Search for millicharged particles in proton-proton collisions at $\sqrt{s}=13.6$ TeV

We report on a search for elementary particles with charges much smaller than the electron charge using a data sample of proton-proton collisions provided by the CERN Large Hadron Collider in 2023–24, corresponding to an integrated luminosity of 124.7~fb${}^{-1}$ at a center-of-mass energy of 13.6~TeV. The analysis presented uses the completed Run 3 milliQan bar detector to set the most stringent constraints to date for particles with charges $\le 0.24\mathrm{e}$ and masses $\ge 0.45\mathrm{G}\mathrm{e}\mathrm{V}$.