ULTRARELATIVISTIC HEAVY ION COLLISIONS. project at HIP/Theory in , review in 2004 Personnel: Site 1 at Jyväskylä:

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1 KJ Eskola RECFA in Helsinki ULTRARELATIVISTIC HEAVY ION COLLISIONS project at HIP/Theory in , review in 004 Personnel: Site 1 at Jyväskylä: Senior members PV Ruuskanen, prof, JYFL KJ Eskola, acadres, SA/HIP projlr Postdoctors P Huovinen, HIP MPLS Site at Helsinki: K Kajantie, prof, HYFL/SA K Rummukainen,prof,HYFL CERN M Salle, HIP K Tuominen, JYFL NORDITA VJ Kolhinen, SA Graduate students H Honkanen, HIP/SA SS Räsänen, GRASPANP H Niemi, SA/HIP A Gynther, GRASPANP T Lappi, grants/hip M Vepsäläinen, SA/grant/HIP A Vuorinen, grants/sa now in a Summer School in Bielefeld AJ Hietanen, HIP/SA Total Funding in keur: HIP %, SA 51%, GRASPANP 11%, JYFL 8%, grants 6 %, HYFL % participated in - EU research and training network proposals ( ) - EU I3HP network proposal for ( ) - INTAS co-operation close connection with CERN: TH (collaboration, Hard Probes), ALICE

2 arxiv:hep-ph/ v1 5 Aug 003; 11 pages Hard probes in heavy ion collisions at the LHC: PDFs, SHADOWING AND pa COLLISIONS HIP /TH Convenors: K J Eskola 1,, J w Qiu 3 (theory), W Geist 4,5 (experiment) Editor: K J Eskola Contributing authors: A Accardi 6,7, N Armesto 8,9, M Botje 10 [ALICE], S J Brodsky 11,1, B Cole 13 [ATLAS], K J Eskola 1,, G Fai 14, L Frankfurt 15, R J Fries 16, W Geist 4,5 [CMS], V Guzey 17, H Honkanen 1,, V J Kolhinen 1,, Yu V Kovchegov 18, M McDermott 19, A Morsch 0, J w Qiu 3, C A Salgado 8, M Strikman 1, H Takai [ATLAS], S Tapprogge [ATLAS], R Vogt 3,4, X f Zhang 14 1 Department of Physics, University of Jyväskylä, Jyväskylä, Finland Helsinki Insititute of Physics, University of Helsinki, Finland 3 Department of Physics and Astronomy, Iowa State University, Ames, IA, USA 4 Institut de Recherches Subatomiques, INP3-CNRS/Université Louis Pasteur, Strasbourg, France 5 Physics Department, University of Notre Dame, Notre Dame, IN, USA 6 Department of Physics, Columbia University, New York, NY, USA 7 Institut für Theoretische Physik der Universität Heidelberg, Heidelberg, Germany 8 Theory Division, CERN, Geneva, Switzerland 9 Departamento de Física, Universidad de Córdoba, Córdoba, Spain 10 NIKHEF, Amsterdam, The Netherlands 11 Stanford Linear Accelerator Center, Stanford University, Stanford, CA, USA 1 Thomas Jefferson National Accelerator Facility (JLab), Newport News, VA, USA 13 Nevis Laboratories, Columbia University, New York, NY, USA 14 Center for Nuclear Research, Department of Physics, Kent State University, Kent, OH, USA 15 Nuclear Physics Department, Tel Aviv University, Tel Aviv, Israel 16 Physics Department, Duke University, Durham, NC, USA 17 Fakultät für Physik und Astronomie, Institut für Theor Physik II, Ruhr-Univ Bochum, Germany 18 Department of Physics, University of Washington, Seattle, WA, USA 19 Department of Mathematical Sciences, Liverpool University, Liverpool, UK 0 Experimental Physics Division, CERN, Geneva, Switzerland 1 Department of Physics, Pennsylvania State University, University Park, PA, USA Brookhaven National Laboratory, Upton, NY, USA 3 Lawrence Berkeley National Laboratory, Berkeley, CA, USA 4 Physics Department, University of California at Davis, Davis, CA, USA Abstract This manuscript is the outcome of the subgroup PDFs, shadowing and pa collisions from the CERN workshop Hard Probes in Heavy Ion Collisions at the LHC In addition to the experimental parameters for pa collisions at the LHC, the issues discussed are factorization in nuclear collisions, nuclear parton distributions (npdfs), hard probes as the benchmark tests of factorization in pa collisions at the LHC, and semi-hard probes as observables with potentially large nuclear effects Also, novel QCD phenomena in pa collisions at the LHC are considered The importance of the pa program at the LHC is emphasized also, a strong contribution by Ruuskanen, Räsänen, Niemi in the photon group

3 Physics of URHIC goal: study QCD matter collider era: RHIC 7/000, LHC/ALICE 007 We focus on I Phenomenology of URHIC (Jyväskylä, Helsinki) Colliding beams: PDF in nuclei; global pqcd fits Primary collision: dominant mechanism for parton production? pqcd+saturation and/or classical gluon fields Numerical classical field calculations of early stage HIC Spacetime evolution of the produced system relativistic hydrodynamics PT, flow Final state hadrons from hydro at decoupling & decays spectra, multiplicities, flow, Hard probes of the QGP DY, direct γ, Q Q, jet cross sections, large-p T hadrons pqcd (npdf needed!) & factorization Thermal electromagnetic probes FTFT rates folded w hydro evolution Comparison with RHIC data Predictions for LHC II 1st-principles calculations (Helsinki) Pressure of hot QCD both at µ = 0 and at large T and/or µ pert theory with dim reduced QCD

4 Some highlights I Phenomenology 1 Classical gluon fields [Lappi, hep-ph/ ] the celebrated results (dashed = Venugopalan et al) for the production of gluons in the Color Glass Condensate model calculated now correctly (solid = Lappi) for the first time! the phenomenology (E/N) now works much better! ~ k/(µr A ) dn/d k ~ k/g µ Parton distribution functions (PDF) DGLAP + nonlinear corrections - comparison with HERA data [Eskola, Honkanen, Kolhinen, Qiu, Salgado, hep-ph/01139, NPB] agreement with data improved enhanced gluons at small x next: enhanced c c production at LHC? extension to nuclei determine the saturation region F (x,q )+c(x) This work, set 1 This work, set a CTEQ6L Q

5 3 Hadron spectra at RHIC - detailed comparison with data 1/ p T dn/dp T d <01 [1/GeV ] RHIC Au+Au s 1/ =130 GeV STAR data 5 % most central T dec = 150 MeV (h - +h + )/ p T [GeV] A pqcd+saturation+hydrodynamics [Eskola, Niemi, Ruuskanen, Räsänen, hep-ph/00630] obtained the bulk (π, K, p) spectra in central Au+Au! T dec = MeV (=high) data shows pqcd (=nonthermal) tail at p T > GeV next: thermal electromagnetic probes NN in )Ed 3 /d q T d (GeV - ) ( N binary / PHENIX data sqrt(s)=130 GeV =0 K= q T (GeV) B Factorization: Nuclear PDF ˆσ pqcd fragmentation functions [Eskola, Honkanen, hep-ph/005048, NPA] pqcd reference spectra at large p T data shows suppression in central, but not in peripheral Au+Au energy losses of fast partons in the QGP = a current hot topic! II First-principles QCD calculations 1 Pressure of Hot QCD up to g 6 log g [Kajantie, Laine, Rummukainen, Schröder, hep-ph/01131, PRD] obtained the last contribution calculable by perturbative means Pressure of QCD up to g 6 log g at finite T and/or µ [Vuorinen, hep-ph/ , hep-ph/0183, PRD] includes all - and 3-loop 1PI vacuum diagrams at large T and/or µ