Charmonia production at the SPS energies
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Charmonia production at the SPS energies Marie-Pierre COMETS IPN Orsay, FRANCE SQM2006, UCLA, Los Angeles, USA, March 26-31, 2006
Goal: study anomalous J/ suppressionin AA collisions as predicted by Matsui and Satz in case of QGP formationNeed of a reference: normal absorption in pA Outline: J/ and productionpA results at SPS - Comparison with E866 and Hera b experimentsAA results pT resultsConclusion and open questions
J/ and normal nuclear absorption NA50 pA at 450 GeVGlauber fit to J/ and absolutecross-sections lead to: presents a larger absorption than J/.
NA50 pA (450 GeV) In our kinematical domain, charmonium formation time small enough to distinguish the 2 states. J/ and normal nuclear absorption xF = x1 x2 (p) (A)
J/ and normal nuclear absorption Drell-Yan cross section per nucleon-nucleon collision for 2.9 < M < 4.5 GeVFit (Drell-Yan) with a power law = 0 A -> Drell-Yan = 0.986 0.020Compatible with 1.In a and abs :Shadowing (antishadowing)Nuclear absorptionAbsorption by comovers -> negligible DY scales with the number of NN collisions -> reference for J/ and NA50 pA at 400 GeV
A=208Q2 = 2.25, 5.39,14.7,39.9,108, and 10000 GeV2For DY: At SPS xF0, MDY3 GeV -> x20.11
shadowing valence quark antishadowing antiquark no nuclear absorption =>aDY1 J/ and normal nuclear absorption: discussion on a
42 GeV38 GeV29 GeVJ/ and normal nuclear absorption:discussion on a
J/ and normal nuclear absorption:discussion on a If ONLY shadowing in a:pA = Aa pp = A RA pp
Open charm: no nuclear absorption antishadowing ~18% -> aopen charm 1.03
E866a due ONLY to shadowing variationbetween xF0 (RA1.2 x20.09)and xF1 (RA0.85 x20.007) 0.06
-> other explanations: F. Arlo et al.: scenario with octet state-nucleon collisions at large xF(Phys. Rev. C61(2000)054906)D. Kharzeev and K. Tuchin:in the CGC framework, J/ production is suppressed at large xF due to saturation of gluons in the nuclear wave function.At smaller xF, nuclear absorption plays a significant role; because of formation time effects, it suppresses the J/ prod. at SPS stronger than at Fermilab. (hep-ph/0510358)J/ and normal nuclear absorption:discussion on a
J/ - NA50Glauber fit of all pA data at 450 and 400 GeV, and pp and pd NA51 -> J/abs =4.18 0.35 mb
J/ and normal nuclear absorption
J//DY: from pp to PbPbAverage path length L traversed by the cc pair in nuclear matter:appropriate to visualize nuclear absorption in different systems.Peripheral PbPb data points, AND all SU data pointscompatible with normal nuclear absorption.PbPb: departure from normal nuclear absorption at mid-centrality
J/ suppression versus pTRatio to the mostperipheral bin (1)J/ suppression ismainly at low pT and increases with centrality For pT>3.5 GeV/c,weak centrality dependenceof J/ suppression Ri = N,i(pT)/NDY,i / N,1(pT)/NDY,1
PbPb 158 GeV/c NA50
of J/ versus centrality increases linearly with L Attributed to parton multiple scattering in the initial state, even in PbPb?Phenomenological description (L) = pp +agNL with pp varying with energy and a common slope agN = 0.081 0.002 GeV2/c2/fm
of J/ versus centralityNA50Saturation of versus ET observedfor central PbPb collisions. S. Gavin and R. Vogt: if broadeningdue only to parton rescattering -> saturation J.P. Blaizot and J.Y. Ollitrault: ina plasma model (scenario in which ALLthe J/ are suppressed whatever theirpT over a certain energy density) -> saturation D. kharzeev et al. predict anincrease followed by a decrease withina plasma model
Is pT a good variable?
/DY: from pp to pPb - NA50Fit of all pA data at 450 and400 GeV -> abs = 7.6 1.1 mb 2 regimes: one for protonand one different for ion-induced reactionsSimilar centralitydependence for SU and PbPb
J/ suppression in InIn collisions Anomalous suppression present in lighter nuclear systems? Variable driving the suppression? NA60 experiment: InIn collisions at 158 GeV/cAnomalous suppression present in InIn. Onset in the range80 < Npart < 100. Saturation at large Npart.
J/ suppression in InIn collisionsThe SU, PbPb and InIn data points do not overlap in theL variable, while the suppression patterns are in fairagreement in the Npartvariable.
J/ suppression in InIn collisionsNone of the models seems to properlyreproduce the observed pattern.J/ absorption by comovers Capella andFerreiro (Eur. Phys. J. C42(2005)419)J/ dissociation and regeneration in QGP and hadronic phases Grandchamp,Rapp,Brown(J. Phys. G30(2004)S1355)c suppression in a percolation modelDigal, Fortunato, Satz (Eur. Phys. J. C32(2004)547)
Conclusions and open questions AT SPS energies:J/ normal nuclear absorption -> NA60 - pA at 158 GeV nuclear absorption at 158 GeV c nuclear dependence
(First upsilon results in pA NA50)ANOMALOUS J/ suppression in PbPb and InIn at s = 17.8 GeV Pt ? What at higher energies? -> RHIC (s = 200 GeV): next talk -> LHC (s = 5.5 TeV): to come
Upsilon production in pA collisionsNA50 pA at 450 GeV