122594393
Minijets and associated production of photons and muons in high energy heavy ion collisions
Due to the large hadronic multiplicities involved in heavy ion collisions at LHC energies, production of photons and muons inside jets cannot be distinguished from production in isolation. Associated production rates for photons and muons in minijets are estimated. It is found that the muon cross section per uranium-uranium collision could be substantial.
122166973
The phase diagram of QCD: methods and logic of the comparison of experiments and theory
Abstract A small review of the phase diagram of QCD is presented. This is followed by a discussion of the conditions under which experimental data on the fluctuations of conserved quantities in heavy-ion collisions can be treated in the grand canonical ensemble. A robust method for detecting the presence of a nearby critical point in experiments is given. There is a short discussion of the need for non-Gaussian error analysis.
119431013
A precise determination of T_c in QCD from scaling
Existing lattice data on the QCD phase transition are analyzed in renormalized perturbation theory. In quenched QCD it is found that T_c scales for lattices with only 3 time slices, and that T_c/Lambda_msbar=1.15 \pm 0.05. A preliminary estimate in QCD with two flavours of dynamical quarks shows that this ratio depends on the quark mass. For realistic quark masses we estimate T_c/Lambda_msbar=0.49 \pm 0.02. We also investigate the equation of state in quenched QCD at 1-loop order in renormalised perturbation theory.
121387686
Hybrid Monte Carlo simulations of a two-dimensional gauge theory
Through a study of the dynamics of the two-dimensional U(1) pure gauge theory we find exponential slowing down in barrier penetration problems. We verify that the dynamical critical exponent in HMC can be tuned exactly to 1, and that normal and gauge fixed updates have equal cost.
123004962
Flavour degrees of freedom and the transition temperature in QCD
We study the finite temperature transition in QCD with four flavours of dynamical quarks. Our simulation is performed on an 8×16 3 lattice for quarks of mass ma=0.01. At the coupling β c =5.15, we find long-lived metastable states, as well as an abrupt change in the entropy density, suggesting a first order phase transition. Using presently available results from corresponding calculations of the hadron masses and the chiral condensate, this gives us a transition temperature T c ≅100 MeV, which is a factor two lower than the transition temperature found in quenched QCD.
17443615
Lattice QCD for RHIC
I briefly introduce the methods by which lattice QCD predictions for RHIC are obtained. Next I deal with lattice determinations of strangeness production and event-to-event fluctuations of conserved quantities. I also present a new diagrammatic method for computing derivatives with respect to chemical potentials, and conclude with discussions of some tests of thermal perturbation theory which follow.
128078572
A preshower photon multiplicity detector for the WA93 experiment
Abstract A fine granularity preshower detector has been designed, fabricated and installed in the WA93 experiment for the first ever measurement of photon multiplicity in ultra-relativistic heavy ion collisions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. The photon detection efficiency estimated using Monte-Carlo and beam test results is found to be ∼65–75% depending on centrality. Simulation and performance results of the detector for counting of photons and rejection of hadrons in the large multiplicity environment of ultra-relativistic heavy ion collisions are described.
14808043
Dynamical growth of the hadron bubbles during the quark hadron phase transition
The rate of dynamical growth of the hadron bubbles in a supercooled baryon free quark-gluon plasma is evaluated by solving the equations of relativistic fluid dynamics in all regions. For a nonviscous plasma, this dynamical growth rate is found to depend only on the range of correlation $\ensuremath{\xi}$ of order parameter fluctuation, and the radius R of the critical hadron bubble, the two length scales relevant for the description of the critical phenomena. Further, it is shown that the dynamical prefactor acquires an additive component when the medium becomes viscous. Interestingly, under certain reasonable assumptions for the velocity of the sound in the medium around the saddle configuration, the viscous and the nonviscous parts of the prefactor are found to be similiar to the results obtained by Csernai and Kapusta and Ruggeri and Friedman (for the case of zero viscosity), respectively.
119118215
AUGMENTED SUPERFIELD APPROACH TO NON-YANG–MILLS SYMMETRIES OF JACKIW–PI MODEL: NOVEL OBSERVATIONS
We derive the off-shell nilpotent and absolutely anti-commuting Becchi–Rouet–Stora–Tyutin (BRST) as well as anti-BRST symmetry transformations corresponding to the non-Yang–Mills (NYM) symmetry transformations of (2+1)-dimensional Jackiw–Pi (JP) model within the framework of "augmented" superfield formalism. The Curci–Ferrari (CF) restriction, which is a hallmark of non-Abelian one-form gauge theories, does not appear in this case. One of the novel features of our present investigation is the derivation of proper (anti-)BRST symmetry transformations corresponding to the auxiliary field ρ that cannot be derived by any conventional means.
122167852
MULTIPLE PHOTON PRODUCTION IN QUANTUM ELECTRODYNAMICS
Multiple production of photons in high-energy processes in quantum electrodynamics is investigated, and the electron-positron annihilation is specially discussed in detail. It is found that at very high energies in cosmic rays, multiple production of up to four or five observable photons can easily take place. But, the probability, according to quantum electrodynamics, for the multiple production of a larger number of observable photons is quite small.
122137195
Neutral charm production in 400 GeV proton-emulsion interactions
A search has been carried out for neutral charm production in 5,108 proton-emulsion interactions at 400 GeV/c. Nine charm candidates have been observed in our fiducial volume which extends from 100 μm-1,000 μm in the forward cone. One of these is a 4-prong and the others are 2-prong events with opening angle>10 mrad and momenta of both decay tracks>150 MeV/c. Search for associated charm decays was made in an extended fiducial volume around the primary stars of these nine candidates. This yielded two neutral 2-prong events, one associated with the 4-prong and the other with a 2-prong candidate. All unassociated candidates are consistent with being backgrounds due toKs, Λ decays, neutral interactions and γ conversions whereas the background to associated events is negligible. Based on the two associated decays the inclusive cross section forD0, −0 production is determined as 27±20 μb/nucleon. Detailed measurements on the 4-prong candidate lead to the identification of one decay track as an electron and another as a kaon. This is interpreted as a semi-leptonic, Cabbibo favouredD0/D−0 decay.