Neutral Higgs Boson Search via H Channel

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Neutral Higgs Boson Search via H -gt ??? Channel

• Michael Anderson
• University of Wisconsin
• CMS Group

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Higgs Decay to Two Photons
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Branching Ratios of Higgs decays

• Decay to 2 photons only useful if
• 120 GeV lt MH lt 150 GeV

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Backgrounds

• Irreducible
• Direct two-photon production
• Reducible
• Photon jet production, with jet misidentified
  as photon

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Double Photon Processes
(available in Pythia v.6.2)
30 GeV lt pt
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PhotonJet Processes
(available in Pythia v.6.2)
30 GeV lt pt
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Higgs Production
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Event Creation

• Simulation done with CMS Software v. 1_2_2
• Uses Pythia v6.227
• Time 5 minutes/event
• Storage 1.2 megabytes/event

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Simulation Process

• Events are generated with Pythia
• Digitization simulates how detector reacts
• Then, reconstruction is done to try and figure
  out what happened

Generator
Digitization
Reconstruction
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Coordinate System

• Pseudorapidity (eta)
• Phi

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Photon Candidate Definition

• Super Cluster in Electromagnetic Calorimeter
  (ECAL)
• Et gt 20 GeV
• no Track with
• pt gt 10 GeV
• Dr lt 0.1

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Generated Photons

• Pseudorapidity of photon pair
• Not a good way to discriminate between
  signal/background!
• Allows one way to check reconstructed data

signal
gg-gt? ? background
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Photons from Higgs

• Transverse momentum/energy

Generated
GeV
Reconstructed
GeV
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Photons from Background

• f f -gt ? ?

Generated
GeV
Reconstructed
GeV
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Photons from Background

• g g -gt ? ?

Generated
GeV
Reconstructed
GeV
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Invariant Mass
p1

• The Invariant Mass of a photon pair

?
?
p2
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Invariant Mass

• Decay width of Higgs to two photons is 1 GeV
• Limited by detector resolution
• 2-photon backgrounds simply fall off smoothly
  (with enough statistics)

Signal
GeV