June 28, 2002BEACH2002 B Physics at the Tevatron B Physics at the Tevatron Jack Cranshaw Texas Tech University For the CDF and D0 Collaborations

June 28, 2002BEACH2002 B Physics at the Tevatron Tevatron Proton- antiproton collider with center of mass energy of 1.96 TeV.

June 28, 2002BEACH2002 B Physics at the Tevatron Why Do B Physics at the Tevatron? Large Cross Section! Produce bottom mesons with all flavor combinations as well as bottom baryons. –B c,  b,  b,... Multipurpose detectors CDF and D0 capable of reconstructing many B final states. Experience with a 110 pb -1 of Run I data ( )

June 28, 2002BEACH2002 B Physics at the Tevatron This Allows Measurements of Mixing in the B d and B s systems. CP violation in the B d and B s systems. Search for rare decays. Properties of the B c meson. Lifetimes Branching Ratios Cross sections

June 28, 2002BEACH2002 B Physics at the Tevatron CP Violation in the B System    11 33  (1,0)   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  ≠ 180 o then evidence for non-SM CP violation

June 28, 2002BEACH2002 B Physics at the Tevatron Types of CP Violation 1.Mixing (  F=2 or indirect CP violation) Is there a relative phase between the mass mixing and the decay widths? 2.Decay (  F=1 or direct CP violation) Is there an asymmetry in the amplitudes and where f is a CP eigenstate? 3.Interference between Decay and Mixing

June 28, 2002BEACH2002 B Physics at the Tevatron CP violation in B Meson Mixing Measure sin(2  q ) using –Measure oscillations between B-Bbar –Since |V ts | >> |V td | the oscillations are much faster in the B s system relative to the B d system need good vertex resolution. –Precise measurement of  m d /  m s Mixing depends on CKM t quark dominates: b q q b q q b b W+W+ W-W- W-W- W+W+ q=d, s q u =u,c,t

June 28, 2002BEACH2002 B Physics at the Tevatron Run I sin(2  ) Measurement CDF Published Result sin(2  )=0.79±0.39±0.16 CDF Result (2001) sin(2  )=0.91±0.32±0.18 Measured using decay channels B d  J/  K s 0, B d  S  K s 0. Babar sin(2  )=0.75±0.09±0.04 Belle sin(2  )=0.82±0.12±0.05 Run I silicon vertexing sufficient for measurement of sin(2  ) in B d mixing

June 28, 2002BEACH2002 B Physics at the Tevatron B s Mixing Reconstruct B s decays using fully hadronic and semileptonic decay channels. Measure x s =  m s /  With 2 fb -1 should cover full range of theoretically predicted values for x s. Afterwards, we can search for CP violation in the B s system (B s  J   Large window for non-SM physics.

June 28, 2002BEACH2002 B Physics at the Tevatron Unitarity Angles ,  Measure/limit  based on B d    , B s  D s    Measure  using combination of –B d     –B s     Challenges –Separation of B d,s  –Understanding penguin contributions (using both decays helps) –In addition there are interference amplitudes due to mixing. However ample statistics for precision observation of asymmetry. DominantSubdominant b d u sbb b W-W- W-W- W-W- W-W- s u d u u Decays related by d,s interchange Fleischer PLB 459 (1999) 306

June 28, 2002BEACH2002 B Physics at the Tevatron Meson/Baryon Spectroscopy Spectroscopy of B mesons with second generation quarks, and B baryons currently available only at hadron colliders. Mass Measurements: m(B s ) = ± ± GeV/c 2 m(  b ) = ± ± GeV/c 2 m(B c ) = 6.40 ± 0.39 ± 0.13 GeV/c 2 Run I Measurements

June 28, 2002BEACH2002 B Physics at the Tevatron  b and B c  b  J/   b  pD 0  , D 0   K -  b  pK - Run II B c  J/  e/  B c  J/  B c  B s  Run I

June 28, 2002BEACH2002 B Physics at the Tevatron 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.

June 28, 2002BEACH2002 B Physics at the Tevatron 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.

June 28, 2002BEACH2002 B Physics at the Tevatron Charm Production As we lower our p T thresholds we see a lot of charm. (~10 6 reconstructed events per pb -1 !) This will lead to a world class charm program.

June 28, 2002BEACH2002 B Physics at the Tevatron Accelerator Upgrades Replace Main Ring with Main Injector Upgrade Pbar storage Tevatron upgrade: – major luminosity increase  5 x  2 x pb -1  2fb -1  15fb -1 – Short interbunch to limit N int /crossing 3.5  s  396 ns  132 ns Average Number of Interactions per crossing Luminosity 6 Bunches 36 bunches 108 bunches Run I Run IIa Run IIb

June 28, 2002BEACH2002 B Physics at the Tevatron Status of Integrated Luminosity Just finished shutdown. Top Run II luminosity so far 2 X 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.

June 28, 2002BEACH2002 B Physics at the Tevatron CDF Run II Detector Muons Calorimeters Tracking l Tracking ä Silicon Vertex Detector - L00 ä Intermediate Silicon ä Central Outer Tracker l Endplug Calorimeter l Muon systems l TOF

June 28, 2002BEACH2002 B Physics at the Tevatron D0 Run II Detector Build on existing strengths Excellent calorimetry with faster readout Upgraded muon system for better  -ID Add new capabilities Inner tracking (silicon tracker, fiber tracker) with 2T superconducting solenoid Preshowers Pipelined 3-level trigger Si Track Trigger (displaced vertices)

June 28, 2002BEACH2002 B Physics at the Tevatron Physics Program, First Stages Stage 1 (50 pb -1 ) –Refine triggers –Lifetime measurements –Cross sections, branching ratios Stage 2 ( pb -1 ) –First B s mixing measurement –Run II sin(2  ) measurement –Charmonium polarization Stage 3 (200+ pb -1 ) –B s, B c,  b properties measurements –Cross sections, branching ratios –…

June 28, 2002BEACH2002 B Physics at the Tevatron 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.

June 28, 2002BEACH2002 B Physics at the Tevatron 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 |  | = 1.5 (IMU) New Plug calorimeter – Add preshower and shower max detector

June 28, 2002BEACH2002 B Physics at the Tevatron 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.

June 28, 2002BEACH2002 B Physics at the Tevatron Jet Tagging Algorithms To measure mixing, must tag the initial flavor of produced B meson. –Away Side Tags (tag the other b quark) 1.Lepton tagging: b  Xl    b  Xl  2.Kaon tagging: b  c  XK    b  c  XK  3.Jet charge tagging: form p T weighted jet charge, b  Q jet 0 4.Vertex Charge tagging –Same Side Tags 1.Soft pion tag: b associated with collinear  -, b associated with collinear  +

June 28, 2002BEACH2002 B Physics at the Tevatron 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 kHz Level2 Trigger asynchronous Accept rate 300 Hz Level3 Trigger (not shown) Farm of 175 PC’s Accept rate 75 Hz Control Infrastructure