Probing the topcolor-assisted technicolor model via the singlet-quark production at the CERN LHC

Abstract

The single t-quark production in proton-proton collisions can proceed through three distinct processes: tq, tb, tW productions. With the running of the Large Hadron Collider (LHC) at CERN, it has good potential to measure each single t-quark production mode. The topcolor-assisted technicolor (TC2) model, one of the promising dynamical theories, predicts some new particles at the several hundred GeV scale: three top-pion bosons ({pi}{sub t}{sup {+-}}, {pi}{sub t}{sup 0}) and one top-Higgs boson (h{sub t}). These particles are regarded as the typical feature of the TC2 model and can contribute to some processes. In this paper, we systematically study the contribution of the TC2 model to the single t-quark production at the Hadron colliders, especially at the LHC. The TC2 model can contribute to the cross section of the single t-quark production in two different ways. First, the existence of the top pions and top Higgs can modify the Wtb coupling via their loop contributions, and such modification can cause the correction to the cross sections of all three production modes. Our study shows that this kind of correction is negative and very small in all cases. Thus it is difficult to observe such a correction even at the LHC.more » On the other hand, there exist the tree-level flavor-changing (FC) couplings in the TC2 model which can also contribute to the cross sections of the tq and tb production processes. The resonant effect can greatly enhance the cross sections of the tq and tb productions. The first evidence of the single t-quark production has been reported by the D0 collaboration and the measured cross section for the single t-quark production of {sigma}(pp{yields}tb+X,tqb+X) is compatible at the 10% level with the standard model prediction. Because the light top pion can make a great contribution to the tb production, the top-pion mass should be very large in order to make the predicted cross section in the TC2 model be consistent with the Tevatron experiments. More detailed information about the top-pion mass and the FC couplings in the TC2 model should be obtained with the running of the LHC.« less