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B Physics results from CDF

B Physics results from CDF. Daniela Bortoletto Purdue University. Introduction Recents results from Run 1  100 pb -1 collected between August 1992-February 1996. Measurement of the B production cross section test of QCD Searches for radiative penguin decays  sensitive to new physics

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B Physics results from CDF

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  1. B Physics results from CDF Daniela Bortoletto Purdue University • Introduction • Recents results from Run 1 •  100 pb-1 collected between August 1992-February 1996. • Measurement of the B production cross section test of QCD • Searches for radiative penguin decays  sensitive to new physics • The measurement of sin(2)  CP violation • Future prospects in Run II • March 2001 • CDF/D0 expects to collect 2 fb-1 in two years Moriond EWK March 2000

  2. u b   b c   B Physics and CKM matrix Vud Vub*+Vcd Vcb*+VtdVtb*=0 • The goal of B-physics is to over-constrain the unitarity triangle to test the CKM ansatz or to expose new physics Vtd,ts (,) d(s) b t  t b d(s) B Vtd,ts  (+i) (1--i)  BDK BJ/K0s   (1,0) (0,0) Moriond EWK March 2000

  3. Hadron collider B-physics • The strong interaction produces b quarks which then fragment into b-hadrons The lowest energy states decay weakly • Test of QCD (unique to hadronic machines): • mb>QCD Perturbation theory can be used to estimate inclusive b production • b production at the Tevatron is dominated by gluon processes Probe gluon structure functions • Study of weak decays and unique capabilities for Bs, b and Bc which are not produced at B factories running at the (4S)

  4. Hadron colliders challenge At 1.8 TeV • Large production cross section • Even larger inelastic cross section (S/B10-3)  specialized triggers: • Single lepton triggers  BR(b  X) =(23.1 1.5)%. Requiring pT()> 7-8 GeV/c <pT(b)>  20 GeV • J/ +  - triggers  Use clean signature of b  J/ X . Requiring pT(2 )> 1.5 GeV/c <pT(b)>  10 GeV • In Run II, L2 trigger on displaced tracks (SVT) will allow CDF to trigger hadronic B decays and study B0 +-,Bs Ds-K+ ... At Z0 At (4S)

  5. Run I CDF detector • Crucial components for B physics: • Silicon vertex detector proper time measurements • impact parameter resolution: d=(13+40/pT) m • typical 2D vertex error (r-)60 m • Central tracking chamber  mass resolution. B=1.4T, R=1.4m (pT/pT)2=(0.0066)2(0.0009pT)2 • typical J/K0Smass resolution  10 MeV/c2 • Lepton detection (triggering and tagging) Moriond EWK March 2000

  6. B Production cross section • The B meson cross section : • engineering number • provides a check of NLO QCD calculations • sensitive to gluon distribution functions • In run 1A (20 pb-1) CDF found the data to be  2 NLO QCD predictions (3) • New analysis uses the full run 1 data sample and the decay B+J/K+. Moriond EWK March 2000

  7. B Production cross section • Both’s must be well measured in the SVX • ct(J/)>100 m • pT(K)>1.25GeV • Fit in 4 pT bins: • 6-9 GeV/c • 9-12 GeV/c • 12-15 GeV/c • 15-25 GeV/c Moriond EWK March 2000

  8. B Production cross section • The cross section is: • QCD NLO central value  1.2 b 0=(mb2+pT2)1/2 =0.006 mb=4.75 GeV fu=0.375 • Data is still higher than theory Moriond EWK March 2000

  9. B Production cross section • Fully correlated Systematic errors 13.1%: • Branching Fraction 10.6% • Kaon decay in flight 4.0% • reconstruction efficiency 3.1 % • Luminosity 5.8% • Fully uncorrelated Systematic errors 2.8-3.6%: • QCD scale 1.5-1.6% • Peterson 0.7-1.6% • Trigger efficiency 1.7-3.1% Moriond EWK March 2000

  10. Radiative Penguins • Radiative penguins are sensitive to physics beyond the SM • CP asymmetry in SM <1% • Extraction of |Vtd/Vts|: • Inclusive b d /bs difficult • Exclusive: Bd /BdK*0 • Exclusive: Bs K*0/Bs • CDF Unique to CDF Moriond EWK March 2000

  11. Radiative Penguins I) Specialized  trigger (22.3 pb-1 in Run 1B and 6.6 pb-1 in Run 1C). • pT()>10 (6) GeV/c+ 2tracks with pT>2 GeV/c • Energy resolution in EM calorimeter  (MB)100 MeV/c2 • Ratios w.r.t. B  e- D0 X (D0 K-+) II)  conversions in the CDF inner detector • trigger with pT > 8 GeV/c electrons (74 pb-1) • CTC pT resolution(MB)45 MeV/c2 • Ratios w.r.t. to B  J/K  e+e-K Position of conversions CTC inner wall

  12. Radiative Penguins • Method I • Reconstruct K* K+- and  K+K- using SVX tracks • impact parameter cut • B isolation, alignment between pT and VT • Systematic errors dominated by statistics of eD0(20%), f**(12%), Br(BeD0X) (14%) and fs/fu (18%) • Method II • Reconstruct K* K+- and  K+K- using SVX tracks • ct(B)>100 m c • B isolation • Systematic errors dominated by statistics of J/K(20%), Br(BK) (10%) and fs/fu (18%)

  13. Radiative Penguins • Combining the two searches CDF finds : • 2 candidates for BdK* while we were expecting B=0.6  0.3. • 0 candidates for Bs while we were expecting B=0.1  0.1 . Moriond EWK March 2000

  14.  Conversions 1 candidate 0 candidate 28 candidates 34 candidates

  15.  Trigger

  16. Radiative Penguins • Search for b • Polarization of  is sensitive to New Physics • Use only conversion trigger • Tracks are not required to be in SVX • Expectations for 2fb-1: • BdK*: 1000 events • Bs: 400 events • Bs K*: 10 events • b Studies are in progress to find optimal trigger

  17. Ks B0 B0 Measurement of sin2 • Requires: • Reconstruction of the signal B0/B0 J/K0S • Measurement of the proper time t • Flavor tagging to determine if we had a B0 or a B0 at the time of production • The effectiveness of flavor tagging algorithms is quantified by: • Measured ACP is reduced by D, while D2 effects  A and (sin2)

  18. Measurement of sin2 • CDF ppbb Abe et al. PRL. 81, 5513 (1998) (June 1998) • 198 17 B0/B0 J/K0S candidates with both muons in the SVX ( S/B  1.2). Measure asymmetry withSame side tagging • Dsin2=0.31 1.1  0.3. • Using D=0.166  0.018 (data)  0.013 (MC) from mixing measurement + MC sin2=1.8 1.1  0.3

  19. Improved measurement • Accepted for publication in PRD, T. Affolder et. Al., FERMILAB-Pub-99/225-E, hep-ex/9909003 • Improve statistical significance • Add candidate events not fully reconstructed in the SVX • Double the signal to 400 events but additional signal has larger (ct) • Use two additional flavor tag methods to establish b flavor at production (Increase D2) • soft lepton and jet charge (both opposite side tagging methods used for the mixing analysis) • calibrated using B-J/K- • Use a maximum likelihood method to combine the tags. Include terms in the likelihood for • Account for detector biases • Prompt background • Long lived background

  20. J/K0SSignal sample Both  in SVX • CDF run1, L=110 pb-1 • 202 events with both muons in SVX(ct) 60 m. • 193 with one or both muons NOT in SVX  (ct) 300-900 m 202 18 events 395 31 events S/B=0.9 One or Both not in SVX 19326 S/B=0.7 S/B=0.5 • Plot normalized mass M-MB/ error on M

  21. Flavor tagging methods • We must determine if we had a B0 or a B0 at the time of production. • Opposite-side flavor tagging (OST) bb produced by QCD Identify the flavor of the other b in the event to infer the flavor of the B0 /B0 J/K0S. At CDF 60% loss in efficiency due the acceptance of the other B0. • Lepton tagging : • b +X b • b -X b • Jet charge tag : • Q(b-jet) > 0.2 b • Q(b-jet) <- 0.2 b B0(bd) J/K0S + - + K0S - Opposite side b + Q(b-jet)>0.2

  22. u - B0 B- B0 B- B**- K0 K+ - + d B0 b b b b b b d u d u s s u d Same side tagging • Same side flavor tagging (SST). Exploits the correlation between the charge of nearby  and the b quark charge due to fragmentation or B** production (Gronau,Nippe,Rosner) • Correlation due to excited B** production B**+ (I=1/2) resonance B**-B0- No K/ separation  higher correlation for charged B d

  23. Flavor Tagging Summary • Soft lepton e: pT(e)>1 GeV/c ; : pT()>2 GeV/c = (5.61.8)% D= (62.5 14.6)% D2= (2.2 1.0)% • Jet charge If there is a soft lepton do not use jet charge = (40.2 3.9)% D= (23.5 6.9)% D2= (2.2 1.3)% • Same side pion tagging =(35.53.7)% D= (16.6 2.2)% in SVX =(38.13.9)% D= (17.4 3.6)% not in SVX • Combined flavor tagging power including correlations and multiple tags • A sample of 400 events has the statistical power of 25 perfectly tagged events • About 80% of the events have a tag D2= (2.1 0.5)% D2= (6.3 1.7)%

  24. +0.41 -0.44 sin2=0.79 Float md (stat.+sys.) Measurement of sin2 • The minimization of the likelihood function yields: sin2=0.790.39(stat)0.16(syst) Statistical error >systematics. • Time integrated measurement sin2=0.710.63 (statsys) • Using Feldman and Cousing frequentist approach 0<sin2<1 @93%C.L. • New world average (Taipei) includes this measurement and a new Aleph results sin2=0.82 0.38

  25. Results in  and  plane 1 bounds • CDF sin2  measurements  fourfold ambiguity {, /2- , +, 3/2-} • Solid lines are the 1  bounds, dashed lines two solutions for  for <1, >0 (shown) • two solutions for >1, <0 (not-shown)

  26. Run II upgrade • New silicon tracking system  3 D information • SVX II: 5 layers, 96 cm, r- and r-z readout • ISL: 2 additional layers • L00 at r=1.4 cm • New central drift chamber  maintain run 1 tracking efficiency and resolution • New trigger: • L1 tracking trigger • L2 trigger on displaced tracks  trigger on hadronic B decays • Time off flight  2  K/ separation for p<1.6 GeV/c • >2 fb-1 of data

  27. Run II expectations • Sin 2  from B0/B0 J/K0S • for 10K events, D2= 6.7% (+2.4% TOF)  (sin2 )0.084 • B expect 8400-15200 events if BR=110-5 • for 5K events , D2=9.1%  A()0.1-0.15 • Modes to study  • Expect 6000 BsJ/ where asymmetry would be sign of new Physics • Bs oscillations • Expected signal 20,000 Bs Ds-+, Ds+-+ with Ds  , K*K • Proper time resolution with L00 • Flavor tagging effectiveness • D2=11.3% with TOF (5.7% with old baseline) Sensitive to xs<63 if S/N=2/1 Sensitive to xs<56 if S/N=1/2 20<xs< 30.8 @96% C.L.

  28. Conclusions • Important contribution to B physics using run I data: • Discovery of the Bc through • First measurement of sin(2) from • Precise measurements of B hadron lifetimes • Neutral B meson oscillation ( measurement of md, limits on ms) • Studies of b-tagging methods • Searches for rare B decays (FCNC ) • B production • Excellent prospects for Run II

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