Summary: QGP Meet’06

1. Summary: QGP Meet’06 The tradition continues: Emergence of Subhashis as the GeNext Organizer-in-Chief: & Establishment of Bedang, Vikash,& Zubayer as the GeNext organizers. Subhashis tried to give an excuse about starting the meeting starting on a Sunday. But this Sunday it was Vishma’s birth-day (Vishma-asthami). And in any case day-names are a western aberration, Indians believed in “tithi”s (number of the day).

2. Ashis Chaudhuri: Valiant Effort to tackle a very tough & challenging problem. • Viscousity: Irreversible transfer of momentum from points where velocity is large to where it is small.

9. Raimond Snellings • Excellent (Near Complete Review!): • Anisotropy of Initial State & Multiple Interactions. • The interactions could also be the radiation of gluons/collisions as a jet traversed the plasma. Different from hydrodynanmic flow. • Validity of hydrodynamics.- Flow develops early in the collision. • Failure of hydrodynamics & recombination model • Higher order harmonics. • Parton cascade models can give flow only if the parton cross-sections are raised by a factor of 50 or so.

10. y x y x x z Manifestations of Collective Flow (radial and anisotropic) • Only type of transverse flow in central collision (b=0) is radial flow • Integrates pressure history over complete expansion phase • Elliptic flow (v2) , hexadecupole flow (v4) , v6, … caused by anisotropic initial overlap region (b > 0) • More weight towards early stage of expansion. • Directed flow (v1) , sensitive to earliest collision stage (b > 0) • pre-equilibrium at forward rapidity, at midrapidity perhaps different origin

11. Dependence on the EOS! • EoS Q and EoS T (both have significant softening) do provide the best description of the magnitude of the mass scaling in v2(pt) • The lattice inspired EoS (EoS qp) in ideal hydro does as poorly as a hadron gas EoS! Pasi Huovinen, arXiv:nucl-th/0505036

12. STAR QM2001 Mass dependence • Identified particle elliptic flow at low pt • Mass dependence in accordance with collective flow. QGP equation of state (phase transition) provides best description Hydro calculation: P. Huovinen et. al.

13. Energy dependence of v2(pt) • Top RHIC energies at dip in v2 • Hydro prediction for lower energies v2 increases? • the radial flow <v> increases monotonically with beam energy (pion multiplicity at fixed impact parameter), is the slope of v2(pt) expected to increase for ideal hydro? • Where are the 62 GeV calculations? Is the slope of v2(pt) more sensitive to the energy dependence? Adapted from P.F. Kolb and U. Heinz, in Quark Gluon Plasma, nucl-th/0305084

14. Munshi Golam Mustafa

20. NLO pQCD with KKP FFinconsistent with the p+pbar data NLO pQCD with AKK FF relatively better than KKP for the p+pbar data NLO pQCD with Kretzer FF inconsistent with data Kretzer differ from KKP, in the gluon to p fragmentation AKK differ from KKP, in the way the light flavor FF are obtained Comparison toNLO pQCD Pawan Kumar Netrakanti

21. Scaling in particle production e+ and e- does not have a parton distribution function. There will be a (sNN )2 multiplied to cross-section in e+e- collisions. For p+p collisions n ~ 6.5 for p, p (pbar)

22. System expansion: Initial vs Final Size Collisions at 200GeV only Smooth expansion of the system from p+p to Au+Au… but not trivial AuAu: system expands pp (dAu): no or less expansion CuCu 200 AGeV is crucial as it helps In understanding the “missing link” STAR PRELIMINARY Proton initial size = 0.89 fm from e-scattering Debashis Das

23. Proportional to dNch/d Freeze out a constant density STAR PRELIMINARY Also see Ref :CERES PRL Nucl-ex/0207008 Constant Freeze out density hypothesis At high energies: Baryon density << Pion density Pion rapidity density  freeze out volume (Rs2RL)

24. nucl-th/0511079 –Rupa Chatterjee, Evan S. Frodermann, Ulrich Heinz and Dinesh K.Srivastava . Fluid velocity along the constantenergy density contour fore=eq(forQGP phase),e=eh (for mixedphase) ande=ef (forhadronic phase ) for x (y=0) (dashedcurve) and y (x=0) (solid curve) . . Velocities ( zero at initial time t0 ) which start differing over extended volume by the end of the QGP phase, becomealmost identicalat the end of hadronic phase. Rupa Chatterjee

25. nucl-th/0511079 • v2 for thermal photons from 200 AGeV Au+Au collision is • shown by the red curve. • .Quark and hadronic contributions to v2 are shown separately. • v2 for pion is also shown in comparison with hadronic v2. • pion v2 tracks the hadronic v2.

26. nucl-th/0511079 Impact parameter dependence of the elliptic flow Impact parameter are chosen to roughly correspond to collision centralities of 0-10%(b=3 fm), 10-20%(b=5.4 fm), 20-30%(b=7 fm), 30-40% (b=8.3 fm), 40-50% (b=9.4 fm), and 50-60% (b=10.4) .

27. Jajati Kesari Nayak

28. No radial flow! Radial expansion?

30. Pradip Kumar Roy Collisional e-loss; Careful evaluation

32. R_AA?

33. Results (contd..) STAR Preliminary STAR Preliminary The centrality dependence of ET/Nch Participant number dependence of electromagnetic fraction of total energy. Hydrodynamic flow effect is reflected in the peripheral collisions. If the expansion is isentropic, dNch/d will remain constant, whereas dET/d will decrease due to the performance of longitudinal work. No significance dependence of electromagnetic fraction on collision centrality.  Tells about the particle production mechanism. R. Sahoo

34. Results (contd..) Production of constant transverse energy per charge particle (~ 0.8 GeV) has been observed from AGS to RHIC.  Energy pumped into the system goes for particle production, instead of increasing energy per particle. Excitation function of ET/Nch Recall: Jean Cleymans & Krzysztof Redlich  Freeze-out along <E>/N= 1 GeV.

35. Pseudorapidity Distribution of photons (CuCu 200 GeV) STAR preliminary ? Upper limit on systematic Error ~ 24% Monika Sharma

36. Pseudorapidity Distribution of photons (CuCu 200 GeV) STAR preliminary Upper limit on systematic Error ~ 24% Monika Sharma

37. Comparison of results from PHOBOS (Charge Particles) Charge particle production at forward rapidities are independent of system size Are these outcome of only soft-collisions? Can you check if <pT> is smaller than at central rapidity?

38. P. Chakrabory; Also quark number susceptibility

39. Jan-e Alam

42. What about P_T distribution ??????

43. Summary • Detectors at forward rapidity region provide the experiment : centrality and trigger • Forward rapidity region provides rich information on particle production certain universality (species, energy) observed • Forward rapidity region provides information on nuclear stopping, baryon transport and energy for particle production • Forward rapidity provides a chance to scan the QCD phase diagram • Forward rapidity provides the best place to study the possible initial conditions at RHIC : CGC • Forward rapidity provides testing ground for NLO pQCD ???? Measurements at forward rapidity (kinematical limits and detector constraints) are also an experimental challenge Bedanga Mohanty

44. Sudhir Bhardwaj; Important step towards measuring v_2

45. MUON Spectrometer aims to measure the signals • As a function of centrality • Identify suppression/enhancement patterns • As a fuction of the size of the colliding system • Distinguish between normal and anomalous suppression • For all onium species • Different survival probabilities probe the temp of the system • As a function of pt • Disentangle QGP model • With good vertex resolution • Distinguish between prompt and secondary charmonium • Verses the reaction plane • Distinguish between Glauber and Comover absorption • Together with other QGP signals

46. MUON Spectrometer aims to measure the signals • As a function of centrality • Identify suppression/enhancement patterns • As a fuction of the size of the colliding system • Distinguish between normal and anomalous suppression • For all onium species • Different survival probabilities probe the temp of the system • As a function of pt • Disentangle QGP model • With good vertex resolution • Distinguish between prompt and secondary charmonium • Verses the reaction plane • Distinguish between Glauber and Comover absorption • Together with other QGP signals

47. Signal Normalization • Drell-Yan above 4 GeV/c2 (NA38/NA50) • At LHC, D-Y completely drowned into the background from semi-leptonic decay of open charm and open beauty • Open Charm (bottom) cross-section • Charm (beauty) thermal production can increase dramatically in QGP with higher temp • Shadowing and/or quenching – suppression of high pt charm/bottom. => Reference dependent on QGP properties • Minimum Bias method • Centrality dependence of the efficiency for Dimuon measurement – accuracy => error • No Normalization • Careful estimation of systematic error

48. MUON Spectrometer aims to measure the signals • As a function of centrality • Identify suppression/enhancement patterns • As a fuction of the size of the colliding system • Distinguish between normal and anomalous suppression • For all onium species • Different survival probabilities probe the temp of the system • As a function of pt • Disentangle QGP model • With good vertex resolution • Distinguish between prompt and secondary charmonium • Verses the reaction plane • Distinguish between Glauber and Comover absorption • Together with other QGP signals Sukalyan Chattopadhyay

49. Signal Normalization • Drell-Yan above 4 GeV/c2 (NA38/NA50) • At LHC, D-Y completely drowned into the background from semi-leptonic decay of open charm and open beauty • Open Charm (bottom) cross-section • Charm (beauty) thermal production can increase dramatically in QGP with higher temp • Shadowing and/or quenching – suppression of high pt charm/bottom. => Reference dependent on QGP properties • Minimum Bias method • Centrality dependence of the efficiency for Dimuon measurement – accuracy => error • No Normalization • Careful estimation of systematic error

50. Production in progress