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Y. B. He

Publications and source records attributed to Y. B. He.

8 recordsLinked to original sources
arXiv1999

J/Psi and Psi' total cross sections and formation times from data for charmonium suppression in $pA$ collisions

The recent data for E866 experiment on the x_F dependence for charmonium suppression in pA collisions at 800 GeV are analyzed using a time- and energy-dependent preformed charmonium absorption cross section σ_{abs}^ψ(τ,\sqrt{s}). For \sqrt{s}=10 GeV the initially (τ=0) produced premeson has an absorption cross section of σ_{pr}~3mb. At the same energy but for τ-> \infty one deduces for the total cross sections σ_{tot}^{J/Psi N}=(2.8\pm 0.3)mb, σ_{tot}^{J/Psi N}= (10.5\pm 3.6)mb. The date are compatible with a formation time τ_{1/2}=0.6 fm/c.

hep-ph↗
arXiv1999

Charmonium suppression by gluon bremsstrahlung in p-A and A-B collisions

Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states while the nuclei still overlap. The spectra and mean number of the prompt gluons are calculated perturbatively and the gluon-Psi inelastic cross section is estimated. The integrated cross sections for AB --> J/Psi (Psi')X for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with some adjustment of one parameter σ(gPsi).

hep-ph↗
arXiv1998

Spinodal and dynamical instabilities at the phase transition from the quark-gluon plasma to hadrons

The stability of an expanding parton plasma is analyzed within quasi-particle models. The effective mass of the parton is calculated self-consistently from a gap equation which is either obtained from the Nambu Jona-Lasinio Lagrangian or from a fit to observables calculated on the lattice. The latter shows an effective confinement. At thermal equilibrium the stability is studied within thermodynamics (mechanical stability) and via a linear response analysis of the Vlasov equation. The instabilities related to a first-order phase transition are found. For a plasma expanding in three and one dimensions far from equilibrium a new type of instability, called dynamical, appears. The relation to cluster formation is shown in a molecular dynamics calculation.

nucl-th↗
arXiv1998

Transport theory with self-consistent confinement related to the lattice data

The space-time development of a quark-gluon plasma is calculated from a Vlasov equation for the distribution function of quasiparticles with medium dependent masses. At each space-time point the masses are calculated selfconsistently from a gap equation, whose form is determined by the requirement that in thermal equilibrium and for a range of temperatures the energy density of the quasi-particle system is identical to the one from lattice calculations . The numerical solutions of the Vlasov equation display confinement. Relations to effective theories like that by Friedberg Lee and Nambu Jona-Lasinio are established.

nucl-th↗
arXiv1997

$ππ$ scattering in the $ρ$-meson channel at finite temperature

We study $ππ$ scattering in the I=1, $J^P=1^-$ channel at finite temperature in the framework of the extended Nambu-Jona-Lasinio model that explicitly includes vector and axial-vector degrees of freedom in addition to the usual scalar and pseudoscalar sector. The S-matrix in the coupled channels $q\bar q$ and $ππ$ is constructed via $ρ$-exchange in the $s$-channel. The self-energy of the $ρ$-meson contains both quark and pion loop contributions. The analytic structure of the S-matrix for $T\geq 0$ is investigated and the motion of the $ρ$-pole as a function of coupling constant and temperature is followed in the complex $\sqrt{s}$-plane. For numerical calculations, parameters are chosen in order that $m_π$, $f_π$ and the experimental $ππ$ phase shifts $δ_1^1$ at zero temperature are reproduced, and then the behavior of the $ρ$-pole as well as the $ππ$ cross section is investigated as a function of the temperature. We find that the position of the $ρ$ mass stays practically constant for $0\leq T\leq 130$ MeV, and then moves down in energy by about 200 MeV for 130 MeV$\leq T\leq 230$ MeV.

nucl-th↗
arXiv1996

Cold Strangelets Formation with Finite Size Effects in High Energy Heavy-Ion Collisions

We have studied the phase diagram and evolution of a strangelet in equilibrium with a finite hadronic gas. Significant finite size modifications of the phase diagram are found and their parameter dependences are studied. With the inclusion of finite size effects we have also been able to obtain the detailed properties of the cold strangelet emerging in the final stage of the isentropic expansion of a finite strange fireball in high energy heavy-ion collisions.

hep-ph↗
arXiv1995

Phenomenology of $x_F$ Dependence of Quarkonium Production in Proton-Nucleus Interactions

We present a phenomenological study of the $x_F$ dependence of quarkonium production in high energy proton-nucleus collisions. The \xf~dependence of comover contributions is introduced to account for the observed quarkonium suppression at low $x_F$. Combining comover contributions, nuclear shadowing effect, energy loss mechanism and nuclear absorption together we reproduce the overall \xf~dependence of E772/E789 data.

hep-ph↗