B Physics at the Tevatron

1. B Physics at the Tevatron Jack Cranshaw Texas Tech University For the CDF and D0 Collaborations BEACH2002 B Physics at the Tevatron

2. Tevatron • Proton-antiproton collider with center of mass energy of 1.96 TeV. BEACH2002 B Physics at the Tevatron

3. Why Do B Physics at the Tevatron? • Large Cross Section! • Produce bottom mesons with all flavor combinations as well as bottom baryons. • Bc, Lb, Sb, ... • Multipurpose detectors CDF and D0 capable of reconstructing many B final states. • Experience with a 110 pb-1 of Run I data (1992-1996) BEACH2002 B Physics at the Tevatron

4. This Allows Measurements of • Mixing in the Bd and Bs systems. • CP violation in the Bd and Bs systems. • Search for rare decays. • Properties of the Bc meson. • Lifetimes • Branching Ratios • Cross sections BEACH2002 B Physics at the Tevatron

5.   a g b f3 f1 (1,0) r CP Violation in the B System Mixing between weak eigenstates and mass eigenstates described by the CKM matrix. Use orthogonality of unitary matrix columns to define unitary triangle, e.g. • Measure all of the angles • determines level of CP violation • if a+b+g≠ 180o then evidence for non-SM CP violation BEACH2002 B Physics at the Tevatron

6. Types of CP Violation • Mixing (DF=2 or indirect CP violation) • Is there a relative phase between the mass mixing and the decay widths? • Decay (DF=1 or direct CP violation) • Is there an asymmetry in the amplitudes <B|f> and <B|f> where f is a CP eigenstate? • Interference between Decay and Mixing BEACH2002 B Physics at the Tevatron

7. W- q q b b W+ W- W+ q b q b CP violation in B Meson Mixing • Measure sin(2bq) using • Measure oscillations between B-Bbar • Since |Vts| >> |Vtd| the oscillations are much faster in the Bs system relative to the Bd system need good vertex resolution. • Precise measurement of Dmd/Dms Mixing depends on CKM t quark dominates: q=d, s qu=u,c,t BEACH2002 B Physics at the Tevatron

8. Run I sin(2b) Measurement Run I silicon vertexing sufficient for measurement of sin(2b) in Bd mixing • CDF Published Result sin(2b)=0.79±0.39±0.16 • CDF Result (2001) sin(2b)=0.91±0.32±0.18 Measured using decay channels BdJ/yKs0, Bd ySKs0. • Babar sin(2b)=0.75±0.09±0.04 • Belle sin(2b)=0.82±0.12±0.05 BEACH2002 B Physics at the Tevatron

9. Bs Mixing • Reconstruct Bs decays using fully hadronic and semileptonic decay channels. • Measure xs=Dms/G. • With 2 fb-1 should cover full range of theoretically predicted values for xs. • Afterwards, we can search for CP violation in the Bs system (BsJ. Large window for non-SM physics. BEACH2002 B Physics at the Tevatron

10. Dominant Subdominant u W- d W- b b u d u W- s W- b s b u Unitarity Angles g, a • Measure/limit a based on Bdp+p-, Bs Ds-p+ • Measure g using combination of • Bdp+p- • BsK+K- • Challenges • Separation of Bd,s pp, pK, KK • Understanding penguin contributions (using both decays helps) • In addition there are interference amplitudes due to mixing. • However ample statistics for precision observation of asymmetry. Decays related by d,s interchange Fleischer PLB 459 (1999) 306 BEACH2002 B Physics at the Tevatron

11. Meson/Baryon Spectroscopy • Spectroscopy of B mesons with second generation quarks, and B baryons currently available only at hadron colliders. Run I Measurements • Mass Measurements: • m(Bs) = 5.3699 ± 0.0023 ± 0.0013 GeV/c2 • m(Lb) = 5.621 ± 0.004 ± 0.003 GeV/c2 • m(Bc) = 6.40 ± 0.39 ± 0.13 GeV/c2 BEACH2002 B Physics at the Tevatron

12. Lb and Bc Run I Run I LbJ/yL LbJ/yL LbpD0p, D0p+K- LbpK- BcJ/ye/ BcJ/yp BcBsp Run II BEACH2002 B Physics at the Tevatron

13. Cross Sections and Branching Ratios • During Run I we measured b inclusive cross sections. • These were systematically above the NLO predictions (by factor ~2.5). • Many measurements of cross sections and branching ratios were calculated with respect to a reference signal to avoid uncertainties on trigger efficiencies and measured luminosity. • In this sense, the ‘B factories’ provide us with valuable ‘calibrations’ for our reference signals. BEACH2002 B Physics at the Tevatron

14. Experimental Challenges • High resolution tracking and vertexing for reconstructing decays and lifetimes. • The ability to trigger on displaced vertices. • Particle identification for flavor tagging. • Excellent muon reconstruction. • Good EM calorimetry for rare decay searches and radiative decays. • Well understood simulation of detector and physics. • Efficient use of trigger bandwidth budget. BEACH2002 B Physics at the Tevatron

15. Charm Production • As we lower our pT thresholds we see a lot of charm. (~106 reconstructed events per pb-1!) • This will lead to a world class charm program. BEACH2002 B Physics at the Tevatron

16. 100. 10. Average Number of Interactions per crossing 6 Bunches 1.0 36 bunches 108 bunches 0.1 1031 1032 1033 1030 Luminosity Accelerator Upgrades • Replace Main Ring with Main Injector • Upgrade Pbar storage • Tevatron upgrade: • major luminosity increase • 1031 5 x 1031  2 x 1032 110pb-1 2fb-1  15fb-1 • Short interbunch to limit Nint/crossing • 3.5 ms  396 ns  132 ns Run IRun IIa Run IIb BEACH2002 B Physics at the Tevatron

17. Status of Integrated Luminosity • Just finished shutdown. • Top Run II luminosity so far 2 X 1031 cm-2 s-1 • Currently the major hurdle for producing Run II physics. • Approximately 30 pb-1 on tape with a variety of triggers and detector conditions. BEACH2002 B Physics at the Tevatron

18. Muons Calorimeters Tracking CDF Run II Detector • Tracking • Silicon Vertex Detector • L00 • Intermediate Silicon • Central Outer Tracker • Endplug Calorimeter • Muon systems • TOF BEACH2002 B Physics at the Tevatron

19. D0 Run II Detector Build on existing strengths • Excellent calorimetry with faster readout • Upgraded muon system for better m-ID Add new capabilities • Inner tracking (silicon tracker, fiber tracker) with 2T superconducting solenoid • Preshowers • Pipelined 3-level trigger • Si Track Trigger (displaced vertices) BEACH2002 B Physics at the Tevatron

20. Physics Program, First Stages • Stage 1 (50 pb-1) • Refine triggers • Lifetime measurements • Cross sections, branching ratios • Stage 2 (50-200 pb-1) • First Bs mixing measurement • Run II sin(2b) measurement • Charmonium polarization • Stage 3 (200+ pb-1) • Bs, Bc, Lb properties measurements • Cross sections, branching ratios • … BEACH2002 B Physics at the Tevatron

21. Conclusion • Exciting physics opportunities at the Tevatron for Run II • Developing new measurements/ techniques • More about status and prospects in Stephen and Rick’s talks. BEACH2002 B Physics at the Tevatron

22. Run II Improvements • Silicon detectors (SVXII, ISL): • Double SVX length for full acceptance (SVX II) • Double sided silicon for 3-D track reconstruction (SVXII) • More silicon layers & forward silicon (ISL) for standalone tracking • Secondary vertex trigger at LV2 (20 ms) (SVT) • Central tracker (COT): • Double the number of stereo layers (COT) • x 6 more sense wires improves occupancy (COT) • Muon system: • Improved coverage: old “holes” fixed and push to |h| = 1.5 (IMU) • New Plug calorimeter • Add preshower and shower max detector BEACH2002 B Physics at the Tevatron

23. Why Do B Physics? • Heaviest quark that can currently be produced in large samples. • CP Violation: Gives access to the unitarity triangle with the simplest interpretation. • Spectroscopy of B mesons. • Heavy quark – light quark pairings more easily understood theoretically. BEACH2002 B Physics at the Tevatron

24. Jet Tagging Algorithms To measure mixing, must tag the initial flavor of produced B meson. • Away Side Tags (tag the other b quark) • Lepton tagging: b Xl-,b Xl+ • Kaon tagging: b  c  XK-,b  c  XK+ • Jet charge tagging: form pT weighted jet charge, b  Qjet<0, b  Qjet>0 • Vertex Charge tagging • Same Side Tags • Soft pion tag: b associated with collinear p-, b associated with collinear p+ BEACH2002 B Physics at the Tevatron

25. CDF Run II Trigger System • Front-end electronics • Level1 Trigger • synchronous, 132 ns • 42 deep pipeline gives 5.5 ms for L1 decision • Accept rate 40-50 kHz • Level2 Trigger • asynchronous • Accept rate 300 Hz • Level3 Trigger (not shown) • Farm of 175 PC’s • Accept rate 75 Hz • Control Infrastructure BEACH2002 B Physics at the Tevatron