Search for fractionally charged particles in $\text{pp}$ collisions at $\sqrt{s}=13\,\text{TeV}$

Every known charged particle has an electric charge that is a multiple of $1/3\,e$. In the absence of a mechanism to explain this quantization, particles with other charges may exist as well. In particular, only weak constraints have been set on the existence of free-propagating particles with charge below $1\,e$ and mass accessible at the LHC. A search is presented for fractionally charged particles using energy loss in the tracking detector as a key variable to suppress backgrounds. Using a data set corresponding to an integrated luminosity of $138\,\text{fb}^{-1}$ of proton-proton collisions collected at a center-of-mass energy of $13\,\text{TeV}$ by the CMS experiment, masses up to $636\,\text{GeV}$ and charges as low as $1/2\,e$ are excluded at $95\%$ confidence level.