Leading neutron production in e+ p collisions at HERAстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The production of neutrons carrying at least 20% of the proton beam energy (\xl>0.2) in e+p collisions has been studied with the ZEUS detector at HERA for a wide range of Q2, the photon virtuality, from photoproduction to deep inelastic scattering. The neutron-tagged cross section, ep→e′Xn, is measured relative to the inclusive cross section, ep→e′X, thereby reducing the systematic uncertainties. For \xl> 0.3, the rate of neutrons in photoproduction is about half of that measured in hadroproduction, which constitutes a clear breaking of factorisation. There is about a 20% rise in the neutron rate between photoproduction and deep inelastic scattering, which may be attributed to absorptive rescattering in the γp system. For 0.64<\xl<0.82, the rate of neutrons is almost independent of the Bjorken scaling variable x and Q2. However, at lower and higher \xl values, there is a clear but weak dependence on these variables, thus demonstrating the breaking of limiting fragmentation. The neutron-tagged structure function, FLN(3)2(x,Q2,\xl), rises at low values of x in a way similar to that of the inclusive \ff of the proton. The total γπ cross section and the structure function of the pion, Fπ2(xπ,Q2) where xπ=x/(1−\xl), have been determined using a one-pion-exchange model, up to uncertainties in the normalisation due to the poorly understood pion flux. At fixed Q2, Fπ2 has approximately the same x dependence as F2 of the proton.