Two-photon production of leptons at hadron colliders in semielastic and elastic cases
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EMENTARY PARTICLES AND FIELDS Theory
Two-Photon Production of Leptons at Hadron Colliders in Semielastic and Elastic Cases A. Yu. Manko1)* and R. G. Shulyakovsky2)** Received April 27, 2015; in final form, August 26, 2015
Abstract—The mechanism of two-photon dilepton production is studied in the equivalent-photon ¨ (Weizsacker–Williams) approximation. This approximation is shown to describe well experimental data from hadron accelerators. The respective total and differential cross sections were obtained for the LHC and for the Tevatron collider at various energies of colliding hadrons. The differential cross sections were studied versus the dilepton invariant mass, transverse momentum, and emission angle in the reference frame comoving with the center of mass of colliding hadrons. The cases of semielastic and inelastic collisions were examined. DOI: 10.1134/S1063778816020125
1. INTRODUCTION We will examine the two-photon dilepton production in the processes [1–6] p) + X, p(¯ p) + p → l− l+ + p(¯
(1)
p(¯ p) + p → l− l+ + X,
(2)
where l is an electron or a muon, X is the final hadron state, p (¯ p) is the primary proton (antiproton). The diagrams that describe these processes are shown in Fig. 1. The processes of two-photon dilepton production can be used to calibrate accelerator luminosities [1–6], to perform searches for newphysics effects, and to study leptons [5, 7] and supersymmetric particles [8]. These processes can be calculated within quantum electrodynamics (QED) to a precision better than 1% [2–4]. In the case of two-photon dilepton-production mechanism, both final-state leptons and final-state hadrons are detected by forward detectors at hadron colliders [1]. The contribution of background processes is small for this particle-production mechanism [3, 9–12], so that one can study it to a high degree of precision at modern accelerators. In the present study, we show that the equivalent-photon approximation describes well experimental data from hadron accelerators. We 1)
Institute of Physics, National Academy of Sciences of Belarus, pr. Nezavisimosti 68, BY-220072 Minsk, Republic of Belarus. 2) Institute of Applied Physics, National Academy of Sciences of Belarus, Akademicheskaya ul. 16, BY-220072 Minsk, Republic of Belarus. * E-mail: [email protected] ** E-mail: [email protected],shulyakovsky@ iaph.bas-net.by
obtain the total and differential cross sections for the LHC and for the Tevatron collider in semielastic (1) and inelastic (2) cases at various energies of colliding hadrons. The elastic case was studied in [1–6, 13]. 2. CALCULATION OF TOTAL AND DIFFERENTIAL CROSS SECTIONS
2.1. Equivalent-Photon Approximation The equivalent-photon method was first proposed ¨ by Fermi [14] and was developed by Weizsacker [15] and Williams [16]. The two-photon mechanism of lepton production was proposed by a group of physicists from Novosibirsk [2–4, 6]. The problem of two-photon dilepton production was first studied by Landau and Lifschitz [17]. They showed that the cross section for two-photon production g
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