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Research of Z generation

Research of Z generation. Ken- ichiro KOIKE. Contents. What is Z boson Event Selection ~ Z candidates Isolation Cut study Z → μμ Cross Section study To Do. Z boson. BR = ( 20.00 ± 0.06 ) % BR = ( 15.6 ± 0.6 ) % BR = ( 11.6 ± 0.4 ) % BR = ( 3.3658 ± 0.0023 ) %.

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Research of Z generation

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  1. Research of Z generation Ken-ichiro KOIKE

  2. Contents • What is Z boson • Event Selection~ Z candidates • Isolation Cut study • Z→μμCross Section study • To Do Ken-ichiro KOIKE

  3. Z boson BR = ( 20.00 ± 0.06 ) % BR = ( 15.6 ± 0.6 ) % BR = ( 11.6 ± 0.4 ) % BR = ( 3.3658 ± 0.0023 ) % • QZ = 0, spin 1, MZ = 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(νe, νμ, ντ) • up-type quark(u, c) • down-type quark(d, s, b) • lepton(e, μ, τ) Ken-ichiro KOIKE

  4. Z Event Selection Jet BackgroundElectroweak BackgroundCosmic Background negligible! heavy-flavor quark → b/c hadrons →muons • Z →ττ→ muons • W →μνw/ second high Pt muon in a jet • t-tbar decay →dimuon • → μ + jet • di boson production small fraction ! Ken-ichiro KOIKE

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

  6. Kinematics(Pt,η,φ) of Zcandidates Leading Pt Phi Eta Second Pt Ken-ichiro KOIKE

  7. Isolation cut μ ~ Tag and Probe method ~ Mass Window : 80 < M < 100 → 74 candidates ∫Ldt = 290 nb-1 Real Data and MC show agreement within the statistical uncertainty. Ken-ichiro KOIKE

  8. Z→μμCross 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% Ken-ichiro KOIKE

  9. Z→μμCross Section • 71 candidates290 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 less than prediction of MC 989nb-1 … Ken-ichiro KOIKE

  10. Summary & To Do • 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. Ken-ichiro KOIKE

  11. Back Up Ken-ichiro KOIKE

  12. Muon Detector 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 Ken-ichiro KOIKE

  13. Inner Detector 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 Ken-ichiro KOIKE

  14. Isolation cut Ken-ichiro KOIKE

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

  16. Invariant Mass ~ Isolation cut comparison ~ Ken-ichiro KOIKE

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