Efficiency Data 17 is used. With RICH reprocessed. D* tagged D K p. The efficiency loss is 3.3 0.3%, with K within RICH acceptance.