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Cold nuclear matter effects on J/psi production:

XLIIIth Rencontres de Moriond : QCD and High Energy Interactions La Thuile , Italy . 14-21 March 2009. Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects. Elena G. Ferreiro Universidade de Santiago de Compostela, Spain.

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Cold nuclear matter effects on J/psi production:

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  1. XLIIIthRencontres de Moriond: QCD and High Energy Interactions La Thuile, Italy. 14-21 March 2009 Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects Elena G. Ferreiro Universidade de Santiago de Compostela, Spain Work done in collaboration with F. Fleuret, J-P. Lansberg and A. Rakotozafindrabe arXiv :0809.4684

  2. Introduction See talk by Z. Conesa del Valle • Too much work trying to understand A+A data (since J/y  QGP signal) • We do not understand p+A data (where no QGP is possible)!!! only cold nuclear matter (CNM) effects are in play here: shadowing and nuclear absorption • In fact, the problem is even more fundamental: we do not know the specific J/y production kinematics even at a partonic level In other words, the partonic process producing the ccand then the J/y • Our goal: Investigate the impact of the specific J/y-production kinematics on the [gluon] shadowing effects E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  3. On the kinematics of J/y production: two approaches • CNM -shadowing- effects depends completly on J/y kinematics (x,Q2) • J/y kinematics depends on the production mechanism => Investigating two production mechanisms (including pT for the J/y): g+g → J/y • intrinsic scheme: the pTof the J/y comes from initial partons g+g → J/y+g • extrinsic scheme: the pTof the J/y is balanced by the outgoing gluon E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  4. Intrinsic J/yproductionkinematics • Intrinsic scheme: 2 → 1 process CEM @ LO g+g → J/y • y, pT can be determined using PHENIX p+p data Phys. Rev. Lett. 98, 232002 (2007) • Easy to handle : yJ/y and pTJ/ydirectly give x1,2 Q2=(2mc)2+(pT)2=mT • Straightforward evaluation of the gluon PDF shadowed in the nucleus at x2 (and x1 in AA) E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  5. Extrinsic J/yproductionkinematics • We deal with a 2 → 2 partonic process with collinear initial gluons g+g → J/y+g • The quadri-momentum conservation results in a complex expression of x2 as a function of (x1, y, pT) • Information from the data alone – the y and pT spectra– is not sufficient to determinex1 and x2: the presence of a final-state gluon authorizes much more freedom to choose (x1, x2) for a given set (y, PT) • Models are mandatory to compute the proper weighting of each kinematically allowed (x1, x2) •We use s—channel cut mechanism Extension of CSM Haberzettl and Lansberg, Phys.Rev.Lett.100,032006 (2008) Good results at low pT E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  6. Extrinsic vs intrinsickinematics Intrinsic scheme Extrinsic scheme For a given set (y, pT): more freedom for x x larger in the extrinsic scheme We expect different shadowing effects in both cases both implemented in a Monte Carlo code E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  7. Shadowing: a cold nuclear mattereffect • Nuclear shadowing is an initial-state effect on the partons distributions • Gluon distribution functions are modified by the nuclear environment • PDFs in nuclei different from the superposition of PDFs of their nucleons E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  8. Resultsford+Au: rapiditydependence I • Different shadowing effects in the 2 approaches RdAu • Antishadowing peak shifted to less negative y in the extrinsic case E.G.F, F. Fleuret, A. Rakotozandrabe. arXiv :0801.4949 • Shadowing alone not able to reproduce data y We need to include nuclear absorption to mach the data Let us add a break-up cross section: sabs intrisic < sabs extrinsic E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  9. Resultsford+Au: rapiditydependence II First choice: Intrinsicscheme sabs=2.8 mb following PHENIX PRC 77, 024912 (2008) Extrinsicscheme sabs=4.2 mb following NA50 measurements at SPS E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  10. Resultsford+Au: centralitydependence Note: PHENIX fit uses different sabs Extrinsic scheme seems to be favorized E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  11. ResultsforAu+Au: centralitydependence Intrinsicscheme: Same CNM suppression at forward and central rapidity Extrinsicscheme: More CNM suppression at forward than central rapidity Extrinsic scheme : RAA @ forward y < RAA@ mid y Hot Nuclear matter effects still needed, but… Less need for recombination effects E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  12. Work in progress: • Determination of sabs using a fit to data that take into account all the experimental errors and their correlations • Consider other parametrisations for the shadowing: EPS, nDS(g)… E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  13. Work in progress: shadowingrapiditydependence • Intrinsic sheme EKS98 EPS08 nDSg • Extrinsic sheme EKS98 EPS08 nDSg E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  14. Work in progress: fit of sabswith EKS, EPS and nDS(g) EKS98: compatible with intrinsic & extrinsic EPS08:extrinsic scheme is favorized nDSg:neither extrinsicnor intrinsic… Best fit: EPS08+extrinsic E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  15. Conclusions… • We have studied the influence of J/y kinematics on shadowing effect: within 2 schemes: intrinsic (2→ 1) and extrinsic (2→2) pT for different shadowings: EKS98, EPS08, nDGg using s-channel cut model as the production model for p+p in 2→ 2 in the framework of a Glauber MC code • For the first time: results @ pT ≠ 0 for J/y shadowing exact J/y kinematics have been taken into account calculation in s-channel cut model • Work is progressing: other shadowing parametrisations other production model in pp : CEM @ NLO, NRQCD, . . . If they are able calculations for LHC in the extrinsic scheme reproduce low pT data E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09 More plots in: http://phenix-france.in2p3.fr/software/jin/index.html

  16. Backupslides • Some other results • Work in progress: RdAu vs Ncoll and RdAu vs pT for EKS98,EPS08, nDSg • On the kinematics of J/y production: detail equations • s-chanel cut model • The Glauber Monte Carlo code • Shadowing models • Nuclear absorption • Work in progress: comparation with Vogt’s results (CEM @ LO without pT) Fit procedure • J/y production mechanisms E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  17. Extrinsic vs intrinsickinematics II For a given couple (y, pT), x2 is larger in the extrinsic scheme Much more freedom to choose (x1, x2) for a given set (y, PT) We expect different shadowing effects in both cases E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  18. Resultsford+Au: transversemomentumdependence Work to do: • Determine best sabs using c2 minimization • Try other shadowing parameterisations But before… let’s see what happens for Au+Au Data not conclusive E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  19. ResultsforAu+Au: rapiditydependence • Intrinsic: flat behaviour • Extrinsic: maximun at y=0 Again, this indicates that less recombination would be required in the extrinsic case E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  20. ResultsforAu+Au: transversemomentumdependence Intrinsicscheme: Extrinsicscheme: Data not conclusive E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  21. Work in progress: reallyprogressing!!! Merci Andry & Fred! E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  22. Work in progress: EKS98 centralitydependence • Intrinsic sheme • Extrinsic sheme EKS98 EKS98 EKS98 E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  23. Work in progress: EPS08 centralitydependence • Intrinsic sheme • Extrinsic sheme EPS08 EPS08 E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  24. Work in progress: nDSgcentralitydependence • Intrinsic sheme • Extrinsic sheme nDSg nDGg E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  25. Work in progress: EKS98 pTdependence • Intrinsic sheme • Extrinsic sheme EKS98 EKS98 E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  26. Work in progress: EPS08 pTdependence • Intrinsic sheme • Extrinsic sheme EPS08 EPS08 E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  27. Work in progress: nDSgpTdependence • Intrinsic sheme • Extrinsic sheme nDSg nDSg E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  28. Work in progress: fit of sabswith EKS, EPS and nDS(g) EPS extrinsic intrinsic Best fit: extrinsic + EPS08 c2 sabs sabs E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  29. On the kinematics of J/y production: equations I shadowing partonic cross section nuclear absorption fit to data s-channel cut model kinematic variables E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Palaiseau 5 March 09

  30. On the kinematics of J/y production: equations II Concerning it can be factorized in the nuclear density distribution, the shadowing modification factor and the usual gluon PDFs: where we have included the centrality dependence of the shadowing: E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Palaiseau 5 March 09

  31. On the kinematics of J/y production: equations III E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  32. s-channel cut model: motivation a suitable production model for low pT J/y E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  33. s-channel cut contributions E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  34. s-channel cut contributions s-channel cut contributions to the basic CSM: • take into account the dynamics of the ccbar in the bound state • need for 4-point coupling ccbar-J/y-g • new degrees of freedom constrained by fits • so far the best description of low-pT data E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  35. s-channel cut contributions: first evaluations E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  36. s-channel cut model vs. other models in the market Various models for the y spectra in p+p [NRQCD calculation] Cooper, Liu & Nayak, Phys. Rev. Lett. 93, 171801 (2004) [g(gg)s + Feed-down] Khoze, Martin, Ryskin Stirling, Eur. Phys. J. C39, 163 (2005) E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  37. The Glauber Monte Carlo code E.G. Ferreiro, F. Fleuret, A. Rakotozandrabe. arXiv :0801.4949 [hep-ph] E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  38. EKS and EPS shadowing model • Introduce an initial parameterisation for nuclear parton distributions RA(x,Q20) based on a fit to DIS data at Q20 = 2.25 GeV2 fiA(x,Q2)  RiA(x,Q2) fi(x,Q2) GRV-LO, CTEQ4L high pT RHIC data at Q20 = 1.69 GeV2 GRV-LO, CTEQ6L1 • The further evolution in Q2 is predicted by the DGLAP equations at LO • RHIC high-pT forward-rapidity hadron data suggest a stronger gluon shadowing than obtained in previous global analyses E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Palaiseau 5 March 09

  39. EKS shadowing model 1. Introduce an initial parameterisation for nuclear parton distributions RA(x,Q20) based on the DIS data at Q20 = 2.25 GeV2 GRV-LO, CTEQ4L • 2. Once the nuclear parton distributions are given at an initial scale Q20>>Λ2QCD the further evolution in Q2 is predicted by the DGLAP eqs: • DGLAP eqs: relation between the logarithmic Q2-evolution of the structure functions and the gluon • distribution, giving the possibility to calculate the value of ratios at any Q2 if an initial value is known • It is assume that • at Q2 >Q20 the scale evolution of the nuclear parton densities is purely perturbative • the initial conditions at Q20 contain the nonperturbative input • the evolution is made at leading order (LO) 3. The slope of the nuclear parton distributions in Q2 is obtained in this way No centrality dependence is included in the model E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  40. EPS shadowing model • Global fit to DIS, DY and high pT RHIC data • LO, Q20 = 1.69 GeV2 • RHIC high-pT forward-rapidity hadron data suggest a stronger gluon shadowing than obtained in previous global analyses E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  41. nDSg shadowing model • Define nPDF using a convolution approach: the free nucleon parton densities are convoluted with very simple weight functions that parameterize nuclear effects Instead of: LO they use: Differences with other parameterizations: • ESK98: less small x shadowing and very little antishadowing at intermediate x in gluon densities •HKM: low x shadowing in the valence distribution (none in HKM), ratios for sea and gluon densities approach 1 as x grows while they strongly rise within HKM • LO and NLO evolution E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  42. Pomeron shadowing model • Approach based on multiple collisions • It takes into account triple pomeron interactions • -equivalente to interaction among gluon- • It leads to a shadowing due to coherence effects • Shadowing corrections: integral of the triple P cross section over the single P one • Reduction of multiplicity from shadowing corrections • Shadowing increases with s (~1/x) and decreases with pT (~ mT) E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  43. Nuclear absorption: a cold nuclear matter effect • The primordial spectrum of particles is altered by interactions with the nuclear matter they traverse on the way out to the detector • Nuclear absorption: interaction of the preresonant c-cbar pair with spectator nucleons • Usual parameterisation: Sabs = exp(-r sabs L ) nuclear matter density break-up cross section path length • Note: some authors consider • Rapidity dependence of the nuclear absorption: sabs at mid y < sabs at forward y • At high energy: the coherence length is large and the projectile interacts with the nucleus as a whole => Smaller nuclear absorption with growing energies E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Palaiseau 5 March 09

  44. EKS shadowing model: intrinsic vs. Vogt’s E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  45. EKS shadowing model: intrinsic & extrinsic vs. Vogt’s E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  46. EPS shadowing model: intrinsic vs. Vogt’s E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  47. EPS shadowing model: intrinsic & extrinsic vs. Vogt’s E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  48. nDSg shadowing model: intrinsic vs. Vogt’s NLO LO E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  49. nDSg shadowing model: intrinsic & extrinsic vs. Vogt’s Vogt’s: LO Ours: NLO NLO LO E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

  50. Fit procedure E. G. Ferreiro USCCNM effects on J/y production: intrinsic and extrinsic Moriond 20 March 09

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