750 GeV Diphoton Excess as a Composite (Pseudo)scalar Boson from New Strong Interaction

P. Ko, Chaehyun Yu, Tzu-Chiang Yuan

Published 2016-03-29Version 1

The diphoton excess at 750 GeV would make a definite signal of new physics beyond the Standard Model, if it is confirmed. In this letter, we consider a possibility that the excess is due to a composite (pseudo)scalar boson, whose constituents are either new vector-like quarks (Q\overline{Q}) or scalar quarks (\widetilde{Q} \widetilde{Q}^\dagger) which feel new QCD-like vectorlike confining force with confinement scale Lambda_h. Assuming m_Q (m_{\widetilde Q}) >> Lambda_h, the observed 750 GeV excess could be either Q\overline{Q} (^1S_0) state with J^{PC} = 0^{-+} or \widetilde{Q} \widetilde{Q}^\dagger (^1S_0) state with J^{PC}=0^{++}. For the Q\bar{Q} scenario, there will be a spin-triplet partner psi_Q which is slightly heavier that eta_Q because of the hyper fine interactions mediated by h-gluon exchange. We consider productions and decays of eta_Q, eta_{\widetilde Q} and psi_Q using the nonrelativistic QCD methods, and identify the parameter regions which can explain the observed diphoton excess. We discuss how to test these scenarios using the Drell-Yan process for psi_Q case, and the dijet azimuthal angular distributions to determine the J^{PC} quantum number of the diphoton excess.