1 Analysis of the dielectron continuum in Au+Au @ 200 GeV with PHENIX Alberica Toia for the PHENIX Collaboration • Physics Motivation • Analysis Strategy (765M events) – Cuts • Single electron cuts • Electron pair cuts: remove hit sharing – Spectra: Foreground, Background (mix events), Subtracted – Efficiency / Acceptance • Cocktail & theory comparison
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1 Analysis of the dielectron continuum in Au+Au @ 200 GeV with PHENIX Alberica Toia for the PHENIX Collaboration Physics Motivation Analysis Strategy (765M.
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Analysis of the dielectron continuum in Au+Au @ 200
GeVwith PHENIX Alberica Toiafor the PHENIX Collaboration
RICH ghosts (like and unlike sign)Post Field Opening Angle < 0.988
--- Foreground: same evt--- Background: mixed evt
like
Cos(PFOA)
DC ghosts (like sign): fabs(dphi) < 0.1 rad fabs(dz) < 1.0 cm
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Systematic error
• Systematic error of simulation – Acceptance difference between real/simulation is
less than: 3%.– Single e eID efficiency difference between
real/simulation is less than 8.8%.• Dep < 1%, emcsdphie < 1%, emcsdze < 1%, n0 <
7%, chi2/npe0 < 1%, disp < 5%.
• Systematic error of real data– Stability of acceptance: 5%– Stability of eID efficiency: 5%
• Other correction factor– Embedding efficiency < 10% (Run2 7%).
• Background Normalization
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Acceptance filter
Roughly parametrized from data
char
ge/
pT
0
0
z vertex
• Decoupling acceptance – efficiency corrections• Define acceptance filter (from real data)• Correct only for efficiency IN the acceptance• “Correct” theory predictions IN the acceptance• Compare
ACCEPTANCE FILTER
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Efficiency2 sets of simulations of dielectron pairs
•White in mass (0-4GeV)•White in pT (0-4GeV)•Vertex(-30,30), rapidity (1unit), phi (0,2)
upper limit: Integral in charm region=0 Normalization factor 8.75
All normalizations agree within 0.5%
All normalizations agree within 0.5%
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The unfiltered calculations
•black: our standard cocktail•red : hadronic spectrum using the VACUUM rho spectral function•green: hadronic spectrum using the IN-MEDIUM rho spectral function•blue : hadronic spectrum using a rho spectral function with DROPPING MASS•magenta : QGP spectrum using the HTL-improved pQCD rate