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

TL;DR

This paper analyzes high-energy proton-proton and antiproton-proton scattering data, revealing that the total cross-section rises faster than previously expected at LHC energies, with implications for theoretical bounds and future physics.

Contribution

It introduces a flexible parametrization for the total cross-section that indicates a rise faster than the Froissart-Martin bound, extending analysis to elastic scattering and discussing physical implications.

Findings

Total cross-section rises faster than log-squared bound at LHC energies.

Elastic-to-total cross-section ratio is consistent with 1/3.

Parametrization fits both total and elastic cross-section data satisfactorily.

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.