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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. (2012). Search for the Standard Model Higgs boson in the H -> WW(*()) -> lvlv decay mode with 4.7 fb(-1) of ATLAS data at root s=7 TeV. Phys. Lett. B, 716(1), 62–81.
Abstract: A search for the Standard Model Higgs boson in the H -> WW(*()) -> lvlv (l = e.mu) decay mode is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb(-1) at a centre-of-mass energy of 7 TeV collected during 2011 with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed. An upper bound is placed on the Higgs boson production cross section as a function of its mass. A Standard Model Higgs boson with mass in the range between 133 GeV and 261 GeV is excluded at 95% confidence level, while the expected exclusion range is from 127 GeV to 233 GeV. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> 4l with 4.8 fb(-1) of pp collision data at root s=7 TeV with ATLAS. Phys. Lett. B, 710(3), 383–402.
Abstract: This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125 GeV, 244 GeV and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2011). Search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) -> 4l with the ATLAS detector. Phys. Lett. B, 705(5), 435–451.
Abstract: A search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) l(+)l(-)l'l'(-), where l = e, mu, is presented. Proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector and corresponding to an average integrated luminosity of 2.1 fb(-1) are compared to the Standard Model expectations. Upper limits on the production cross section of a Standard Model Higgs boson with a mass between 110 and 600 GeV are derived. The observed (expected) 95% confidence level upper limit on the production cross section for a Higgs boson with a mass of 194 GeV, the region with the best expected sensitivity for this search, is 0.99 (1.01) times the Standard Model prediction. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges 191-197, 199-200 and 214-224 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). Search for the Standard Model Higgs boson decay to mu(+)mu(-) with the ATLAS detector. Phys. Lett. B, 738, 68–86.
Abstract: A search is reported for Higgs boson decay to mu(+)mu(-) using data with an integrated luminosity of 24.8 fb(-1) collected with the ATLAS detector in pp collisions at root s = 7 and 8 TeV at the CERN Large Hadron Collider. The observed dimuon invariant mass distribution is consistent with the Standard Model background-only hypothesis in the 120-150 GeV search range. For a Higgs boson with a mass of 125.5 GeV, the observed (expected) upper limit at the 95% confidence level is 7.0 (7.2) times the Standard Model expectation. This corresponds to an upper limit on the branching ratio BR(H -> mu(+)mu(-)) of 1.5 x10(-3).
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Xie, J. J., & Oset, E. (2019). Search for the Sigma* state in Lambda(+)(c) -> pi(+)pi(0)pi(-)Sigma(+) decay by triangle singularity. Phys. Lett. B, 792, 450–453.
Abstract: A Sigma* resonance with spin-parity J(P) = 1/2(-) and mass in the vicinity of the (K) over barN threshold has been predicted in the unitary chiral approach and inferred from the analysis of CLAS data on the gamma p -> K+pi(0)Sigma(0) reaction. In this work, based on the dominant Cabibbo favored weak decay mechanism, we perform a study of Lambda(+)(c) -> pi(+)pi(0)Sigma* with the possible Sigma* state decaying into pi(-)Sigma(+) through a triangle diagram. This process is initiated by Lambda(+)(c) -> pi(+)(K) over bar *N, then the (K) over bar* decays into (K) over bar pi and (K) over barN produce the Sigma* through a triangle loop containing (K) over bar *N (K) over bar which develops a triangle singularity. We show that the pi(-)Sigma(+) state is generated from final state interaction of (K) over barN in S-wave and isospin I = 1, and the Lambda(+)(c) -> pi(+)pi(0)pi(-)Sigma(+) decay can be used to study the possible Sigma* state around the (K) over barN threshold. The proposed decay mechanism can provide valuable information on the nature of the Sigma* resonance and can in principle be tested by facilities such as LHCb, BelleII and BESIII.
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