Eur. Phys. J. C 69, 85-93 (2010)
https://doi.org/10.1140/epjc/s10052-010-1392-5

Diffraction and correlations at the LHC: definitions and observables

¹ Institute for Particle Physics Phenomenology, University of Durham, Durham, DH1 3LE, UK
² Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg, 188300, Russia

k.c.zapp@durham.ac.uk

Received: 28 May 2010
Revised: 5 July 2010
Published online: 12 August 2010

Abstract

We note that the definition of diffractive events is a matter of convention. We discuss two possible “definitions”: one based on unitarity and the other on Large Rapidity Gaps (LRG) or Pomeron exchange. LRG can also arise from fluctuations and we quantify this effect and some of the related uncertainties. We find care must be taken in extracting the Pomeron contribution from LRG events. We show that long-range correlations in multiplicities can arise from the same multi-Pomeron diagrams that are responsible for LRG events, and we explain how early LHC data can illuminate our understanding of ‘soft’ interactions.