Understanding diboson anomalies

TL;DR

This paper analyzes hypercharged fields of various spins to understand the LHC diboson excess, identifying viable candidates and constraints within a model-independent effective theory framework.

Contribution

It provides a model-independent analysis of hypercharged fields, identifying which spins can explain the diboson anomaly and deriving bounds on associated new particles.

Findings

Hypercharged scalar and spin 2 cannot explain the anomaly at tree level.

Hypercharged vector can explain the anomaly if a Z' is introduced.

Bounds on Z' mass are consistent with LHC and electroweak data.

Abstract

We conduct a model-independent effective theory analysis of hypercharged fields with various spin structures towards understanding the diboson excess found in LHC run I, as well as possible future anomalies involving $WZ$ and $WH$ modes. Within the assumption of no additional physics beyond the standard model up to the scale of the possible diboson resonance, we show that a hypercharged scalar and a spin 2 particle do not have tree-level $WZ$ and $WH$ decay channels up to dimension 5 operators, and cannot therefore account for the anomaly, whereas a hypercharged vector is a viable candidate provided we also introduce a $Z'$ in order to satisfy electroweak precision constraints. We calculate bounds on the $Z'$ mass consistent with the Atlas/CMS diboson signals as well as electroweak precision data, taking into account both LHC run I and II data.