40 research outputs found
Rapidity Gap Survival in Enhanced Pomeron Scheme
We apply the phenomenological Reggeon field theory framework to investigate
rapidity gap survival (RGS) probability for diffractive dijet production in
proton-proton collisions. In particular, we study in some detail rapidity gap
suppression due to elastic rescatterings of intermediate partons in the
underlying parton cascades, described by enhanced (Pomeron-Pomeron interaction)
diagrams. We demonstrate that such contributions play a subdominant role,
compared to the usual, so-called "eikonal", rapidity gap suppression due to
elastic rescatterings of constituent partons of the colliding protons. On the
other hand, the overall RGS factor proves to be sensitive to color fluctuations
in the proton. Hence, experimental data on diffractive dijet production can be
used to constrain the respective model approaches
On the prompt contribution to the atmospheric neutrino flux
The prompt contribution to the atmospheric neutrino flux is analyzed. It is
demonstrated that the corresponding theoretical uncertainties related to
perturbative treatment of charm production, notably, the ones stemming from the
low and high behavior of parton distribution functions, can be conveniently
studied at the level of charm quark production. Additionally, we discuss the
non-perturbative contribution to the prompt neutrino flux, related to the
intrinsic charm content of the proton, and analyze its main features.Comment: v2: accepted versio
Signatures of the transition from galactic to extragalactic cosmic rays
We discuss the signatures of the transition from galactic to extragalactic
cosmic rays in different scenarios, giving most attention to the dip scenario.
The dip is a feature in the diffuse spectrum of ultra-high energy (UHE) protons
in the energy range eV, which is caused by
electron-positron pair production on the cosmic microwave background (CMB)
radiation. The dip scenario provides a simple physical description of the
transition from galactic to extragalactic cosmic rays. Here we summarize the
signatures of the pair production dip model for the transition, most notably
the spectrum, the anisotropy and the chemical composition. The main focus of
our work is however on the description of the features that arise in the
elongation rate and in the distribution of the depths of shower maximum in the dip scenario. We find that the curve for shows a
sharp increase with energy, which reflects a sharp transition from an iron
dominated flux at low energies to a proton dominated flux at
eV. We also discuss in detail the shape of the distributions for
cosmic rays of given energy and demonstrate that this represents a powerful
tool to discriminate between the dip scenario and other possible models of the
transition.Comment: Version accepted for publication in Physical Review