2025/02/04 by Caucal, Paul, Salazar, Farid
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Nuclear Theory (nucl-th)
paper · doi:10.48550/arxiv.2502.02634
We consider the differential cross-section for single-inclusive jet production with transverse momentum P_⊥ in Deep Inelastic Scattering (DIS) at small Bjorken x\rm Bj, mediated by a virtual photon with virtuality Q2. Unlike most studies at small x, which focus on particle production in the current fragmentation region, we investigate the kinematic regime where the jet is produced in the target fragmentation hemisphere of the Breit frame, and with P_⊥ ≪ Q. For a longitudinally polarised photon, we demonstrate that this cross-section is not power suppressed in P_⊥/Q and we derive a factorised expression in terms of transverse momentum dependent (TMD) quark and gluon jet fracture functions. Our formula, valid at next-to-leading order in αs at small x, is akin to the Altarelli-Martinelli identity for the longitudinal DIS structure function. Numerical estimates show that the TMD quark jet fracture function is the most sensitive to saturation effects in large nuclei.