A search for R-parity violating decays of the top squark in four-jet final state with the ATLAS experiment at $\sqrt{s} = 13$~TeV

We present a search for direct production of pairs of top squarks, each decaying into a $b$- and an $s$-quark through R-parity violating couplings. The analysis uses $3.2$ fb$^{-1}$ of proton-proton collision data recorded at $\sqrt{s} = 13$~TeV by the ATLAS experiment at the LHC in 2015. Four jets, two of which are $b$-tagged, are selected and paired according to their angular separation. Signal regions are defined by imposing requirements on the masses of the two resonance candidates and their angular distribution. The average mass of the resonances is then used as the final discriminant. No significant excess is observed above the background prediction and a 95\% confidence level lower limit on the mass of the top squark in the model considered is derived to be 345~GeV.