Soft processes at the LHC, II: Soft-hard factorization breaking and gap survival

TL;DR

The paper analyzes rapidity-gap survival in diffractive LHC processes, separating contributions from eikonal and enhanced rescattering that break soft-hard factorization. It develops a multi-component Pomeron framework to quantify S^2_enh and combines it with S^2_eik to predict overall gap survival for central exclusive production, including Higgs bosons. Despite enhanced absorption, the authors find only modest suppression for heavy exclusive states at the LHC and argue that, with NLO effects, the black disc regime is not reached and the energy dependence of S^2 is gradual. Tevatron exclusive data broadly support the approach, providing conservative lower limits for LHC predictions and encouraging prospects for observing exclusive Higgs production.

Abstract

We calculate the probability that the rapidity gaps in diffractive processes survive both eikonal and enhanced rescattering. We present arguments that enhanced rescattering, which violates soft-hard factorization, is not very strong. Accounting for NLO effects, there is no reason to expect that the black disc regime is reached at the LHC. We discuss the predictions for the survival of the rapidity gaps for exclusive Higgs production at the LHC.

Figures (6)

• Figure 1: The mechanism for the exclusive process $pp \to p+A+p$, with the eikonal and enhanced survival factors shown symbolically. The thick lines on the Pomeron ladders, either side of the subprocess ($gg \to A$), indicate the rapidity interval $\Delta y$ where enhanced absorption is not permitted thrJHEPkkmr.
• Figure 2: (a) The ladder structure of the triple-Pomeron amplitude between diffractive eigenstates $|\phi_i\rangle,|\phi_k\rangle$ of the proton; the rapidity $y$ spans an interval 0 to $Y={\rm ln}s$. (b) A multi-Pomeron diagram.
• Figure 3: Pure elastic eikonal scattering.
• Figure 4: (a) The bare pole amplitude; (b) the triple-Pomeron diagram describing high mass, $M$, diffractive dissociation; (c) the contribution of the triple-Pomeron coupling to central exclusive production.
• Figure 5: (a): A symbolic representation of (\ref{['eq:M']}); (b) and (c): diagrams relevant for the computation of $S^2_{\rm enh}$ and $S^2_{\rm eik}S^2_{\rm enh}$ of (\ref{['eq:sym1']}) and (\ref{['eq:sym2']}), where $\underline\Omega$ is the opacity when the screening corrections embracing the hard matrix element are neglected.