Search for anomalous production of events with same-sign dileptons and $b$ jets in 14.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

A search is presented for exotic processes that result in final states containing jets including at least one $b$ jet, sizable missing transverse momentum, and a pair of leptons with the same electric charge. There are several models that predict an enhanced rate of production of such events beyond the expectations of the Standard Model (SM); the ones considered in this note are pair production of chiral $b^\prime$ quarks, pair production of vector-like quarks, enhanced four top quark production and production of two positively-charged top quarks. Using a sample of 14.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =8$ TeV recorded by the ATLAS detector at the Large Hadron Collider, with selection criteria optimised for each signal, no significant excess of events over the background expectation is observed. This observation is interpreted as constraining the signal hypotheses, and it is found at 95% confidence level that: the mass of the $b^\prime$, assuming 100% branching fraction to $Wt$, must be $> 0.72$ TeV; the mass of a vector-like $B$ ($T$) quark, assuming branching ratios to $W$, $Z$, and $H$ decay modes consistent with the $B$ or $T$ being a singlet, must be $>$ 0.59 (0.54) TeV; the four top production cross section must be $< 85$ fb in the SM and $< 59$ fb for production via a contact interaction; the mass of an sgluon must be $> 0.80$ TeV; in the context of models with two universal extra dimensions the inverse size of the extra dimensions must be $>0.90$ TeV; and the cross section for production of two positively-charged top quarks must be $< 210$ fb.