HERA分解光子过程中的双喷注产生

Two-Jet Production via Resolved Photon Processes at HERA

在次领头级（ＮＬＯ）近似下计算了ＨＥＲＡ分解光子过程中的双喷注截面．结果表明：在分解光子过程中，ＮＬＯ修正量（当不变质量大于２０ＧｅＶ时）约为ＬＯ的０．５到１．这一结果可解释ＺＥＵＳ的数据分析结果：“ＬＯＱＣＤ理论值比实验值低１．５到２个因子．”当双喷注不变质量ＭＪＪ＜３０ＧｅＶ），快度ｙＪＪ＜－１时，光子的胶子分布决定了双喷注截面．利用这一特点可测量光子的胶子分布．当双喷注不变质量较大时（例如：ＭＪＪ＞３０ＧｅＶ），－１＜ｙＪＪ＜０时，光子的夸克分布决定了双喷注截面，利用这一特点可测量光子的夸克分布．

Numerical reasults are presented for the photoproduction of twojets via resolved quasi-real photons at HERA in next-to-leading order(NLO) QCD. It shows that the NLO contribution is about a factor of 0.5 to 1 of the LO contribution. This may provide an explanation to the ZEUS results: 'the LO QCD results is below data a factor of 1.5 to 2'. When the invariant mass of two-jet system is not too large, say less than 30GeV, the cross section is dominated by the photon gluon distributionin.This may be used to measure the gluon structure of photon. When the invariant mass of two-jet system is larger, say than 30GeV, the cross section is dominated by the photon quark distributionin. This may be used to measure the quark structure of photon.