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Shadowing and cold nuclear matter effects on quarkonium production

Low x workshop Santiago de Compostela, June 2-7, 2011. Shadowing and cold nuclear matter effects on quarkonium production. Elena Ferreiro Universidade de Santiago de Compostela. E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011.

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Shadowing and cold nuclear matter effects on quarkonium production

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  1. Low x workshop Santiago de Compostela, June 2-7, 2011 Shadowing and cold nuclear matter effects on quarkonium production Elena Ferreiro Universidade de Santiago de Compostela E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  2. Introduction I: theintringuingstory of J/yproduction V(r) r Potential between q-anti-q pair grows linearly at large distances Screening of long range confining potential at high enough temperature or density. What happens when the range of the binding force becomes smaller than the radius of the state? V(r) different states “melting” at different temperatures due to different binding energies. Matsui and Satz: J/y destruction in a QGP by Debye screening J/Y suppression = QGP signature E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  3. Introduction II: motivation • A lot of work trying to understand A+A data (since J/y  QGP signal) Quakonium as a hint of deconfinement QGP hint • Here we focalise on p+A data (where no QGP is possible) only cold nuclear matter (CNM) effects are in play here: shadowing and nuclear absorption nPDF hint Quakonium as a hint of coherence • In fact, the question is even more fundamental: p+p data we do not know the specific production kinematics at a partonic level: CS vs CO Quakonium as a hint of QCD QCD hint E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  4. Quarkonium as a tool of COLD and HOT effects •cold effects: wo thermalisation NO QGP CGC gluon shadowing gribov shadowing partonic comovers percolation hadronic comovers parton saturation nuclear structure functions in nuclei ≠ superposition of constituents nucleons dissociation of the c-cbar pair with the dense medium produced in the collision partonic or hadronic non-lineal effects favoured by the high density of partons become important and lead to eventual saturation of the parton densities NI@SPS, IMP@RHIC suppression by a dense medium, not thermalized nuclear absorption multiple scattering of a pre-resonance c-cbar pair within the nucleons of the nucleus non thermal colour connection Others: Cronin effect energy loss IMP@SPS, RHIC? w thermalisation QGP •hot effects: QGP sequential suppression recombination E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  5. Collisions p+p: Quakonium as a hint of QCD E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  6. J/y production mechanisms p soft g c p J/y c c J/y c p hard g p 2→2 g+g → J/y+g • Color Singlet Model: • perturbative creation of the ccbar pair in color singlet state with subsequent binding to J/y with same quantum numbers • hard gluon emission • underpredicts J/ production cross section, predicts no polarization • Color Evaporation Model: • phenomenological approach • perturbative creation of the ccbar pair in the color octet state with subsequent non-perturbativehadronization to color singlet via unsuppressed soft gluon emission • predicts no polarization 2→1 g+g → J/y • NRQCD Color Octet Model: • uses NRQCD formalism to describe the non-perturbativehadronization of the ccbar color octet to the color singlet state via soft gluon emission • factorizes the charmonium production into a short distance hard part and a long distance matrix element which is claimed to be universal • Predicts large transverse polarization at high pT(not seen by data) Abigail Bickley, August 9, 2007 E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  7. Collisions p+A: Quakonium as a hint of nuclear PDFs E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  8. Shadowing: a initialcold 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 Shadowing effects increases with energy (1/x) and decrease with Q2 (mT) antishadowing The shadowing corrections strongly depend on the partonic process producing the J/Y since it affects kinematics (x,Q2) shadowing Obtained from fit to data+DGLAP eqs E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  9. Anillustration: J/y resultsford+Au @ RHIC 2→1 g+g → J/y 2→2 g+g → J/y+g for a given y x larger in extrinsic • shadowing depends on the partonic process: 2→1 or2→2 • antishadowingpeak shifted toward larger y in the extrinsic case • in order to reproduce data: nuclear absorption sabsextrinsic > sabsintrinsic arXiv:0912.4498 PRC E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  10. Fit of sabswith EKS, EPS and nDS(g) fromRdAu EKS98: compatible with intrinsic & extrinsic EPS08:extrinsic scheme is favorized EGF, F. Fleuret , and A. Rakotozafindrabe, EPJC61 (2009) EGF, F. Fleuret, J-P. Lansberg and A. Rakotozafindrabe, PLB680 (2009) EGF, F. Fleuret, JP. Lansberg, N. Matagne and A. Rakotozafindrabe, PRC81 (2010) nDSg:neither extrinsicnor intrinsic… E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  11. Work in progress: J/y @ LHC centralitydependence • CNM effectshavetobetakeninto account as a baselinefor a right interpretation of the J/Y as a QGP signal • CNM effectsdependonthepartonic productionmechanism E. G. Ferreiro USCCNM effects on quarkoniumSubatech 21 October 10

  12. Too many fits…: Pomeron shadowing from Alexei Kaidalov and Alphonse Capella E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  13. More analytical approach to the shadowing E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  14. ApplicationtoJ/y resultsford+Au @ RHIC • Comparation: • EKS98 (fit to data) • Pomeron shadowing E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  15. Applicationtomultiplicities @ RHIC • Maximal multiplicity in absence of shadowing dNAA/dy=A4/3 This is a general property of Gribov's Reggeon Field Theory which is known as AGK cancellation (analogous to the factorization theorem in perturbative QCD) and valid for soft collisions in the absence of triple Pomeron diagrams. • Multiplicity with shadowing corrections AGK violated by triple P dNAA/dy=Aa a=1.13 E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

  16. Applicationtomultiplicities @ LHC 2.76 TeV 5.50 TeV • Based on : • Deep inelastic scattering data and the problem of saturation in small-x physics • Capella, E. G. Ferreiro, A. B. Kaidalov, C. A: Salgado, PRD63 (2001) 054010 • A unitary model for structure functions and diffractive production at small x • A. Capella, E. G. Ferreiro, A. B. Kaidalov, C. A: Salgado, NPB593 (2001) 336 E. G. Ferreiro USC Low x workshopSantiago de Compostela June 2011

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