Parton Radiative Energy Loss In Hot And Dense Matter

One of the confident predictions of QCD is that at sufficiently high temperature and high density hadronic matter should undergo a thermodynamic phase transition to a color deconfined state of matter-popularly called the Quark-Gluon Plasma (QGP).In high energy heavy ion collisions, the suppression of the yield of final state high transverse momentum hadrons is considered to be a important signal of exiting Quark-Gluon Plasma. In the process of Nucleus-Nucleus(AA) collisions, hard scattering is on the initial stage. High transverse momentum partons which come from hard scattering will propagate in the strong interaction medium and interact with matter. These partons are expected to lose their energy in the medium by gluon bremsstrahlung, which is called Jet Quenching.In BNL/RHIC Runl ((S_NN)^1/2 = 130GeV) and Run2 (((S_NN)^1/2 = 200GeV), comparing the yield of leading particle in nucleus-nucleus collisions with nucleon-nucleon collision finds that charged and neutral pions are suppressed. For the most central and the most peripheral collisions, run2 gets R_*aa( 0.5 and R_aa 1.0. It shows that the hot and dense matter is formed in central AA collisions. However, the peripheral AA collisions don't produce this kind of matter.The energy loss of heavy quarks in a quark-gluon plasma of finite size is studied within the light-cone path integral approach. A simple analytical formulation of the radiative energy loss of heavy quarks is derived. This provides a convenient way to quantitatively estimate the quark energy loss. Our results show that if the energy of a heavy quark is much larger than its mass, the radiative energy loss approaches the radiative energy loss of light quarks.Based on the above approach, the parton shower evolution law in the hot and dense matter is studied by using the spectrum of parton radiative energy loss. At the same energy, the numerical results indicate that the splitting probability of parton,in the medium, is large than those in the vacuum. And when the density of medium is higher, the splitting probability of parton is larger. This result is in agreement with the suppression of leading particles production in BNL/RHIC,it indicates that the hot and dense matter has already been produced at RHIC energy.