Bound-free pair production in relativistic nuclear collisions from the NICA to the HE LHC colliders
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Regular Article - Theoretical Physics
Bound-free pair production in relativistic nuclear collisions from the NICA to the HE LHC colliders D. A. Bauer1, D. V. Karlovets2,a , V. G. Serbo1,3 1
Novosibirsk State University, 630090 Novosibirsk, Russia Tomsk State University, Lenina Ave. 36, 634050 Tomsk, Russia 3 Sobolev Institute of Mathematics, 630090 Novosibirsk, Russia
2
Received: 7 June 2020 / Accepted: 22 July 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Communicated by Reinhard Alkofer
Abstract We consider the electron-positron pair production in relativistic heavy ion collisions, in which the produced electron is captured by one of the nuclei resulting, thus, in the formation of a hydrogen-like ion. These ions emerge from the collision point and hit the vacuum chamber wall inside superconducting magnets. Therefore, this process may be important for the problems of beam life time and for the quenching the irradiated magnet. A theoretical investigation for such a bound-free pair production (BFPP) at the colliders from NICA to HE LHC is presented. We obtain an approximate universal formula for the total cross section of the process. We compare it with the results of available numerical calculations and estimate that an accuracy of our calculations is better than 30% at the energies of the NICA collider and becomes of the order of a few percent for the RHIC and HE LHC colliders. Based on the obtained result, the detailed calculations are performed for future experiments at the NICA collider. We find that the expected BFPP cross sections for the Au79+ –Au79+ and Bi83+ –Bi83+ collisions are in the range from 10 to 70 barn, while for the p–Au79+ and p–Bi83+ collisions they are in the range of a few mbarn.
1 Introduction In this paper we discuss the process of the bound-free pair production, in which the produced electron is captured by one of the nuclei resulting, thus, in the formation of a hydrogenlike ion, Z 1 + Z 2 → Z 1 + e+ + (Z 2 + e− )1s1/2 ,
(1)
where the bound system is denoted by the round brackets. For definiteness, we assume (if it is not stated otherwise) that the a e-mail:
[email protected] (corresponding author)
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electron is captured by the second nucleus into the ground ionic state. One of the dominant processes at the colliders with heavy ions is electron–positron pair production, whose cross section is huge. For example, the cross section of the creation of a free e+ e− pair at the Pb82+ –Pb82+ collisions on LHC reaches hundreds of kilobarns [1–6]. In contrast, the BFPP process has orders of magnitude smaller cross section than free-free pair production. Nevertheless, its investigation is of great importance for two reasons. In free-free e+ e− production, the scattered nuclei lose only a very small fraction of their energy and acquire tiny scattering angles, and thus do not leave the beam. In contrast, if one of the colliding ions captures an electron, it changes its charge and it is bent out from the beam in a co
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