The top quark chromomagnetic dipole moment in the SM from the 4-body vertex function

Abstract

A new proposal to compute the anomalous chromomagnetic dipole moment of the top quark, , in the Standard Model is presented. On the basis of the five-dimensional effective Lagrangian operator that characterizes the quantum-loop induced chromodipolar vertices and , the anomaly is derived via radiative correction at the 1-loop level from the non-Abelian 4-body vertex function . We evaluate as a function of the energy scale s = ±E 2, for E = [10, 1000] GeV, taking into account the running of the quark masses and alpha strong through the scheme. In particular, we find that at the typical energy scale E = m Z for high-energy physics, similarly to , and , the spacelike evaluation yields = −0.025 + 0.00384i and the timelike = −0.0318 − 0.0106i. This Re = −0.025 from is even closer to the experimental central value −0.024, than that coming from the known 3-body vertex function , −0.0224. Once again, the Im part is due to the contribution of virtual charged currents, just like in the case. We can infer that the spacelike prediction is the favored one.