Double lepton pair production with electron capture in relativistic heavy-ion collisions

A N Artemyev,V G Serbo,A Surzhykov

doi:10.1140/epjc/s10052-014-2829-z

Abstract

We present a theoretical study of a double lepton pair production in ultra--relativistic collision between two bare ions. Special emphasis is placed to processes in which creation of (at least one) $e^+ e^-$ pair is accompanied by the capture of an electron into a bound ionic state. To evaluate the probability and cross section of these processes we employ two approaches based on (i) the first--order perturbation theory and multipole expansion of Dirac wavefunctions, and (ii) the equivalent photon approximation. With the help of such approaches, detailed calculations are made for the creation of two bound--free $e^+ e^-$ pairs as well as of bound--free $e^+ e^-$ and free--free $\mu^+ \mu^-$ pairs in collisions of bare lead ions Pb$^{82+}$. The results of the calculations indicate that observation of the double lepton processes may become feasible at the LHC facility.

Highlights

Strong electromagnetic fields, induced in relativistic ion– ion as well as ion–atom collisions, may lead to a creation of electron–positron pairs
Special emphasis was given to the processes involving creation of bound–free e+e− pairs
The first one is traced back to the first-order perturbation theory and the partialwave expansion of the Dirac wavefunctions, while the second employs simple analytical expressions derived within the framework of the equivalent photon approximation

Summary

Introduction

Strong electromagnetic fields, induced in relativistic ion– ion as well as ion–atom collisions, may lead to a creation of electron–positron pairs. While in the past most of the studies have dealt with single e+e− pairs, much of today interest is focused on the multiple pair production Such a process, in which few electrons and positrons are created in a single collision event, is of high order in the electromagnetic coupling α and is predicted to have a sufficiently large cross section [4,5]. Due to a large background signal these measurements were unsuccessful, indicating a need for an alternative scenario of the experiment This scenario can be provided by the investigation of multiple e+e− creation events accompanied by the electron capture into bound ionic states. The processes (1)–(2) and (3) can be investigated experimentally by detecting residual helium-like or two hydrogen-like ions, and without the need for observation of positrons These measurements can become feasible in the near future owing to (relatively) large corresponding cross sections which, being proportional to α14, may reach the order of 10 mb.

Theoretical background

First-order perturbation theory

Results and discussion

Summary