W and Z with 10 fb1 of data

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W and Z with 10 fb-1 of data

• Kamal Benslama
• Kevin Black
• Stephane Willocq

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Outline

• Introduction Why Z/W
• What we know today
• Basic Theoretical Framework
• Current Bounds
• What we can hope to do in 10 fb-1 of data?
• Update of Z Rome Analysis
• Start of W Analysis
• Plans

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Introduction Why new Gauge Bosons?

• Standard model based on local gauge invariance
• SU(3)C x SU(2)Wx U(1)Y
• Natural to ask Are these all of the fundamental
  interactions of nature? What are the limits on
  more?
• The Standard Model is an effective theory
  likely to break down at the electroweak scale
  natural to think that we might find evidence for
  new gauge forces at this scale

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What kind?

• Three types
• Confined Perhaps some of the particles we see
  today are composites bound by some new confined
  force (eg, Top color)
• Coulomb More forces that are so week we havent
  seen them yet
• Higgs type Heavier cousins of the W and Z
  getting mass from some scaled up version of the
  Higgs
• Focus on new Gauge Bosons with Standard Model
  like coupling
• First worry about finding new physics, then
  find out what it is

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Where could the Z/W come from?

• Many good reasons to look for new gauge bosons
  (just as we look for new fermions)
• Many theories argue for the existence of new
  gauge bosons to shed light on mysteries of the SM
• GUT with large gauge groups break down to SM
  extra gauge bosons at lower energies
• Extra Dimensions- Bulk has copies (KK modes) of
  SM gauge bosons which are massive
• TopColor-gtbreak electroweak symmetry breaking
• Little Higgs
• New SUSY theories

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Limits
MW gt 842 GeV (205 pb-1) MZ gt 845 GeV(448
pb-1) ?Br lt 24 fb
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Samples

• Note BF(g/Z/Z ? ??-) factored into the
  calculation of the luminosity

• Samples Z ? ? ?- with SM-like
  couplingsSamples generated and simulated at U.
  MontrealPythia process 141 q q-bar ?
  gamma/Z/Z ? ? ?-with low mass cutoff of 500
  GeV for SSM 1000 SSM 2000
  1000 GeV for SSM 3000 SSM 4000

1 TeV W-gtl nu with SM-like couplings
(Benslama/Black) 10.0.1 20 K events, W-gt?? (?BF
3312.6 fb) 4.8 fb-1
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Muon Perfomrance at very high Pt
Muon (AOD) efficiencies resolution (rel.10.0.4)
efficiency
efficiency
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Z-gt? ?

• Event Requirements
• Two Muons with opposite charge
• ??lt2.5
• pTgt 10 GeV
• less than 20 GeV of energy in cone of 0.4 around
  muon
• HighPt Algorithm only, both inner detector and
  muon spectrometer track

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Invariant Mass Distributions (1 TeV)
Fit to Breit-Wigner 1st order polynomial
Fit to Gaussian 1st order polynomial
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At 2 TeV
Fit to Breit-Wigner 1st order polynomial
Fit to Gaussian 1st order polynomial
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At 3 TeV
Fit to Gaussian 1st order polynomial
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At 4 TeV
Not enough statistics for fit ? ignore
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Z Summary
Simple fit to a Gaussian 1st order polynomial?
anticipated number of observed Z ? ? ?- signal
decays
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Z Backgrounds
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Background Distribution
Apply all cuts except dimuon charge, high-pT alg
and combined mu requirements
Plots normalized to 10 fb-1
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Background Distributions
Apply all cuts except dimuon charge, high-pT alg
and combined mu requirements
Plots normalized to 10 fb-1
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Background Distributions
Apply all cuts
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Background Distributions
Apply all cuts
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W Signal and Background

• Selection
• ET gt 100 GeV
• Muon
• Isolated,
• highPt Algorithm only
• both inner and muon detector track
  (pT match within 20)
• pT gt 75 GeV

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Backgrounds
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W Signal and Background
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W Summary
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Event Count

• For simple cuts, 3987 events for a 1 TeV W in 10
  fb-1 of data
• Most backgrounds are very small after cuts,
  however in the far tails of the distribution need
  more MC to extract meaningful numbers (study W-gtl
  nu in fast MC to get a better estimate) , fakes
  will take more work to get a reasonable handle on

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Conclusions and Plans

• As expected, backgrounds for both Z and W
  appear very small (though long tail of Drell-Yan
  needs to be very well understood)
• Both should be easily observable up to a few
  TeV with 10 fb-1 of data
• Plans
• Continue to work on reconstruction performance
  (wanted to use more recent version of
  simulation/digitization/reconstruction but some
  bugs)
• November, trigger simulator should be in testing
  stage (Black) has agreed to test muon trigger for
  UTF. Use Z, W as test case.
• Look at ?e, and ? channels