ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2014). Search for Scalar Diphoton Resonances in the Mass Range 65-600 GeV with the ATLAS Detector in pp Collision Data at root s=8 TeV. Phys. Rev. Lett., 113(17), 171801–18pp.
Abstract: A search for scalar particles decaying via narrow resonances into two photons in the mass range 65-600 GeV is performed using 20.3 fb(-1) of root s = 8 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95% confidence level on the production cross section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches.
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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. (2014). Evidence for Electroweak Production of W(+/-) W(+/-) jj in pp Collisions at root s=8 TeV with the ATLAS Detector. Phys. Rev. Lett., 113(14), 141803–19pp.
Abstract: This Letter presents the first study of W(+/-)W(+/-)jj, same-electric-charge diboson production in association with two jets, using 20.3 fb(-1) of proton-proton collision data at root s = 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two reconstructed same-charge leptons (e(+/-)e(+/-), e(+/-)mu(+/-), and mu(+/-)mu(+/-)) and two or more jets are analyzed. Production cross sections are measured in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. First evidence for W(+/-)W(+/-)jj production and electroweak-only W(+/-)W(+/-)jj production is observed with a significance of 4.5 and 3.6 standard deviations, respectively. The measured production cross sections are in agreement with standard model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings.
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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. (2015). Measurements of the Nuclear Modification Factor for Jets in Pb plus Pb Collisions at root SNN=2.76 TeV with the ATLAS Detector. Phys. Rev. Lett., 114(7), 072302–18pp.
Abstract: Measurements of inclusive jet production are performed in pp and Pb + Pb collisions at root SNN = 2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb(-1), respectively. The jets are identified with the anti-k(t) algorithm with R = 0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32 < pT < 500 GeV and absolute rapidity |y| < 2.1 and as a function of collision centrality. The nuclear modification factor R-AA is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The RAA shows a slight increase with pT and no significant variation with rapidity.
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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. (2015). Search for Higgs Boson Pair Production in the gamma gamma b(b)over-bar Final State Using pp Collision Data at root s=8 TeV from the ATLAS Detector. Phys. Rev. Lett., 114(8), 081802–19pp.
Abstract: Searches are performed for resonant and nonresonant Higgs boson pair production in the gamma gamma b (b) over bar final state using 20 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X -> hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.
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ATLAS and CMS Collaborations(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Combined Measurement of the Higgs Boson Mass in pp Collisions at root s=7 and 8 TeV with the ATLAS and CMS Experiments. Phys. Rev. Lett., 114(19), 191803–33pp.
Abstract: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H --> gamma gamma and H --> ZZ --> 4l decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is m(H) = 125.09 +/- 0.21 (stat) +/- 0.11 (syst) GeV.
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