Anomalous couplings in the standard model and beyond at the LHC
Benemérita Universidad Autónoma de Puebla
"This work is divided in four parts. In chapter one a new estimate of the one loop contributions of the standard model to the chromomagnetic dipole moment (CMDM) ˆµq (q 2 ) of quarks is presented with the aim to address a few disagreements arising in previous calculations. The most general case with arbitrary q 2 is considered and analytical results are obtained in terms of Feynman parameter integrals and Passarino-Veltman scalar functions, which are then expressed in terms of closed form functions when possible. It is found that while the QCD contribution to the static CMDM (q 2 = 0) is infrared divergent, which agrees with previous evaluations and stems from the fact that this quantity has no sense in perturbative QCD, the off-shell CMDM (q 2 6= 0) is finite and gauge independent, which is verified by performing the calculation for arbitrary gauge parameter ξ via both a renormalizable linear Rξ gauge and the background field method. It is thus argued that the off-shell ˆµq (q 2 ) can represent a valid observable quantity".