QCD predictions for polarised deep inelastic scattering accompanied by a forward jet in the low x region of possible HERA measurements

We estimate the cross-section and asymmetry relevant for the production of forward jets in polarised deep inelastic scattering in the region of small values of x which can be probed at possible polarised HERA measurements. The kinematical cuts implemented in our analysis are the same as those which were used in the unpolarised deep inelastic scattering at HERA. The calculations are based on the double ln(1/x) resummation which controls the polarised deep inelastic scattering for small values of the Bjorken parameter x. We show that this resummation substantially enhances the corresponding cross-section and asymmetry. The predicted value of the asymmetry is found to vary between −0.01 and −0.04 within the small x region which can possibly be probed at polarised HERA measurements. The polarised deep inelastic scattering at small x is dominated by the effects of the double ln(1/x) resummation [1, 2, 3]. Here, as usual, x = Q/(2pq), where Q = −q with q and p denoting the four momentum transfer between leptons and four momentum of the proton respectively. It has been pointed out in [4] that, apart from the structure function measurement, a process which probes the effects of double ln(1/x) resummation might be the deep inelastic scattering accompanied by a forward energetic jet. The idea of studying the deep inelastic ep scattering with an identified forward jet as a probe of the low x behaviour of QCD was proposed by Mueller [5]. Since then it has been successfully applied to the case of unpolarised deep inelastic scattering (DIS) at HERA [6, 7, 8]. The Mueller’s proposal was to study the unpolarised deep inelastic events (x,Q) containing an identified forward jet (xJ , k 2 J), where the longitudinal momentum fraction xJ of the proton carried by a forward jet and jet e-mail: [email protected] e-mail: [email protected]