A search for $B-L$ $R$-Parity violating scalar top decays in $\sqrt{s} = 8$ TeV $pp$ collisions with the ATLAS experiment

A search is presented for direct scalar top pair production where the scalar tops decay via an $R$-parity-violating coupling to a final state with two leptons and two identified $b$-jets. The analysis uses $20.3~\mathrm{fb}^{-1}$ of $\sqrt{s} = 8~\mathrm{TeV}$ proton-proton collision data collected with the ATLAS detector at the LHC. No significant excess is observed over the Standard Model background. Assuming a supersymmetric minimal $B-L$ extension to the Standard Model, limits on the scalar top mass are placed between $500~\mathrm{GeV}$ and $1~\mathrm{TeV}$ with a branching fraction above 20% for the scalar top to decay to an electron or a muon and a $b$-quark.