Constraints on Anomalous $\mu^+\mu^+$ and Like-sign Top Quark Pair Production

A previous search for like-sign dimuon production based on 1.6 fb$^{-1}$ of integrated luminosity is slightly extended to separately analyze specifically $\mu^+\mu^+$ production with the goal of constraining like-sign top quark production. Muon pairs are selected by requiring two isolated, positively charged muons in the ATLAS detector, with transverse momenta greater than 20 (10) GeV for the leading (subleading) muon. The data are interpreted in terms of an upper limit on anomalous production of $\mu^+\mu^+$ pairs within a kinematic range matching the experimental selection cuts, observed to be 8.7 fb for $m(\mu^+\mu^+)$ > 200 GeV at 95% confidence level. In addition, the data are used to constrain pair production of top quarks with the same electric charge via a flavor-changing $Z'$ boson. The resulting cross-section limits range between 2.9 and 4.1 pb depending on the $Z'$ mass.