The Tensor Pomeron and Low-x Deep Inelastic Scattering

Apr 11, 2019, 10:45 AM
Cavallerizza Reale - Aula Multifunzione

Cavallerizza Reale - Aula Multifunzione

Via Verdi, 9 Turin
Parallel Session Talk WG2: Low-x and Diffraction WG2: Small-x and Diffraction


Carlo Ewerz (EMMI, GSI and Heidelberg University)


The tensor-pomeron model is applied to low-x deep-inelastic lepton-nucleon scattering and photoproduction. We consider c. m. energies in the range 6 - 318 GeV and $Q^2 < 50$ GeV$^2$. In addition to the soft tensor pomeron, which has proven quite successful for the description of soft hadronic high-energy reactions, we include a hard tensor pomeron. We also include $f_2$-reggeon exchange which turns out to be particularly relevant for real-photon-proton scattering at c. m. energies in the range up to 30 GeV. The combination of these exchanges permits a description of the absorption cross sections of real and virtual photons on the proton in the same framework. In particular, a detailed comparison of this two-tensor-pomeron model with the latest HERA data for $x < 0.01$ is made. Our model gives a very good description of the transition from the small-$Q^2$ regime where the real or virtual photon behaves hadron-like to the large-$Q^2$ regime where hard scattering dominates. Our fit allows us, for instance, a determination of the intercepts of the hard pomeron as $1.3008({}^{+73}_{−84})$, of the soft pomeron as $1.0935(^{+76}_{−64})$, and of the $f_2$ reggeon. We find that in photoproduction the hard pomeron does not contribute within the errors of the fit. We show that assuming a vector instead of a tensor character for the pomeron leads to the conclusion that it must decouple in real photoproduction.


Primary authors

Carlo Ewerz (EMMI, GSI and Heidelberg University) Otto Nachtmann (U) Daniel Britzger (Max-Planck-Institut für Physik München) Stefan Schmitt (Deutsches Elektronen-Synchrotron (DE)) Alexander Glazov (Deutsches Elektronen-Synchrotron (DE))

Presentation materials