WG4 (QGP) REPORT Sudhir Raniwala, MG. Mustafa, S.K. Ghosh, R.S. Bahalerao, L. Ramello, Jajati Nayak, Rajarshi Ray, S.C. Phatak, V.K. Tiwari, R.V. Gavai, A.M. Srivastava, G.C. Mishra, A.P. Mishra, A.K. Rath, P.K. Sahu Some formal talks and some ‘informal’ talks  led to discussions and identifying problems

TOPICS DISCUSSED 1. Charmonium Suppression 2. Jets 3. Thermal and Direct Photons 4. Hydrodynamic description of elliptic flow Experimental data, unanswered questions Theory, Predictions Implementation and comparing techniques 5. Phi production at RHIC

TOPICS DISCUSSED Contd. 6. Bound states above critical temperature 7. Higher order susceptibilities 8. Ads/CFT – QCD/QGP ? 9. Neutrino emission from crystalline color superconducting quark matter

1. Charmonium Suppression Talk by Luciano Ramello (INFN, Italy) Results from NA50 and NA60 experiment. Improved technique for background J/Ψ absorption σ ~ 4.3 mb (p-A data only) earlier using S+U also, obtained ~7mb Significant suppression in Pb+Pb and In+In Suppression observed in RHIC New models also including charm recombination No single model able to describe details of the data on In+In and Pb+Pb Recombination needed at RHIC

2. Jets Identify jets using Fourier expansion (S.C.Phatak) Method based on analysis of p T weighted flow coeff. To be tested with jets in events in relativistic heavy ion collision environment Cone algorithm, k T algorithm (Kosower, Contreras) Some features that test goodness of the algorithms Infrared safe, Collinear safe, Independent of renormalization and factorization scale Amenable to comparison between theory and experiment Suggested a problem for the LHC nvironment: Study the dependence on the number, energy, rapidity of the jets and the influence of the underlying event which may include mini jets

3. Thermal and Direct Photons Discussion led by Terry Awes NLO pQCD predictions describe direct photon p+p data well, at low √s where k T broadening has been introduced to explain. Direct photons observed in Pb+Pb collisions at SPS energies (√s =17.GeV) can be described by thermal emission (QGP+HG) with high initial temperature (~300MeV). additional k T broadening. Direct photons at RHIC agree with NLO pQCD in p+p and at high p T in central Au+Au. Results for central Au+Au are consistent with thermal emission with initial T up to ~600MeV. Other new techniques to extract low p T direct photon signal such as  -  HBT,  - flow, and low mass electron pairs are being pursued.

4. Hydrodynamic Description of Elliptic Flow Discussion led by R. Bhalerao Ideal hydrodynamics does not quantitatively reproduce p T -dependent flow of identified particles in centrality- selected bins Estimated Mach, Knudsen and Reynolds numbers for RHIC and argued inadequacy of ideal hydrodynamics Emphasised the need for Relativistic Dissipative Hydrodynamics…described the broad framework “Three p T regions” of elliptic flow at RHIC Comparison of different techniques for different experimental conditions (Standard Method, Lee-Yang zeroes)

5. Phi production at RHIC Talk by Jajati Nayak Production and evolution of strange particles Extract effective degrees of freedom that characterize the coexisting phase and set a lower limit on T c and g eff Overproduction takes place in mixed phase if T c beyond 160 MeV

6. Bound states above T c R. Ray, S. K. Ghosh & M. G. Mustafa New lattice results indicate bound states above T c  Spectral analysis for bound states J/, ’ etc.  Heavier bound states survive up to larger T (~2T c ) Lattice equation of state deviates from SB Quarks and gluons not free Pressure puzzle: resolved by putting colored b.s. ( quasiparticles, coloured & colourless b.s.) These have large σ…..leading to collective flow and low viscosity…..the sQGP  Existence of binding potential Tasks: Improvise on potential and equation of motion, improve determination of m, M D,  s

7. Higher Order Susceptibilities Discussion led by R.Gavai Lattice results on quark number susceptibilities provide new insights  2 behaves like an order parameter  4 and  6 also behave drastically around T c pQCD and existing models failed to explain these results  need for improved models !!! Model which can explain EOS as well as all 

8. Ads/CFT – QCD/QGP ? Discussion led by Balram RHIC results indicate formation of “perfect liquid” η/S ~ 0.1 – 0.2, strongly coupled system, motivating description as hydrodynamic behaviour with low η Need reliable estimates of transport coefficients in FT-QCD in strong coupling limit AdS/CFT correspondence with N = 4 supersymmetric YM theory with FT in strong coupling limit may put a lower bound η/S ~ 0.1 (Liquid He ~9, Water ~380) AdS/CFT  QCD/QGP ? (coincidence or reality?)

9. Neutrino emission from crystalline color superconducting quark matter P.Jaikumar and H. Mishra Identifying the proper ground state Determine the excitation spectrum (considering simple case) Use dispersion relation to compute neutrino emissivity and specific heat capacity Determine the cooling rate and compare with data on observed Neutron Star temperature