Sarah Campbell For the PHENIX Collaboration

Sarah Campbell For the PHENIX Collaboration
Dielectron Continuum Measurements in √sNN = 200GeV Au+Au and Cu+Cu Collisions at PHENIX Sarah Campbell For the PHENIX Collaboration

Sarah Campbell for PHENIX Quark Matter 2006
Outline Motivation Analysis Au+Au results Cu+Cu status Hadron Blind Detector Conclusions 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Motivation R. Rapp nucl-th/ QGP E&M probe – e+ e- No color charge  No final state interactions Integrated over the full time evolution of the system Diverse Physics Signals Direct virtual photons Dalitz decays Hadronic decays Semi-leptonic heavy flavor decays Medium modification Chiral Symmetry Restoration Mass shift, broadening in light vector mesons mee (GeV/c2) CERES Pb-Au 158 GeV NA60 nucl-ex/ e- e+ 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Electron Identification
Require a RICH Cherenkov Ring and EMC Shower ( p)% momentum resolution Remove pion contamination Remove events where there are parallel tracks (ie shared RICH rings) Conversion Photon rejection Remove e+ e- pairs that are opened by the magnetic field Charges ordered In the plane perpendicular to the magnetic field We know conversions so well we are able to image the conversion sources e+ e- p 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 Support Structure Beampipe

Combinatorial Background and Event Mixing
Combinatorial Background grows proportionally to multiplicity squared; signal grows proportionally to multiplicity In high multiplicity RHIC collisions, signal-to-background is a key consideration Event Mixing Method Generate Combinatorial Background Shape Mix across events with similar centralities, z-vertices Background negligible contribution to statistical error Signal + Combinatorial BG Generated BG from Event Mixing Method Normalized Generated BG mee 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Normalization A Single Normalization Factor for all masses & pTs 4 Normalization Methods Event counting: Nevents / Nmixedevents Independent Production: <N+-> = <N+><N-> Ideal for jets Pair Production: ∫BG+- = 2√∫FG++ ∫FG— Ideal for leptons Like-sign yield: ½(∫FG++/ ∫BG++ + ∫FG--/ ∫BG--) Integrals excluded the region of MeV Avoid like-sign signal from π0 dalitz decays and photon conversions Normalization Agreement In Au+Au: within 0.5%, systematic error of 0.25% In Cu+Cu: within 0.85%, systematic error of 0.47% Like-sign Signal 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

As of Quark Matter 2005…. Au+Au Min Bias Spectrum: PHENIX Preliminary Systematic and Normalization Error PHENIX Preliminary Systematic Error Normalization Error 870 Million Min Bias events 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au -- MB Cocktail Comparison
PHENIX Preliminary PHENIX Preliminary No additional scaling between cocktail and data ie. Not scaled by 1/Nπ0 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au -- Central 0-10% 10-20% PHENIX Preliminary Raw Counts/(Event *Bin Width) in Uncorrected PHENIX PHENIX Preliminary New to Quark Matter 2006 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au – Mid to Peripheral
20-40% 40-60% PHENIX Preliminary Raw Counts/(Event *Bin Width) in Uncorrected PHENIX PHENIX Preliminary 60-100% 60-100% New to Quark Matter 2006 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au – Mass Ratios Ratio of yield in various mass regions to the yield within the π0 mass range, MeV PHENIX Preliminary 150 – 300 MeV 300 – 450 MeV PHENIX Preliminary 450 – 600 MeV PHENIX Preliminary 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

Au+Au – Mass Ratios Ratio of yield in specific mass regions to the yield within the π0 mass range, MeV PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary PHENIX Preliminary 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

Au+Au – Intermediate Region (IMR)
PHENIX Preliminary PHENIX Preliminary Possible IMR Sources Correlated Charm pairs Thermal Sources 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Nuclear Modification in IMR
PHENIX preliminary 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

PHENIX preliminary Similar to high pT single electron suppression pattern Attributed to charm suppression Fukutaro Kajihara’s talk on 11/18 Shape Comparison Only 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

PHENIX Preliminary Similar suppression pattern as J/Psi Taku Gunji’s talk on Sat Nov 18 Shape Comparison Only 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

Cu+Cu Status Better signal to background Lower multiplicity Conservative estimate of systematic error Precision measurement No acceptance or efficiency corrections Uncorrected PHENIX aperture includes dead channels and detector response PHENIX preliminary Systematic Error Normalization Error PHENIX preliminary Systematic and Normalization Error Φ ω 552 Million Min Bias events 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

Cu+Cu – MB Cocktail Comparison
PHENIX preliminary Systematic and Normalization Error Acceptance and efficiency corrections have not been applied to the data Uncorrected PHENIX aperture includes dead channels and detector response Cocktail reflects the uncorrected PHENIX aperture and detector response Cocktail scaled arbitrarily to match the data in the π0 region 0 – 160 MeV 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006 New to Quark Matter 2006

Hadron Blind Detector Windowless CF4 Cherenkov detector Sasha Milov’s talk on 11/15 Reduce combinatorial BG in Au+Au by factor of 100 Dalitz rejection Installed & available for Run 7 signal electron partner positron needed for rejection 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Conclusions Background shape and normalization well understood Au+Au Hint of low mass excess in most central Dielectron charm suppression similar to J/Psi suppression and similar to charm suppression from the single electron result New data -- Cu+Cu Higher statistics Better signal to background Better precision Future: Run 7 Au+Au -- HBD Reduce combinatorial background Increased throughput in data acquisition Great promise and high productivity in dilepton physics at PHENIX 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Backup 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Baryon Density at RHIC Vector mesons equally interact with baryons and anti-baryons “anti-baryons important at RHIC” – Ralf Rapp on 11/15 Sum baryon anti-baryon densities, not net baryon density taken from Jorgen Randrup’s slide 11/13 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

p-p Annihilation Low mass enhancement due to pp annihilation Produces thermal dileptons Spectral shape dominated r meson Vacuum r propagator Vacuum values of width and mass In medium r propagator Rapp-Wambach melting resonances Collisional broadening of spectral function Indirectly related to chiral symmetry restoration Effective Lagrangians Medium modifications driven by baryon resonances NA60, CERES p r* g* e- e+ Rapp and Wambach hep-ph/ 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Theory: Mass Shifts Brown-Rho scaling Dropping masses as chiral symmetry is restored NJL model Hatsuda & Lee QCD Sum Rules Indirect link between quark condensate and medium properties Alpha = 0.16 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Cocktail Generation Fit the pion spectra At high pt: π0 At low pt: (π+ + π-) /2 Done separately for Au+Au, Cu+Cu Use mT scaling and meson to π0 ratios to get other mesons contributions Ex. η/π0 = 0.45 ±0.10 J/ψ yield is adjusted to reflect J/ψ suppression Filtered into the Ideal PHENIX acceptance Charm contribution generated using PYTHIA Scaled by Ncoll Doesn’t consider charm suppression (ie the PHENIX single electron measurement) (π+ + π–)/2 π0 Au+Au pion spectra 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au Cuts Event Cuts – 25 cm bbcz Single Electron ID Cuts: pt [0.20, 20.0] Ecore > GeV N0 >=3 phototubes Chisq < 10 EMC and PC3 Matching 3 sigma Disp < 5 (ring displacement) Dep (an E/p like variable) > -2 sigma Pair Cuts Cos(PFOA) < (Event veto) PhiV (Pair cut) Mass 0.6, phiV 0.04; Mass 0.03 phiV 0.25 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Cu+Cu Cuts Event Cuts – 25 cm bbcz Single Electron ID Cuts: pt [0.20, 20.0] N0 >=2 Chisq < 15 EMC Matching 3 sigma (self-calibrated) Disp 3 sigma (self-calibrated) E/p > -2 sigma (self-calibrated) Pair Cuts Cos(PFOA) < (Event veto) RICH Ring dcross 2.5 sigma cut (Event veto) PhiV (Pair cut) Mass 0.6, phiV 0.04; Mass 0.03 phiV 0.25 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Au+Au Acceptance Ideal PHENIX Acceptance Filter applied to cocktail Acceptance corrections applied to the data to match the Ideal PHENIX acceptance 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

Cu+Cu Acceptance Cu+Cu data are in the uncorrected PHENIX acceptance, not the ideal No acceptance corrections applied to the data Cocktail is in the uncorrected PHENIX acceptance, not the ideal 11/27/2018 Sarah Campbell for PHENIX Quark Matter 2006

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Sarah Campbell For the PHENIX Collaboration

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