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

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

3. Sayfa 3 Introduction  This is a short introduction to some current topics in B-Physics in ATLAS Detector at LHC.  We will look at briefly  the LHC  the ATLAS detector

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

5. Sayfa 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 = 10 11  Bunch diameter = 16 μm (hair 50 μm)  Max Luminosity: L = 10 34 cm ‒ 2 s ‒ 1  Collision frequency f = 1/25 ns = 40,000,000 Hz = 40 MHz Debris of a collision E = m c 2

6. Sayfa 6 LHC Detectors CMS

7. Sayfa 7

8. Sayfa 8 16/11/2007 YFD 22 m 44 m ATLAS Detector (http://atlas.ch)

9. Sayfa 9 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

10. Sayfa 10 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

11. Sayfa 11 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

12. Sayfa 12 ATLAS B-Physics Programme B-Physics programme covers many aspects of beauty flavour physics.  by measuring production cross-sections of beauty and charm hadrons and of heavy-flavour quarkonia (J/ψ and Y (upsilon)), ATLAS will provide sensitive tests of QCD predictions.  ATLAS will study the properties of entire family of B-mesons (B +, B d, B s, B c ) and B-baryons (Y, Λ b )  Precise measurements of weak B-hadrons decays  Rare decays of B-hadrons

13. Sayfa 13  The rate of B-hadron production at the LHC is enormous thanks to the large hadronic cross-section for b-quark production and the high luminosity of the machine (L = 10 33 / s.cm 2 )  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 from LHCb, which is a dedicated B-physics experiment. ATLAS and CMS will improve the combined precision of B-physics measurements from the LHC.

14. Sayfa 14  In ATLAS, B-Physics potential begins during early data taking at low luminosity (L = 10 31 / s.cm 2 )  Main B-Physics measurements will be made at the luminosity of L = 10 33 / s.cm 2.  With the integrate luminosity of L int = 10 pb -1 ATLAS will be able to register about 1.3x10 5 events containing  either directly produced from p-p collisions  or indirectly from decays of B-hadrons.

15. Sayfa 15  During the period of L int = 10 – 100 pb -1  B-physics and heavy quarkiona signatures will help understand the detector performance and muon trigger  promt J/ψ and Y events and B-hadron decays to muon pairs via J/ψ will be analysed  followind exclusive decays will be stuied  During the period of L int = 200 pb -1 – 1 fb -1  Statistics will be simalar to Tevatron  SM rare decays will be studied (e.g. )  During the period of L int = 10 – 30 fb -1 (around 3 years)  Luminosity will mostly be L = 10 33 / s.cm 2  Measuremnts of Λ b and osciallation pghenomena of Bs – Bs_bar

16. Sayfa 16 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 p T > 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.

17. Sayfa 17 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.

18. Sayfa 18 Example Reconstruction