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title: 'Search for direct pair production of supersymmetric partners to the lepton in proton-proton collisions at $\sqrt{s}=13\TeV$'
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Introduction {#sec:intro}
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Supersymmetry (SUSY) [@Ramond:1971gb; @Golfand:1971iw; @Neveu:1971rx; @Volkov:1972jx; @Wess:1973kz; @Wess:1974tw; @Fayet:1974pd; @Nilles:1983ge] is a possible extension of the standard model (SM) of particle physics, characterized by the presence of superpartners for SM particles. The superpartners have the same quantum numbers as their SM counterparts, except for the spin, which differs by half a unit. One appealing feature of SUSY is that the cancellation of quadratic divergences in quantum corrections to the Higgs boson mass from SM particles and their superpartners could resolve the fine tuning problem [@Gildener:1976ai; @Veltman:1976rt; @'tHooft:1979bh; @Witten:1981nf]. Another feature is that the lightest supersymmetric particle (LSP) is stable in SUSY models with $R$-parity conservation [@Farrar:1978xj], and could be a dark matter (DM) candidate [@Goldberg:1983nd; @Ellis:1983ew; @darkmatter].

The hypothetical superpartner of the lepton, the slepton (), is the focus of the search reported in this paper. Supersymmetric models where a light is the next-to-lightest supersymmetric particle are well motivated in early universe -neutralino coannihilation models that can accommodate the observed DM relic density [@WMAP; @Griest:1990kh; @Vasquez; @King; @Battaglia:2001zp; @Arnowitt:2008bz]. The existence of a 