Electric dipole moments from colour-octet scalars

Abstract

We present the contributions to electric dipole moments (EDMs) induced by the Yukawa couplings of an additional electroweak doublet of colour-octet scalars. The full set of one-loop diagrams and the enhanced higher-order effects from Barr-Zee diagrams are computed for the quark (chromo-)EDM, along with the two-loop contributions to the Weinberg operator. Using the stringent experimental upper limits on the neutron EDM, constraints on the parameter space of the Manohar-Wise model are derived.

W-boson mass and electric dipole moments from colour-octet scalars

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New coloured scalars in the Manohar-Wise model give sizeable contributions to the Electric Dipole Moment (EDM) of the neutron through one-loop and two-loop diagrams, computed in Reference [1]. Contributions from neutral scalars cancel out for degenerate values of the masses, whose difference is related to the oblique parameters S and T .

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“…Figure 1: Barr-Zee type diagrams contributing to the quark EDM and chromo-EDM; and leading contributions to the Weinberg operator in the MW model [1].…”

“…It is interesting to compare the size of one-and two-loop contributions across the quark flavours. If the Yukawa couplings of the new scalars are proportional to the quark masses, the light-quark EDMs are typically dominated by two-loop Barr-Zee contributions, which are enhanced by the top-quark mass [1]. With the same argument, the EDM of heavy quarks should be dominated by one-loop contributions.…”