Constraining the monochromatic gamma-rays from dark matter annihilation   by the LHC
  The installation of forward detectors in CMS and ATLAS turn the LHC to an effective photon-photon collider. The elastic scattering of the beam-protons via the emission of photons, which can be identified by tagging the intact protons in the forward detectors, provides a powerful diagnostic of the central production of new particles through photon-photon annihilation. In this letter we study the central production of dark matter particles and the potential of LHC to constrain the cross section of this process. By virtue of the crossing symmetry, this limit can immediately be used to constrain the production of monochromatic gamma-rays in dark matter annihilation, a smoking gun signal under investigation in indirect dark matter searches. We show that with the integrated luminosity $\mathcal{L}=30~{\rm fb}^{-1}$ in LHC at center-of-mass energy $\sqrt{s}=$ 13 TeV, for dark matter masses $\sim (50-600)$ GeV, a model-independent constraint on the cross section of dark matter annihilation to monochromatic gamma-rays at the same order of magnitude as the current Fermi-LAT and the future limits from CTA, can be obtained. 
Arman Esmaili, Sara Khatibi and Mojtaba Mohammadi Najafabadi
hep-ph astro-ph.HE hep-ex