EFFECTS OF SCREENING ON QUARK-ANTIQUARK CROSS-SECTIONS IN QUARK-GLUONPLASMA

Lowest-order cross sections for q (q) over bar production and annihila tion can be approximately corrected for higher-order QCD effects by us ing a corrective K-factor. For energies where quark masses cannot be i gnored, the K-factor is dominated by the wave function distortion aris ing from the initial- or final-state interaction between the quark and the antiquark. We evaluate this K-factor for q (q) over bar productio n and annihilation in a quark-gluon plasma by taking into account the effects of Debye screening through a color-Yukawa potential. We presen t the corrective K-factor as a function of dimensionless parameters wh ich may find applications in other systems involving attractive or rep ulsive Yukawa interactions. Prominent peaks of the K-factor occur for an attractive q-(q) over bar, color-Yukawa interaction with Debye scre ening lengths of 0.835 and 3.23 times the Bohr radius, corresponding t o two lowest s-wave q (q) over bar bound states moving into the contin uum to become q (q) over bar resonances as the Debye screening length decreases. These resonances, especially the c (c) over bar and the b ( b) over bar resonances, may be utilized to study the quark-gluon plasm a by examining the systematics of the temperature dependence of heavy- quark pair production just above the threshold.