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B Physics results from CDF

This presentation by Daniela Bortoletto from Purdue University focuses on the latest results in B-physics obtained from the CDF experiment, highlighting the measurement of B production cross sections, tests of quantum chromodynamics (QCD), searches for radiative penguin decays, and the implications for new physics. The talk also discusses the significance of measuring CP violation through sin(2β) and explores anticipated developments in Run II. The extensive data collected, together with sophisticated triggers and detector technologies, promise exciting opportunities for further discoveries.

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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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