Charge asymmetry of heavy quarks at hadron colliders

Abstract

A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order $\alpha_s$ and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts up to 15\% for the differential distribution in suitable chosen kinematical regions. The resulting integrated forward-backward asymmetry of 4--5\% could be measured in the next round of experiments. At the LHC the asymmetry can be studied by selecting appropriately chosen kinematical regions. Furthermore, a slight preference at LHC for centrally produced antitop is predicted, with top quarks more abundant at large positive and negative rapidities.Comment: LaTeX, 16pp, 14 figures, uses revtex. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints

Effective-field-theory approach to top-quark production and decay

“…The SM prediction is dominated by O(α 3 S ) QCD interference effects and is 5% in the lab frame [46,47,48,49]. There is a discrepancy of about 2σ between theory and experiment.…”

Top quark charge asymmetry: searching for light axigluons in t t ¯ $$ t\overline{t} $$ + jet production at the LHC

“…The anti-symmetric part of the pure SM contribution,σ g A , receives a contribution only from the interference of diagrams (a) and (b) and this part is proportional to d 2 abc , the symmetric structure constants of SU(3) [3]. This can be seen as follows.…”

“…At the Tevatron the charge asymmetry has been measured as a forward-backward asymmetry at the level of the top quarks [4,5] and at the level of the decay products in the semileptonic [6,7] and double leptonic decay [8,9]. While CDF found deviations from the NLO Standard Model prediction [2,3,[10][11][12][13][14][15][16][17] in particular in the region of high invariant mass of the tt pair, M tt , and at large rapidity differences, ∆y, the most recent analyses from D0 agree with the SM prediction if all analysis channels are combined. At the LHC, measurements of the top-quark charge asymmetry in semi-leptonic [18][19][20] and double-leptonic decays [21,22] agree with the SM prediction; however, the errors are still very large [23].…”

“…This charge asymmetry has been studied for top quarks at the Tevatron and LHC experiments in [2,3]. At the Tevatron the charge asymmetry has been measured as a forward-backward asymmetry at the level of the top quarks [4,5] and at the level of the decay products in the semileptonic [6,7] and double leptonic decay [8,9].…”

Distinguishing among technicolor/warped scenarios in dileptons

“…This conclusion holds beyond the parton level as it only depends on the coupling. First, note that the Z production is qq initiated, and there is no contamination from gluon-initiated processes as discussed in [65]. But LHC is a p p collider, and identifying the direction of the incoming q orq is not straightforward.…”