WG4 (QGP) REPORT

1. 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

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

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

4. 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

5. 2. Jets • Identify jets using Fourier expansion (S.C.Phatak)  Method based on analysis of pT weighted flow coeff. • To be tested with jets in events in relativistic heavy ion collision environment • Cone algorithm, kT 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

6. 3. Thermal and Direct Photons • Discussion led by Terry Awes • NLO pQCD predictions describe direct photon p+p data well, at low √s where kT 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 kT broadening. • Direct photons at RHIC agree with NLO pQCD in p+p and at high pT 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 pT direct photon signal such as -  HBT, -flow, and low mass electron pairs are being pursued.

7. 4. Hydrodynamic Description of Elliptic Flow • Discussion led by R. Bhalerao • Ideal hydrodynamics does not quantitatively reproduce pT-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 pT regions” of elliptic flow at RHIC • Comparison of different techniques for different experimental conditions (Standard Method, Lee-Yang zeroes)

8. 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 Tc and geff • Overproduction takes place in mixed phase if Tc beyond 160 MeV

9. 6. Bound states above TcR.Ray, S. K. Ghosh & M. G. Mustafa New lattice results indicate bound states above Tc Spectral analysis for bound states J/, ’ etc.  Heavier bound states survive up to larger T (~2Tc) • 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, MD, s

10. 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 Tc • pQCD and existing models failed to explain these results  need for improved models !!! Model which can explain EOS as well as all 

11. 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?)

12. 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