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The European Physical Journal C
ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)
Abstract Volume 4 Issue 4 (1998) pp 631-639
DOI 10.1007/s100529800814
theoretical physics:
Helicity amplitudes for the small-angle lepton pair production in $e^+e^-$ or $\mu^+ \mu^-$ collisions
E.A. Kuraev (1), A. Schiller (2), V.G. Serbo (3), D.V. Serebryakova (4)
(1) Joint Institute of Nuclear Research, 141980, Dubna, Russia (e-mail: kuraev@thsun1.jinr.dubna.su)
(2) Institut für Theoretische Physik and Naturwissenschaftlich-Theoretisches Zentrum, Universität Leipzig, D-04109 Leipzig, Germany (e-mail: schiller@tph204.physik.uni-leipzig.de)
(3) Novosibirsk State University, 630090, Novosibirsk, Russia (e-mail: serbo@math.nsc.ru)
(4) Institute of Mathematics, 630090, Novosibirsk, Russia
Received: 23 October 1997 / Published online: 24 March 1998
Abstract. The lepton pair production $e^- e^+ \!\! \to \! e^- e^+ l^- l^+$ or $\mu^- \mu^+ \to \mu^- \mu^+ l^- l^+ $ is studied in the dominant cross section region of scattering angles ${m_j}/{E_j} \lesssim \theta_j \ll 1$. An analytical expression is found for all 64 helicity amplitudes of these processes. The accuracy of the obtained formulae is given omitting only terms of the order of ${m_j^2}/{E_j^2}$, $\theta_j^2$, and $ \theta_j {m_j}/{E_j}$. The result has a compact form convenient both for analytical and numerical calculations of various cross sections in this dominating scattering regime.
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Online publication: July 20, 1998
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