1. 30/Jul/20101 Research of Z generation Ken-ichiro KOIKE

2. 30/Jul/20102 Contents Ken-ichiro KOIKE  What is Z boson  Event Selection ~ Z candidates  Isolation Cut study  Z→μμ Cross Section study  To Do

3. 30/Jul/20103 Z boson  Q Z = 0, spin 1, M Z = 91.1876±0.023 GeV  mediate weak force  Discovery Gargamelle bubble chamber observed Weak Neutral Current in 1973 In May 1983, Z bozon was discovered with UA1 and UA2 experiment at Super Proton Synchrotron(SPS)  Decay mode neutrino(ν e, ν μ, ν τ ) up-type quark(u, c) down-type quark(d, s, b) lepton(e, μ, τ) BR = ( 20.00 ± 0.06 ) % BR = ( 15.6 ± 0.6 ) % BR = ( 11.6 ± 0.4 ) % BR = ( 3.3658 ± 0.0023 ) % Ken-ichiro KOIKE

4. 30/Jul/20104 Z Event Selection FitCollision EventHigh Pt Event Z->μμ Event Best Match|Zvtx| < 150 mmCombinedOpposite Charge Match χ square < 100Pt > 15 GeVPt > 15, 20 GeV Fit χ square < 100|η| < 2.5|η| < 2.5, 2.4 ΣPt/Pt < 0.2 80 < Mμμ < 100 GeV Jet Background Electroweak Background Cosmic Background Z → ττ → muons W → μν w/ second high Pt muon in a jet t-tbar decay → di muon → μ + jet di boson production small fraction ! negligible! heavy-flavor quark → b/c hadrons → muons Ken-ichiro KOIKE

5. 5 di-muon Invariant Mass Mass Window : 80 < M < 100 → 71 candidates of Z boson ∫Ldt = 290 nb -1 Constant 20.58±3.38 Mean 90.79±0.36 Sigma 3.12±0.38 status (Monte Carlo) Monte Carlo histogram is scaled to Real Data by Integrated Luminosity 30/Jul/2010 Ken-ichiro KOIKE

6. 6 Kinematics(Pt,η,φ) of Z candidates Leading Pt Second Pt Phi Eta 30/Jul/2010 Ken-ichiro KOIKE

7. 7 Isolation cut FitCollision EventHigh Pt Event Z->μμ Event Best Match|Zvtx| < 150 mmCombinedOpposite Charge Match χ square < 100Pt > 15 GeVPt > 15, 20 GeV Fit χ square < 100|η| < 2.5|η| < 2.5, 2.4 ΣPt/Pt < 0.2 80 < Mμμ < 100 GeV μ Mass Window : 80 < M < 100 → 74 candidates 30/Jul/2010 Ken-ichiro KOIKE ~ Tag and Probe method ~ Real Data and MC show agreement within the statistical uncertainty. ∫Ldt = 290 nb -1

8. 8 Z→μμ Cross Section formula for calculation of cross section  # of Z candidate  acceptance  efficiency (reconstruction, trigger)  integrated luminosity the cross section is predicted to be 989 pb (√s=7 TeV) by Pythia Monte Carlo uncertainty is about 3% 30/Jul/2010 Ken-ichiro KOIKE

9. 9 Z→μμ Cross Section 71 candidates 290 nb -1  reconstruction efficiency ・・・ relative efficiency technique (ID and MS) Scale Factor : 0.989±0.010(stat.)±0.038(sys.)  trigger efficiency ・・・ L1_MU0 trigger Scale Factor : 0.970±0.012(stat.)±0.037(sys.) acceptance : 45.32±0.02(stat.)% 572.33±0.0156(stat.)±0.053(sys.) pb -1 30/Jul/2010 Ken-ichiro KOIKE less than prediction of MC 989nb -1 …

10. 10 Summary & To Do 30/Jul/2010 Ken-ichiro KOIKE Summary  I researched the Z boson generation.  71 candidates of Z→μμ were discovered with my event selection.  Study of Isolation Cut showed agreement between real data and MC.  Z cross section from real data was less than prediction from MC. To Do  More research with much amount of statistics  Study other physics quantities  Check the cause of disagreement of Z→μμ cross section  More and more study for myself Thank you so much.

11. 11 Back Up 30/Jul/2010 Ken-ichiro KOIKE

12. 12 Muon Detector 30/Jul/2010 Ken-ichiro KOIKE MDT RPC TGC ・・・ Barrel : |η|<1.0 End Cap : 1.0<|η|<2.4 ・・・ Barrel : |η|<1.05 ・・・ End Cap : 1.0<|η|<2.7

13. 13 Inner Detector 30/Jul/2010 Ken-ichiro KOIKE Pixel SCT TRT ・・・ B layer : |η|<2.5 Barrel : |η|<1.7 End Cap : 1.7<|η|<2.5 ・・・ Barrel : |η|<1.4 End Cap : 1.4<|η| <2.5 ・・・ Barrel : |η|<0.7 End Cap : 0.7<|η|<2.5

14. 14 Isolation cut 30/Jul/2010 Ken-ichiro KOIKE

15. 15 Invariant Mass ~ Isolation cut comparison ~ 30/Jul/2010 Ken-ichiro KOIKE ∫Ldt = 290 nb -1

16. 16 Invariant Mass ~ Isolation cut comparison ~ 30/Jul/2010 Ken-ichiro KOIKE