LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurement of CP asymmetries in D-+/- -> eta 'pi(+/-) and D-S(+/-) -> eta 'pi(+/-) decays. Phys. Lett. B, 771, 21–30.
Abstract: A search for CP violation in D-+/- -> eta 'pi(+/-) and D-S(+/-) -> eta 'pi(+/-) decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 3 fb(-1), recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The measured CP-violating charge asymmetries are A(CP)(D-+/- -> eta 'pi(+/-)) = (-0.61 +/- 0.72 +/- 0.53 +/- 0.12)% and A(CP)(D-S(+/-) -> eta 'pi(+/-)) = (-0.82 +/- 0.36 +/- 0.22 +/- 0.27)%, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the A(CP)(D-+/- -> K-S(0)pi(+/-)) and A(CP)(D-S(+/-) -> phi pi(+/-)) measurements used for calibration. The results represent the most precise measurements of these asymmetries to date.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Search for CP violation in Lambda(0)(b)-> pK(- )and Lambda(0)(b) -> p pi(-) decays. Phys. Lett. B, 787, 124–133.
Abstract: A search for CP violation in Lambda(0)(b)-> pK(- )and Lambda(0)(b) -> p pi(-) decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0fb(-1). The CP-violating asymmetries are measured to be A(CP)(pK- )( = -0.020 +/- 0.013 +/- 0.019 and A(CP)(p pi-) = -0.035 +/- 0.017 +/- 0.020, and their difference A(CP)(pK-) – A(CP)(p pi-) = 0.014 +/- 0.022 +/- 0.010, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.
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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 dark matter in association with a Higgs boson decaying to b-quarks in pp collisions at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 765, 11–31.
Abstract: A search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks is presented, using 3.2 fb(-1) of pp collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum b (b) over bar system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected backgrounds. Results are interpreted using a simplified model with a gauge boson mediating the interaction between dark matter and the Standard Model as well as a two-Higgs-doublet model containing an additional Z' boson which decays to a Standard Model Higgs boson and a new pseudoscalar Higgs boson, the latter decaying into a pair of dark matter particles.
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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). Search for Higgs boson decays into a pair of light bosons in the bb μμfinal state in pp collision at root s=13 TeV with the ATLAS detector. Phys. Lett. B, 790, 1–21.
Abstract: A search for decays of the Higgs boson into a pair of new spin-zero particles, H -> aa, where the a-bosons decay into a b-quark pair and a muon pair, is presented. The search uses 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95% confidence level are placed on the branching ratio (sigma(H)/sigma(SM)) x B(H -> aa -> bb μmu), ranging from 1.2 x 10(-4) to 8.4 x 10(-4) in the a-boson mass range of 20-60 GeV. Model-independent limits are set on the visible production cross-section times the branching ratio to the bb μμfinal state for new physics, sigma(vis)(X) x B(X -> bb μmu), ranging from 0.1 fb to 0.73 fb for m(mu mu) between 18 and 62 GeV.
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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 diphoton events with large missing transverse momentum in 1 fb(-1) of 7 TeV proton-proton collision data with the ATLAS detector ATLAS Collaboration. Phys. Lett. B, 710(4-5), 519–537.
Abstract: A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics. The limits depend on each model parameter space and vary as follows: sigma < (22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, sigma < (27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8), and sigma < (15-27) fb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 805 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass. Lower limits of 145 TeV and 1.23 TeV are set on the SPS8 breaking scale Lambda and on the UED compactification scale 1/R, respectively. These limits provide the most stringent tests of these models to date.
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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 diphoton events with large missing transverse momentum in 7 TeV proton-proton collision data with the ATLAS detector. Phys. Lett. B, 718(2), 411–430.
Abstract: A search for diphoton events with large missing transverse momentum has been performed using proton-proton collision data at is root s = 7 TeV recorded with the ATLAS detector, corresponding to an integrated luminosity of 4.8 fb(-1). No excess of events was observed above the Standard Model prediction and model-dependent 95% confidence level exclusion limits are set. In the context of a generalised model of gauge-mediated supersymmetry breaking with a bino-like lightest neutralino of mass above 50 GeV, gluinos (squarks) below 1.07 TeV (0.87 TeV) are excluded, while a breaking scale Lambda below 196 TeV is excluded for a minimal model of gauge-mediated supersymmetry breaking. For a specific model with one universal extra dimension, compactification scales 1/R < 1.40 TeV are excluded. These limits provide the most stringent tests of these models to date.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for direct CP violation in D-0 -> h(-)h(+) modes using semileptonic B decays. Phys. Lett. B, 723(1-3), 33–43.
Abstract: A search for direct CP violation in D-0 -> h(-)h(+) (where h = K or pi) is presented using data corresponding to an integrated luminosity of 1.0 fb(-1) collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. The analysis uses D-0 mesons produced in inclusive semileptonic b-hadron decays to the D-0 μX final state, where the charge of the accompanying muon is used to tag the flavour of the D-0 meson. The difference in the CP-violating asymmetries between the two decay channels is measured to be Delta A(CP) = A(CP)(K-K+) – A(CP)(pi(-)pi(+)) = (0.49 +/- 0.30 (stat) +/- 0.14 (syst))%. This result does not confirm the evidence for direct CP violation in the charm sector reported in other analyses.
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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 events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton-proton collision data with the ATLAS detector. Phys. Lett. B, 714(2-5), 180–196.
Abstract: A search for events with large missing transverse momentum, jets, and at least two tau leptons has been performed using 2 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed and a 95% CL upper limit on the visible cross section for new phenomena is set, where the visible cross section is defined by the product of cross section, branching fraction, detector acceptance and event selection efficiency. A 95% CL lower limit of 32 TeV is set on the gauge-mediated supersymmetry breaking (GMSB) scale Lambda independent of tan beta. These limits provide the most stringent tests to date in a large part of the considered parameter space.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., et al. (2020). Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb(-1) of pp collisions at root s=13 TeV with the ATLAS experiment. Phys. Lett. B, 800, 135082–21pp.
Abstract: A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb(-1) of proton-proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tq gamma coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC t gamma production via a left-handed (right-handed) tu gamma coupling of 36 fb (78 fb) and on the branching ratio for t -> gamma u of 2.8 x 10(-5) (6.1 x 10(-5)). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC t gamma production via a left-handed (right-handed) tc.coupling of 40 fb (33 fb) and on the branching ratio for t -> gamma c of 22 x 10(-5) (18 x 10(-5)).
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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. (2016). Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb(-1) of proton-proton collision data at root s=13 TeV. Phys. Lett. B, 760, 647–665.
Abstract: A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb(-1)of proton-proton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.
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