Single-top-quark production at hadron colliders

Abstract

Single-top-quark production probes the charged-current weak interaction of the top quark, and provides a direct measurement of the CKM matrix element V_{tb}. We perform two independent analyses to quantify the accuracy with which the W-gluon fusion (gq -> t\bar{b}q) and (q\bar{q} -> t\bar{b}) signals can be extracted from the backgrounds at both the Tevatron and the LHC. Although perturbation theory breaks down at low transverse momentum for the W-gluon fusion \bar{b} differential cross section, we show how to obtain a reliable cross section integrated over low \bar{b} transverse momenta up to a cutoff. We estimate the accuracy with which V_{tb} can be measured in both analyses, including theoretical and statistical uncertainties. We also show that the polarization of the top quark in W-gluon fusion can be detected at the Fermilab Tevatron and the CERN LHC.Comment: Version to appear in PRD, 31 pages, LaTeX, 8 ps figure

Associated production of aZboson and a single heavy-quark jet

“…The b distribution function is needed for the above-mentioned Higgs-production process as well as for inclusive Higgs production, bb → h [20,21,22]. It is also needed for the single-top production processes qb → q ′ t [12,23] and gb → W − t [24,25], and the charged-Higgs production process gb → H − t [26,27,28]. The process gQ → γQ is much more sensitive to the charm distribution function than to that of bottom, due to the greater electric charge of the charm quark [30,31].…”

FCNC-induced heavy-quark events at the LHC from supersymmetry

“…For instance, for the bs final states misidentification of b quarks as c quarks in cs-production from charged currents may obscure the possibility that the bs events can be really attributed to Higgs boson FCNC decays. This also applies to the tc final states [39], where misidentification of b quarks as c quarks in e.g. tbproduction, might be a source of background to the tc events, although in this case the clearcut top quark signature should be much more helpful (specially after performing a study of the distribution of the signal versus the background).…”

Flavor gauge bosons at the Fermilab Tevatron

“…In order to estimate the sensitivity of the Tevatron in Run II to the flavoron contribution to single top production, we take only the dominant flavoron diagram, t-channel mediated ud → tb. We compare this contribution to the s-channel SM assuming these will be separately observed with the use of double btagging [18]. In Fig.…”