parton distribution function : w asymmetry
DESCRIPTION
Parton distribution function : W asymmetry. W and Z production : Leading order process,. For measurable rapidity range, | Y |TRANSCRIPT
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Parton distribution function : W asymmetry
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ssvvvvW
W
dudu
dududuA
WWWWA
)/()(
)/()(
ZWqq /For measurable rapidity range, |Y|<2.5, x remains within 5×10−4 < x < 5 ×10−2
With the assumption
At high Q2, gluon is dominant parton ⇨ sea quarks are generated by flavour blind g→qq splitting. Production rate is related to gluon distribution function
W and Z production : Leading order process,
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X dQxfQxfdxdxd ˆ),(),( 22
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Some information from Generator (W)
• Asymmetry is nearly flat over pt
• Slight dependency on pseudorapidity
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Some information from Generator ()
• Asymmetry is nearly flat for pt (not much statistics in high pt region)
• Almost flat over the detector acceptance region (e.g., || < 2.5)
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Variables to study
• Production rate as a function of pt and • Asymmetry as a function of Pt and • Main goal : try to choose the best pdf and constrain it’s parameters
– Is it really possible to choose the best pdf ?
• Looked events with different existing pdf in PYTHIA first
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Comparison of different pdf : Generator W
• There is almost no difference in rate/shape• GRV94L : Statistics is low, should have been normalised
W Production rate
W Asymmetry
CTEQ5L
CTEQ3L
CTEQ5M1
GRV94L
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Comparison of different pdf : Generator W
• There is almost no difference in rate/shape
W Production rate
W Asymmetry
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Comparison of different pdf :Generator
• There is almost no difference in rate/shape
• Apparently, it is impossible to choose one pdf by rejecting others
Muon Production rate
Muon Asymmetry
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Signal and backgrounds
• f + fbar' -> g + W+/- 24.65 nb
• f + g -> f' + W+/- 21.19 nb
• All these processes, where decay chains are W→τ () ~17%
• f + fbar -> Z0 1.87 nb
• f + fbar -> g + Z0 2.36 nb
• f + g -> f + Z0 1.92 nb
• g + g -> t tbar ~1 nb (Yet to look)
1. Physics backgrounds :
2. Other backgrounds :• From bottom and charm decays, but associated with jets
• From kaon and pion decay
• Other detector backgrounds
f + fbar' -> W+/- 19.54 nb Signal
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Signals for single W→µν and Rapidity of W
• Isolated single muon
– Global muons in CMSSW
– Energy in all calorimeters due to this muon
– Energy associated with the muon
– Tracks associated with the muon
• Large missing transverse momentum
– Main difficult job is to calculate W direction from muon 4-vector . Two fold ambiguities and also need precise measurement of missing PT.
• No jetsYet to have any selection criteria, but just look at those variables and expected suggestions from you
Used private sample: Gen+Sim with _1_4_5 and Digi+Reco with 1_6_0
Preselection : || < 1.75
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Event shape variables : Number of muons
• No, normalisation at all, just a distribution
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Pt of muon
• Use Pt > 20 GeV and also number of muon ==1
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Missing Et
• Use missing Et >20 GeV
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Eta of muon
Single W W + jet Single Z Z+ jet
→
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Muon associated Hcal energy
• Except last on all are nearly same, which is expected
Single W W + jet Single Z Z+ jet
→
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Tracks momentum with cone 0.5
Single W W + jet Single Z Z+ jet
→
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Calorimeter energy within cone 0.5
• All are muon sample, thus all are nearly same
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Number of jets
• Why “Single W” events has more jets that “W+jet” ????
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Pt of jets
Single W W + jet Single Z Z+ jet
→
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Event shape variables : Eta of jets
Single W W + jet Single Z Z+ jet
→
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Summary
• Why LO ‘single W’ and ‘W+q/g’ has nearly same spectrum of jet (Used default Pythia setup)
• May return back to generated information
• Do not expect to select the best pdf, but need to constraint those parameters for all sets.
• Goal is for pdf, but if we can move fast, this analysis may also use in the initial stage of CMS run to establish the SM.
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WW
WW
WW
WW
bWW
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Xijjiij
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Ys
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dQxfQxfdxdxd
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Comparison of different pdf :Generator
Muon Production rate
Muon Asymmetry
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Comparison of different pdf :Generator
• There is almost no difference in rate/shape
• Apparently, it is impossible to choose one pdf by rejecting others
Muon Production rate
Muon Asymmetry