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

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

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Introduction II: motivation A lot of work trying to understand A+A data (since J/ QGP signal) 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 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 deconfinement Quakonium as a hint of coherence Quakonium as a hint of QCD QGP hint nPDF hint QCD hint E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011

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

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

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Abigail Bickley, August 9, Color Singlet Model: –perturbative creation of the ccbar pair in color singlet state with subsequent binding to J/ with same quantum numbers –hard gluon emission –underpredicts J/ production cross section, predicts no polarization J/ production mechanisms NRQCD Color Octet Model: –uses NRQCD formalism to describe the non-perturbative hadronization 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 p T (not seen by data) Color Evaporation Model: –phenomenological approach –perturbative creation of the ccbar pair in the color octet state with subsequent non-perturbative hadronization to color singlet via unsuppressed soft gluon emission –predicts no polarization p p J/ soft g c c p p J/ hard g c c 2→2 g+g → J/ g 2→1 g+g → J/ E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011

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

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Obtained from fit to data+DGLAP eqs 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: a initial cold nuclear matter effect Shadowing effects increases with energy (1/x) and decrease with Q 2 (m T ) shadowing antishadowing The shadowing corrections strongly depend on the partonic process producing the J/ since it affects kinematics (x,Q 2 ) E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011

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An illustration: J/ results for RHIC antishadowing peak shifted toward larger y in the extrinsic case in order to reproduce data: nuclear absorption abs extrinsic > abs intrinsic for a given y x larger in extrinsic 2→2 g+g → J/ g 2→1 g+g → J/ shadowing depends on the partonic process: 2→1 or 2→2 arXiv: PRC E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011

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EKS98: compatible with intrinsic & extrinsic EPS08: extrinsic scheme is favorized nDSg: neither extrinsic nor intrinsic… Fit of abs with EKS, EPS and nDS(g) from R dAu E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011 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)

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Work in progress: J/ LHC centrality dependence E. G. Ferreiro USC CNM effects on quarkoniumSubatech 21 October 10 CNM effects have to be taken into account as a baseline for a right interpretation of the J/ as a QGP signal CNM effects depend on the partonic production mechanism

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

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

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Application to J/ results for RHIC Comparation: EKS98 (fit to data) Pomeron shadowing E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011

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Application to RHIC Maximal multiplicity in absence of shadowing E. G. Ferreiro USC Low x workshop Santiago de Compostela June 2011 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. dN AA /dy=A 4/3 Multiplicity with shadowing corrections AGK violated by triple P dN AA /dy=A

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Application to LHC E. G. Ferreiro USC Low x workshop Santiago de Compostela June TeV 5.50 TeV Based on : Deep inelastic scattering data and the problem of saturation in small-x physics A.Capella, E. G. Ferreiro, A. B. Kaidalov, C. A: Salgado, PRD63 (2001) 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

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