Light Color Scalars from Low Energy to Proton Decay
Starts 26 Jun 2012 17:30
Ends 26 Jun 2012 20:00
Central European Time
Leonardo da Vinci Building Luigi Stasi Seminar Room
Strada Costiera, 11
I - 34151 Trieste (Italy)
Abstract. A colored weak singlet scalar state with hypercharge 4/3 is one of the possible candidates for the explanation of the unexpectedly large forward-backward asymmetry in t tbar production as measured by the CDF and D0 experiments. We investigate the role of this state in a plethora of flavor changing neutral current processes and precision observables of down-quarks and charged leptons. Our analysis includes tree- and loop-level mediated observables in the K and B systems, the charged lepton sector, as well as the Z to b bbar decay width. We perform a global fit of the relevant scalar couplings. This approach can explain the (g-2)_mu anomaly while tensions among the CP violating observables in the quark sector, most notably the nonstandard CP phase (and width difference) in the Bs system cannot be fully relaxed. The results are interpreted in a class of grand unified models which allow for a light colored scalar with a mass below 1TeV. We identify contributions of this leptoquark to dimension-six operators, mediated through a box diagram, and tree-level dimension-nine operators, that would destabilize proton if sizable leptoquark and diquark couplings were to be simultaneously present.