An updated analysis on the rise of the hadronic total cross-section at the LHC energy region

Abstract

A forward amplitude analysis on $pp$ and $\bar{p}p$ elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the $pp$ total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section (${\sigma }_{tot}$) is parametrized as ${\ln }^{\gamma }(s/s_h)$, where $\gamma$ and $s_h$ are free \textit{real} fit parameters. Singly-subtracted derivative dispersion relations are used to connect ${\sigma }_{tot}$ and the rho parameter ($\rho$) in an analytical way. Different fit procedures are considered, including individual fits to ${\sigma }_{tot}$ data, global fits to ${\sigma }_{tot}$ and $\rho$ data, constrained and unconstrained data reductions. The results favor a rise of the ${\sigma }_{tot}$ faster than the log-squared bound by Froissart and Martin at the LHC energy region. The parametrization for ${\sigma }_{tot}$ is extended to fit the elastic cross-section (${\sigma }_{el}$) data with satisfactory results. The analysis indicates an asymptotic ratio ${\sigma }_{el}/{\sigma }_{tot}$ consistent with 1/3 (as already obtained in a previous work). A critical discussion on the correlation, practical role and physical implications of the parameters $\gamma$ and $s_h$ is presented. The discussion confronts the 2002 prediction of ${\sigma }_{tot}$ by the COMPETE Collaboration and the recent result by the Particle Data Group (2012 edition of the Review of Particle Physics). Some conjectures on possible implications of a fast rise of the proton-proton total cross-section at the highest energies are also presented.

Comments: 32 pages, 9 figures, discussion on the 8 TeV TOTEM data extended (2 tables and 1 figure added), typos/grammar corrected, conclusions unchanged, matches journal version