No like-sign tops at Tevatron: Constraints on extended models and implications for the tt asymmetry
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Top quarkStandard modelHadronic colliders
Aguilar-Saavedra, J.A.; Pérez-Victoria, M. No like-sign tops at Tevatron: Constraints on extended models and implications for the tt asymmetry. Physics Letters B, 701(1): 93-100 (2011). [http://hdl.handle.net/10481/30545]
PatrocinadorThis work has been partially supported by projects FPA2010-17915 (MICINN), FQM 101 and FQM 437 (Junta de Andalucía) and CERN/FP/116397/2010 (FCT).
We use a recent upper limit from CDF on like-sign top pair production to place constraints on general new vector bosons and scalars mediating u u -> t t. The possible vector bosons comprise neutral colour singlets or octets, and charge 4/3 colour triplets or sextets, whereas the new scalars can be neutral colour singlets or octets and charge 4/3 colour sextets. We also estimate the expected bounds from like-sign top pair production at LHC in the near future. Then, we address the implications of these limits for the forward-backward asymmetry in t tbar production measured at Tevatron. In particular, we find that models explaining the observed asymmetry by the exchange of a single t-channel heavy Z' boson are already excluded. On the other hand, light Z' bosons with a mass M_Z' ~ 150 GeV, which could also account for a recent CDF dijet excess in W+jet production, are barely allowed.