Large Rapidity Gap Method to Select Soft Diffraction Dissociation at the LHC

Emily Nurse,Sercan Sen

doi:10.1155/2016/5082847

Abstract

In proton-proton (pp) collisions, any process involves exchanging the vacuum quantum numbers is known as diffractive process. A diffractive process with no largeQ2is called soft diffractive process. The diffractive processes are important for understanding nonperturbative QCD effects and they also constitute a significant fraction of the total pp cross section. The diffractive events are typically characterized by a region of the detector without particles, known as a rapidity gap. In order to observe diffractive events in this way, we consider the pseudorapidity acceptance in the forward region of the ATLAS and CMS detectors at the Large Hadron Collider (LHC) and discuss the methods to select soft diffractive dissociation for pp collisions ats=7 TeV. It is shown that, in the limited detector rapidity acceptance, it is possible to select diffractive dissociation events by requiring a rapidity gap in the event; however, without using forward detectors, it seems not possible to fully separate single and double diffractive dissociation events. The Zero Degree Calorimeters can be used to distinguish the type of the diffractive processes up to a certain extent.

Highlights

The measurement of the main characteristics of diffractive interactions is essential to improve our understanding of pp collisions
Pseudorapidity and rapidity are equal for massless particles) The large rapidity gap can be defined as the difference between the rapidity of the diffractively scattered proton and that of the particle closest to it inrapidity
Methods to select soft diffraction dissociation at the Large Hadron Collider (LHC) experiments ATLAS and CMS are studied by using large rapidity gaps in the events

Summary

Introduction

The measurement of the main characteristics of diffractive interactions is essential to improve our understanding of pp collisions. The modelling of diffraction is still mainly generator dependent and there is no unique, agreed upon experimental definition of diffraction [1, 2]. While the physics of diffractive dissociation at the LHC are very important, the detector capabilities in the forward region are limited. In this paper, using the rapidity gap technique and by considering the forward rapidity coverage of the LHC experiments ATLAS [3] and CMS [4], a number of studies are carried out to select soft diffraction dissociation. The potential of Zero Degree Calorimeter for diffractive events selection is discussed

Event Classification

Diffractive Kinematical Variables

Measuring Diffractive Events

Findings

Conclusions