الفهرس 
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Abstract
This thesis describes a monophoton studies for searching the Dark matter, where the final
state of a photon (γ) and missing transverse energy (ET ) are used to test the Standard
Model. We exploit the production of 𝑍(𝜈𝜈)𝛾 because it is a precise process and sensitive
for new physics events. At the same time, this constitutes an irreducible background for
new physics searches with the same final state. The standard model 𝑍(𝜈𝜈)𝛾 cross section
is measured as a function of the transverse momentum of photon. This dissertation
discusses a measurement of associated Zγ production, where Z decays into neutrinos.
Thesis data were collected with the CMS detector at LHC run at CERN, Geneva,
Switzerland during the 2017 and 2018, and correspond to an integrated luminosity of
41.53 fb−1 and 59.97 fb−1 of proton-proton collisions at a center of mass energy of √𝑠 =
13 TeV.