María Moreno Llácer

Measurement of the Lambda_b lifetime and mass in the ATLAS experiment

Aad, G.; et al., [Unknown]; Aben, R.; Beemster, L.J.; Bentvelsen, S.; Berglund, E.; Bobbink, G.J.; Bos, K.; Boterenbrood, H.; Colijn, A.P.; de Jong, P.; de Nooij, L.; Deluca, C.; Deviveiros, P.O.; Doxiadis, A.D.; Ferrari, P.; Garitaonandia, H.; Geerts, D.A.A.; Gosselink, M.; Hartjes, F.; Hessey, N.P.; Igonkina, O.; Kayl, M.S.; Klous, S.; Kluit, P.; Koffeman, E.; Lee, H.; Lenz, T.; Linde, F.; Luijckx, G.; Massaro, G.; Mechnich, J.; Mussche, I.; Ottersbach, J.P.; Pani, P.; Rijpstra, M.; Ruckstuhl, N.; Ta, D.; Tsiakiris, M.; Turlay, E.; van der Deijl, P.C.; van der Geer, R.; van der Graaf, H.; van der Leeuw, R.; van der Poel, E.; van Vulpen, I.; Verkerke, W.; Vermeulen, J.C.; Vranjes Milosavljevic, M.; Vreeswijk, M.A measurement of the Λb lifetime and mass in the decay channel Λ 0 b → J/ψ(μ+μ−)Λ0(pπ−) is presented. The analysis uses a signal sample of about 2200 Λb and Λ̄ 0 b decays that are reconstructed in 4.9 fb −1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Λb lifetime and mass. They are measured to be τΛb = 1.449± 0.036(stat)± 0.017(syst) ps and mΛb = 5619.7± 0.7(stat)± 1.1(syst) MeV. ar X iv :1 20 7. 22 84 v3 [ he pex ] 2 0 A pr 2 01 3 Measurement of the Λ0b lifetime and mass in the ATLAS experiment The ATLAS Collaboration (Dated: May 2, 2014) A measurement of the Λb lifetime and mass in the decay channel Λ 0 b → J/ψ(μ+μ−)Λ0(pπ−) is presented. The analysis uses a signal sample of about 2200 Λb and Λ̄ 0 b decays that are reconstructed in 4.9 fb−1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Λb lifetime and mass. They are measured to be τΛb = 1.449± 0.036(stat)± 0.017(syst) ps and mΛb = 5619.7± 0.7(stat)± 1.1(syst) MeV.

Muon performance and related ATLAS first physics

Muon final states provide clean signatures for many physics processes at the LHC. Therefore, an excellent identification of muons and momentum resolution in a very wide energy range is required. The performance of the ATLAS muon reconstruction and identification is here studied with the cosmic rays data recorded during the commissioning period and the first LHC proton-proton collision data at = 7 TeV. Measured resolutions, efficiencies, muon isolation and residual distributions of reconstructed muon tracks are well reproduced by the Monte-Carlo simulation. In addition, the first observation in the ATLAS experiment of W and Z bosons in the muon channel at = 7 TeV collisions is described. The selection yields to 40 W ? ?? and 2 Z ? ?? candidates in a total integrated luminosity of approximately of 6.4 nb?1 and 7.9 nb?1 respectively, in agreement with Monte-Carlo expectations.Muon final states provide clean signatures for many physics processes at the LHC. Therefore, an excellent identification of muons and momentum resolution in a very wide energy range is required. The performance of the ATLAS muon reconstruction and identification is here studied with the cosmic rays data recorded during the commissioning period and the first LHC proton-proton collision data at = 7 TeV. Measured resolutions, efficiencies, muon isolation and residual distributions of reconstructed muon tracks are well reproduced by the Monte-Carlo simulation. In addition, the first observation in the ATLAS experiment of W and Z bosons in the muon channel at = 7 TeV collisions is described. The selection yields to 40 W → μν and 2 Z → μμ candidates in a total integrated luminosity of approximately of 6.4 nb−1 and 7.9 nb−1 respectively, in agreement with Monte-Carlo expectations.