1. Mike HildrethEPS/Aachen, July 17-23 2003 B Physics Results from DØ Mike Hildreth Université de Notre Dame du Lac DØ Collaboration for the DØ Collaboration Outline:  Overview of DØ @ Run II  Lifetimes  Spectroscopy  Prospects CP&Mixing: See Paul Balm’s talk this afternoon

2. Mike HildrethEPS/Aachen, July 17-23 2003 The RunII DØ Detector Fiber Tracker Silicon Tracker Solenoid

3. Mike HildrethEPS/Aachen, July 17-23 2003 Detector Performance SMT: 91% operational CFT: 99% operational CAL: >99.9% operational MUON: >99.5% operational Track Calibration Samples:   dt = ~171 pb -1 (LP: 114 pb -1 ) (April 2002  July 13, 2003) Data Taking  = 89% (M,J) B Physics Triggers: muons: |  | 3.5 GeV 1 2-2.5 GeV di-  single-   +jets, EM e  (CAL) coming soon... L1 track-muon match (p T >1.5 GeV |  |<1.7) L2 SMT Track trigger  =7 MeV  =3 MeV

4. Mike HildrethEPS/Aachen, July 17-23 2003 Tracker Performance Displaced vertices:    p+p+ 00 Impact Parameters: Z  :  =7.6 GeV multiple tracks with ~cm impact parameters

5. Mike HildrethEPS/Aachen, July 17-23 2003 Inclusive b Cross Section  Begin with  +jet sample, measure cross section for this process:  Using muon p T spectrum, fit for b and non-b content in bins of jet E T  Jet trigger eff. ~100% at E T = 20 GeV  Muon trigger efficiency ~55-70%  Muon reco efficiency (43.7±0.8±2.2)% p(  +jet) jet  Data Pythia 0.5 Cone Jets |  jet |<0.6, |   |<0.8 p T  >6 GeV/c  R(jet,  )<0.7 Data Background Signal Fit d  /dE T [nb/10 GeV] (3.4 pb -1 of data)

6. Mike HildrethEPS/Aachen, July 17-23 2003 Inclusive b Cross Section fraction of b-jets from fit: DØ Run II Preliminary Dominant Errors:  jet energy resolution  energy scale uncertainty  “Pythia” = Pythia+CTEQ4M,  R<0.3  Run I was compared to NLO(+MRSA’)  Different. Not directly comparable, Nucl. Phys. B483 321 (1997) but still 2-3x higher than predictions b production cross section: b fraction uncertainty Data Pythia Jet E T (GeV) d  /dE T (nb/10GeV)  Energy resolution function used to “unfold” cross section to true jet energy

7. Mike HildrethEPS/Aachen, July 17-23 2003 J/   +   Sample Our “in” to B Physics:  ~1/6 from b-decay  di-  trigger running unprescaled since ~ Day 1  access to many interesting/rare decays  very clean signal  (also helps in tracking commissioning) DØ Run II Preliminary N J/  = 151k N  = 4100  =71 MeV  = 114 pb -1 Cuts:  Tracks: p T >1.5 GeV, >3 SMT hits, >4 CFT hits  p T (J/  ) > 3 GeV  (Yield very cut-dependent) Comments:  J/  mass about 1/3  low; calibration not finalized yet (material, magnetic field)  mass resolution close to MC expectation

8. Mike HildrethEPS/Aachen, July 17-23 2003 Inclusive B lifetime Transverse Decay Length:  Use B  J/  X decays  Decay length L xy given by the primary vertex and the J/  vertex:  But, p T of B unknown: Infer c  B from c  J/  by using MC correction:  Correction varies from 0.8-0.9 over visible momentum range (Pythia+QQ, Run I tune) DØ Run II Preliminary

9. Mike HildrethEPS/Aachen, July 17-23 2003 Inclusive B Lifetime Proper B decay length:  Prompt components: - J/  : pp  ccX - combinatorics - modelled as 2 Gaussians  Exponential components: - B signal: b  cX - semileptonic b, c decays  Gaussian params, background normalization from J/  sidebands  Fit for:  B fraction  decay length  B fraction: 14.6%  Prompt J/  : 64.6%  Background: 21.3%  B = 1.561 ± 0.024 ± 0.074 ps PDG:  B = 1.564 ± 0.014 ps  = 47 pb -1

10. Mike HildrethEPS/Aachen, July 17-23 2003 CFT SMT Ladders c Reconstruction  Photon conversions:  Looking for b  c +X (Br ~ 1-2%)  Find  c in  c  J/ ,   e + e     ~ 0.4%, but 27% of J/  come from  c ! (CDF Run I, PRL 79, 578 (1997 )  can’t yet separate  c1,  c2 - fit with fixed  M 1,2 = 46 MeV  PDG M(J/  )-M(J/  ) = 414 MeV  more data, improvements coming  = 47 pb -1

11. Mike HildrethEPS/Aachen, July 17-23 2003 Exclusive B ± decays J/  (p T >4 GeV) associated with K track from same jet Simple cuts:  p T (K)>0.5 GeV, b(K)/  b >3  L(B + )/  L > 3  cos(  (L,p B ))> 0.9  b(B + )/  b <4  no particle ID (K/  )  Fully-reconstructed decays: - lifetime measurements - mixing (proper time resolution), flavor tagging studies DØ Run II Preliminary  = 114 pb -1

12. Mike HildrethEPS/Aachen, July 17-23 2003 Exclusive B d decays 0 Combine J/  with  or K  :  p T (K s )> 0.5 GeV  p T (K * )> 1 GeV (same cuts as B + analysis) DØ Run II Preliminary  = 114 pb -1

13. Mike HildrethEPS/Aachen, July 17-23 2003 Exclusive B s decays Combine J/  with  : DØ Run II Preliminary B s  J/   one of the useful modes for CP violation in the B s sector: Im( J/  ) =(1-ƒ odd ) sin2  s  Measurement of asymmetry requires analysis of final state angular momentum  could be diluted by cancellation of CP-odd and CP-even contributions  large asymmetry would be unambiguous sign of new physics!  B s Lifetime   s Stay tuned!  = 114 pb -1

14. Mike HildrethEPS/Aachen, July 17-23 2003 Exclusive  b Decays Combine J/  with a  :  b  J/   now updated with full RunII statistics  Being used for  b lifetime measurement  look for result at Lepton-Photon  = 114 pb -1

15. Mike HildrethEPS/Aachen, July 17-23 2003 Charged B Lifetime DØ Run II Preliminary Proper B decay length: Using B ±  J/  K ± mode  full reconstruction - no hadronization uncertainties - excellent proper time resolution Details:  B + event selection without decay length cut  R. Sideband used for background  Non-(B ±  J/  K ± ) contribution (12%) from other B decays taken from MC  B + = 1.76 ± 0.24 (stat) ps PDG:  B + = 1.674 ± 0.018 ps B ±  J/  K ± N(B ± )~180  = 47 pb -1

16. Mike HildrethEPS/Aachen, July 17-23 2003 Inclusive Semi-leptonic B Decays  Single muon triggers! –|  | 2-3.5 GeV  simple cuts: –p T (  ) >2 GeV, p T ( ,K)>1 GeV –(b( ,K)/  b ) 2 > 6, L(D)/  L > 4 –cos(  (L,p D ))>0.95 –  –2.3 GeV < M(  D) < 5.5 GeV  Here, only D 0  K  mode used –Obviously, can also use B   D * X B   D  X B   D s X DØ Run II Preliminary  = 2.2 pb -1  High Yield!  excellent source of B hadrons for tagging, trigger, physics studies

17. Mike HildrethEPS/Aachen, July 17-23 2003Conclusions/Prospects  DØ is well-positioned to contribute substantially to our B-physics knowledge in RunII –excellent tracking, muon coverage –high-efficiency running –high yields in many useful final states –flavor tags look promising (See Paul Balm’s talk)  Many new results coming for Lepton-Photon –updates on lifetimes (B +,  b,B s,...) –first look at B d /B s semi-leptonic decays –rare decays  Expect DØ to be competitive!