A Loop-philic Pseudoscalar

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.