A Loop-philic Pseudoscalar

TL;DR

This paper proposes a renormalizable model where a pseudoscalar explains the 750 GeV diphoton excess, predicts new exotic quarks, and offers a dark matter candidate, with all decays loop-induced for enhanced predictability.

Contribution

It introduces a novel weakly-coupled model with a pseudoscalar from a complex singlet, explaining the diphoton excess and predicting new exotic quarks and dark matter.

Findings

Loop-induced decays enhance diphoton rate.

Model predicts two nearly degenerate exotic quarks.

Rich collider and dark matter phenomenology expected.

Abstract

We construct a weakly-coupled renormalizable model to explain the $750\mbox{GeV}$ diphoton excess. The $750\mbox{GeV}$ resonance (denoted as $X(750)$) is interpreted as a pseudoscalar coming from a complex singlet. The model also naturally provides a dark matter candidate. One most attractive feature of the model is that decays of $X(750)$ are all loop-induced so the diphoton rate is not diluted by unwanted tree level branching fractions. Relevant Yukawa interactions need not to be tuned to near non-perturbative region to explain the rate. The model is highly predictive, including the pseudoscalar nature of $X(750)$, and two nearly mass-degenerate exotic quarks carrying electric charge $5/3$ and $2/3$, respectively. Rich phenomenology is expected with respect to collider searches, flavor physics and dark matter detection, if $X(750)$ can be pinned down by future LHC experiments.