Leading neutron production in e+ p collisions at HERA

S. Chekanov, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Yoshida, M. C K Mattingly, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. CorradiS. De Pasquale, P. Giusti, G. Iacobucci, G. Levi, A. Margotti, R. Nania, F. Palmonari, A. Pesci, G. Sartorelli, A. Zichichi, G. Aghuzumtsyan, D. Bartsch, I. Brock, J. Crittenden, S. Goers, H. Hartmann, E. Hilger, P. Irrgang, H. P. Jakob, A. Kappes, U. F. Katz, R. Kerger, O. Kind, E. Paul, J. Rautenberg, R. Renner, H. Schnurbusch, A. Stifutkin, J. Tandler, K. C. Voss, A. Weber, D. S. Bailey, N. H. Brook, J. E. Cole, B. Foster, G. P. Heath, H. F. Heath, S. Robins, E. Rodrigues, J. Scott, R. J. Tapper, M. Wing, M. Capua, A. Mastroberardino, M. Schioppa, G. Susinno, J. Y. Kim, Y. K. Kim, J. H. Lee, I. T. Lim, M. Y. Pac, A. Caldwell, M. Helbich, X. Liu, B. Mellado, S. Paganis

    Research output: Contribution to journalArticlepeer-review


    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 γ p 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, F2LN(3) (x, Q2, xL), rises at low values of x in a way similar to that of the inclusive F2(x, Q2) of the proton. The total γπ cross section and the structure function of the pion, F2π (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, F2π has approximately the same x dependence as F2 of the proton. © 2002 Published by Elsevier Science B.V.
    Original languageEnglish
    Pages (from-to)3-56
    Number of pages53
    Issue number1-3
    Publication statusPublished - 19 Aug 2002


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