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Charmonia in Heavy Ion Collisions. Roberta Arnaldi INFN Torino (Italy). Strongly Interacting Matter Under Extreme Conditions Hirschegg, 17-23 January 2010. Outline. Charmonia suppression in AA collisions is already a 25 years long story. SPS. RHIC. LHC. 17 GeV/c. 200 GeV/c. - PowerPoint PPT Presentation
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Charmonia in Heavy Ion Collisions
Strongly Interacting Matter Under Extreme ConditionsHirschegg, 17-23 January 2010
Roberta ArnaldiINFN Torino (Italy)
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Outline
Charmonia suppression in AA collisions is already a 25 years long story
SPS RHIC LHC
17 GeV/c 200 GeV/c 5.5 TeV/c√s
years 1990 ~2000 20101986
Last year, new high precision data (HERA-B, NA60, PHENIX/STAR) have been presented
improvements in the understanding of the charmonium behavior, taking advantage of the different energy and kinematics exploited domains
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Physics motivation: AA collisions
Study of charmonium production/suppression in pp, pA and AA collisions
AA collisions
• Charmonia suppression has been proposed, more than 20 years ago, as a signature for QGP formation
• Sequential suppression of the resonances is a thermometer of the temperature reached in the collisions
T/TC
J/(1S)
c(1P)
’(2S)
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Physics motivation: pp, pA collisions
allow the understanding the J/ behaviour in the cold nuclear medium complicate issue, because of many competing mechanisms:
pp collisions
provide information on production models (CSM, NRQCD, CEM…)
provide a reference for the study of charmonia dissociation in a hot medium approach followed at SPS and similarly at RHIC (with dAu data)
pA collisions
provide a reference for nuclear collisions results
Final state: cc dissociation in the medium, final energy loss
p
μ
μJ/
Initial state: shadowing, parton energy loss, intrinsic charm
(not covered by this talk)
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Fixed target experiments
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AA collisions
NA38 S-U 200 GeV/nucleon, 0<y<1 (M.C. Abreu et al., PLB449(1999)128)
NA50 Pb-Pb 158 GeV/nucleon, 0<y<, pT<5 GeV (B. Alessandro et al., EPJC39 (2005)335)
NA60 In-In 158 GeV/nucleon, 0<y<1, pT<5 GeV (R. Arnaldi et al., PRL99(2007) 132302, Nucl. Phys. A 830 (2009) 345)
pA collisions
HERAB p-Cu (Ti) 920 GeV,-0.34<xF<0.14,pT<5 GeV
(I. Abt et al., arXiv:0812.0734) E866 p-Be,Fe,W 800 GeV,-0.10<xF<0.93,pT<4 GeV
(M. Leitch et al., PRL84(2000) 3256) NA50 p-Be,Al,Cu,Ag,W,Pb,400/450 GeV,-0.1<xF<0.1,pT<5 GeV (B. Alessandro et al., EPJC48(2006) 329)
NA3 p-p p-Pt, 200 GeV, 0<xF<0.6, pT<5 GeV (J. Badier et al., ZPC20 (1983) 101)
NA60 p-Be,Al,Cu,In,W,Pb,U 158/400 GeV,-0.1<xF<0.35,pT<3 GeV (E. Scomparin et al., Nucl. Phys. A 830 (2009) 239)
Fixed target experimental landscape(Relatively) large amount of fixed-target data (SPS, FNAL, HERA)
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Fixed target experimental resultsAnomalous J/ suppression in AA is evaluated wrt to a reference obtained extrapolating, from pA to AA, the CNM effects affecting the J/
In-InPb-Pb
absJ/ = 4.2±0.5 mb,
(J//DY)pp =57.5±0.8 (Glauber analysis)
Observed suppression in AA exceeds nuclear absorption
AA collisions
• extrapolated to AA at 158 GeV assuming
• obtained from pA at 400/450 GeV (NA50)
In the NA50 approach:all initial/final CNM effects are described through an effective abs. cross section abs
J/
absJ/ (158 GeV) = abs
J/ (400/450 GeV)
(J//DY)pp rescaled from 450/400 to 158 GeV
• Onset of the suppression at Npart 80• Good overlap between Pb and In
pA collisions
~e−ρLσabs
(R. Arnaldi et al., PRL99(2007) 132302)
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Cold nuclear matter effects
I. Abt et al., arXiv:0812.0734
ApppA
• E866 vs HERAB (similar √s) agreement in the common xF range
• E866/HERAB vs NA50
These effects can be quantified, in pA collisions, in two ways:
decreases when decreasing √s
Satisfactory theoretical description still unavailable!
Strong xF dependence of
(R. Vogt, Phys. Rev. C61(2000)035203, K.G.Boreskov A.B.Kaidalov JETP Lett. D77(2003)599)
Because of the dependence on xF and energy the reference for the AA suppression must be obtained under the same kinematic/energy domain as the AA data
To understand the J/ dissociation in the hot matter created in AA collisions, cold nuclear matter effects have to be under control
absLpppA Ae ~
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New NA60 pA data
NA60 has collected pA data (using 7 different targets):
158 GeV: no data available up to now. First pA data at the same energy as AA collisions400 GeV: already investigated by NA50 (cross check)
A-dependence of the relative cross sections is fitted using the Glauber model and abs is extracted
shadowing neglected, as usual (but not correct!) at fixed target
abs J/ (158 GeV) = 7.6 ± 0.7 ± 0.6 mbabs J/ (400 GeV) = 4.3 ± 0.8 ± 0.6 mb
Using
(158 GeV) = 0.882 ± 0.009 ± 0.008 (400 GeV) = 0.927 ± 0.013 ± 0.009
ApppA
Very good agreement with the NA50 value
E. Scomparin et al., Nucl. Phys. A 830 (2009) 227
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Comparison between experiments: vs xF
NA60 pA results can be compared with values from other experiments
In the region close to xF=0, increase of with √s
NA60 158 GeV: smaller , hints of a decrease
towards high xF ?
NA60 400 GeV very good agreement with
NA50
Systematic error on for the new NA60 points ~0.01
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Comparison between experiments: vs x1,2
pattern vs x1 at lower energies resembles HERA-B+E866 but systematically lower
shadowing effects and nuclear absorption scale with x2 (V. Tram and F. Arleo, arXiv:0612043) clearly other effects are present
yT esmx /1
yT esmx /2
2
21~
x
xms JNJ
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Kinematical dependence of nuclear effects
need to disentangle the different contributions
Size of shadowing-related effects may be large and should be taken into account when comparing results at different energies
• anti-shadowing (with large uncertainties on gluon densities!)• final state absorption…
158 GeV free proton pdf158 GeV free proton pdfEKS98
Interpretation of results not easy many competing effects affect J/ production/propagation in nuclei
with antishadowing (EKS) = 9.3± 0.7± 0.7 mbwithout antishadowing: 7.6± 0.7± 0.6 mb
abs J/ (158 GeV)
Significantly higher than the “effective” value
C. Lourenco et al., arXiv:09013054
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Kinematic dependence of nuclear effects (2)Apart from shadowing, other effects not very well known, as parton energy loss, intrinsic charm may complicate the picture even more
First attempts of a systematic study recently appeared (C. Lourenco, R. Vogt and H.Woehri, JHEP 0902:014,2009, INT Seattle workshop 2009, F. Arleo and Vi-Nham Tram Eur.Phys.J.C55:449-461,2008, arXiv:0907.0043 )
No coherent picture from the data no obvious scaling of or abs with any kinematical variable
Clear tendency towardsstronger absorption at low √s
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Reference for AA dataa precise reference for the J/ behavior in AA collisions can be determined
abs shows an energy/kinematical
dependencereference now obtained from 158 GeV pA data (same energy/kinematical range as the AA data, contrarily to what was done in the past)
B. Alessandro et al., EPJC39 (2005) 335
R. Arnaldi et al., Nucl. Phys. A (2009) 345
In-In analysis based on another centrality estimator (number of tracks) ongoing, to check the observed pattern
AA collisions shadowing affects not only the target, but also the projectile
proj. and target antishadowing taken into account in the reference determination
R.A., P. Cortese, E. Scomparin Phys. Rev. C 81, 014903
Using the new reference:
• Central Pb-Pb: still anomalously suppressed• In-In: almost no anomalous suppression?
In-In 158 GeV (NA60)Pb-Pb 158 GeV (NA50)
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Collider experiments
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Collider experimental landscape
Experiments
PHENIX J/e+e- |y|<0.35 & J/+- |y| [1.2,2.2] STAR J/e+e- |y|<1
pp, dA collisions
pp 200 GeV/nucleon PHENIX, PRL 98, 232002 (2007) STAR, Phys. Rev. C 101 041902 (2009) dAu 200 GeV/nucleon PHENIX, Phys.Rev.C 77 024912 (2008) Nucl.Phys.A 830 (2009) 227
Data from RHIC, waiting for high energy LHC collisions…
All data have been collected with the same collision energy (√s = 200 GeV) and kinematics
AA collisions
Au-Au 200 GeV/nucleon PHENIX, PRL 98 232301 (2007) Nucl.Phys.A 830 (2009) 331Cu-Cu 200 GeV/nucleon PHENIX, PRL 101 122301 (2008) STAR, Phys. Rev. C 101 041902 (2009)
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pp experimental results
RHIC J/ results are usually provided as in terms of nuclear modification factor
The pp reference, used up to now, is based on Run 5 improvement expected from new Run 6 high statistics data
pp results should help to • understand the J/ production mechanism• provide a reference for AA collisions (RAA)
arXiv:0904.0439
ppJcoll
AAJ
AA dNN
dNR
C.L. da Silva, Nucl. Phys. A 830 (2009) 227
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AA experimental results
The Npart dependence of RAA for CuCu and AuAu is consistent
PRL 101, 122301 (2008)
J/ suppression is stronger at forward rapidity wrt. to midrapidity
Phys. Rev. Lett 98, 232301 (2007)
AuAu
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BackwardMid Forward
CNM effects from dAuIn a similar way as at SPS, CNM effects are obtained from dAu data
RdAu is fitted with a theoretical calculation assuming
y
Phys. Rev. C 77, 024912 (2008)
RHIC data exploit different x2 regions corresponding to shadowing (forward and midrapidity) anti-shadowing (backward rapidity)
• nuclear modified PDF distibutions• breakup
The result is the extrapolated to AA
results from dAu Run 3 do not allow to draw conclusions on AA results, because of the large breakup
error
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CNM effects from dAu (2)Furthermore CNM effects may depend on the assumed J/ production mechanisms (E. Ferreiro et al. arXiv:0809.4684)
intrinisic (gg J/) extrinsic (gg J/ + g) (emission of a hard gluon)
J/ produced through different partonic processes involve gluons in different x2 region different shadowing corrections
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The Run8 dAu dataNow high statistics dAu data (Run8 ~ 30x Run3) are available
a single value of break-up cannot reproduce the RCP ratios
A new approach has been proposed, to evaluate CNM effects(T. Frawley ECT*,INT quarkonium,Joint Cathie-TECHQM workshop)
RCP vs. centrality is fitted for each y bin with
a breakup for each y range a shadowing parameterization
EKS98: 0,1,…4,…mb
RCP flat vs centrality at backward rapidity, but falls at forward y
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RAA/RAA (CNM)
the trend at high y is similar to the one observed by E866 the suppression beyond CNM
effects is found to be similar at y=0 and at y=1.7 There is essentially no dependence of
these results on the shadowing model used to parameterize the dAu RCP
Result is then extrapolated to AA
(T. Frawley Joint Cathie-TECHQM workshop)
midrapidity
backward y forward y
breakup shows a strong rapidity dependence
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Comparison with SPS results vs NPart
Measured/Expected SPS results are compared with RHIC RAA results normalized to RAA(CNM)
Both Pb-Pb and Au-Au seem to depart from the reference curve at NPart~200
For central collisions more important suppression in Au-Au with respect to Pb-Pb
Systematic errors on the CNM reference are shown for all points
still some model dependence also in this approach: Cu results are fitted using breakup from dAu, since dCu data do not exist
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Comparison with SPS results
Results are shown as a function of the multiplicity of charged particles (~energy density, assuming SPS~RHIC)
Comparison can also be done in terms of * Bjorken energy density
energy density evaluation is based on several assumptions
A
dydET
0
dET/d from WA98 data for SPS data no dET/d for CuCu, so AuAu data at the same NPart are used
complicate issue, in particular when comparing results from different experiments
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Interpretation of the resultsSeveral theoretical models have been proposed in the past, starting from the following observations
• RAA at forward y is smaller than at midrapidity• RAA at RHIC and SPS are similar, in spite of the very different √s
Different approaches proposed:
SPS RHIC LHC
s (GeV) 17.2 200 5500
Ncc ≈ 0.2 ≈10 ≈100-200
1) Only J/ from ’ and c decays are suppressed at SPS and RHIC
The 2 effects may balance: suppression similar to SPS
2) Also direct J/ are suppressed at RHIC but cc multiplicity high
J/ regeneration ( Ncc2) contributes to the J/ yield
same suppression is expected at SPS and RHIC results do not seem to reflect the sequential suppression
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RecombinationModels including J/ regeneration qualitatively describe the RAA data
(X. Zhao, R. Rapp arXiv:0810.4566, Z.Qu et al. Nucl. Phys. A 830 (2009) 335)
J/ elliptic flow J/ should inherit the positive heavy quark flow
J/ y distribution should be narrower wrt pp
J/ pT distribution should be softer (<pT
2>) wrt pp
Results are not precise enough to assess the amount of regeneration
Indirect way some distributions should be affected by regeneration
Direct way for quantitative estimate accurate measurement of charm
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High pT J/ in Cu-Cu
RCuCu up to pT = 9 GeV/c suppression looks roughly constant up to high pT
PHENIX (minimum bias) STAR (centrality 0-20% & 0-60%)
RCuCu =1.4±0.4±0.2 (pT>5GeV/c) RAA increases from low to high pT
Difference between high pT results, but strong conclusions limited by poor statistics
Both results in contradiction with AdS/CFT+Hydro
Increase at high pT already seen at SPS
NA50: Pb-Pb
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Statistical hadronizationJ/ production by statistical hadronization of charm quarks (Andronic, BraunMunzinger, Redlich and Stachel, PLB 659 (2008) 149)
• charm quarks produced in primary hard collisions• survive and thermalize in QGP • charmed hadrons formed at chemical freeze-out (statistical laws)• no J/ survival in QGP
yA. Andronic et al. arXiv:0805.4781
Good agreement between data and model
Recombination should be tested on LHC data!
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LHC perspectives
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Quarkonium physics at LHC
Factor 10 (100) increase in charmonia (bottomonia) with respect to RHIC
Bottomonium physics will be accessible
High charm quark multiplicity (NCC~100)
J/ regeneration (not yet well defined at RHIC) might become dominant
New scenarios will be accessible, thanks to the high beam energy
Pb ions will be accelerated (√s=5.5 TeV)p collisions will be also studied (√s=7 – 14 TeV)
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Charmonium performances @ LHCCharmonia measurements will be carried out by all the LHC experiments under different kinematical conditions
LHCbCMSATLASALICE
Comparison of J/ measurement in central PbPb collisions
Acc
(M)
S/BpT
ALICE(+-) ALICE(e+e-) ATLAS(+-) CMS(+-)
2.5<<4 -0.9<<0.9 -2.7<<2.7 -2.4<<2.4
70 MeV 30 MeV
0.13 (7)
>0 GeV/cindirect id.
1.2 (5)
>0 GeV/c
yes yes? yes?
>2 GeV/c >2 GeV/c
35 MeV
1.2
70 MeV
0.15
prompt/displ.
Simulations with dNch/d~2500-5000
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ALICEALICE is the LHC experiment dedicated to nucleus-nucleus collisions
Central Barrel:-0.9<<0.9e+e- decay channel
Forward Muon Arm2.5<<4+- decay channel
Quarkonium production will be measured in the central barrel and in the forward muon spectrometer in p-p and Pb-Pb collisions
Quarkonium physics that will be addressed:
Suppression of in AA collisions to study the created medium
Differential distributions (y,pT,polarization) to constrain production models to provide a reference for AA
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Quarkonium in central Pb-Pb
Central rapidity Forward rapidity
• e- identification in TPC+TRD• integrated J/ acceptance ~29%
• identified in a Muon Spectrometer• integrated J/ acceptance ~4.6%
J/
N. 200 103 103
M MeV/c2 30 80
S/B 1.2 1.1
S/√(S+B) 245 21
J/ (2S)
N. 130 103 3.7 103 1.3 103
M MeV/c2 70 100 100
S/B 0.2 0.01 1.7
S/√(S+B) 150 7 29
J/ and significances not so different smaller statistics compensated by background reductionWorst situation for the ’ statistics , but much larger background
Quarkonium in central Pb-Pb collisions (106 s running time, L=51026cm-2 s-1)
Simulations with dNch/dy~3000 Simulations with dNch/dy~8000
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With the expected statistics (~7 105 J/ in 1 month of data taking): J/ suppression can be studied as a function of centrality and pT (up to ~10GeV/c), allowing the discrimination between the different theoretical scenarios J/ polarization study will be performed as a function of pT
Quarkonium in Pb-Pb
A fraction of the J/ produced at LHC comes from the B hadron decay useful to evaluate the beauty production cross section need to be disentangled to study prompt J/ production
At midrapidity prompt and secondary J/ can be discriminated thanks to the vertexing capabilities.At forward y J/ from B can be determined only indirectly
Higher charmonia states (’, c) can be measured cleaner signal for theory feasible in pp, much more complicate in Pb-Pb because of the lower significance
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First ALICE dimuons!
First dimuons seen in ALICE in pp at √s=900GeV, even if out of the ~20 observed dimuons… not yet a J/!
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ConclusionsJ/ suppression is a good signature for QGP studies
J/ behaviour in cold nuclear matter is already a complicate issue: many competing initial/final state effects
Many steps forward thanks to new high precision data
but for a correct evaluation of anomalous effects, cold nuclear matter effects have to be under control
Signal of anomalous suppression has been observed at SPS and RHIC
Important to understand J/ behaviour from lower to higher energy in a coherent scenario
New LHC data will soon be available!
They will help to discriminate among the different processes (suppression, regeneration…) affecting the J/
In the future, the “J/ picture” will be enriched by the results from CBM, exploring a baryon rich matter, and maybe from a NA60-like experiment filling the gap between FAIR and top SPS energy
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Backup
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NA60 pA data
NA60 has collected pA data:
158 GeV: no data available up to now. First pA data at the same energy as AA collisions400 GeV: already investigated by NA50 (cross check)
3-day long data taking, largely motivated by the need of a reference sample taken in the same conditions of In-In (NA60) and Pb-Pb (NA50) data useful to enlarge the vs xF systematics
bulk of the NA60 p-A data taking results released up to now
• sub-sample with same exp. set-up used at 158 GeV• useful as a cross-check (same energy/kinematic domain of the large statistics data sample collected by NA50)
Kinematical window where acceptance is >0 for all targets
• 3.2 < ylab < 3.70.28 < ycm < 0.78 (158 GeV)
-0.17 < ycm < 0.33 (400 GeV)
• | cos CS | <0.5
158 GeV
400 GeV
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all targets simultaneously on the beam
beam luminosity factors Niinc cancel out
(apart from a small beam attenuation factor) no systematic errorsBeBe
tBe
incBe
JBe
AAtA
incA
JA
JBe
JA
ANN
N
ANN
N
arg
/
arg
/
/
/
each target sees the vertex spectrometer under a (slightly) different angle
acceptance and reconstruction efficiencies do not completely cancel out
Estimate of nuclear effects through relative cross sections:
Efficiency map(4th plane, sensor 0)
These quantities, and their time evolution, are computed for each target separately
DY
J/, ’
DD
Comb.bck.
p-Pb
NJ/ 2 103Not enough DY statistics to extract (as in NA50) B J//DY target by target
New NA60 pA results
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Comparison between experiments: abs vs xF
absJ/ calculated from cross section
ratios for HERA-B, E866,NA3
As already observed for , there is:
• a strong xF dependence• a √s dependence…but NA3 shows values closer to the high energy experiments (E866/HERA-B)
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Results with old and new referenceabs J/ (158 GeV) > abs J/ (400 GeV)
Anomalous suppression in In-In is quite small ( 10%)
new reference
In-In 158 GeV (NA60)Pb-Pb 158 GeV (NA50)
published results
B. Alessandro et al., EPJC39 (2005) 335R. Arnaldi et al., PRL99 (2007) 132302
smaller anomalous suppression expected with respect to previous results
In-In analysis based on another centrality estimator (number of tracks) ongoing, to check the observed pattern
Anomalous suppression in Pb-Pb up to 30%
42
Antishadowing contribution
In AA collisions the initial state effects (shadowing) affect not only the target, but also the projectile
Even in absence of anomalous suppression, the use of the standard reference (no shadowing) induces a 5-10% suppression signal sizeable effect
Using the new reference (shadowing in the projectile and target)
• Central Pb-Pb: still anomalously suppressed• In-In: almost no anomalous suppression?
proj. and target antishadowing taken into account in the reference determination
R.A., P. Cortese, E. Scomparin Phys. Rev. C 81, 014903
43
CNM effects from dAu
As discussed for SPS data, a good knowledge of the initial/final state effects in nuclear matter helps to understand the J/ behaviour in AA
CNM effects at RHIC energies can be inferred from dAu data, using different approaches
1st method
• RdAu is fitted with a theoretical calculation assuming a shadowing parameterization and a breakup common to the whole y range.
• The result is the extrapolated to AA
y
Phys. Rev. C 77, 024912 (2008)
• Since breakup is common, results in the two y ranges strongly depend on nPDF
44
CNM effects from dAu
2nd method
• RdAu data are fitted with a theoretical model including a breakup for each y range and shadowing parameterization
• Results are limited by the low Run 3 statistics
3rd methodNpart
PRL 101, 122301 (2008)
• The approach is based on a combination of RdAu data at different y, to predict CNM RAA for AuAu
• The method works only for AuAu, since RdAu is used directly
• Results at different y are independent, but they again suffer the Run 3 low statistics
J. Phys. G34, S955 (2007)
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abs vs. y
46
High pT J/ @ SPS
pT (GeV/c)
RC
P 33-47%
NA60: In-In @ 158 GeV
NA50: Pb-Pb @ 158 GeV
pT (GeV/c)
RC
P 0-1.5%
pT dependence of the J/ suppression already investigated at SPS energies:
strong pT dependence of RCP
only the low pT J/ψ are suppressed !
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First Upsilon results @ RHIC
PHENIX, STAR pp @ √s=200GeV
PHENIX Au-Au @ √s=200GeV
STAR dAu @√s=200GeV
Cross section follows CEM expectations
RdAu = 0.98 ± 0.32 ± 0.28
RAuAu [8.5,11.5] < 0.64 at 90% C.L.
very low statistics
as expected from CNM + sequential melting
PHENIX
Upsilons suppressed:
consistent with Nbin scaling
in the future:
Upcoming 50 pb-1 200 GeV p+p run (5.6 pb-1 in run6 p+p)
RHIC II: high luminosity → separation of 1S, 2S, 3S states
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…and more results on…
STAR: arXiv:0904.0439
Small bck contribution allows the study of high pT J/ - hadron azimuthal correlations
STAR pp @ √s=200GeV
from the comparison with model calculations BJ/ fraction = 13% ±5%
PHENIX pp @ √s=200GeV
• v2 = –10 ± 10 %@ |y|<0.35 & –9.3 ± 9.2 %@1.2<|y|<2.2
• does not allow to differentiate between different models
in the measure pT range
J/ azimuthal flow measurement limited by statistics
PHENIX AuAu@√s=200GeV
N(J/) = 9.9 4.1 1.0
First measurement of J/ψ photoproduction in ultraperipheral collisions cross section (7633(stat)11(syst) b) consistent with theoretical predictions
49
Sequential melting
In a color screening suppression scenario, a sequential melting, starting from the most loosely bound charmonia state, is expected
can the c and ’ feed down account for the observed J/ suppression?
are other mechanisms (e.g. color glass condensate) needed to explain the different suppression at midrapidity vs forward rapidity?
are the SPS and RHIC J/ suppression in the hot medium similar enough to justify this assumption?
50
RecombinationIn a dense medium, J/ may be formed by a c and a c belonging to a different initial cc pair 2
ccNN J
regeneration is expected to be more important at midrapidity
A good accuracy in the open charm cross section measurement should help to quantify the importance of this process
Thews Eur.Phys.J C43, 97 (2005)
Grandchamp, Rapp, BrownPRL 92, 212301 (2004)
RHIC patterns are qualitatively reproduced
51
RecombinationModels including J/ regeneration qualitatively describe the RAA data
(X. Zhao, R. Rapp arXiv:0810.4566)
J/ elliptic flow J/ should inherit the positive heavy quark flow
J/ y distribution should be narrower wrt pp
J/ pT distribution should be softer (<pT
2>) wrt pp
Results are not precise enough to assess the amount of regeneration
Regeneration should affect several distributions: