Heavy Ion Collisions at the LHC

Last Call for Predictions

Monday May 14th to Friday June 8th 2007

Seminars


1. Monday May 14th 2007, ALICE Club, 1.45pm, room 160-1-009
Author: D. E. Kharzeev (BNL)
Title: Non-linear evolution in QCD and hadron multiplicity predictions for the LHC
Abstract: Non-linear QCD evolution equations will be discussed, with an emphasis on their implications for hadron multiplicities in pp, pA and AA collisions at the LHC.

2. Tuesday May 15th 2007, 11am, TH Auditorium (4-3-005)
Author: B. Sinha (VECC)
Title: Ratio of Dileptons to Photons - Universal Signals of Quark Gluon Plasma

3. Wednesday May 16th 2007, 11am, TH Auditorium (4-3-005)
Author: Alex Kovner (Connecticut)
Title: Wannabe dipoles and multigluon production at high energy

4. Friday May 18th 2007, 9.30am, TH Auditorium (4-3-005)
Author: Simon Wicks (Columbia)
Title: Perturbative jet energy loss mechanisms: Learning from RHIC, extrapolating to LHC
Abstract: The WHDG model combined DGLV radiative loss with a leading log calculation of collisional energy loss. The essential physical contribution of the collisional loss was thus included, with fluctuations given by a gaussian width from the fluctuation-dissapation theorem. But there is more to the physics of collisions in the QGP. As the expected number of (hard) collisions of a jet with the medium is small, it is necessary to evaluate the full fluctuation spectrum of a single collision and the poissonian convolution of this for multiple collisions. This collisional spectrum has interesting qualitative features that have a quantitative effect, such as an energy gain contribution, that are neglected in Bjorken-like calculations. The comparison of the spectrum of momentum transfers with that for vacuum propagators or the GW model reveals interesting contrasts, and also gives an indication of theoretical uncertainties inherent in models used.

5. Monday May 21st 2007, ALICE Club, 1.45pm, room 160-1-009
Author: Peter Levai (RMKI Budapest)
Title: Hadron Production from Quark Coalescence at the LHC

6. Monday May 21st 2007, Heavy Ion Forum, 3.30pm, room 13-2-005
Author: William Horowitz (Columbia)
Title: Possible String Theoretic Deviations from pQCD in Heavy Quark Energy Loss at the LHC
Abstract: For the first few years of its running, pQCD techniques applied to high-pt jets at RHIC were highly successful in explaining the observed normalization and momentum dependence of jet suppression. However, there were signs that the picture of a weakly coupled, perturbatively understandable QGP was overly naive: the observed intermediate-pt azimuthal anisotropy was too large; the number of nonphotonic electrons and the viscosity over entropy ratio too small. Infinitely-coupled super Yang-Mills calculations have been computed using string theoretic approaches, first as applied to the eta over s ratio, and recently to jet energy loss. Since none of the RHIC experiments currently has the ability to discern the charm versus bottom quark contribution to the nonphotonic electron spectrum, one cannot distinguish between the possible pQCD versus string theoretic solutions to the heavy quark quench puzzle. Nonetheless, pQCD gives very strong and specific predictions for the momentum dependence of charm and bottom energy loss. Deviations from this would point to new physics, and we provide several possibilities of a different dependence given by string theory calculations. The unique position of the LHC due to both its particle identification abilities and its enormous momentum reach should permit an observation of a possible discrepancy within the first year of LHC running.

7. Tuesday May 22nd 2007, 11am, TH Auditorium (4-3-005)
Author: Alejandro Ayala
Title: Collisional parton energy loss in a finite QCD medium revisited

8. Tuesday May 22nd 2007, Particle Physics Seminar, 4.30pm, Main Auditorium
Author: Helmut Satz (Bielefeld)
Title: Thermal Hadron Production and Hawking-Unruh Radiation in QCD
Abstract: Multiparticle production in high energy interactions, from $e^+e^-$ annihilation to hadronic and heavy ion collisions, shows remarkable thermal features in species abundances and transverse momentum spectra; these indicate a universal temperature around 150 - 200 MeV. What is the common basis for this behaviour? We conjecture that because of color confinement, the physical vacuum forms an event horizon for quarks and gluons. This can be crossed only by quantum tunneling, i.e., through the QCD counterpart of Hawking radiation from black holes. Since such radiation cannot transmit information to the outside, it must be thermal, of a temperature determined by the strong force at the confinement surface; it also has to maintain color neutrality. This phenomenon can provide a common mechanism for thermal hadron production in all high energy interactions.

9. Wednesday May 23rd 2007, 11am, TH Auditorium (4-3-005)
Author: Igor M. Dremin (LPI Moscow)
Title: Cherenkov gluons (predictions and proposals)
Abstract: Three predictions, which stem from the idea about Cherenkov gluons, and proposals for their verification are discussed. First experimental data about heavy ion collisions favoring this idea are briefly described. Conclusions about the properties of the nuclear medium at high energies are presented.

10. Thursday May 24th 2007, 11am, TH Auditorium (4-3-005)
Author: Yuri M. Sinyukov (BITP Kiev)
Title: Interferometry signatures of new states of matter in hydrodynamic picture of A+A collisions
Abstract: The main advantage of hydrodynamic approach in nucleus-nucleus collisions is possibility to analyze the evolution of the created matter including the transitions from one forms (phases) of the matter to others. To provide such an analysis for wide class of hydrodynamic models we use “observables” which conserve their values during the evolution. It was found that totally averaged phase-space density (APSD) and specific entropy are integrals of motion at chemically frozen evolution and their experimental values depend only on temperature and chemical potential at freeze-out – final stage of the hadronic matter evolution when the system decays. The plateau found in the pion APSD behavior vs collision energy at Super Proton synchroton (SPS) level is associated, apparently, with the deconfinement phase transition at low SPS energies. A saturation of this quantity at the energies available at BNL RHIC and CERN LHC will indicate the limiting Hagedorn temperature for hadronic matter. The behavior of the pion specific entropy demonstrate, probably, that the critical temperature of the hadron-quark/gluon phase transition is reached between SPS and RHIC energies. The results also shed light on the HBT puzzle – unexpected behavior of the interferometry volumes with energy.

11. Friday May 25th 2007, 11am, TH Auditorium (4-3-005)
Author: Rainer J. Fries (Texas A&M)
Title: Initial Energy Density, Momentum and Flow in Heavy Ion Collisions
Abstract: It is widely believed that the inital stage of a collision of large nuclei at high center of mass energy is described by the color glass condensate. Here we use this picture to compute the energy and momentum densities produced in the earlierst stage of the collision. We also present constraints for the initial energy density, pressure and flow in the subsequent plasma phase. Phenomenological consequences for RHIC and LHC are discussed.

12. Monday June 4th 2007, 11am, TH Auditorium (4-3-005)
Author: W. Cassing (Giessen)
Title:
Properties of the sQGP at RHIC and LHC energies

13. Monday June 4th 2007, ALICE Club, 1.45pm, room 160-1-009
Author: I. P. Lokhtin (SINP MSU)
Title: Monte-Carlo simulation of jet quenching and high transverse momentum observables at LHC
Abstract: The model to simulate jet quenching effect in ultrarelativistic heavy ion collisions is presented. The model is the fast Monte-Carlo tool implemented to modify a standard PYTHIA jet event. The model has been generalized to the case of the ``full'' heavy ion event (the superposition of soft, hydro-type state and hard multi-jets) using a simple and fast simulation procedure for soft particle production. The model is capable of reproducing main features of the jet quenching pattern at RHIC (the transverse momentum dependence of the nuclear modification factor and the suppression of azimuthal back-to-back correlations). The model is applied to probe jet quenching in various new channels at LHC: jet nuclear modification factor and jet anisotropy, jet fragmentation function measured by leading particles, b-jets, dilepton-jet correlations, high-mass dimuon and secondary charmonium spectra. The further development of the model focusing on a more detailed description of low transverse momentum particle production is in the progress.


14. Tuesday June 5th 2007, 11am, TH Auditorium (4-3-005)
Author: Ulrich Heinz (OSU)
Title: Recent results on spectra and v2 from (2+1)-d viscous hydrodynamics

15. Tuesday June 5th 2007, 2pm, TH Auditorium (4-3-005)
Author: Jorge Casalderrey-Solana (LBL)
Title:
Momentum Broadening  of  Heavy Probes in  Strongly Coupled Plasmas
Abstract: We compute the momentum broadening of a heavy fundamental charge  propagating through a $\mathcal{N}=4$ Yang Mills plasma at large t' Hooft coupling. We do this by expressing the medium modification of the probe's density matrix in terms of a Wilson loop averaged over the plasma. We then use the AdS/CFT correspondence to evaluate this loop, by identifying the dual semi-classical string solution. The calculation introduces the type ``1'' and type ``2'' fields of the thermal field theory and associates the corresponding sources with the two boundaries of the AdS space containing a black hole. The transverse fluctuations of the endpoints of the string determine $\kappa_T = \sqrt{\gamma \lambda} T^3 \pi$ -- the mean squared momentum transfer per unit time. ($\gamma$ is the Lorentz gamma factor of the quark.) The result reproduces previous results for the diffusion coefficient of a heavy quark.

16. Wednesday June 6th 2007, 2pm, Wednesday Theory Colloquium, TH Auditorium (4-3-005)
Author: Carlos Salgado (Rome La Sapienza)
Title: A new look to heavy ion collisions: preparing to the LHC
Abstract:
A new way of understanding the dynamics of high-density QCD is been developed thanks to the reach of collider energies in heavy ions. In a general presentation, I will review our present knowledge, in particular as given by the interpretation of experimental data, as well as the new theoretical developments where several fields begin to overlap. The new regimes accessible at the LHC, where three of the four experiments have a heavy-ion program, are qualitatively different from those reached at present energies, opening new opportunities to understand the properties of hot and dense QCD matter.

17. Thursday June 7th 2007, 11am, TH Auditorium (4-3-005)
Author: K. Werner (Subatech)
Title: The physics of EPOS
Abstract: We discuss briefly how EPOS extends the simple parton model by treating consistently multiple scattering and by considering carefully projectile and target remnants. We then discuss so-called nuclear effects due to splitting of parton ladders. This is in particular important for proton-nucleus scattering, but it also leads to important reductions of cross sections and particle production in very high energy proton-proton collisions. We finally discuss hydro-like collective phenomena, based on EPOS initial conditions. Concerning results, we discuss mainly soft observables, in particular their change from RHIC to LHC.

18. Friday June 8th 2007, 11am, TH Auditorium (4-3-005)
Author: A.M. Snigirev (SINP MSU)
Title: Alignment as a result from QCD jet production or new still unknown physics at the LHC?
Abstract: The hypothesis of the relation between the observed alignment of spots in the x-ray film in cosmic ray emulsion experiments and the features of events in which jets prevail at super high energies is tested. Due to strong dynamical correlation between jet axis directions and that between momenta of jet particles (almost collinearity), the evaluated degree of alignment is considerably larger than that for randomly selected chaotically located spots in the x-ray film. It appears comparable with experimental data provided that the height of primary interaction, the collision energy and the total energy of selected clusters meet certain conditions. The Monte Carlo generator PYTHIA, which basically well describes jet events in hadron-hadron interactions, was used for the analysis. New physical issues from the alignment phenomenon at the LHC is discussed.