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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2012). Search for a Supersymmetric Partner to the Top Quark in Final States with Jets and Missing Transverse Momentum at root s=7 TeV with the ATLAS Detector. Phys. Rev. Lett., 109(21), 211802–18pp.
Abstract: A search for direct pair production of supersymmetric top squarks ((t) over tilde (1)) is presented, assuming the (t) over tilde (1) decays into a top quark and the lightest supersymmetric particle, (chi) over tilde (0)(1), and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5(-3.6)(+3.7) (4.4(-1.3)(+1.7)) events in two signal regions based on integral Ldt = 4.7 fb(-1) of pp collision data taken at root s = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the (t) over tilde (1) versus (chi) over tilde (0)(1) mass plane is evaluated: 370 < m(<(t)over tilde>1) < 465 GeV is excluded for m(<(chi)over tilde>10) similar to 0 GeV while m((t) over tilde1) = 445 GeV is excluded for m((chi) over tilde 10) <= 50 GeV.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2012). Search for Direct Top Squark Pair Production in Final States with One Isolated Lepton, Jets, and Missing Transverse Momentum in root s=7 TeV pp Collisions Using 4.7 fb(-1) of ATLAS Data. Phys. Rev. Lett., 109(21), 211803–18pp.
Abstract: A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at root s = 7 TeV. The measurement is based on 4.7 fb(-1) of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2014). Observation of an Excited B-c(+/-) Meson State with the ATLAS Detector. Phys. Rev. Lett., 113(21), 212004–18pp.
Abstract: A search for excited states of the B-c(+/-) meson is performed using 4.9 fb(-1) of 7 TeV and 19.2 fb(-1) of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decayB(c)(+/-) -> J/psi pi(+/-). The state appears in the m(B-c(+/-)pi(+)pi(-)) – m(B-c(+/-)) – 2m(pi(+/-)) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842 +/- 4 +/- 5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the B-c(+/-) meson, B-c(+/-)(2S).
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for a Standard Model Higgs Boson in the H -> ZZ -> l(+)l(-)v(v)over-bar Decay Channel with the ATLAS Detector. Phys. Rev. Lett., 107(22), 221802–18pp.
Abstract: A search for a heavy standard model Higgs boson decaying via H -> ZZ -> l(+)l(-)v (v) over bar, where l = e, mu, is presented. It is based on proton-proton collision data at root s = 7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340 < m(H) < 450 GeV at the 95% confidence level.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Search for New Phenomena in Dijet Angular Distributions in Proton-Proton Collisions at root s=8 TeV Measured with the ATLAS Detector. Phys. Rev. Lett., 114(22), 221802–17pp.
Abstract: A search for new phenomena in LHC proton-proton collisions at a center-of-mass energy of root s = 8 TeV was performed with the ATLAS detector using an integrated luminosity of 17.3 fb(-1). The angular distributions are studied in events with at least two jets; the highest dijet mass observed is 5.5 TeV. All angular distributions are consistent with the predictions of the standard model. In a benchmark model of quark contact interactions, a compositeness scale below 8.1 TeV in a destructive interference scenario and 12.0 TeV in a constructive interference scenario is excluded at 95% C.L.; median expected limits are 8.9 TeV for the destructive interference scenario and 14.1 TeV for the constructive interference scenario.
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