LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Study of CP violation in B0 → DK*(892)0 decays with D → Kπ(ππ), ππ(ππ), and KK final states. J. High Energy Phys., 05(5), 025–30pp.
Abstract: A measurement of CP-violating observables associated with the interference of B-0 -> (DK)-K-0*(892)(0) and B-0 -> (D) over bar K-0*(892)(0) decay amplitudes is performed in the D-0 -> K-+/- pi(+/-)(pi(+)pi(-)), D-0 -> pi(+) pi(-)(pi(+)pi(-)), and D-0 -> K+ K- final states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb(-1). CP-violating observables related to the interference of B-s(0) -> D-0 (K) over bar*(892)(0) and B-s(0) -> (D) over bar (0) (K) over bar*(892)(0) are also measured, but no evidence for interference is found. The B-0 observables are used to constrain the parameter space of the CKM angle. and the hadronic parameters gamma(DK*) (0)(B) and delta(DK*) (0)(B) with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2024). Test of CP-invariance of the Higgs boson in vector-boson fusion production and in its decay into four leptons. J. High Energy Phys., 05(5), 105–65pp.
Abstract: A search for CP violation in the decay kinematics and vector-boson fusion production of the Higgs boson is performed in the H -> ZZ* -> 4l ( l = e, mu) decay channel. The results are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 13TeV and recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb(-1). Matrix element-based optimal observables are used to constrain CP-odd couplings beyond the Standard Model in the framework of Standard Model effective field theory expressed in the Warsaw and Higgs bases. Differential fiducial cross-section measurements of the optimal observables are also performed, and a new fiducial cross-section measurement for vector-boson-fusion production is provided. All measurements are in agreement with the Standard Model prediction of a CP-even Higgs boson.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Search for electroweak production of supersymmetric particles in final states with two τ-leptons in √s=13 TeV pp collisions with the ATLAS detector. J. High Energy Phys., 05(5), 150–65pp.
Abstract: Three searches for the direct production of tau-sleptons or charginos and neutralinos in final states with at least two hadronically decaying tau-leptons are presented. For chargino and neutralino production, decays via intermediate tau-sleptons or W and h bosons are considered. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of 139 fb(-1), recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13TeV. No significant deviation from the expected Standard Model background is observed and supersymmetric particle mass limits at 95% confidence level are obtained in simplified models. For direct production of (X) over tilde +/-(1) (X) over tilde -1, chargino masses are excluded up to 970 GeV, while (X) over tilde +/-(1) 1 and (X) over tilde (0)2 masses up to 1160 GeV (330 GeV) are excluded for (X) over tildeC(+/-) (1) (X) over tilde (0)(2) /(X) over tilde (+)(1) (X) over tilde -1 production with subsequent decays via t -sleptons ( W and h bosons). Masses of tau-sleptons up to 500 GeV are excluded for mass degenerate (tau) over tildeL, R scenarios and up to 425 GeV for (tau) over tilde (L) -only scenarios. Sensitivity to (tau) over tilde (R) -only scenarios from the ATLAS experiment is presented here for the first time, with (tau) over tilde (R) masses excluded up to 350 GeV.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). ATLAS Run 2 searches for electroweak production of supersymmetric particles interpreted within the pMSSM. J. High Energy Phys., 05(5), 106–57pp.
Abstract: A summary of the constraints from searches performed by the ATLAS collaboration for the electroweak production of charginos and neutralinos is presented. Results from eight separate ATLAS searches are considered, each using 140 fb(-1) of proton-proton data at a centre-of-mass energy of root s = 13TeV collected at the Large Hadron Collider during its second data-taking run. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, where R-parity conservation is assumed and the lightest supersymmetric particle is assumed to be the lightest neutralino. Constraints from previous electroweak, flavour and dark matter related measurements are also considered. The results are presented in terms of constraints on supersymmetric particle masses and are compared with limits from simplified models. Also shown is the impact of ATLAS searches on parameters such as the dark matter relic density and the spin-dependent and spin-independent scattering cross-sections targeted by direct dark matter detection experiments. The Higgs boson and Z boson 'funnel regions', where a low-mass neutralino would not oversaturate the dark matter relic abundance, are almost completely excluded by the considered constraints. Example spectra for non-excluded supersymmetric models with light charginos and neutralinos are also presented.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Electron and photon efficiencies in LHC Run 2 with the ATLAS experiment. J. High Energy Phys., 05(5), 162–65pp.
Abstract: Precision measurements of electron reconstruction, identification, and isolation efficiencies and photon identification efficiencies are presented. They use the full Run 2 data sample collected by the ATLAS experiment in pp collisions at a centre-of-mass energy of 13 TeV during the years 2015-2018, corresponding to an integrated luminosity of 139 fb(-1). The measured electron identification efficiencies have uncertainties that are around 30%-50% smaller than the previous Run 2 results due to an improved methodology and the inclusion of more data. A better pile-up subtraction method leads to electron isolation efficiencies that are more independent of the amount of pile-up activity. Updated photon identification efficiencies are also presented, using the full Run 2 data. When compared to the previous measurement, a 30%-40% smaller uncertainty is observed on the photon identification efficiencies, thanks to the increased amount of available data.
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