LHC predictions from a tevatron anomaly in the top quark forward-backward asymmetry

Abstract

Abstract:We examine the implications of the recent CDF measurement of the top-quark forward-backward asymmetry, focusing on a scenario with a new color octet vector boson at 1-3 TeV. We study several models, as well as a general effective field theory, and determine the parameter space which provides the best simultaneous fit to the CDF asymmetry, the Tevatron top pair production cross section, and the exclusion regions from LHC dijet resonance and contact interaction searches. Flavor constraints on these models are more subtle and less severe than the literature indicates. We find a large region of allowed parameter space at high axigluon mass and a smaller region at low mass; we match the latter to an SU(3) 1 × SU(3) 2 /SU(3) c coset model with a heavy vector-like fermion. Our scenario produces discoverable effects at the LHC with only 1 − 2 fb −1 of luminosity at √ s = 7 − 8 TeV. Lastly, we point out that a Tevatron measurement of the b-quark forwardbackward asymmetry would be very helpful in characterizing the physics underlying the top-quark asymmetry.

Forward–backward asymmetries of the bottom and top quarks in warped extra-dimensional models: LHC predictions from the LEP and Tevatron anomalies

“…For instance, effective axigluon-inspired scenarios can cure these anomalies [24,25] (note that the parameter space explored here is not the same as the one considered in Ref. [25] and our resonance width is larger) if one makes sure that the axigluon exchanges do not affect drastically the well behaved tt (differential) cross sections.…”

Top-pair forward-backward asymmetry beyond next-to-leading order

“…Many attempts to explain these results in terms of new physics scenarios have been made, see e.g. [11][12][13][14][15][16][17][18][19][20][21]. The task is complicated by the fact that the new physics contributions should not spoil the good agreement between theory and measurements for the total pair-production cross section and the differential distribution in the pair invariant mass.…”

AFBtmeets LHC

“…We focus on the production of color-octet and color-singlet vector resonances, noting that the color-octet case is a candidate that generates [12,25] the observed top-quark forwardbackward asymmetry at the Tevatron. The reconstruction techniques described above were developed for vector exchange contributions to top pair production, and some modification would be required to account for the different acceptances associated with scalar and tensor resonances.…”

“…In particular, broad resonances with large couplings can easily generate [25] the magnitude of the effect observed at the Tevatron. Such non-resonant contributions to top pair production can yield significant deviations in the invariant mass spectrum at large values of M tt .…”

“…In addition to modifications of A t F B , virtually all of the candidate theories result in an increase in tt production at large invariant mass, M tt , and the differential cross section dσ tt /dM tt can be a sensitive discriminant between various models [25][26][27]. In fact, the unprecedented kinematic reach afforded by the LHC may allow production of new states which could contribute only virtually to Tevatron processes, revealing new tt resonances.…”