Production of dark matter in association with a Higgs boson via exclusive photon fusion in $pp$ collisions at $\sqrt{s}=13$ TeV

In this work we study the production of a dark matter (DM) particle in association with a Higgs boson via a central exclusive photon-fusion initiated process. We explore this type of production through the Inert Doublet Model plus a complex Singlet (IDMS), where an extension of the Standard Model by an additional $U(1)_X$ gauge symmetry and a $SU(2)$ inert scalar doublet gives rise to a DM candidate $χ$. This particular process involves the collision of two protons exchanging two colorless particles (in our case, photons), from which a central process occurs. Such interaction can be detected in the LHC using forward proton detectors, where the resulting missing mass spectrum can be observed after proton reconstruction, thus allowing a search for physics Beyond the Standard Model (BSM). We present results for different values of the difference of masses of a heavy scalar coming from the complex singlet, the DM candidate and the Higgs boson, $Δ= M_S - M_χ- M_h$, which is the phase space available for the final state in the central exclusive process.