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Particles and Fields


Eur. Phys. J. C 21, 81-91 (2001)
DOI: 10.1007/s100520100733

Single top production in e+ e-, e- e-, $\gamma e$ and $\gamma \gamma$ collisions

E. Boos1, 2, M. Dubinin1, 2, A. Pukhov1, M. Sachwitz2 and H.J. Schreiber2

1  Institute of Nuclear Physics, Moscow State University, 119899 Moscow, Russia
2  DESY Zeuthen, 15738 Zeuthen, Germany

(Received: 27 April 2001 / Revised version: 31 May 2001 / Published online: 19 July 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )

Abstract
Single top quark cross section evaluations for the complete sets of tree-level diagrams in the e+ e-, e- e-, $\gamma e$ and $\gamma \gamma$ modes of the next linear collider with unpolarized and polarized beams are performed within the standard model and beyond. From a comparison of all possibilities we conclude that the process $\gamma_+ e^-_{\mathrm {L}} \to e^- t \bar b$ is extremely favored due to large cross sections, there being no $t \bar t$ background, the high degrees of beam polarization, and the exceptional sensitivities to Vtb and anomalous Wtb couplings. Similar reasons favor the process $e^- e^- \to e^- \nu_e \bar t b$ for probing top quark properties despite a considerably lower cross section. Less favorable are processes like $e^+ e^-, \gamma \gamma \to e^- \nu_e t \bar b$. Three processes were chosen to probe their sensitivities to anomalous Wtb couplings, with best bounds found for $\gamma_+ e^-_{\mathrm {L}} \to e^- t \bar b$ and $e^+_{\mathrm {R}} e^-_{\mathrm {R}} \to e^-
\nu_e t \bar
b$.



© Società Italiana di Fisica, Springer-Verlag 2001