Scaling behavior at highpTand thep/πratio

Abstract

We first show that the pions produced at high pT in heavy-ion collisions over a wide range of high energies exhibit a scaling behavior when the distributions are plotted in terms of a scaling variable. We then use the recombination model to calculate the scaling quark distribution just before hadronization. From the quark distribution it is then possible to calculate the proton distribution at high pT , also in the framework of the recombination model. The resultant p/π ratio exceeds one in the intermediate pT region where data exist, but the scaling result for the proton distribution is not reliable unless pT is high enough to be insensitive to the scale-breaking mass effects.

Anisotropic flow inCu+Aucollisions atsNN=200GeV

“…The transition from the partonic matter to the hadronic matter is achieved using a simple coalescence model, which combines the two nearest quark and antiquark into mesons and the three nearest quarks or antiquarks into baryons or antibaryons that are close to the invariant mass of these partons. The present coalescence model is thus somewhat different from the ones recently used extensively [33][34][35][36] for studying hadron production at intermediate transverse momenta. By using parton scattering cross sections of 6−10 mb, the AMPT model with string melting was able to reproduce both the centrality and transverse momentum (below 2 GeV/c) dependence of the elliptic flow [10] and pion interferometry [22] measured in Au + Au collisions at √ s = 130A GeV at RHIC [37,38].…”

Hadron production from quark coalescence and jet fragmentation

“…The resulting baryon to meson ratio at intermediate transverse momenta is predicted to be larger than that seen in experiments at higher center of mass energies. Recently, there has been renewed interest in using the quark coalescence or recombination model to study hadron production in ultrarelativistic heavy ion reactions [1][2][3][4][5][6][7][8][9]. These studies were largely triggered by two surprising observations in measured hadron spectra from Au + Au collision at √ s NN = 200 GeV at the BNL Relativistic Heavy Ion Collider (RHIC) [1,[10][11][12].…”

Quark and Gluon Degrees of Freedom in High-Energy Heavy Ion Collisions

“…This puts tight limits on the applicability of the fragmentation picture to nuclear collisions with thousands of particles created. Rather, with phase space filled with partons in a thermalized medium, hadron production should proceed through recombination or coalescence of quarks into the valence structure of hadrons [6,7,8,9,10]. Most implementations of the recombination process use an instant projection of quark states onto hadron states utilizing the wave function ψ of the baryon or meson and assuming thermal distribution functions f for quarks.…”