Factorization breaking in dijet photoproduction with a leading neutron

Abstract

Abstract. The production of dijets with a leading neutron in ep-interactions at HERA is calculated in leading order and next-to-leading order of perturbative QCD using a pion-exchange model. Differential cross sections for deep-inelastic scattering (DIS) and photoproduction are presented as a function of several kinematic variables. By comparing the theoretical predictions for DIS dijets to recent H1 data, the pion flux factor together with the parton distribution functions of the pion is determined. The dijet cross sections in photoproduction show factorization breaking if compared to the H1 photoproduction data. The suppression factor is S = 0.48 (0.64) for resolved (global) suppression.PACS. 12.38.Bx Perturbative QCD calculations -13.60.-r Photon interactions with hadrons

Factorisation issues in diffraction

“…It is expected also for events with a transition p → n, neutron γp → jet + jet + n + X has been investigated to test factorisation breaking [31]. In these events soft rescattering is expected between the photon remnant and the neutron reducing the normalisation of the cross section.…”

“…The NLO QCD calculations [31] for dijet production with a final state forward neutron are compared with the measured cross sections in both the DIS and photoproduction regimes [32]. In this analysis jets are identified using the cone algorithm and are selected by requiring E jet T,1(2) > 7 (6) GeV.…”

“…In the pion exchange model, the cross section for leading neutron production is the product of the non-perturbative pion flux factor, describing the splitting function of a proton into a pion and a neutron, and the parton distribution function of the pion. In [31] the pion flux normalisation factor for the dijet photoproduction cross section was determined from the measurement of the DIS dijet cross section, where no absorptive interactions is expected. Figure 16 Figure 16.…”

“…Differential cross sections for dijet production with a leading neutron in DIS (left) and photoproduction (right). The H1 measurement [32] is compared to perturbative QCD predictions in LO and NLO [31].…”

QCD analysis of forward neutron production in DIS

“…This strategy is consistent with the factorisation theorem. The resulting set of proton-to-neutron fracture functions (nFFs) could then be used in hard-scattering factorisation tests [24] in forward neutron tagged dijet photoproduction in ep collisions, as already measured at HERA [25,26], where factorisation is expected to hold only for the so-called direct component of the cross section. Even more intriguing appears to be the possibility of using nFFs for predicting the cross section for the associated production of a forward neutron and a Drell-Yan pair or dijet system in hadronic collisions.…”