J production in Cu Cu and Au Au collisions at vsNN 200 GeV measured by PHENIX at RHIC

1
J/? production in CuCu and AuAu collisions at
vsNN 200 GeV measured by PHENIX at RHIC

• Andry Rakotozafindrabe
• LLR École Polytechnique

42nd Rencontres de Moriond QCD session Italy
(March 2007)
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Physics motivation the starting point

• What are the properties of the hot and dense
  matter produced in relativistic heavy ion
  collisions ?
• c and b are produced in the initial parton
  collisions, so they can be used to probe the
  created medium
• open charm (or beauty) energy loss ? energy
  density
• Topic already covered this morning by Alan Dion
• , (quarkonia) suppressed by color
  screening ? deconfinement
• At lower energy, NA50 (CERN) experiment measured
  an anomalous J/? suppression in PbPb collisions,
  in excess of the normal suppression expected from
  the nuclear absorption.
• NA50 Collaboration, Eur. Phys. J. C39 (2005) 335
• At lower energy, NA60 (CERN) recent results in
  InIn
• At RHIC energy ?
• 10x vsNN
• 2-3x gluon density

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Screening the J/? in a QGP

• Production
• 60 direct production J/?
• 30 via ?c? J/? x
• 10 via ?? J/? x
• Temperature of dissociation Td
• for ?c and ? Td 1.1 Tc
• for J/? Td 1.5 to 2 Tc

• Sequential dissociation as the temperature (or
  energy density) increases

?c
?
J/?

• Energy density (t0 1fm) vs the max. vs for SPS,
  RHIC and LHC

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Physics motivation a few complications

• Final state
• Normal nuclear absorption
• Absorption by (hadronic ?) comovers ?
• Color screening ?
• In-medium formation (recombination) ?
• Flow ?

• Sensitive to
• Initial state
• Modification of the parton distribution functions
  (shadowing, CGC)
• pT broadening (Cronin effect)
• Parton energy loss in the initial state ?

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J/? in PHENIX capsule history
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PHENIX detector

• J/? ? ee
• y lt 0.35
• Pe gt 0.2 GeV/c
• ?? ?
• Tracking, momentum measurement with drift
  chambers, pixel pad chambers
• e ID with EmCAL RICH

• J/??µµ
• 1.2lt y lt 2.2
• Pµ gt 2 GeV/c
• ?? 2?
• Tracking, momentum measurement with cathode
  strip chambers
• µ ID with penetration depth / momentum match

Centrality measurement, vertex position
Beam-beam counters (charged particle production)
Zero-degree calorimeters (spectator neutrons)
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Production baseline (Run5) pp?J/? _at_ vs 200
GeV
hep-ex/0611020
Cross section vs rapidity better constraints on
available J/? production mechanisms

• Total cross section in pp
• Bll.?pp(J/? ) 178 3(stat)
• 53(sys) 18(norm) nb
• in agreement with COM

Cross section vs pT Forward rapidity ltpT2gt 3.59
0.06 0.16 Central rapidity
pp?J/? measurement used as a reference for
AB?J/?
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Heavy ion results _at_ vs 200 GeV

• AuAu final results nucl-ex/0611020
• CuCu preliminary results (QM05)
• but forthcoming final results (article in
  preparation) with
• increased statistics in the dielectron channel (a
  factor 2)
• significant improvement of systematic errors
• better precision measurement than the present
  AuAu results for Npartlt100

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RHIC beyond cold nuclear matter effects

• Available dAu data
• ?qCNM
• Weak shadowing and weak nuclear absorption (sabs
  1mb favored) derived from model Vogt PRC71,
  054902 (2005)
• AuAu data even compared to the  worst  sabs
  2mb case shown here
• suppression beyond cold effects for
• Npartgt100 at y1.7
• Npartgt200 at y0
• Need to improve the knowledge of CNM effects at
  RHIC

nucl-ex/0611020
RHIC CNM effects s abs 0, 1, 2 mb _at_ y0, y2
Cold nuclear matter predictions from Vogt,
nucl-th/0507027 (shadowing sabs)
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RHIC different amount of suppression at
different rapidities
nucl-ex/0611020

• RAA vs Npart
• Stronger suppression at forward rapidity than at
  central rapidity
• Ratio forward/central 0.6 for Npartgt100
• CGC (initial state effect) ?
• models predicts less heavy quark production at
  forward rapidity than at mid rapidity
• K. L. Tuchin J.Phys. G30 (2004) S1167

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RHIC vs SPS

• SPS _at_ 0ltylt1
• vs 17 GeV
• CNM normal nuclear absorption sabs 4.18
  0.35 mb
• Maximum e 3 GeV/fm3 (t0 1)
• Compare to RHIC _at_ ylt0.35
• x10 vs
• CNM shadowing nuclear absorption sabs from 0
  to 2mb (Vogt, nucl-th/0507027)
• Maximum e 5 GeV/fm3 (t0 1), higher than at
  SPS
• Same pattern of J/? suppression for the same
  rapidity!
• Suppression beyond CNM larger at RHIC

Bar uncorrelated error Bracket correlated
error Global error 12 is not shown
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RHIC vs SPS (II) extrapolating suppression
models

• Suppression models in agreement with NA50 data
  extrapolated at RHIC energies
• Opposite suppression behaviour vs rapidity
• Unmatched suppression pattern at central rapidity
• Recombination at work at RHIC ?

Dissociation by thermal gluons (R. Rapp et al.,
nucl-th/0608033 Nu Xu et al., Phys.Rev.Lett. 97
(2006) 232301)
Dissociation by comovers (Capella et al.,
hep-ph/0610313)
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Recombination at RHIC ?

• Suppressionrecombination predictions compared to
  data
• RAA vs Npart

Better matching with the data but regeneration
goes as the (single) charm density which is
poorly known at RHIC What about the other
variables ?
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Recombination at RHIC ?

• Suppressionrecombination predictions compared to
  data
• RAA vs Npart
• Yield vs rapidity

RMS 1.320.06
RMS 1.300.05
Recombination predicts a narrower rapidity
distribution with an increasing
Npart Data shows a slight decrease of the
RMS with increasing centrality
Thews Mangano, PRC73 (2006) 014904c
RMS 1.430.04
RMS 1.400.04
nucl-ex/0611020
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Recombination at RHIC ?

• Suppressionrecombination predictions compared to
  data
• RAA vs Npart
• Yield vs rapidity
• ltpT2gt vs Ncoll

No recombination
Recombination predicts a narrower pT
distribution with an increasing centrality, thus
leading to a lower ltpT²gt Data shows a rather
flat dependence of ltpT²gt with centrality
With recombination
Thews, Eur.Phys.J. C43 (2005) 97, Phys.Rev. C73
(2006) 014904 (and private communication).
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Ending where it began revisiting the sequential
dissociation (I)

• Karsch, Kharzeev Satz, PLB 637 (2006) 75
• Sequential melting ? overall J/? survival
  probability (measured/expected)
• S 0.6 S direct J/ ? 0.4 S J/???, ?c
• Recent lattice QCD results direct J/? melting
  at 10-30 GeV/fm3
• ? S 0.6 at RHIC
• RAA/CNM vs.
• Bjorken energy density

Sequential dissociation of ? and ?c only does
not seem to be consistent with the data
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Refinement 3D hydro sequential dissociation
(II)

• Gunji et al., hep-ph/0703061
• Charmonia
• initial spatial distribution from collisions in
  the Glauber model
• free streaming in a full (3D1) hydro
• J/? survival probability ( RAA/CNM with CNM
  shadowing nuclear absorption sabs 1mb )
• S (1 fFD) S direct J/ ? fFD S J/???, ?c
• 3 free parameters feed-down fFD , melting
  temperatures TJ/? and T?,?c
• (3D1) hydro same setup as the one used to
  reproduce charged dN/d? measured at RHIC
• Assuming thermalization for t0.6fm, initial
  energy density distribution in the transverse
  plane, EOS of the medium (TltTc and TgtTc),

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Refinement 3D hydro sequential dissociation
(II)

• Gunji et al., hep-ph/0703061
• Charmonia
• J/? survival probability ( RAA/CNM with CNM
  shadowing nuclear absorption sabs 1mb )
• S (1 fFD) S direct J/ ? fFD S J/???, ?c
• 3 free parameters Feed-down fFD , melting
  temperatures TJ/? and T?,?c
• (3D1) hydro
• ? best fit with
• TJ/? 2.12 Tc
• T?,?c 1.34 Tc
• fFD 0.25
• 0.10 due to uncertainty
• on sabs (1 1mb)

Better matching with the data
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Summary (I)

• PHENIX final results on J/??dileptons at forward
  and mid-rapidity in pp, AuAu, and preliminary
  results in CuCu
• Improved baseline
• Run 5 pp with x10 more statistics than Run 3
• Suppression pattern
• Beyond cold nuclear effects for Npart gt 200
• More suppression at forward than at central
  rapidity
• Ratio forward/central 0.6 for Npartgt100
• May be accounted for by CGC models
• Suppression models (comover) predicts the
  opposite behaviour
• Similar to SPS suppression in the same rapidity
  region? despite a higher energy density reached
• Understandable as recombinations that
  partially compensate the J/? suppression ?
• Still open question (test vs ltpT²gt dependance and
  rapidity distribution)

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Summary (II)

• Alternate explanations ?
• Sequential dissociation with feed-down assumed to
  be 40 and direct J/? not melting at present
  energy densities is not consistent with data
• (3D1) hydro sequential dissociation in
  agreement with mid-rapidity data if direct J/? is
  melting (at T 2.12 Tc) and if feed-down is
  assumed to be (25 10)
• Feed-down not measured at RHIC energies
• At lower energies, large deviations between
  experiments
• Need to improve knowledge on cold nuclear effects
  at RHIC
• Stay tuned forthcoming final results for CuCu
  !
• Improved precision for the measurements in the
  range Npart lt 100

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Back-up
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Hint of things to come

• Final results for CuCu
• What about the forward vs central suppression at
  lower Npart ?
• Improved reference pp
• x3 higher statistics from run 6
• Future measurements in ? ?
• Future measurements in ?c
• Planning AuAu (1 nb-1 vs 0.24 nb-1 in run 4 )
  with high luminosity during Run 7
• Later runs dAu with higher luminosity (28 nb-1
  vs 2.7 nb-1 in run 3) ?

Work under progress
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Upsilon measurement
PHENIX QM05
Dimuon mass spectrum for the two muon arms added
together.
y1.7 10 counts
PHENIX 1st Upsilons at RHIC from 3pb-1
collected during the 2005 pp run.
y0 50 cnts
STAR QM06
STAR Preliminary pp 200 GeV
ee- Minv Background
Subtracted
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STAR results and near future
M. Cosentino, QWG06
STAR Preliminary
STAR J/? Run5 pp
STAR J/? Run4 AuAu

• Dataset AuAu_at_200 GeV
• No trigger due to high background
• Just a faint signal
• For efficient J/y trigger, full barrel ToF is
  needed (just patch in Run5)
• pp_at_200GeV (Run5)
• trigger commissioning (1.7M events)
• Run 6 expect 500-1000 (work in progress)

Upsilon
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J/? production

• Production
• 60 direct production J/?
• 30 via ?c? J/? x
• 10 via ?? J/? x
• Large deviations between experiments ?c
  feed-down fraction vs vs
• Not measured at RHIC energies

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Invariant yield vs tranverse momentum
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ltpT2gt vs Npart

• A closer look at ltpT2gt vs Npart

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Cold nuclear effects dAu?J/?
gluons in Pb / gluons in p
x
Nucl. Phys. A696 (2001) 729-746

• Available dAu data ? CNM
• Weak shadowing (modification of gluon
  distribution) and weak nuclear absorption (sabs
  1mb favored) derived from model Vogt PRC71,
  054902 (2005)
• Data driven parametrizations of CNM
• Karsch, Kharzeev Satz, PLB 637 (2006) 75
• Granier de Cassagnac, hep-ph/0701222

y 0 intermediate xAu 0.020
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RHIC beyond cold nuclear effects (II) ?

• Comparison to a data driven parametrization of
  CNM (Granier de Cassagnac, hep-ph/0701222) in the
  same centrality classes
• CNM RAA(y, b) ScollisionsRdA(-y,b1i).RdA(y,b
  2i)/Ncoll
• Essentially the same conclusions as the previous
  slide
• But statsyst error that comes from dAu data are
  visible
• Need a higher luminosity dAu sample

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J/? production in dAu vs centrality
High x2 0.09

• Small centrality dependence
• Model with absorption shadowing ( black lines
  )
• shadowing EKS98
• sabs 0 to 3 mb
• sabs 1 mb good agreement
• sabs 3 mb is an upper limit
• weak shadowing and weak nuclear absorption

Low x2 0.003
Colored lines FGS shadowing for 3 mb
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SPS vs RHIC (III) RAA/CNM vs Npart
NA50 at SPS (0ltylt1) PHENIX at RHIC
(ylt0.35) PHENIX at RHIC (1.2ltylt2.2)

• SPS _at_ 0ltylt1
• CNM normal nuclear absorption sabs 4.18
  0.35 mb
• Compare to RHIC _at_ ylt0.35
• CNM shadowing nuclear absorption sabs1 mb
  (Vogt, nucl-th/0507027)
• Additionnal syst. error from uncertainity on CNM
• Need to improve knowledge on cold nuclear effects
  at RHIC
• Suppression beyond CNM larger at RHIC

Bar uncorrelated error Bracket correlated
error Global errors (12 and 7) are not shown
here. Box uncertainty from CNM effect
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Recombination at RHIC ?
RAA vs y
100 Recombination(shape only)
R. Vogt nucl-th/0507027 (EKS)
R. L. Thews, M. L. Mangano Phys.Rev. C73 (2006)
014904
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Charm flow
S. Sakai QM06
M. Djordjevic et al., Phys.Lett.B632 (2006) 81
c and b quark pT distributions at mid-rapidity
before fragmentation b contribution is dominant
at high pT

• Significant flow observed for heavy flavor
  electrons
• Main source is D meson
• (1) Consistent with c-quark thermalization
• (2) large cross section is needed in AMPT 10 mb
• (3) Resonance state of D B in sQGP
• Charm quark strongly coupled to the matter

Phys.Lett. B595 202-208
PRC72,024906
PRC73,034913
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Computing the J/? yield
Invariant yield
i i-th bin (centrality for e.g.)

• number of s reconstructed
• probability for a thrown and embeded
  
• into real data to be found
• (considering reconstruction and trigger
  efficiency)
• total number of events
• BBC trigger efficiency for events with a
• BBC trigger efficiency for minimum bias events

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Collision geometry and centrality (eg CuCu)

• For a given b, Glauber model (Woods-Saxon
  function) predicts
• Npart (No. participants)
• Ncoll (No. binary collisions)

Monte-Carlo Glauber model Probability for a
given Npart Each participant contributes to a
Negative Binomial distribution of hits Fit BBC
charge distribution
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Energy density

• Longitudinally expanding plasma
• dET/d? measurement at mid-rapidity by PHENIX
  EMCal
• Which t0 ?