Aug 22nd, 2024
ATLAS Collab.
Combination of searches for singly produced vector-like top quarks in pp collisions at √s=13 TeV with the ATLAS detector
A combination of searches for the single production of vector-like top quarks (T) is presented. These analyses are based on proton−proton collisions at √s=13 TeV recorded in 2015−2018 with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. The T-quark decay modes considered in this combination are into a top quark and either a Standard Model Higgs boson or a Z boson (T→Ht and T→Zt). The individual searches used in the combination are differentiated by the number of leptons (e, μ) in the final state. The observed data are found to be in good agreement with the Standard Model background prediction. Interpretations are provided for a range of masses and couplings of the vector-like top quark for benchmark models and generalized representations in terms of 95% confidence level limits. For a benchmark signal prediction of a vector-like top quark SU2 singlet with electroweak coupling, κ, of 0.5, masses below 2.1 TeV are excluded, resulting in the most restrictive limits to date.
ATLAS Collab.
The DAMA/LIBRA signal: an induced modulation effect?
R. S. James et al.
The persistence of the DAMA/LIBRA (DAMA) modulation over the past two decades has been a source of great contention within the dark matter community. The DAMA collaboration reports a persistent, modulating event rate within their setup of NaI(Tl) scintillating crystals at the INFN Laboratori Nazionali del Gran Sasso (LNGS) underground laboratory. A recent work alluded that this signal could have arisen due to an analysis artefact, caused by DAMA not accounting for time variation of decaying background radioisotopes in their analysis procedure. In this work, we examine in detail this 'induced modulation' effect, arguing that a number of aspects of the DAMA signal are incompatible with an induced modulation arising from decays of background isotopes over the lifetime of the experiment. Using a toy model of the DAMA/LIBRA experiment, we explore the induced modulation effect under different variations of the activities of the relevant isotopes - namely, 3H and 210Pb - highlighting the various inconsistencies between the resultant toy datasets and the DAMA signal. We stress the importance of the SABRE experiment, whose goal is to unambiguously test for the presence of such a modulating signal in an experiment using the same target material and comparable levels of background.
CMS-SMP-22-010
Measurement of the Drell-Yan forward-backward asymmetry and of the effective leptonic weak mixing angle in proton-proton collisions at √s = 13 TeV
The forward-backward asymmetry in Drell-Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at √s = 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb−1. The measurement uses both dimuon and dielectron events, and is performed as a function of the dilepton mass and rapidity. The unfolded angular coefficient A4 is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain sinθℓeff = 0.23157 ± 0.00031, where the uncertainty includes the experimental and theoretical contributions. The measured value agrees with the standard model fit result to global experimental data. This is the mosprecise sinθℓeff measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD.