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arXiv · 1010.2402

New physics in t-> b W decay at next-to-leading order in QCD

Jure Drobnak·Svjetlana Fajfer·Jernej F. Kamenik
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Abstract

We consider contributions of non-standard tbW effective operators to the decay of an unpolarized top quark into a bottom quark and a W gauge boson at next-to-leading order in QCD. We find that the dipole operator O_{LR} contribution to the transverse-plus W helicity fraction F_+ is significantly enhanced compared to the leading order result at non-vanishing bottom quark mass. Nonetheless, presently the most sensitive observable to direct O_{LR} contributions is the longitudinal W helicity fraction F_L. In particular, the most recent CDF measurement of F_L already provides the most stringent upper bound on O_{LR} contributions, even when compared with indirect bounds from the rare decay B -> X_s gamma.

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Jure Drobnak, Svjetlana Fajfer, Jernej F. Kamenik. 2010-11-12. New physics in t-> b W decay at next-to-leading order in QCD. https://doi.org/10.1103/physrevd.82.114008

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