A search for an unexpected asymmetry in the production of e+mu- and e-mu+ pairs in proton-proton collisions recorded by the ATLAS detector at sqrt(s) = 13 TeV

This search, a type not previously performed at ATLAS, uses a comparison of the production cross sections for and pairs to constrain physics processes beyond the Standard Model. It uses of proton–proton collision data recorded at 13 TeV at the LHC. Targeting sources of new physics which prefer final states containing e+mu- to e-mu+, the search contains two broad signal regions which are used to provide model-independent constraints on the ratio of cross sections at the 2% level. The search also has two special selections targeting supersymmetric models and leptoquark signatures. Observations using one of these selections are able to exclude, at 95% confidence level, singly produced smuons with masses up to 640 GeV in a model in which the only other light sparticle is a neutralino when the R-parity-violating coupling is close to unity. Observations using the other selection exclude scalar leptoquarks with masses below 1880 GeV when , at 95% confidence level. The limit on the coupling reduces to for a mass of 1420 GeV.