Studies of new Higgs boson interactions through nonresonant HH production in the final state in pp collisions at = 13 TeV with the ATLAS detector

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.

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 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.

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 .

The European Physical Journal C

A search for the production of single-top-quarks in association with missing energy is performed in proton–proton collisions at a centre-of-mass energy of with the ATLAS experiment at the large hadron collider using data collected in 2012, corresponding to an integrated luminosity of  fb. In this search, the boson from the top quark is required to decay into an electron or a muon and a neutrino. No deviation from the standard model prediction is observed, and upper limits are set on the production cross-section for resonant and non-resonant production of an invisible exotic state in association with a right-handed top quark. In the case of resonant production, for a spin- resonance with a mass of  GeV, an effective coupling strength above is excluded at 95 confidence level for the top quark and an invisible spin- state with mass between and  GeV. In the case of non-resonant production, an effective …

A search for a new heavy boson produced via gluon-fusion in the four-lepton channel with missing transverse momentum or jets is performed. The search uses proton-proton collision data equivalent to an integrated luminosity of 139 fb at a centre-of-mass energy of 13 TeV collected by the ATLAS detector between 2015 and 2018 at the Large Hadron Collider. This study explores the decays of heavy bosons: and , where is a CP-even boson, is a CP-odd boson, is a CP-even boson, and is considered to decay into invisible particles that are candidates for dark matter. In these processes, and . The boson associated with the heavy scalar boson decays into all decay channels of the boson. The mass range under consideration is 390-1300 (320-1300) GeV for the () boson and 220-1000 GeV for the boson. No significant deviation from the Standard Model backgrounds is observed. The results are interpreted as upper limits at a 95% confidence level on the cross-section times the branching ratio of the heavy resonances.

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.

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 …

Journal of High Energy Physics

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb− 1 of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the WZ+ jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models …

Journal of High Energy Physics

Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb− 1. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b-tagged, are selected. The fiducial cross-section is measured to be fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and …

Journal of high energy physics

This paper presents a measurement of the production cross-section of a boson in association with - or -jets, in proton-proton collisions at TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb. Inclusive and differential cross-sections are measured for events containing a boson decaying into electrons or muons and produced in association with at least one -jet, at least one -jet, or at least two -jets with transverse momentum GeV and rapidity . Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected -jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

Journal of High Energy Physics

New GeV-scale dark forces coupling predominantly to quarks offer novel signatures that can be produced directly and searched for at high-luminosity colliders. We compute the photon-proton and electron-proton cross sections for producing a GeV-scale gauge boson arising from a U (1) B gauge symmetry. Our calculation relies on vector meson dominance and a phenomenological model for diffractive scattering used for vector-meson photoproduction. The parameters of our phenomenological model are fixed by performing a Markov Chain Monte Carlo fit to existing exclusive photoproduction data for ω and ϕ mesons. Our approach can be generalized to other GeV-scale dark gauge forces.

Journal of high energy physics

Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum in the range 8<< 15 GeV/c. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial-and final-state radiation. The relative transverse activity classifier,, is used to group events according to their UE activity, where is the charged-particle multiplicity per event in the transverse region and is the mean …

Journal of High Energy Physics

We explain how equivariant localization may be applied to AdS/CFT to compute various BPS observables in gravity, such as central charges and conformal dimensions of chiral primary operators, without solving the supergravity equations. The key ingredient is that supersymmetric AdS solutions with an R-symmetry are equipped with a set of equivariantly closed forms. These may in turn be used to impose flux quantization and compute observables for supergravity solutions, using only topological information and the Berline-Vergne-Atiyah-Bott fixed point formula. We illustrate the formalism by considering AdS 5× M 6 and AdS 3× M 8 solutions of D= 11 supergravity. As well as recovering results for many classes of well-known supergravity solutions, without using any knowledge of their explicit form, we also compute central charges for which explicit supergravity solutions have not been constructed.

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.

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 …

Journal of High Energy Physics

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb− 1 of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the WZ+ jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models …

Journal of high energy physics

Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum in the range 8<< 15 GeV/c. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial-and final-state radiation. The relative transverse activity classifier,, is used to group events according to their UE activity, where is the charged-particle multiplicity per event in the transverse region and is the mean …

Journal of High Energy Physics

Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb− 1. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b-tagged, are selected. The fiducial cross-section is measured to be fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and …

Journal of high energy physics

This paper presents a measurement of the production cross-section of a boson in association with - or -jets, in proton-proton collisions at TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb. Inclusive and differential cross-sections are measured for events containing a boson decaying into electrons or muons and produced in association with at least one -jet, at least one -jet, or at least two -jets with transverse momentum GeV and rapidity . Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected -jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

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.

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 …

Journal of High Energy Physics

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb− 1 of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the WZ+ jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models …

Journal of High Energy Physics

Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb− 1. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b-tagged, are selected. The fiducial cross-section is measured to be fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and …

Journal of high energy physics

This paper presents a measurement of the production cross-section of a boson in association with - or -jets, in proton-proton collisions at TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb. Inclusive and differential cross-sections are measured for events containing a boson decaying into electrons or muons and produced in association with at least one -jet, at least one -jet, or at least two -jets with transverse momentum GeV and rapidity . Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected -jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

Journal of High Energy Physics

The flow of shape eigenmodes of the small fluctuation operator around BPS 2-vortex solutions is calculated, as a function of the intervortex separation 2d. For the rotationally-invariant 2-vortex, with d= 0, there are three discrete modes; the lowest is non-degenerate and the upper two are degenerate. As d increases, the degeneracy splits, with one eigenvalue increasing and entering the continuous spectrum, and the other decreasing and asymptotically coalescing with the lowest eigenvalue, where they jointly become the eigenvalue of the 1-vortex radial shape mode. The behaviour of the eigenvalues near d= 0 is clarified using a perturbative analysis, and also in light of the 2-vortex moduli space geometry.