Charmonium production from nonequilibrium charm and anticharm quarks in quark-gluon plasma

Parameterizing the charm and anticharm quark momentum distributions by the Tsallis distribution, we study the nonequilibrium effect on the charmonium production rate in a quark-gluon plasma up to the next-to-leading order in perturbative QCD. We find that nonequilibrium charm and anticharm quarks suppress the charmonium production rate compared to that from equilibrated ones. We further show that the suppression factor calculated with the charm quark relaxation time, which has been frequently used in the literature, is close to our results.Comment: 8 pages, 5 figure

Maximum order-index of matrices over commutative inclines: an answer to an open problem

AbstractThis paper proves that the maximum order-index of n×n matrices over an arbitrary commutative incline equals (n−1)2+1. This is an answer to an open problem “Compute the maximum order-index of a member of Mn(L)”, proposed by Cao, Kim and Roush in a monograph Incline Algebra and Applications, 1984, where Mn(L) is the set of all n×n matrices over an incline L

Approximate Model Checking of Real-Time Systems for Linear Duration Invariants

Real-time systems are usually modelled with timed automata and real-time requirements relating to the state durations of the system are often specifiable using Linear Duration Invariants, which is a decidable subclass of Duration Calculus formulas. Various algorithms have been developed to check timed automata or real-time automata for linear duration invariants, but each needs complicated preprocessing and exponential calculation. To the best of our knowledge, these algorithms have not been implemented. In this paper, we present an approximate model checking technique based on a genetic algorithm to check real-time automata for linear durration invariants in reasonable times. Genetic algorithm is a good optimization method when a problem needs massive computation and it works particularly well in our case because the fitness function which is derived from the linear duration invariant is linear. ACM Computing Classification System (1998): D.2.4, C.3

Charmonium production in heavy-ion collisions from SPS to LHC

Using the two-component model that includes charmonium production from initial nucleon-nucleon hard scattering and regeneration in the produced quark-gluon plasma, we study $J/\psi$ production in heavy ion collisions at SPS, RHIC and LHC. For the expansion dynamics of produced hot dense matter, we use a schematic viscous hydrodynamic model with the specific shear viscosity taken, respectively, to be twice and ten times the lower bound of $1/4\pi$ suggested by the Ads/CFT correspondence in the quark-gluon plasma and in the hadron gas. For the initial dissociation and the subsequent thermal decay of charmonia in the hot dense matter, we use the screened Cornell potential to describe the properties of charmonia and the perturbative QCD to calculate their dissociation cross sections. Including regeneration of charmonia in the quark-gluon plasma via a kinetic equation with in-medium chamonium decay widths, we obtain a good description of measured nuclear modification factors at SPS and RHIC. A reasonable description of measured nuclear modification factor of $J/\psi$s of high transverse momenta in heavy ion collisions at LHC is also obtained if we include the contribution to the $J/\psi$ yield from the decay of bottomed hadrons.Comment: 10 pages, 11 figure