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Introduction to B Physics in ATLAS Detector at LHC

Introduction to B Physics in ATLAS Detector at LHC. Ahmet BİNGÜL Department of Engineering Physics University of Gaziantep. Feb 2010. Outline. Introduction Physics in ATLAS Experiment ATLAS B-Physics Programme Trigger Simulation of the Events Example Reconstruction. Introduction.

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Introduction to B Physics in ATLAS Detector at LHC

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  1. Introduction to B Physics in ATLAS Detector at LHC Ahmet BİNGÜL Department of Engineering Physics • University of Gaziantep Feb 2010

  2. Outline • Introduction • Physics in ATLAS Experiment • ATLAS B-Physics Programme • Trigger • Simulation of the Events • Example Reconstruction

  3. Introduction • This is a short introduction to some current topics in B-Physics in ATLAS Detector at LHC. • Wewilllook at briefly • the LHC • the ATLAS detector

  4. LHC: Large Hadron Collider • PHYSICS • Higgs Boson(s) • Supersymmetric particles • furher quarks and/or hadrons • Big-Bang and mini-black holes • Circumference 27 km • ~100 m underground • Protons ve Pb nuclei will collide • Cost: 3 billions € EP328 – Particle Physics

  5. LHC About p-p collisions • Max proton energy: E = 7 TeV • Velocity: v = 0.999999991 c ~ 300,000 km/s • 2808 x 2808 bunches of protons • # of p / bunch = 1011 • Bunch diameter = 16 μm (hair 50 μm) • Max Luminosity: L = 1034 cm‒2s‒1 • Collision frequency f = 1/25 ns = 40,000,000 Hz = 40 MHz Debris of a collision E = mc2

  6. LHC Detectors CMS

  7. ATLAS Detector (http://atlas.ch) 22 m 44 m YFD

  8. Physics Groups in ATLAS https://twiki.cern.ch/twiki/bin/view/Atlas/AtlasResults • Standard Model (SM) • QCD • W/Z and jets • Electroweak measurements • Higgs • Discovery of SM Higgs Boson (for several decay channels) • Charged Higgs Boson searces

  9. Physics in ATLAS • B-Physics • Heavy quarkonium physics with early ATLAS data • Production cross-sections measurements • Study of B-hadrons • Rare B-dacays • Top Physics • t-tbar pair cross-section • Top mass, charge, spin measurements • Rare top decays

  10. Physics in ATLAS • SUSY • Discovery of SUSY particles • Test of SUSY models • Exotics • Black hole Production • New quarks and leptons • Heavy Ion • Results of Pb-Pb collisions • Heavy quark production • Jet studies • Quarkonia Reconstruction

  11. ATLAS B-Physics Programme B-Physicsprogrammecoversmanyaspects of beautyflavourphysics. • bymeasuringproductioncross-sectionsof beautyandcharmhadronsandof heavy-flavourquarkonia (J/ψand Y (upsilon)),ATLAS willprovidesensitivetests of QCD predictions. • ATLAS willstudytheproperties of entirefamily of B-mesons (B+, Bd, Bs, Bc) andB-baryons (Y, Λb ) • Precisemeasurements of weakB-hadronsdecays • Raredecays of B-hadrons

  12. The rate of B-hadron production at the LHC is enormous thanks to the large hadronic cross-sectionfor b-quark production and the high luminosity of the machine (L = 1033 / s.cm2) • About one collision in every hundred will produce a b-quark pair. (better S:N ratio wrt Tevatron) • At the LHC, ATLAS and CMS will face stiff competition fromLHCb, which is a dedicated B-physics experiment.ATLAS and CMS will improve the combined precision of B-physicsmeasurements from the LHC.

  13. In ATLAS, B-Physicspotentialbeginsduringearly data taking at lowluminosity (L = 1031/ s.cm2) • MainB-Physicsmeasurementswill be made at theluminosity of L = 1033/ s.cm2. • Withtheintegrateluminosity of Lint = 10 pb-1ATLAS will be abletoregisterabout1.3x105eventscontaining • eitherdirectlyproducedfrom p-p collisions • orindirectlyfromdecays of B-hadrons.

  14. During the period of Lint = 10 – 100 pb-1 • B-physics and heavy quarkiona signatures will helpunderstand the detector performance and muon trigger • promt J/ψ and Y events andB-hadron decays to muon pairs via J/ψ will be analysed • followind exclusive decays will be stuied • During the period of Lint = 200 pb-1 – 1 fb-1 • Statistics will be simalar to Tevatron • SM rare decays will be studied (e.g. ) • During the period of Lint = 10 – 30 fb-1 (around 3 years) • Luminosity will mostly be L = 1033/ s.cm2 • Measuremnts of Λb and osciallation pghenomena of Bs – Bs_bar

  15. Trigger • All B-Physics studies include trigger reconstruction • ATLAS have three levels of trigger • L1 – Hardware trigger • L2 - L3 – Software trigger • B-Physics events is initiated • by a L1 di-muon trigger • by a L1 single-muon trigger • L2 is used to combine ID tracks with L1 muon • each muon has to have pT > 4 GeV (later rising to 6-8 GeV) • After getting L1 muon(s), cuts on invariant mass and secondary vertex reconstruction of B decay products are used.

  16. Simulation of Events • Some 1 million B-hadron events, along with 4x105 prompt J/ψ and Y as well as c-cbar events were produced using PYHTIA 6.4. • The events were passed trough detector simulation based on GEANT4.

  17. Example Reconstruction

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