Search for dark matter using proton-proton collisions at 13 TeV at LHC, using events with a narrow jet and large missing transverse momentum.

Despite the success of the Standard Model, there are observations which point to its incompleteness and motivate improvements to our understanding of the world around us. Several astrophysical observations motivate new kind of matter as one of the possibilities to explain those phenomenon. In this presentation, we will look at a search for new physics using events containing an imbalance in transverse momentum and one or more energetic narrow jets with lower multiplicity(~2) of charged particles than typical QCD jets. A data sample of proton-proton collisions at $\sqrt{s}=13$ TeV, collected with the CMS detector at the LHC during 2016-2018 and corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$, is used. This is the first time this signal is being looked at in CMS/ATLAS, the mass of the hypothetical Z' being searched for is ~1 GeV. The results are interpreted in terms of dark matter production cross section in simplified models with vector and axial-vector mediators. Machine learning techniques are used to enhance signal sensitivity.