Probes of multiparticle production at the LHC

TL;DR

This paper explores how high-energy proton-proton collisions at the LHC can be described using parton cascades and multi-Pomeron exchange, introducing an infrared cutoff that links soft and semihard interactions.

Contribution

It extends the parton approach to soft and semihard processes at high energies by incorporating an energy-dependent infrared cutoff from Pomeron interactions.

Findings

The effective infrared cutoff k_{sat} increases with collider energy.

Minijet production with p_t ≥ k_{sat} dominates soft secondary production.

Proposed measurements at the LHC can probe Pomeron interactions and the ridge effect.

Abstract

We discuss how the main features of high-energy `soft' and `semihard' pp collisions may be described in terms of parton cascades and multi-Pomeron exchange. The interaction between Pomerons produces an effective infrared cutoff, k_{sat}, by the absorption of low k_t partons. This provides the possibility of extending the parton approach, used for `hard' processes, to also describe high-energy soft and semihard interactions. In particular, the presence of the cutoff k_{sat}, which increases with collider energy, means that the production and hadronization of minijets with p_t\gapproxeq k_{sat} are the main source of the soft secondaries. We propose several measurements which can be made at the LHC, that can further illuminate our understanding of the mechanism which drives the soft and semihard interactions. We show that the structure of Pomeron-Pomeron interactions may be studied in Double-Pomeron-Exchange processes and in the p_t distributions of secondaries near the edge of large rapidity gaps. The so-called `ridge effect' is another manifestation of the interaction of two partonic cascades.