Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 36: Electromagnetic Probes V, CERN, HERA Results
HK 36.3: Talk
Tuesday, March 17, 1998, 18:00–18:15, B
Leading proton spectra from DIS at HERA — •A. Szczurek1, N.N. Nikolaev2,3, J. Speth2, and N. Cartiglia4 — 1Institute of Nuclear Physics, PL-31-342 Kraków — 2Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich — 3L. D. Landau Institute, Moscow, Russia — 4Columbia University, Nevis Laboratories, Irvington N.Y., 10533 USA
For secondary particles h produced in semi-inclusive DIS e p → e′ X h, the QCD hardness scale gradually diminishes from the hard scale, Q2, in the virtual photon (current) fragmentation region to soft, hadronic, scale in the proton fragmentation region. This suggests similarity of the inclusive spectra of leading protons and neutrons, h=p,n, in high energy hadron-proton collisions and in DIS at small x, which we explore extending to DIS peripheral mechanisms of fragmentation. While the production of leading neutrons is known to be exhausted by DIS off charged pions, in the production of leading protons DIS off neutral pions must be supplemented by a contribution from isoscalar reggeon (f0) exchange extrapolated down to moderate values of xL. With the reggeon exchange parameters deduced form diffractive DIS, we find a good quantitative agreement with the ZEUS data on leading proton production. We comment on the x and Q2 dependence of leading proton production as a probe of a universal pattern of the x,Q2 evolution of the nucleon and meson (reggeon) structure functions at small x.