Light Vector Mesons and the Dielectron Continuum in

  • Slides: 69
Download presentation
Light Vector Mesons and the Dielectron Continuum in PHENIX Sarah Campbell for the PHENIX

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

Outline • Detector • Light vector mesons – Hadronic and dielectron decays – HI

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

 • At RHIC PHENIX – p+p, d+Au, Cu+Cu, Au+Au • Tracking – Good

• At RHIC PHENIX – p+p, d+Au, Cu+Cu, Au+Au • Tracking – Good quality track in DCH, PC 1 p • p. T /p. T = 0. 7% 1% p. T • Electron ID e- – RICH ring & EMC shower • Particle ID – TOF dτ ~ 100 ns – EMC dτ ~ 500 ns – Aerogel dτ ~ 500 ns Resonance Workshop -- 3/7/2012 e+

Light vector meson: Motivation • Light vector mesons: , , φ – Masses modified

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+KResonance Workshop -- 3/7/2012

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

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

p. T Spectra • →e+e- agree with → , → Resonance Workshop -- 3/7/2012

p. T Spectra • →e+e- agree with → , → Resonance Workshop -- 3/7/2012 • ϕ→e+e- agree with ϕ→K+K-

Cold Nuclear Matter Resonance Workshop -- 3/7/2012 • No strong cold nuclear matter effects

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

ϕ modifications in HI • ϕ mass, unchanged • ϕ suppression at high p.

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

HI Modifications -- RAA • , ϕ are suppressed – ϕ, , KS at

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

Dielectron Continuum: Motivation • e+ e– – Broad mass distribution Short lifetime Broadening (and/or

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

Cocktail Generation • Hadrons from Exodus using data – Pion p. T spectra fit

Cocktail Generation • 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 σcc = 544 ± 39(stat) ± 142(sys) ± 200 (model) μb • agrees with non-photonic single eσcc = 567 ± 57(stat) ± 193 (sys) μb – d+Au, Cu+Cu, Au+Au NColl scale A Adare PLB 670 313 (2009) • Filter into PHENX ideal acceptance Resonance Workshop -- 3/7/2012

Backgrounds • • Combinatorial Conversions RICH Ring overlap Double dalitz Generate with event mixing

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

Background Removal – 2 Methods • Component subtraction – Use like-sign pairs to normalize

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 Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

p+p and d+Au Min Bias measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

Au+Au Min Bias & Cu+Cu 0 -10% measurement Resonance Workshop -- 3/7/2012 PRC 81

Au+Au Min Bias & Cu+Cu 0 -10% measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

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

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

Compare p+p and d+Au • No cold nuclear matter effects 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/NPart scaled Resonance Workshop -- 3/7/2012 • Onset of

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

Yields vs NPart Resonance Workshop -- 3/7/2012

Yields vs NPart Resonance Workshop -- 3/7/2012

p+p in p. T slices • Matches at low p. T • High p.

p+p in p. T slices • Matches at low p. T • High p. T IMR excess – No bottom in cocktail – p+p non-photonic single electron p. T not well described by PYTHIA • High p. T 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

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

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

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

LMR p. T Spectra TEff • Calculate local inverse slopes in m ranges (0

LMR p. T Spectra TEff • Calculate local inverse slopes in m ranges (0 - 0. 6), (0. 6 – 2. 5) • Soft component at m ~ 0. 5 – TEff ~ 100 Me. V – Over 50% of the excess Resonance Workshop -- 3/7/2012

Conclusions • , ϕ – ϕ mass, unmodified – Dielectron , ϕ decays agree

Conclusions • , ϕ – ϕ mass, unmodified – Dielectron , ϕ decays agree with hadronic decays – No strong cold nuclear matter effects – ϕ RAA at low and intermediate p. T – Baryon meson difference in RAA • 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 Workshop and Au+Au at low Resonance mass, low p. T -- 3/7/2012

If there was more time… • • PRD 83 052004 (2011) ϕ in Cu+Cu

If there was more time… • • PRD 83 052004 (2011) ϕ in Cu+Cu PRD 84 044902 (2011) / ratios in p+p, d+Au, Cu+Cu, Au+Au ϕ→K+K- in 62 Ge. V ϕ→ + - in the forward direction KS→ , K*→ K More neutral mesons: → , → , ’→ Talis fits to p+p p. T spectra – Extract integrated yields – Temperature • • PRD 83 052004 (2011) 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 Workshop -- 3/7/2012 • High mass d+Au MBResonance dielectron spectrum PRC 81 034911 (2010)

Backup Resonance Workshop -- 3/7/2012

Backup Resonance Workshop -- 3/7/2012

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

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

Kaons Resonance Workshop -- 3/7/2012

Kaons Resonance Workshop -- 3/7/2012

RAA Kaons Resonance Workshop -- 3/7/2012

RAA Kaons Resonance Workshop -- 3/7/2012

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

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

RAA ϕ Resonance Workshop -- 3/7/2012

RAA ϕ Resonance Workshop -- 3/7/2012

RAA Resonance Workshop -- 3/7/2012

RAA Resonance Workshop -- 3/7/2012

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

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

p+p pt spectra 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

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

Resonance Workshop -- 3/7/2012

Resonance Workshop -- 3/7/2012

Baryon Meson differences Resonance Workshop -- 3/7/2012

Baryon Meson differences Resonance Workshop -- 3/7/2012

Stat models Resonance Workshop -- 3/7/2012

Stat models Resonance Workshop -- 3/7/2012

 / ratios Resonance Workshop -- 3/7/2012

/ ratios Resonance Workshop -- 3/7/2012

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

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

Backup pt 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

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 nonphotonic p. T spectra with random angular orientation – Contains charm and bottom correlations Cocktail with Pythia Cocktail with Random Resonance Workshop -- 3/7/2012 A Adare et al PRL 98 172301

Combinatorial Background • Largest background in HI – Large multiplicities, combinatorial goes as multiplicity

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

Backgrounds Conversions B z Conversion B y x e+ e- Dalitz z decay Ring

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

Backgrounds Double Dalitz Jets • Decays with multiple e+e– Like-, unlike-sign at same rate

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

Resonance Workshop -- 3/7/2012

Resonance Workshop -- 3/7/2012

PHENIX vs STAR: Acceptance: low pt • PHENIX – +/- 0. 5 rapidity –

PHENIX vs STAR: Acceptance: low pt • PHENIX – +/- 0. 5 rapidity – Single electrons p. T >0. 2 Ge. V – Pairs m. T > 0. 4 Ge. V • STAR efficiency at low p. T? Resonance Workshop -- 3/7/2012

PHENIX vs STAR p+p 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

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

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

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

p+p Measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

p+p Measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

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

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

Au+Au measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

Au+Au measurement Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

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

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

Like Sign subtraction – p+p A+A 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

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

Compare peripheral HI • 1/NColl scaled Resonance Workshop -- 3/7/2012 • Slight IMR excess

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

Most Peripheral HI Bins • 1/NColl scaled Resonance Workshop -- 3/7/2012 • Slight IMR

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

Resonance Workshop -- 3/7/2012

Resonance Workshop -- 3/7/2012

Cu+Cu 10 -20% and 20 -40% in p. T slices High p. T LMR

Cu+Cu 10 -20% and 20 -40% in p. T slices High p. T LMR & IMR excess Resonance Workshop -- 3/7/2012

Cu+Cu 40 -94% in p. T slices • IMR excess at low p. T

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

LMR m Spectra in p. T Slices • p+p matches the cocktail fairly well,

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. Ts -- 3/7/2012 • Au+Au LMRResonance excess. Workshop is largest low pair p. T PRC 81 02391 (2010)

High p. T LMR Excess • High pt (p. T > 1) – Quasi-real

High p. T LMR Excess • High pt (p. T > 1) – Quasi-real virtual photons • mee << p. T for mee < 0. 3 – Direct photon component, fdir, shape known: • Filtered by PHENIX acceptance • Smeared by resolution – R = (data - cocktail)/fdir • 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 Resonance Workshop -- 3/7/2012 PRL 104 132301 (2010)

Photons from dielectrons • • m << pt S=1, L=1 From the fit, •

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

LMR Theory in p. T Slices K. Dusling and I. Zahed W. Cassing and

LMR Theory in p. T Slices K. Dusling and I. Zahed W. Cassing and E. Bratkovskaya R. Rapp and H. van Hees • In the high p. T ranges, 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 Resonance Workshop -- 3/7/2012 PRC 81 02391 (2010)

Theory Comparison Hadronic gas VDM broadening HSD Dropping rho w/ broadening Currentcurrent correl. func.

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

IMR Theory 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

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

LMR Theory p. T Spectra R. Rapp and H. van Hees K. Dusling and

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 Resonance Workshop -- 3/7/2012 • q + g -> q + e+e-