ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Study of the rare decays of B0 and B-0 mesons into muon pairs using data collected during 2015 and 2016 with the ATLAS detector. J. High Energy Phys., 04(4), 098–47pp.
Abstract: A study of the decays B0 s ! + and B0 ! + has been performed using 26 : 3 fb of 13 TeV LHC proton-proton collision data collected with the ATLAS detector in 2015 and 2016. Since the detector resolution in + invariant mass is comparable to the B0 s -B0 mass di ff erence, a single fi t determines the signal yields for both decay modes. This results in a measurement of the branching fraction B (B0 s ! +) = 3 : 2 +1:1 10 and an upper limit B (B0 ! +) < 4 : 3 10 at 95% con fi dence level. The result is combined with the Run 1 ATLAS result, yielding B (B0 s ! +) = 2 : 8 +0:8 10 and B (B0 ! +) < 2 : 1 10 at 95% con fi dence level. The combined result is consistent with the Standard Model prediction within 2.4 standard deviations in the B (B0 ! +)B (B0 s ! +) plane.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of the ZZ production cross section in proton-proton collisions at root s=8 TeV using the ZZ -> l(-) l(+) l '(-) l '(+) and ZZ -> l(-) l(+) nu(nu)over-bar decay channels with the ATLAS detector. J. High Energy Phys., 01(1), 099–53pp.
Abstract: A measurement of the ZZ production cross section in the l(-)l(+)l'(-)l'(+) and l(-)l(+) nu(nu) over bar channels (l = e, mu) in proton-proton collisions at root s = 8TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb(-1) collected by the ATLAS experiment in 2012 is presented. The fi ducial cross sections for ZZ -> l(-)l(+)l'(-)l'(+) and ZZ -> l(-)l(+) nu(nu) over bar are measured in selected phase-space regions. The total cross section for ZZ events produced with both Z bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be 7.3 +/- 0.4 (stat) +/- 0.3 (syst) (-0.2)(-0.1) (lumi) pb, which is consistent with the Standard Model prediction of 6.6(-0.6)(+0.7) pb. The di ff erential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading Z boson is used to set limits on anomalous neutral triple gauge boson couplings in ZZ production.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2018). Search for new phenomena in high-mass final states with a photon and a jet from pp collisions at root s=13 TeV with the ATLAS detector. Eur. Phys. J. C, 78(2), 102–25pp.
Abstract: A search is performed for new phenomena in events having a photon with high transverse momentum and a jet collected in 36.7 fb(-1) of proton-proton collisions at a centre-of-mass energy of root s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The invariant mass distribution of the leading photon and jet is examined to look for the resonant production of new particles or the presence of new high-mass states beyond the Standard Model. No significant deviation from the background-only hypothesis is observed and cross-section limits for generic Gaussian-shaped resonances are extracted. Excited quarks hypothesized in quark compositeness models and high-mass states predicted in quantum black hole models with extra dimensions are also examined in the analysis. The observed data exclude, at 95% confidence level, the mass range below 5.3 TeV for excited quarks and 7.1 TeV (4.4 TeV) for quantum black holes in the Arkani-Hamed-Dimopoulos-Dvali (Randall-Sundrum) model with six (one) extra dimensions.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for new phenomena in high-mass diphoton final states using 37 fb(-1) of proton-proton collisions collected at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 775, 105–125.
Abstract: Searches for new phenomena in high-mass diphoton final states with the ATLAS experiment at the LHC are presented. The analysis is based on pp collision data corresponding to an integrated luminosity of 36.7 fb(-1) at a centre-of-mass energy root s = 13 TeV recorded in 2015 and 2016. Searches are performed for resonances with spin 0, as predicted by theories with an extended Higgs sector, and for resonances with spin 2, using a warped extra-dimension model as a benchmark model, as well as for non-resonant signals, assuming a large extra-dimension scenario. No significant deviation from the Standard Model is observed. Upper limits are placed on the production cross section times branching ratio to two photons as a function of the resonance mass. In addition, lower limits are set on the ultraviolet cutoff scale in the large extra-dimensions model.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Studies of Z gamma production in association with a high-mass dijet system in pp collisions at root s=8 TeV with the ATLAS detector. J. High Energy Phys., 07(7), 107–47pp.
Abstract: The production of a Z boson and a photon in association with a high-mass dijet system is studied using 20.2 fb(-1) of proton-proton collision data at a centre-of-mass energy of root s = 8TeV recorded with the ATLAS detector in 2012 at the Large Hadron Collider. Final states with a photon and a Z boson decaying into a pair of either electrons, muons, or neutrinos are analysed. Electroweak and total pp -> Z gamma jj cross-sections are extracted in two fiducial regions with different sensitivities to electroweak production processes. Quartic couplings of vector bosons are studied in regions of phase space with an enhanced contribution from pure electroweak production, sensitive to vector-boson scattering processes VV -> Z gamma. No deviations from Standard Model predictions are observed and constraints are placed on anomalous couplings parameterized by higher-dimensional operators using effective field theory.
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