Resonance Workshop -- 3/7/2012 Sarah Campbell for the PHENIX Collaboration Resonance Workshop 2012 March 6, 2012 Austin, TX Light Vector Mesons and the Dielectron Continuum in PHENIX

Resonance Workshop -- 3/7/2012 Outline Detector Light vector mesons –Hadronic and dielectron decays –HI and cold nuclear matter effects Dielectron Continuum –Generating a cocktail –Comparisons to cocktail and between data Centrality and p T bins Conclusions

Resonance Workshop -- 3/7/2012 e+e+ ee  PHENIX At RHIC –p+p, d+Au, Cu+Cu, Au+Au Tracking –Good quality track in DCH, PC1  pT /p T = 0.7%  1% p T Electron ID –RICH ring & EMC shower Particle ID –TOF d τ ~ 100 ns –EMC d τ ~ 500 ns –Aerogel d τ ~ 500 ns

Resonance Workshop -- 3/7/2012 Light vector meson: Motivation Light vector mesons: , , φ –Masses modified by medium? LVM  e+ e- –E&M probe, no color charge , φ Hadron decays –   ,   , φ  K+K-

Resonance Workshop -- 3/7/2012 p+p

Resonance Workshop -- 3/7/2012 p T Spectra  →e+e- agree with  → ,  →  ϕ →e+e- agree with ϕ →K+K-

Resonance Workshop -- 3/7/2012 No strong cold nuclear matter effects in , ϕ Cold Nuclear Matter

Resonance Workshop -- 3/7/2012 ϕ modifications in HI ϕ mass,  unchanged ϕ suppression at high p T –R AA Cu+Cu and Au+Au agree

Resonance Workshop -- 3/7/2012 HI Modifications -- R AA , ϕ are suppressed – ϕ, , K S at high pt like ,  – ϕ like K+, e HF at low pt; ϕ not like ,  at mid. pt Baryon Meson difference in R AA

Resonance Workshop -- 3/7/2012 Dielectron Continuum: Motivation Possible modifications   e+ e- –Broad mass distribution –Short lifetime –Broadening (and/or mass shift) –EM probe, no color charge Diverse Physics Signals –Direct virtual photons –Dalitz decays –Hadronic decays –Semi-leptonic heavy flavor –Vector mesons Broadening/dropping mass –Full time evolution of QGP Suppression Chiral symmetry restoration Continuum enhancement Thermal radiation Modification of vector mesons Thermal radiation Modified heavy flavor Suppression or Enhancement

Resonance Workshop -- 3/7/2012 Hadrons from Exodus using data –Pion p T spectra fit –m T scaling: –When possible use measured mesons p T distributions J/ ψ suppression, J/ψ and ψ’ rad. tails Charm, Bottom, Drell Yan from Pythia –In p+p, measure the σ cc agrees with non-photonic single e- σ cc = 567 ± 57(stat) ± 193 (sys) μb –d+Au, Cu+Cu, Au+Au N Coll scale Filter into PHENX ideal acceptance Cocktail Generation σ cc = 544 ± 39(stat) ± 142(sys) ± 200 (model) μb A Adare PLB (2009)

Resonance Workshop -- 3/7/2012 Backgrounds Combinatorial Conversions RICH Ring overlap Double dalitz –Primarily ,  →  –Like-, unlike-sign pairs at same rate Jets –Like-, unlike-sign pairs at same rate Remove with cuts Generate with event mixing e- 00 e+ e- e+  Simulate with Exodus-like code Simulate with Pythia π0π0 π0π0 e+e+ e-e- e+e+ e-e- γ γ π0π0 e-e- γ e+e+

Resonance Workshop -- 3/7/2012 Background Removal – 2 Methods Component subtraction –Use like-sign pairs to normalize BGs –Subtract each of the BG components Like-sign acceptance corrected subtraction –Correct the like-sign pairs to have the unlike-sign pair acceptance –Subtract like-sign pairs from unlike-sign pairs In p+p, Au+Au, Cu+Cu both methods are consistent

Resonance Workshop -- 3/7/2012 p+p and d+Au Min Bias measurement PRC (2010)

Resonance Workshop -- 3/7/2012 Au+Au Min Bias & Cu+Cu 0-10% measurement PRC (2010)

Resonance Workshop -- 3/7/2012 Centrality Dependence N Coll ordered Central Peripheral d+Au p+p

Resonance Workshop -- 3/7/2012 Compare p+p and d+Au No cold nuclear matter effects

Resonance Workshop -- 3/7/2012 Most Central HI Spectra 1/N Part scaled Onset of LMR excess

Resonance Workshop -- 3/7/2012 Yields vs N Part

Resonance Workshop -- 3/7/2012 p+p in p T slices Matches at low pT High pT IMR excess –No bottom in cocktail –p+p non-photonic single electron p T not well described by PYTHIA High pT LMR excess from thermal photons

Resonance Workshop -- 3/7/2012 Au+Au MB and Cu+Cu 0-10% in p T slices LMR excess at low pT High pT LMR excess from thermal photons

Resonance Workshop -- 3/7/2012 Thermal photons T=233+/-14+/-19 T=221+/-19+/-19 T=217+/-18+/-16

Resonance Workshop -- 3/7/2012 LMR p T Spectra  T Eff Calculate local inverse slopes in m ranges ( ), (0.6 – 2.5) Soft component at m ~ 0.5 – T Eff ~ 100 MeV –Over 50% of the excess

Resonance Workshop -- 3/7/2012 Conclusions , ϕ – ϕ mass,  unmodified –Dielectron , ϕ decays agree with hadronic decays –No strong cold nuclear matter effects – ϕ R AA at low and intermediate p T –Baryon meson difference in R AA Dielectrons –No cold nuclear matter effects –Thermal photons in p+p, d+Au, Cu+Cu, Au+Au at low mass, high p T –Soft enhancement in central Cu+Cu and Au+Au at low mass, low p T

Resonance Workshop -- 3/7/2012 If there was more time… ϕ in Cu+Cu  in Cu+Cu  /  ratios in p+p, d+Au, Cu+Cu, Au+Au ϕ →K+K- in 62 GeV ϕ →  +  - in the forward direction K S → , K* →  K More neutral mesons:  → ,  → ,  → ,  ’ →  Talis fits to p+p p T spectra –Extract integrated yields –Temperature m T scaling in p+p Statistical model comparisons in p+p Dielectron p T spectra in p+p Au+Au Theory comparisons to Au+Au MB dielectrons –in mass, in mass in p T slices, in m T - m 0 High mass d+Au MB dielectron spectrum PRD (2011) PRD (2011) PRD (2011) PRC (2010)

Resonance Workshop -- 3/7/2012 Backup

Resonance Workshop -- 3/7/2012 Backup eta pi eta prime

Resonance Workshop -- 3/7/2012 Kaons

Resonance Workshop -- 3/7/2012 RAA Kaons

Resonance Workshop -- 3/7/2012 Backup – ϕ → KK two ways

Resonance Workshop -- 3/7/2012 RAA ϕ

Resonance Workshop -- 3/7/2012 RAA 

Resonance Workshop -- 3/7/2012 Pt fits in p+p

Resonance Workshop -- 3/7/2012 p+p pt spectra

Resonance Workshop -- 3/7/2012 Tallis distribution Expo fails at higher pt –Failure points at different locations for different mesons  recombination Parameters: –n, T and norm. Extract int. yield

Resonance Workshop -- 3/7/2012

Baryon Meson differences

Resonance Workshop -- 3/7/2012 Stat models

Resonance Workshop -- 3/7/2012  /  ratios

Resonance Workshop -- 3/7/2012 Backup detector resolution

Resonance Workshop -- 3/7/2012 Backup pt

Resonance Workshop -- 3/7/2012 Is Pythia the right way to model the heavy quark components? p+p non-photonic electron p T not well described by PYTHIA Au+Au suppression of high p T non-photonic electrons Model a random heavy quark component, using Au+Au non- photonic p T spectra with random angular orientation –Contains charm and bottom correlations A Adare et al PRL Cocktail with Pythia Cocktail with Random

Resonance Workshop -- 3/7/2012 Combinatorial Background Largest background in HI –Large multiplicities, combinatorial goes as multiplicity squared Shape determined by event mixing

Resonance Workshop -- 3/7/2012 Backgrounds All Pairs Passing pairs Failing pairs Beam pipe conversions Support structure Air conversions z y x e+e+ e-e- B Conversion z y x e+e+ e-e- B Dalitz decay All Pairs Passing pairs Failing pairs Like-signUnlike-sign Require pairs are separated by twice the nominal ring size Conversions Ring Overlap Cut pairs with opening angle ┴ to B, low mass and charge ordered

Resonance Workshop -- 3/7/2012 Backgrounds Double Dalitz Jets e- 00 e+ e- e+  Unlike-signLike-sign Simulated ,  Background Decays with multiple e+e- –Like-, unlike-sign at same rate –Exodus-like simulation  0  e+e-e+e-,   0  0  0 π0π0 π0π0 e+e+ e-e- e+e+ e-e- γ γ π0π0 e-e- γ e+e+ Pairs from  0 in jet correlated by jet –Like-, unlike-sign at same rate –Pythia simulation All pairs Underlying evt Subtracted Near Away Like-sign

Resonance Workshop -- 3/7/2012

PHENIX vs STAR: Acceptance: low pt PHENIX –+/- 0.5 rapidity –Single electrons p T >0.2 GeV –Pairs m T > 0.4 GeV STAR efficiency at low p T ?

Resonance Workshop -- 3/7/2012 PHENIX vs STAR p+p

Resonance Workshop -- 3/7/2012 PHENIX vs STAR Au+Au MB

Resonance Workshop -- 3/7/2012 p+p Normalization region

Resonance Workshop -- 3/7/2012 p+p Measurement PRC (2010)

Resonance Workshop -- 3/7/2012 d+Au Min Bias at high mass

Resonance Workshop -- 3/7/2012 Au+Au measurement PRC (2010)

Resonance Workshop -- 3/7/2012 Cu+Cu 0-10% measurement Like-sign Unlike-sign All Pairs Combinatorial All Pairs - Combinatorial Common Ancestor Jet

Resonance Workshop -- 3/7/2012 Like Sign subtraction – p+p A+A

Resonance Workshop -- 3/7/2012 p+p d+Au comparison

Resonance Workshop -- 3/7/2012 Compare peripheral HI 1/N Coll scaled Slight IMR excess in peripheral HI

Resonance Workshop -- 3/7/2012 Most Peripheral HI Bins 1/N Coll scaled Slight IMR excess in peripheral HI

Resonance Workshop -- 3/7/2012

Cu+Cu 10-20% and 20-40% in p T slices High pT LMR & IMR excess

Resonance Workshop -- 3/7/2012 Cu+Cu 40-94% in p T slices Most of IMR excess yield is at low p T IMR excess at low pT High pT LMR excess from thermal photons Extends out to higher masses?

Resonance Workshop -- 3/7/2012 LMR m Spectra in p T Slices p+p matches the cocktail fairly well, high p T excess There exists LMR excess in Au+Au at all p T s Au+Au LMR excess is largest low pair p T PRC (2010)

Resonance Workshop -- 3/7/2012 High pt (p T > 1) –Quasi-real virtual photons m ee << p T for m ee < 0.3 –Direct photon component, f dir, shape known: Filtered by PHENIX acceptance Smeared by resolution –R = (data - cocktail)/f dir flat even at higher masses Low p T (p T < 1) –R is not flat Must be something other than quasi-real virtual photons –Medium modified masses Two sources of LMR excess High p T LMR Excess PRL (2010)

Resonance Workshop -- 3/7/2012 Photons from dielectrons m << pt  S=1, L=1 From the fit, –r= direct  /inclusive  Extrapolate to m=0 Dashed Taa scaled p+p Solid Taa scaled p+p + exp T=233+/-14 +/-19 T=221+/-19+/-19 T=217+/-18+/-16

Resonance Workshop -- 3/7/2012 LMR Theory in p T Slices In the high p T ranges, the theories are close but still low –Should including virtual photon processes, q + g ->q e+ e- At low p T, none describe the Au+Au MB data R. Rapp and H. van HeesK. Dusling and I. Zahed W. Cassing and E. Bratkovskaya PRC (2010)

Resonance Workshop -- 3/7/2012 Theory Comparison Fail to describe the excess Hadronic gas VDM broadening Current- current correl. func. Hadronic gas Hydro evol. HSD Dropping rho w/ broadening

Resonance Workshop -- 3/7/2012 IMR Theory

Resonance Workshop -- 3/7/2012 p T Spectra of LMR Corrected to the full 2  acceptance Solid lines cocktail Dashed lines cocktail + virtual photon

Resonance Workshop -- 3/7/2012 LMR Theory p T Spectra R. Rapp and H. van Hees K. Dusling and I. Zahed W. Cassing and E. Bratkovskaya None really describe the data –Cassing and Bratkovskaya closest –Benefit from including the virtual photon q + g -> q + e+e-