Experimental Heavy Quark Physics XXX Nathiagali Summer College 27 June - 2 July 2005 Experimental Heavy Quark Physics Fabrizio Bianchi University of Torino, Italy and INFN - Torino Fabrizio Bianchi

XXX Nathiagali Summer College 27 June - 2 July 2005 Outline Lecture 1: Fundamental Questions in Particle Physics Goals of Heavy Quark Physics Tools for Heavy Quark Physics Lecture 2: CP Primer Observation of Direct CP Violation Measurement of sin2b Lecture 3: Measurement of a and g Measurement of |Vcb| and |Vub| F. Bianchi XXX Nathiagali Summer College Fabrizio Bianchi

Fundamental Questions in Particle Physics: Generation and Masses In the SM, Gauge Forces do not distinguish fermions of different generations: • e,µ have same electrical charge • quarks have same color charge Why generations ? Why 3 ? Why fermion masses are so different ? F. Bianchi XXX Nathiagali Summer College

Fundamental Questions in Particle Physics: What happened to antimatter ? All Matter no Antimatter Matter Antimatter Symmetric Big Bang F. Bianchi XXX Nathiagali Summer College

Fundamental Questions in Particle Physics: Baryogenesis Sakharov criteria: • Baryon-number violation • CP violation • Non-equilibrium SM satisfies prerequisites for baryogenesis • Baryon-number violation at high temperatures (DB=DL) • Non-equilibrium during phase transitions (symmetry breaking) CP violation in the quark and lepton sectors Fundamental connection between particle physics and cosmology! F. Bianchi XXX Nathiagali Summer College

Luminosity and Energy Frontiers Study of Flavor Physics is complementary to the discovery of new particles at high energy Any extension of the SM that can solve the hierarchy problem contains many new flavor parameters If New Physics exists at or below a TeV, its effects should show up in flavor physics! Flavor and CP-violating couplings can only be studied using precision measurements at highest luminosity F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College Example: the top quark Couplings ( |Vts| ~ 0.04 and |Vtd| ~ 0.003) measured in B physics. Mass prediction based on precision electro weak measurements. Direct production has proved existence and measured mass and spin. Study of Flavor Physics is an essential part of the roadmap for the exploration of new energy scales, now and even in the LHC era. F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College CKM Matrix I SM accounts for flavor changing quark transition through the coupling of the V-A charged current operator to a W boson: where: Vij are the elements of the CKM matrix i, j run on the three quark generations F. Bianchi XXX Nathiagali Summer College

Wolfenstein Parameterization CKM Matrix II CKM matrix can be regarded as a rotation from the quark mass eigenstates (d, s, b) to a set of new states (d’, s’, b’) with diagonal coupling to u, c, t Complex matrix described by 4 independent real parameters (including one phase) l~ 0.22 sinθC Cabibbo angle Wolfenstein Parameterization 2 ® 1 ~l 3 ® 2 ~l2 3 ® 1 ~l3 h changes sign under CP F. Bianchi XXX Nathiagali Summer College

Product of 1st and 3rd columns Unitarity Triangle Product of 1st and 3rd columns (1 of 6 relations) Can be represented as a triangle in the complex plane a = f2 g = f3 b = f1 Dividing all sides by F. Bianchi XXX Nathiagali Summer College

Normalized Unitarity Triangle h Apex at r, h a g b r F. Bianchi XXX Nathiagali Summer College

Goals of Heavy Quark Physics Precise determinations of the elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix Measure sides and angles of the Unitarity Triangle Over constraint r and h Tests of the CKM mechanism of flavor and CP violation Search for deviations from the SM F. Bianchi XXX Nathiagali Summer College

What you want to achieve… F. Bianchi XXX Nathiagali Summer College

Averaging Results of Different Experiments Heavy Flavor Averaging Group http://www.slac.stanford.edu/xorg/hfag/ Averages results from different experiments. UTfit: http://utfit.roma1.infn.it/ Uses Bayesan approach described in: hep-ph/0012308 to makes global fits to UT CKM Fitter: http://www.slac.stanford.edu/xorg/ckmfitter/ckm_welcome.html Uses Frequentistic approach to makes global fits to UT F. Bianchi XXX Nathiagali Summer College

To do Heavy Quark Physics… XXX Nathiagali Summer College 27 June - 2 July 2005 To do Heavy Quark Physics… You need: To produce a lot of b & c hadrons Hadrons vs. e+e- machines To build a detector with: high tracking efficiency good tracking and vertexing to have good mass resolution good particle identification capability to distinguish among different modes and reject background good g and p0 reconstruction capability to reconstruct neutral hadrons F. Bianchi XXX Nathiagali Summer College Fabrizio Bianchi

Hadronic vs e+e- colliders I Hadronic machines: • enormous production of c and b-hadrons (sbb ~ 50 mb) • all b-hadrons can be produced • trigger is challenging • complicated many-particles events • incoherent production of B mesons Tevatron @ FNAL: CDF, D0, BTEV LHC @ CERN: CMS, ATLAS, LHCB F. Bianchi XXX Nathiagali Summer College

Hadronic vs e+e- colliders II e+ e- collider at the Y(4S) (b-factory): • Trigger is moderately easy. • Simpler events, easier to reconstruct. Copious production of b, c and t. sbb = 1.05 nb scc = 1.30 nb stt = 0.94 nb F. Bianchi XXX Nathiagali Summer College

Hadronic vs e+e- colliders III B Physics at an e+ e- collider at the Y(4S): • only B0 and B+ can be produced. all the final state particles come from B decays. • coherent production of B mesons in a L=1 state. • B are produced almost at rest in the Y(4S) rest frame. Travel ~26 mm before decaying in that frame. Solution: use beams of different energies to boost the Y(4S) rest frame w.r.t. the lab frame increasing the spatial separation of the decays making it measurable. PEP-II @ SLAC: BaBar KEK-B @ KEK: Belle F. Bianchi XXX Nathiagali Summer College

Hadronic vs e+e- colliders IV XXX Nathiagali Summer College 27 June - 2 July 2005 Hadronic vs e+e- colliders IV Others e+ e- colliders (mostly charm/t physics): CESR-c @ Cornell (3 < < 5 GeV): CLEO-c BEPC @ IHEP (3 < < 4 GeV ): BES Plan to start in 2007 with L ~ 1034 cm2 s-1 From now on, I’ll discuss mainly b-factories F. Bianchi XXX Nathiagali Summer College Fabrizio Bianchi

XXX Nathiagali Summer College KEK-B vs PEP-II Both started in summer 1999. KEK-B: 8.0 GeV electrons and 3.5 GeV positrons bg = 0.42 PEP-II: 9.0 GeV electrons and 3.1 GeV positrons bg = 0.56 mean separation between decay vertices: 260 mm CM boost: • folds particles forward • Increases momentum range to cover with Particle ID F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College PEP-II F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College Interaction Region F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College PEP-II Luminosity F. Bianchi XXX Nathiagali Summer College

Trickle injection at the B Factories XXX Nathiagali Summer College 27 June - 2 July 2005 Trickle injection at the B Factories Best shift, no trickle Best shift, LER only trickle Nov 2003 Best shift, double trickle Mar 2004 PEP-II: ~5 Hz continuous KEKB: at ~5-10 min intervals PEP-II Lumi HER current LER current F. Bianchi XXX Nathiagali Summer College Fabrizio Bianchi

XXX Nathiagali Summer College BABAR Detector F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College BABAR Detector F. Bianchi XXX Nathiagali Summer College

Silicon Vertex Tracker I Performance Requirements: • Single vertex resolution along z-axis better than 80 μm • Stand-alone tracking for 50 < pt < 120 MeV/c with high efficiency PEP II Constraints: • Dipole magnets (B1) at +/-20 cm from interaction point • Polar angle: 17.2o < q < 150o • Bunch Crossing Period 4.2 ns • Radiation exposure at innermost layer: average 33 Krad/year in beam plane: 240 Krad/year F. Bianchi XXX Nathiagali Summer College

Silicon Vertex Tracker II 5 layers of double-sided AC-coupled Silicon 340 Si wafers, 150K channels Custom rad-hard readout IC (the AToM chip) Stand-alone tracking for slow particles: • inner 3 layers for angle and impact parameter measurement • outer 2 layers for pattern recognition and low pt tracking F. Bianchi XXX Nathiagali Summer College

Silicon Vertex Tracker III F. Bianchi XXX Nathiagali Summer College

Silicon Vertex Tracker: Performances z side Phi side SVT Hit Resolution vs Incident Track Angle Average hit efficiency ~97% Slow pion efficiency >70 % for pT > 50MeV Average hit resolution 10-40 μm, depending on angle of track No change observed so far due to radiation F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College Drift Chamber I 40 layers of wires (7104 cells) Helium:Isobutane 80:20 gas, Al field wires, Beryllium inner wall, and all readout electronics mounted on rear endplate Particle identification from ionization loss (7% resolution) F. Bianchi XXX Nathiagali Summer College

Drift Chamber: Performances F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College Tracking sPt/Pt ~ 1% @ 3 GeV Doca resolution vs pt F. Bianchi XXX Nathiagali Summer College

Detection of Internally Reflected Cherenkov light I Ring imaging Cherenkov detector based on total internal reflection. Uses long, rectangular bars made from synthetic fused silica ("quartz") as both radiator and light guide. A charged particle traversing a DIRC quartz bar with velocity produces Cherenkov light if nb > 1. Through internal reflections, the Cherenkov light from the passage of a particle is carried to the ends of the bar and to an array of 11,000 2.5 cm-diameter phototubes. F. Bianchi XXX Nathiagali Summer College

Detection of Internally Reflected Cherenkov light II The high optical quality of the quartz preserves the angle of the emitted Cherenkov light. The measurement of this angle, in conjunction with knowing the track angle and momentum from the drift chamber, allows a determination of the particle mass. qc = arcos (1/nb) F. Bianchi XXX Nathiagali Summer College

Detection of Internally Reflected Cherenkov light III F. Bianchi XXX Nathiagali Summer College

DIRC: Control samples for p and K Projection for 2.5 < p < 3 GeV/c F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College DIRC Impact Impact on D0 purity: Background rejection factor ~ 5 F. Bianchi XXX Nathiagali Summer College

Electromagnetic Calorimeter 6580 CsI(Tl) crystals with photodiode readout About 18 X0 0 s = 5.0% F. Bianchi XXX Nathiagali Summer College

Instrumented Flux Return Up to 21 layers of resistive-plate chambers (RPCs) between iron plates of flux return Muon identification > 800 MeV/c Neutral Hadrons (KL) detection; also with EMC/ECL Bakelite RPCs Problems with QC, dark current, and stability Forward end cap replaced in 2003; barrel replaced with LST in 2004- 2006 F. Bianchi XXX Nathiagali Summer College

Instrumented Flux Return F. Bianchi XXX Nathiagali Summer College

Electron and Muon ID Muon ID Efficiency & Electron ID Efficiency p Mis-ID Probability Electron ID Efficiency & p Mis-ID Probability F. Bianchi XXX Nathiagali Summer College

XXX Nathiagali Summer College F. Bianchi XXX Nathiagali Summer College