NLO QCD Corrections to ($\gamma^{*}\rightarrow Q \bar{Q}$)-Reggeon Vertex

Abstract

Next-to-leading order QCD corrections to the $\gamma^{*} \longrightarrow Q\bar{Q}-Reggeon$ vertex are calculated, where $Q\bar{Q}$ denotes a heavy quark pair $c\bar c$ or $b\bar b$. The heavy quark mass effects on the photon impact factor are found to be significant, and hence may influence the results of high energy photon-photon scattering and heavy quark pair leptoproduction. In our NLO calculation, similar to the massless case, the ultraviolate(UV) divergences are fully renormalized in the standard procedure, while the infrared (IR) divergences are regulated by the parameter $\epsilon_{IR}$ in dimensional regularization. For the process $\gamma^* + q \to Q\bar{Q} + q$, we calculate all NLO coefficients in terms of $\epsilon_{IR}$, and find they are enhanced due to the heavy quark mass, as compared with the light quark case, and the enhancement factors increase rapidly as the quark mass increases. This might essentially indicate the quark mass effect, in spite of the absence of real corrections that are needed in a complete NLO calculation. Moreover, unlike the $\gamma^{*}$ to massless-quark-Reggeon vertex, the results in the present work may apply to the real photon case.