Vivek Sharma University of California, San Diego BaBar Physics Status Vivek Sharma University of California, San Diego 9.14.1999 V.Sharma DOE Review

Outline of This Talk UCSD physics effort BaBar physics infrastructure responsibilities CP physics and B Mixing analyses BaBar physics preparation : snapshots First events and the  (4S) scan Reminder: CP Asymmetry measurement checklist Luminosity B reconstruction Flavor tagging Delta Z measurement Status of BaBar physics software Tracking and vertex reconstruction Particle identification and flavor tag Charm and B meson reconstruction Near future physics plans and requirements Precision tracking and vertexing Efficient and Accurate b quark flavor identification Data access, Simulation and Computing 9.14.1999 V.Sharma DOE Review

BaBar Physics Infrastructure Responsibilities Charged Particle Reconstruction Coordinator Gerhard Raven BaBar MicroDST Data-Format Development Riccardo Faccini Vertexing and Particle Composition Tools : Development and Validation Riccardo Faccini, Shahram Rahatlou, David MacFarlane and Vivek Sharma Primary Vertex Reconstruction Particle Identification (dE/dx) in DCH Fergus Wilson 9.14.1999 V.Sharma DOE Review

Current UCSD Physics Analysis Activities  (4S) Scan Riccardo Faccini B Reco in B  Charmonium X modes Shahram Rahatlou, Carsten Hast, Riccardo Faccini and Vivek Sharma B Reco in B  D/D* X Modes Shahram Rahatlou, Fergus Wilson, David MacFarlane and Vivek Sharma Time-dependent B0 Mixing Gerhard Raven, David MacFarlane,Vivek Sharma and Shahram Rahatlou Data Validation : UCSD group 9.14.1999 V.Sharma DOE Review

MicroDST Development For BaBar Physics Analyses Objective : Fill a gaping hole in BaBar Data Analysis Concept To speed up analysis time, create a OO Database of information for each reconstructed event which Is fast to access Possesses comprehensive info about all attributes of event for physics analysis Is small in size ~ 3Kb/event Interfaces with (comprehensive but rather bulky and slow ) BaBar reconstruction software OO environment Implementation Contains lists of candidate charged tracks, calorimeter objects etc variables describing each candidate in an event (e.g., momentum, energy, track error matrix, basic subsystem information etc ) Result “Micro” is THE Database used by all BaBar physicists for physics analysis (e.g. LP99). Designed and Implemented by R.Faccini 9.14.1999 V.Sharma DOE Review

First Data ! : 26 May 1999 9.14.1999 V.Sharma DOE Review

Energy Scan for (4S) Next Step : Scan for the peak of (4S) and sit at the peak Have sat on the peak mostly with modest off-Y(4s) running Analysis and feedback done “on the fly” with micro DST: R.Faccini 9.14.1999 V.Sharma DOE Review

Time Dependent CP Asymmetry Measurement Btag Bcp lepton Kaon Z  Three Requirements 1. Large samples of reconstructed “CP-interesting” decays of B Mesons => Luminosity at (4s) 2. Ability to measure the Z between the tag B and the CP B  Precision tracking and Vertexing 3. Ability to tag flavor of the other B(tag) via leptons or Kaon => Particle Identification Relatively quick consolidation on all three requirements achieved in early BaBar data 9.14.1999 V.Sharma DOE Review

The Interaction Region First Determine average location of beam “ribbon” (run-by-run) X Y Z 9.14.1999 V.Sharma DOE Review

Primary Vertex X Vs Z position Beams Are Tilted in Z Primary Vertex X Vs Z position Tilt ~ 20 mrad 9.14.1999 V.Sharma DOE Review

Impact Parameter Resolution : Trajectory near IP Critical for time-dependent CP Asymmetry Measurement B Decay IP Very close to expected precision, will be better with SVT/DCH alignment resolution ( see Raven talk next ) 9.14.1999 V.Sharma DOE Review

Ks Reconstruction and Lifetime Clean Ks signal with high ~ 60% efficiency Evidence for good estimate of tracking efficiency and errors Ks lifetime consistent with PDG 9.14.1999 V.Sharma DOE Review

Specific Ionization In Drift Chamber dE/dx resolution of 7.5% is close to design Useful for low momentum particle ID Expect final calibration in next few weeks 9.14.1999 V.Sharma DOE Review

DIRC Particle ID Performance Critical for high momentum tracks where dE/dx can not separate /K Factor of ~ 14 pion rejection Efficiency ~ 67% 9.14.1999 V.Sharma DOE Review

Muon Identification 9.14.1999 V.Sharma DOE Review

Electron Identification and  Rejection Compare E/P : energy deposited in EMC with momentum measured in DCH Electrons Pions Needs Better Calibration of EMC 9.14.1999 V.Sharma DOE Review

Inclusive Electron Spectrum Preliminary look at the lepton spectrum, shown in the Y(4s) rest frame Identification efficiencies and fake rate under study. Shape of the spectrum agrees with MC prediction for lepton spectrum in B decays Kinematic end point 9.14.1999 V.Sharma DOE Review

CP-Interesting B Meson Decays “CP Interesting” B Decay Modes Most B decay final states contain J/, D* or Ks Their efficient reconstruction is critical 9.14.1999 V.Sharma DOE Review

Identification After EMC calibration, will be sensitive to very low energy (>50 MeV) 9.14.1999 V.Sharma DOE Review

Inclusive D* Reconstruction D* and D masses and resolution consistent with expectations 9.14.1999 V.Sharma DOE Review

Inclusive D* Reconstruction 9.14.1999 V.Sharma DOE Review

Slow Pion From D* Fitted Thru The Interaction Point D*-D mass resolution limited by slow pion momentum reconstruction ~ 0.8 MeV Precision in low pion trajectory reconstruction limited due to large mult. coulomb scattering. Can use IP coordinates as a constraint to better define slow pion  and  Leads to much better resolution D* -D Mass Diff(GeV) Hope to refine technique to have ~180 KeV resolution, measure D* natural width if large 9.14.1999 V.Sharma DOE Review

Inclusive J/Psi Production 9.14.1999 V.Sharma DOE Review

Inclusive J/ Production Signal/noise will improve with better electron/muon selection and better DCH-SVT alighnment 9.14.1999 V.Sharma DOE Review

DCH/SVT Misalignment and Impact on Mass Resolution 500  SVT-DCH Misalignment 9.14.1999 V.Sharma DOE Review

Fully Reconstructed B Mesons Lepton Photon 99: first event fully reconstructed 9.14.1999 V.Sharma DOE Review

9.14.1999 V.Sharma DOE Review

Fully Reconstructed B Decays UCSD ! 9.14.1999 V.Sharma DOE Review

B Meson Reconstruction Shown today is a fraction of the decay modes that we plan to reconstruct Reconstruction rate is comparable to CLEO, but we will do better after EMC and DIRC are calibrated  Better particle identification and resolution Encouraging that within 3 months of beginning of data taking, we are cleanly reconstructing B mesons from data recorded so far 9.14.1999 V.Sharma DOE Review

Luminosity Projections Expect ~ by Christmas 99. This is “CP engineering data” Expect by July 2000. With this dataset we will start being sensitive to …(depending on its true value ) 9.14.1999 V.Sharma DOE Review

Immediate Physics Goals Align and fine-tune the tracking system for optimal tracking efficiency and impact parameter(vertex) resolution IN PROGRESS (see Raven talk next) Calibrate EMC, DIRC and optimize Muon ID efficiency in IFR. Optimize global particle Identification and b flavor tag Crucial test of “CP-Readiness” will be precise measurements of Time Dependent Mixing B Lifetime With the 1999 BaBar data 9.14.1999 V.Sharma DOE Review

UCSD Physics Goals Continue fine-tuning BaBar charged particle tracking for CP studies Build large samples of fully reconstructed B and Charm mesons B  X,  ‘X and other Charmonium modes B  D*X, DX etc Use this sample for Time-dependent mixing Studies B lifetime is a by-product of Mixing studies Expect first B-mixing results by Spring 2000 Concentrate on measurement of 9.14.1999 V.Sharma DOE Review

UCSD leading CP physics effort in BaBar 9.14.1999 V.Sharma DOE Review

Computing Challenges Ahead The data taking and analysis experience of last few months has pointed to inadequacies in the current model of BaBar computing ( see MacFarlane talk later today) Amongst other problems, access and analysis of processed data is quite painful and time-consuming Turn around time for ~0.2 is ~weeks already will get worse with 10 level data BaBar has realized that this could be a show-stopper and is working towards a non-Objectivity based solution which still utilises existing software Needs careful attention in the next months 9.14.1999 V.Sharma DOE Review

Summary and Conclusions BaBar is off to a very good start Tracking system has worked flawlessly from the beginning Calibration and fine tuning of EMC, DIRC etc in progress BaBar is able to reconstruct the intermediate states ( Ks, D*,  ) necessary for reconstructing “cp-interesting” B decays B mixing is the first major goal towards CP violation searches Can expect sensitivity to By next year if the machine continues its excellent run towards high luminosity 9.14.1999 V.Sharma DOE Review