Scalar-mediated $t\bar{t}$ forward-backward asymmetry

Abstract

A large forward-backward asymmetry in $t\bar{t}$ production, for large invariant mass of the $t\bar{t}$ system, has been recently observed by the CDF collaboration. Among the scalar mediated mechanisms that can explain such a large asymmetry, only the t-channel exchange of a color-singlet weak-doublet scalar is consistent with both differential and integrated $t\bar{t}$ cross section measurements. Constraints from flavor changing processes dictate a very specific structure for the Yukawa couplings of such a new scalar. No sizable deviation in the differential or integrated $t\bar{t}$ production cross section is expected at the LHC.

Comments: 22 pages, 1 figure and 2 tables. v2: Corrected Eqs.(50,51,74), adapted Fig.1, Tab.1 and relevant discussions. Extended discussion of top decay and single top