Direct production of SM-singlet scalars at the muon collider

The present work proposes a minimal extension of the Standard Model~(SM) where a gauge-singlet scalar~($\phi$) can be directly produced at the muon colliders without relying on its mixing with any other doublet state present in the theory. The New Physics~(NP) interactions include a TeV-scale scalar leptoquark of electromagnetic charge 1/3 arising naturally in a grand unifying gauge formulation. Within the proposed framework, the SM-singlet scalar can effectively couple to various SM fields at the one-loop level, out of which the $\bar{\mu}\mu\phi$ and $\gamma\gamma\phi$ couplings are crucial to produce it at the future muon colliders. Assuming $\mathcal{O}(1)$ NP couplings, the decay widths and production cross-section of the singlet scalar have been discussed in detail over the considered parameter space. Depending on the resonance scale, di-lepton and/or di-gluon channels can be significant to test/falsify the model.