Diagnosing the top-quark angular asymmetry using LHC intrinsic charge asymmetries

Abstract

Flavor-violating interactions involving new heavy particles are among proposed explanations for the tt forward-backward asymmetry observed at the Tevatron. Many of these models generate a tt-plus-jet signal at the LHC. In this paper we identify several new charge asymmetric variables in ttj events that can contribute to the discovery of such models at the LHC. We propose a data-driven method for the background, largely eliminating the need for a Monte Carlo prediction of tt-plus-jets, and thus reducing systematic errors. With a fast detector simulation, we estimate the statistical sensitivity of our variables for one of these models, finding that charge-asymmetric variables could materially assist in the exclusion of the Standard Model across much of the mass and coupling range, given 5 inverse fb of data. Should any signal appear, our variables will be useful in distinguishing classes of models from one another.

Bottom-Quark Forward-Backward Asymmetry in the Standard Model and Beyond

“…Prospects for discovery at the LHC are discussed in [36,37,42,[44][45][46][47][48][51][52][53][54][55] works by taking into account the resonance effects of the Z, and limiting ourselves to the energy regime accessible at the Tevatron. In particular, we are interested in seeing if the NP contribution to A bb F B can be large enough to be distinguishable from the SM predictions we computed above based on the expected sensitivities given in [7].…”

“…For the stringent constraints that these models must overcome see [46][47][48][49][50][51][52][53][54][55]. Prospects for discovery at the LHC are discussed in [36,37,42,[44][45][46][47][48][51][52][53][54][55] works by taking into account the resonance effects of the Z, and limiting ourselves to the energy regime accessible at the Tevatron.…”

Top quark forward-backward asymmetry andW′bosons

“…Some models envision new s-channel processes [4] like axigluons, or other exotic scenarios [5]. Other models invoke new particles, such as W ′ bosons [6][7][8][9][10][11] or Z ′ bosons [12][13][14] that enter via virtual t-channel exchange. There are also modelindependent ideas about the tt asymmetry [15][16][17].…”

“…To avoid direct constraints from singletop-quark production, we consider a non-standard W ′ which couples to one first and one third generation righthanded quark. The relevant interaction Lagrangian for * Electronic address: Zack.Sullivan@IIT.edu † Electronic address: haozhang@anl.gov this model [6][7][8][9][10][11] may be written as…”

A New Method for Indirect Mass Measurements using the Integral Charge Asymmetry at the LHC

“…For example, in attempts to explain the large forward-backward asymmetries of the tt production measured at the TEVATRON by both the CDF [59] and the D0 [60] experiments, some studies were carried out at the LHC to constrain possible contributions from an extra W ′± boson. See for example [61][62], using a differential charge asymmetry with respect to a three-body invariant mass, and also [63], using an integral charge asymmetry, and the references therein. Such analyses, using charge asymmetries with respect to the tt system rapidity, invariant mass and transverse momentum, have also been performed by the AT-LAS and CMS collaborations, see [64] and [65], respectively.…”