Abstract
We consider a Z' model where the Z' boson couples only to up and top quarks. As a simple setup, one can consider a family-dependent $U(1)'$ symmetry, under which only right-handed up-type quarks are charged. After symmetry breaking, the right-handed quarks mix with each other and top flavor-changing neutral currents (FCNCs) mediated by the Z' boson can be generated at tree level. We take into account several processes to probe the top FCNCs, and find that the same sign top quark pair production or the triple top quark production is the most capable of testing the top FCNCs. We also consider a few non-FCNC processes to probe the Z' boson, for example, dijet production at the LHC.
Highlights
The Standard Model (SM) has passed through stringent tests in various experiments
The right-handed quarks mix with each other, and top flavor-changing neutral currents (FCNCs) mediated by the Z0 boson can be generated at tree level
Comparing the result for the upper bound on gut at the production level, we find that the same-sign top quark pair production could provide a much more stringent bound than the triple top quark production over the whole range of mZ0 ≥ 1 TeV
Summary
The Standard Model (SM) has passed through stringent tests in various experiments. It is, widely believed that the SM is not the end of the story and new physics beyond the SM will be probed at experiments, e.g., the LHC. Depending on Uð1Þ0 charge assignment and the strength of FCNCs, flavor-violating processes may be more efficient to probe the Z0 model in comparison with the conventional dilepton or dijet production. Mixing between a meson and antimeson is very sensitive to Z0 interaction with FCNCs relevant to quarks Such FCNCs can contribute to the mixing at tree level or via box diagrams depending on underlying models describing interactions. In the case of top-Higgs FCNCs via t-q-H (q 1⁄4 u or c) couplings, Atwood et al [8] discussed three processes, pp → ttðttÞ, pp → tjðtjÞ, and pp → tjHðtjHÞ, where j denotes a jet, and found that the last process is the most capable of yielding the best upper bound on the top FCNCs. In this work, we consider top FCNCs, which are generated by a new gauge boson, Z0, heavier than the top quark.
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