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30/Jul/2010 1 Research of Z generation Ken-ichiro KOIKE

Research of Z generation

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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 ) %. - PowerPoint PPT Presentation

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Page 1: Research of Z generation

30/Jul/2010 1

Research of Z generation

Ken-ichiro KOIKE

Page 2: Research of Z generation

30/Jul/2010 2

Contents

Ken-ichiro KOIKE

What is Z boson

Event Selection ~ Z candidates

Isolation Cut study

Z→μμ Cross Section study

To Do

Page 3: Research of Z generation

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Z boson

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 modeneutrino(νe, νμ, ντ)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

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Z Event SelectionFit Collision Event High Pt Event Z->μμ  EventBest Match |Zvtx| < 150 mm Combined Opposite Charge

Match χ square < 100 Pt > 15 GeV Pt > 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

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di-muon Invariant MassMass Window : 80 < M < 100 → 71 candidates of Z boson

∫Ldt = 290 nb-1Constant 20.58±3.38Mean 90.79±0.36Sigma 3.12±0.38

status (Monte Carlo)

Monte Carlo histogram is scaled to Real Data by Integrated Luminosity

30/Jul/2010 Ken-ichiro KOIKE

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Kinematics(Pt,η,φ) of Z candidatesLeading Pt

Second Pt

Phi

Eta

30/Jul/2010 Ken-ichiro KOIKE

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Isolation cutFit Collision Event High Pt Event Z->μμ  EventBest Match |Zvtx| < 150 mm Combined Opposite Charge

Match χ square < 100 Pt > 15 GeV Pt > 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

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Z→μμ Cross Section

LdtA

NZZ

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%

ZN

A

trigreco

Ldt

30/Jul/2010 Ken-ichiro KOIKE

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Z→μμ Cross Section

ZN

A

trigreco

Ldt 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 triggerScale Factor : 0.970±0.012(stat.)±0.037(sys.)

acceptance : 45.32±0.02(stat.)%

LdtA

NZZ

572.33±0.0156(stat.)±0.053(sys.)  pb-1

30/Jul/2010 Ken-ichiro KOIKE

less than prediction of MC 989nb-1 …

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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.

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Back Up

30/Jul/2010 Ken-ichiro KOIKE

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Muon Detector

30/Jul/2010 Ken-ichiro KOIKE

MDTRPCTGC

・・・ Barrel : |η|<1.0 End Cap : 1.0<|η|<2.4・・・ Barrel : |η|<1.05・・・ End Cap : 1.0<|η|<2.7

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Inner Detector

30/Jul/2010 Ken-ichiro KOIKE

PixelSCTTRT

・・・ 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

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Isolation cut

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Invariant Mass ~ Isolation cut comparison ~

30/Jul/2010 Ken-ichiro KOIKE

∫Ldt = 290 nb-1

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Invariant Mass ~ Isolation cut comparison ~

30/Jul/2010 Ken-ichiro KOIKE