Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a Z boson in the ℓ+ ℓ− tt¯ and ν ν¯ bb¯ final states using 140 fb− 1 of data collected with the …

The vector-boson production cross-section for the Higgs boson decay in the channel is measured as a function of kinematic observables sensitive to the Higgs boson production and decay properties as well as integrated in a fiducial phase space. The analysis is performed using the proton--proton collision data collected by the ATLAS detector in Run 2 of the LHC at center-of-mass energy, corresponding to an integrated luminosity of 139 fb. The opposite lepton flavor final state is studied by selecting an electron and a muon originating from a pair of bosons and compatible with the Higgs boson decay. The data are corrected for the effects of detector inefficiency and resolution, and the measurements are compared with different state-of-the-art theoretical predictions. The differential cross-sections are used to constrain anomalous interactions described by dimension-six operators in an Effective Field Theory.

Measurements of inclusive, differential cross-sections for the production of events with missing transverse momentum in association with jets in proton-proton collisions at ~TeV are presented. The measurements are made with the ATLAS detector using an integrated luminosity of 140~fb and include measurements of dijet distributions in a region in which vector-boson fusion processes are enhanced. They are unfolded to correct for detector resolution and efficiency within the fiducial acceptance, and are designed to allow robust comparisons with a wide range of theoretical predictions. A measurement of differential cross sections for the process is made. The measurements are generally well-described by Standard Model predictions except for the dijet invariant mass distribution. Auxiliary measurements of the hadronic system recoiling against isolated leptons, and photons, are also made in the same phase space. Ratios between the measured distributions are then derived, to take advantage of cancellations in modelling effects and some of the major systematic uncertainties. These measurements are sensitive to new phenomena, and provide a mechanism to easily set constraints on phenomenological models. To illustrate the robustness of the approach, these ratios are compared with two common Dark Matter models, where the constraints derived from the measurement are comparable to those set by dedicated detector-level searches.

The European Physical Journal C

The inclusive Higgs boson production cross-section is measured in the di-photon and the decay channels using 31.4 and 29.0 fb of pp collision data respectively, collected with the ATLAS detector at a centre-of-mass energy of  . To reduce the model dependence, the measurement in each channel is restricted to a particle-level phase space that closely matches the channel’s detector-level kinematic selection, and it is corrected for detector effects. These measured fiducial cross-sections are   fb, and   fb, in agreement with the corresponding Standard Model predictions of  fb and  fb. Assuming Standard Model acceptances and branching fractions for the two channels, the fiducial measurements are extrapolated to the full phase space yielding total cross-sections of  pb and  pb at 13.6  from the di-photon and  …

Minor Planet Bulletin

We report the discovery and confirmation of a previously unknown satellite of the main-belt asteroid 5457 Queen's (1980 TW5) via GPS-time-stamped video recordings of two stellar occultations. The first occultation on 2023 September 4.93059 resulted in three positive chords from the Czech Republic and Switzerland for the main body, allowing an elliptical fit of 24.6±0.9 km× 16.2±0.7 km, and in a 2.0±0.2 km chord of the presumed satellite. 15.07 days later, on September 20.00597, the satellite was confirmed by an observer in Greece, who determined a chord of 17.5±0.5 km for the main body and a chord of 2.8±0.5 km for the satellite. Using both satellite chords as diameters of spherical bodies, we derived the following satellite distances from the main body: 2023 September 4.93059: separation 11.4±0.7 mas, pa 52.2±3.0; 2023 September 20.00597: separation 20.4±0.5 mas, pa 248.8±3.0. Further observations …

A search for R-parity-violating supersymmetry in final states with high jet multiplicity is presented. The search uses of proton--proton collision data at collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature prompt gluino-pair production decaying directly to three jets each or decaying to two jets and a neutralino which subsequently decays promptly to three jets. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted. Gluinos with masses up to 1800 GeV are excluded when decaying directly to three jets. In the cascade scenario, gluinos with masses up to 2340 GeV are excluded for a neutralino with mass up to 1250 GeV

Measurements of inclusive and normalized differential cross sections of the associated production of top quark-antiquark and bottom quark-antiquark pairs, ttbb, are presented. The results are based on data from proton-proton collisions collected by the CMS detector at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb− 1. The cross sections are measured in the lepton+ jets decay channel of the top quark pair, using events containing exactly one isolated electron or muon and at least five jets. Measurements are made in four fiducial phase space regions, targeting different aspects of the ttbb process. Distributions are unfolded to the particle level through maximum likelihood fits, and compared with predictions from several event generators. The inclusive cross section measurements of this process in the fiducial phase space regions are the most precise to date. In most cases, the measured inclusive cross sections exceed the predictions with the chosen generator settings. The only exception is when using a particular choice of dynamic renormalization scale, µR= 12 ni= t, t, b, b m1/4

arXiv preprint arXiv:2402.05383

Daya Bay presents the first measurement of cosmogenic He isotope production in liquid scintillator, using an innovative method for identifying cascade decays of He and its child isotope, Li. We also measure the production yield of Li isotopes using well-established methodology. The results, in units of 10gcm, are 0.3070.042, 0.3410.040, and 0.5460.076 for He, and 6.730.73, 6.750.70, and 13.740.82 for Li at average muon energies of 63.9~GeV, 64.7~GeV, and 143.0~GeV, respectively. The measured production rate of He isotopes is more than an order of magnitude lower than any other measurement of cosmogenic isotope production. It replaces the results of previous attempts to determine the ratio of He to Li production that yielded a wide range of limits from 0 to 30\%. The results provide future liquid-scintillator-based experiments with improved ability to predict cosmogenic backgrounds.

Measurements of inclusive and normalized differential cross sections of the associated production of top quark-antiquark and bottom quark-antiquark pairs, ttbb, are presented. The results are based on data from proton-proton collisions collected by the CMS detector at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb− 1. The cross sections are measured in the lepton+ jets decay channel of the top quark pair, using events containing exactly one isolated electron or muon and at least five jets. Measurements are made in four fiducial phase space regions, targeting different aspects of the ttbb process. Distributions are unfolded to the particle level through maximum likelihood fits, and compared with predictions from several event generators. The inclusive cross section measurements of this process in the fiducial phase space regions are the most precise to date. In most cases, the measured inclusive cross sections exceed the predictions with the chosen generator settings. The only exception is when using a particular choice of dynamic renormalization scale, µR= 12 ni= t, t, b, b m1/4

arXiv preprint arXiv:2402.18731

Searches for the exclusive decays of the Higgs boson into and of the boson into and can probe flavour-violating Higgs and boson couplings to light quarks. Searches for these decays are performed with a collision data sample corresponding to an integrated luminosity of fb collected at TeV between 2016-2018 with the ATLAS detector at the CERN Large Hadron Collider. In the and channels, the observed (expected) 95 confidence-level upper limits on the respective branching fractions are , , while the corresponding results in the channel are .

This Letter presents the first study of the energy-dependence of diboson polarization fractions in ????????→ ℓ????ℓ′ ℓ′(ℓ, ℓ′= ????, ????) production. The data set used corresponds to an integrated luminosity of 140 fb− 1 of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector. Two fiducial regions with an enhanced presence of events featuring two longitudinally-polarized bosons are defined. A non-zero fraction of events with two longitudinally-polarized bosons is measured with an observed significance of 5.3 standard deviations in the region with 100< ????????????≤ 200 GeV and 1.6 standard deviations in the region with ???????? ????> 200 GeV, where ???? ???? ???? is the transverse momentum of the ???? boson. This Letter also reports the first study of the Radiation Amplitude Zero effect. Events with two transversely-polarized bosons are analyzed for the Δ???? (ℓ???? ????) and Δ???? (????????) distributions defined respectively as the rapidity difference between the lepton from the ???? boson decay and the ???? boson and the rapidity difference between the ???? boson and the ???? boson. Significant suppression of events near zero is observed in both distributions. Unfolded Δ???? (ℓ???? ????) and Δ???? (????????) distributions are also measured and compared to theoretical predictions.

Measurements of inclusive, differential cross-sections for the production of events with missing transverse momentum in association with jets in proton-proton collisions at ~TeV are presented. The measurements are made with the ATLAS detector using an integrated luminosity of 140~fb and include measurements of dijet distributions in a region in which vector-boson fusion processes are enhanced. They are unfolded to correct for detector resolution and efficiency within the fiducial acceptance, and are designed to allow robust comparisons with a wide range of theoretical predictions. A measurement of differential cross sections for the process is made. The measurements are generally well-described by Standard Model predictions except for the dijet invariant mass distribution. Auxiliary measurements of the hadronic system recoiling against isolated leptons, and photons, are also made in the same phase space. Ratios between the measured distributions are then derived, to take advantage of cancellations in modelling effects and some of the major systematic uncertainties. These measurements are sensitive to new phenomena, and provide a mechanism to easily set constraints on phenomenological models. To illustrate the robustness of the approach, these ratios are compared with two common Dark Matter models, where the constraints derived from the measurement are comparable to those set by dedicated detector-level searches.

The associated production of Higgs and bosons via vector-boson fusion (VBF) is highly sensitive to the relative sign of the Higgs boson couplings to and bosons. In this Letter, two searches for this process are presented, using 140 fb of proton-proton collision data at = 13 TeV recorded by the ATLAS detector at the LHC. The first search targets scenarios with opposite-sign couplings of the and bosons to the Higgs boson, while the second targets Standard Model-like scenarios with same-sign couplings. Both analyses consider Higgs decays into a pair of -quarks and decays with an electron or muon. The opposite-sign coupling hypothesis is excluded with significance much greater than , and the observed (expected) upper limit set on the cross-section for VBF production is 9.0 (8.7) times the Standard Model value.

The ratio of branching ratios of the boson to muons and electrons, , has been measured using 140 fb of collision data at TeV collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the production cross-section in the , and dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio for the boson measured in inclusive and events. By using the precise value of determined from colliders, the ratio is determined to be . The three uncertainties correspond to data statistics, experimental systematics and the external measurement of , giving a total uncertainty of 0.0045, and confirming the Standard Model assumption of lepton flavour universality in -boson decays at the 0.5% level.

Journal of High Energy Physics

Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at= 13 TeV and with an integrated luminosity of 140 fb− 1. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory.

Chinese physics C

The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using TeV proton–proton collision data with an integrated luminosity of 140 fb collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.

The Large Hadron Collider is at the high-energy frontier of particle physics, having produced protonproton collisions during Run 2, from 2015 to 2018, at an unprecedented centre-of-mass energy of 13 TeV. The ATLAS experiment has a broad programme to thoroughly explore this uncharted territory, to seek out new exotic particles predicted by theories that boldly go beyond the Standard Model. Although the Standard Model has been very successful, it leaves many questions unanswered, prompting novel ideas about particles that could be hiding in the data, waiting to be discovered by intrepid explorers. These include dark-matter candidates, hidden-sector particles, new vector resonances, leptoquarks, and vector-like quarks, to name a few examples. Searches for new particles are reported here, with the exception of searches for supersymmetry or extended Higgs sectors as these are the subjects of separate reports.

Journal of High Energy Physics

A search for nonresonant Higgs boson pair production in the final state is performed using 140 fb− 1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this final state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs (H) boson self-coupling modifier κ λ but also of the quartic HHVV (V= W, Z) coupling modifier κ 2V. No significant excess above the expected background from Standard Model processes is observed. An observed upper limit μ HH< 4.0 is set at 95% confidence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confidence intervals for the coupling modifiers are− 1.4< κ λ< 6.9 and− 0.5< κ 2V< 2.7, assuming …

Chinese physics C

The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using TeV proton–proton collision data with an integrated luminosity of 140 fb collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.

Measurements of inclusive and normalized differential cross sections of the associated production of top quark-antiquark and bottom quark-antiquark pairs, ttbb, are presented. The results are based on data from proton-proton collisions collected by the CMS detector at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb− 1. The cross sections are measured in the lepton+ jets decay channel of the top quark pair, using events containing exactly one isolated electron or muon and at least five jets. Measurements are made in four fiducial phase space regions, targeting different aspects of the ttbb process. Distributions are unfolded to the particle level through maximum likelihood fits, and compared with predictions from several event generators. The inclusive cross section measurements of this process in the fiducial phase space regions are the most precise to date. In most cases, the measured inclusive cross sections exceed the predictions with the chosen generator settings. The only exception is when using a particular choice of dynamic renormalization scale, µR= 12 ni= t, t, b, b m1/4

arXiv preprint arXiv:2402.18731

Searches for the exclusive decays of the Higgs boson into and of the boson into and can probe flavour-violating Higgs and boson couplings to light quarks. Searches for these decays are performed with a collision data sample corresponding to an integrated luminosity of fb collected at TeV between 2016-2018 with the ATLAS detector at the CERN Large Hadron Collider. In the and channels, the observed (expected) 95 confidence-level upper limits on the respective branching fractions are , , while the corresponding results in the channel are .