This Letter presents the first search for a heavy particle decaying into an e(+/-)mu(-/+) final state in root s = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except lambda(311)' = 0.11 and lambda(312) = 0.07. In a lepton flavor violating model, a Z'-like vector boson with masses of 0.70-1.00 TeV and corresponding cross sections times branching ratios of 0.175-0.183 pb is excluded. These results extend to higher mass R-parity violating sneutrinos and lepton flavor violating Z's than previous constraints from the Tevatron. RI valente, paolo/A-6640-2010; Fazio, Salvatore /G-5156-2010; Castro, Nuno/D-5260-2011; Doyle, Anthony/C-5889-2009; Andreazza, Attilio/E-5642-2011; Jakubek, Jan/E-6530-2011; Smirnov, Sergei/F-1014-2011; Marti-Garcia, Salvador/F-3085-2011; Conde Muino, Patricia/F-7696-2011; Stoicea, Gabriel/B-6717-2011; Robson, Aidan/G-1087-2011; Kladiva, Eduard/G-6305-2011; Losada, Marta/B-2261-2010; Jones, Roger/H-5578-2011; Gutierrez, Phillip/C-1161-2011; Ferrando, James/A-9192-2012; collins-tooth, christopher/A-9201-2012; Perrino, Roberto/B-4633-2010; De Cecco, Sandro/B-1016-2012; branchini, paolo/A-4857-2011; Wolter, Marcin/A-7412-2012; McKee, Shawn/B-6435-2012; Rotaru, Marina/A-3097-2011; O'Shea, Val/G-1279-2010; Buttar, Craig/D-3706-2011; Takai, Helio/C-3301-2012; Britton, David/F-2602-2010; Pina, Joao /C-4391-2012; Li, Xuefei/C-3861-2012; Smirnova, Lidia/D-8089-2012; Gladilin, Leonid/B-5226-2011; Kramarenko, Victor/E-1781-2012; Prokoshin, Fedor/E-2795-2012; Alexa, Calin/F-6345-2010; Pacheco Pages, Andres/C-5353-2011; Moorhead, Gareth/B-6634-2009; Livan, Michele/D-7531-2012; Petrucci, Fabrizio/G-8348-2012; Wemans, Andre/A-6738-2012; Fabbri, Laura/H-3442-2012; Kurashige, Hisaya/H-4916-2012; Villa, Mauro/C-9883-2009; Kuzhir, Polina/H-8653-2012; Delmastro, Marco/I-5599-2012

Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector in root s=7 TeV pp collisions at the LHC