A Model for Dark Moments of the W Boson

TL;DR

This paper explores how portal matter fields can induce dark moments for the W boson, leading to new interactions with a dark photon, but these effects are challenging to observe at the LHC due to background noise.

Contribution

It extends the concept of dark moments to the W boson using a scalar triplet and singlet portal matter, analyzing their production and detection prospects at the LHC.

Findings

W+dark photon production rate is very small and hard to detect.

Scalar portal matter production has larger, potentially observable signatures.

LHC constraints already limit properties of portal matter states.

Abstract

Loops of portal matter (PM) fields carrying both dark and Standard Model (SM) quantum numbers can lead to the kinetic mixing (KM) of the SM photon and the analogous dark photon (DP) of a phenomenologically interesting magnitude. However, in specific frameworks, different loops of these same PM fields can also lead to other new types of interactions between some of the SM fields and the DP via the generation of `dark moment'-like couplings, even though the SM fields carry a zero dark charge at tree-level. In recent work, this possibility has been explored for the case when these SM fields are fermionic. In this paper, we extend this idea to the case of the SM $W$ boson employing a previously examined model wherein PM consists of a complex scalar triplet plus a complex singlet, both of which obtain vevs and thus also generate the DP mass. While this setup results in a somewhat stronger interaction between the DP and the $W$ than in the familiar KM setup, the rate for $W+$DP production at the LHC is shown to still be rather small and is very difficult to observe due to large SM backgrounds. The direct production of the scalar PM itself, however, is shown to lead to similar new physics signatures but with much larger rates and are considered here in their own right. The properties of such new PM states may already be constrained by LHC searches in both the $W^\pm+$MET and $W^+W^-+$MET channels.