B. Allen

This article documents the performance of the ATLAS muon identification and reconstruction using the LHC dataset recorded at $$\sqrt{s} = 13$$ TeV in 2015. Using a large sample of $$J/\psi \rightarrow \mu \mu $$ and $$Z\rightarrow \mu \mu $$ decays from 3.2 fb $$^{-1}$$ of pp collision data, measurements of the reconstruction efficiency, as well as of the momentum scale and resolution, are presented and compared to Monte Carlo simulations. The reconstruction efficiency is measured to be close to $$99~\%$$ over most of the covered phase space ( $$|\eta |<2.5$$ and $$5 < p_{\mathrm {T}} < 100$$ GeV). The isolation efficiency varies between 93 and $$100~\%$$ depending on the selection applied and on the momentum of the muon. Both efficiencies are well reproduced in simulation. In the central region of the detector, the momentum resolution is measured to be $$1.7~\%$$ ( $$2.3~\%$$ ) for muons from $$J/\psi \rightarrow \mu \mu $$ ( $$Z\rightarrow \mu \mu $$ ) decays, and the momentum scale is known with an uncertainty of $$0.05~\%$$ . In the region $$|\eta |>2.2$$ , the $$p_{\mathrm {T}} $$ resolution for muons from $$Z\rightarrow \mu \mu $$ decays is $$2.9~\%$$ while the precision of the momentum scale for low- $$p_{\mathrm {T}} $$ muons from $$J/\psi \rightarrow \mu \mu $$ decays is about $$0.2~\%$$ .

A search for high-mass dielectron and dimuon resonances in the mass range of 250 GeV to 6 TeV is presented. The data were recorded by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of s=13 TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb−1. A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes, and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses. The derived limits are shown to be applicable to spin-0, spin-1 and spin-2 signal hypotheses. For a set of benchmark models, the limits are converted into lower limits on the resonance mass and reach 4.5 TeV for the E6-motivated Zψ′ boson. Also presented are limits on Heavy Vector Triplet model couplings.

The luminosity determination for the ATLAS detector at the LHC during pp collisions at $$\sqrt{s} =$$ 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of $$\delta \mathcal{L}/ \mathcal{L} = \pm 1.9\%$$ is obtained for the $$22.7\,\mathrm {fb}^{-1}$$ of pp collision data delivered to ATLAS at $$\sqrt{s} =$$ 8 TeV in 2012.

This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations.

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of $3.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between ${E}_{\mathrm{T}}^{\mathrm{miss}}&gt;250\text{ }\text{ }\mathrm{GeV}$ and ${E}_{\mathrm{T}}^{\mathrm{miss}}&gt;700\text{ }\text{ }\mathrm{GeV}$. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.

High-precision measurements by the ATLAS Collaboration are presented of inclusive W+→ℓ+ν , W-→ℓ-ν¯ and Z/γ∗→ℓℓ ( ℓ=e,μ ) Drell-Yan production cross sections at the LHC. The data were collected in proton-proton collisions at s=7TeV with an integrated luminosity of 4.6fb-1 . Differential W+ and W- cross sections are measured in a lepton pseudorapidity range |ηℓ|<2.5 . Differential Z/γ∗ cross sections are measured as a function of the absolute dilepton rapidity, for |yℓℓ|<3.6 , for three intervals of dilepton mass, mℓℓ , extending from 46 to 150GeV . The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive e±p scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element |Vcs| is also provided.

Results of a search for new physics in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 139 fb$^{-1}$ at a center-of-mass energy of 13 TeV collected in the period 2015-2018 with the ATLAS detector at the Large Hadron Collider. Compared to previous publications, in addition to an increase of almost a factor of four in the data size, the analysis implements a number of improvements in the signal selection and the background determination leading to enhanced sensitivity. Events are required to have at least one jet with transverse momentum above 150 GeV and no reconstructed leptons ($e$, $\mu$ or $\tau$) or photons. Several signal regions are considered with increasing requirements on the missing transverse momentum starting at 200 GeV. Overall agreement is observed between the number of events in data and the Standard Model predictions. Model-independent 95 % confidence-level limits on visible cross sections for new processes are obtained in the range between 736 fb and 0.3 fb with increasing missing transverse momentum. Results are also translated into improved exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, supersymmetric particles in several compressed scenarios, axion-like particles, and new scalar particles in dark-energy-inspired models. In addition, the data are translated into bounds on the invisible branching ratio of the Higgs boson.

This Letter describes a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model in 3.6 fb$^{-1}$ of proton-proton collisions with a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the smoothly falling prediction of the Standard Model. The data are also compared to a Monte Carlo simulation of Standard Model angular distributions derived from the rapidity of the two jets. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% CL, quantum black holes with threshold masses below 8.3 TeV, 8.1 TeV, or 5.3 TeV in three different benchmark scenarios; resonance masses below 5.2 TeV for excited quarks, 2.6 TeV in a $W^\prime$ model, a range of masses starting from $m_{Z^\prime}=1.5$ TeV and couplings from $g_q = 0.2$ in a $Z^\prime$ model; and contact interactions with a compositeness scale below 12.0 TeV and 17.5 TeV respectively for destructive and constructive interference between the new interaction and QCD processes. These results significantly extend the ATLAS limits obtained from 8 TeV data. Gaussian-shaped contributions to the mass distribution are also excluded if the effective cross-section exceeds values ranging from approximately 50-300 fb for masses below 2 TeV to 2-20 fb for masses above 4 TeV.

Measurements of the yield and nuclear modification factor, RAA, for inclusive jet production are performed using 0.49 nb−1 of Pb+Pb data at sNN=5.02TeV and 25 pb−1 of pp data at s=5.02TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-kt algorithm with radius parameter R=0.4 and are measured over the transverse momentum range of 40–1000 GeV in six rapidity intervals covering |y|<2.8. The magnitude of RAA increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of RAA also increases towards peripheral collisions. The value of RAA is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.

A search for long-lived, massive particles predicted by many theories beyond the Standard Model is presented. The search targets final states with large missing transverse momentum and at least one high-mass displaced vertex with five or more tracks, and uses 32.8 fb$^{-1}$ of $\sqrt{s}$ = 13 TeV $pp$ collision data collected by the ATLAS detector at the LHC. The observed yield is consistent with the expected background. The results are used to extract 95\% CL exclusion limits on the production of long-lived gluinos with masses up to 2.37 TeV and lifetimes of $\mathcal{O}(10^{-2})$-$\mathcal{O}(10)$ ns in a simplified model inspired by Split Supersymmetry.

This paper presents measurements of W±Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider and correspond to an integrated luminosity of 20.3 fb−1. The measured inclusive cross section in the detector fiducial region is σW±Z→ℓ′νℓℓ=35.1±0.9(stat)±0.8(sys)±0.8(lumi) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0±2.1 fb. Cross sections for W+Z and W−Z production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the W±Z system. From the analysis of events with a W and a Z boson associated with two or more forward jets an upper limit at 95% confidence level on the W±Z scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13±0.01 fb. Limits on anomalous quartic gauge boson couplings are also extracted.9 MoreReceived 8 March 2016DOI:https://doi.org/10.1103/PhysRevD.93.092004This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.© 2016 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasExtensions of gauge sectorParticle productionPhysical SystemsW & Z bosonsParticles & Fields

A detailed study of multiparticle azimuthal correlations is presented using pp data at √s=5.02 and 13 TeV, and p+Pb data at √sNN=5.02 TeV, recorded with the ATLAS detector at the CERN Large Hadron Collider. The azimuthal correlations are probed using four-particle cumulants cn{4} and flow coefficients vn{4}=(−cn{4})1/4 for n=2 and 3, with the goal of extracting long-range multiparticle azimuthal correlation signals and suppressing the short-range correlations. The values of cn{4} are obtained as a function of the average number of charged particles per event, ⟨Nch⟩, using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The standard method is found to be strongly biased by short-range correlations, which originate mostly from jets with a positive contribution to cn{4}. The three-subevent method, on the other hand, is found to be least sensitive to short-range correlations. The three-subevent method gives a negative c2{4}, and therefore a well-defined v2{4}, nearly independent of ⟨Nch⟩, which implies that the long-range multiparticle azimuthal correlations persist to events with low multiplicity. Furthermore, v2{4} is found to be smaller than the v2{2} measured using the two-particle correlation method, as expected for long-range collective behavior. Finally, the measured values of v2{4} and v2{2} are used to estimate the number of sources relevant for the initial eccentricity in the collision geometry. The results based on the subevent cumulant technique provide direct evidence, in small collision systems, for a long-range collectivity involving many particles distributed across a broad rapidity interval.7 MoreReceived 14 August 2017DOI:https://doi.org/10.1103/PhysRevC.97.024904Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.©2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasH & He induced nuclear reactionsParticle correlations & fluctuationsQuark-gluon plasmaResonance reactionsNuclear Physics

Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450--1800 GeV. The analyzed data set has an integrated luminosity of up to $29.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.

This paper presents a measurement of the double-differential cross section for the Drell-Yan Z/γ ∗ → ℓ + ℓ − and photon-induced γγ → ℓ + ℓ − processes where ℓ is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, m ℓℓ, between 116 GeV and 1500 GeV using a sample of 20.3 fb−1 of pp collisions data at centre-of-mass energy of $$ \sqrt{s}=8 $$ TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of m ℓℓ is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low m ℓℓ. A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.

A measurement of the associated production of a top-quark pair ($t\bar{t}$) with a vector boson ($W$, $Z$) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented, using $36.1$ fb$^{-1}$ of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. Events are selected in channels with two same- or opposite-sign leptons (electrons or muons), three leptons or four leptons, and each channel is further divided into multiple regions to maximize the sensitivity of the measurement. The $t\bar{t}Z$ and $t\bar{t}W$ production cross sections are simultaneously measured using a combined fit to all regions. The best-fit values of the production cross sections are $\sigma_{t\bar{t}Z} = 0.95 \pm 0.08_{\mathrm{stat.}} \pm 0.10_{\mathrm{syst.}}$ pb and $\sigma_{t\bar{t}W} = 0.87 \pm 0.13_{\mathrm{stat.}} \pm 0.14_{\mathrm{syst.}}$ pb in agreement with the Standard Model predictions. The measurement of the $t\bar{t}Z$ cross section is used to set constraints on effective field theory operators which modify the $t\bar{t}Z$ vertex.

A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. The analysis in this paper uses 36.1 fb−1 of proton-proton collision data at √s=13 TeV recorded in 2015–2016. The search employs techniques for reconstructing vertices of long-lived particles decaying into jets in the muon spectrometer exploiting a two-vertex strategy and a novel technique that requires only one vertex in association with additional activity in the detector that improves the sensitivity for longer lifetimes. The observed numbers of events are consistent with the expected background and limits for several benchmark signals are determined.6 MoreReceived 21 November 2018DOI:https://doi.org/10.1103/PhysRevD.99.052005Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.© 2019 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)SupersymmetryResearch AreasParticle decaysSupersymmetryParticles & Fields

A search for a right-handed gauge boson WR, decaying into a boosted right-handed heavy neutrino NR, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton–proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb−1. The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared to the expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the WR and NR mass plane. Mass values of the WR smaller than 3.8–5 TeV are excluded for NR in the mass range 0.1–1.8 TeV.

Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p+Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of sNN=5.02TeV. Charged particles are reconstructed over pseudorapidity |η|<2.3 and transverse momentum between 0.1GeV and 22GeV in a dataset corresponding to an integrated luminosity of 1μb−1. The results are presented in the form of charged-particle nuclear modification factors, where the p+Pb charged-particle multiplicities are compared between central and peripheral p+Pb collisions as well as to charged-particle cross sections measured in pp collisions. The p+Pb collision centrality is characterized by the total transverse energy measured in −4.9<η<−3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p+Pb collision are carried out using the Glauber model and two Glauber–Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. A broad peak is observed for all centralities and rapidities in the nuclear modification factors for charged-particle transverse momentum values around 3GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus.

The reconstruction and calibration algorithms used to calculate missing transverse momentum ($E_{\rm T}^{\rm miss}$) with the ATLAS detector exploit energy deposits in the calorimeter and tracks reconstructed in the inner detector as well as the muon spectrometer. Various strategies are used to suppress effects arising from additional proton-proton interactions, called pileup, concurrent with the hard-scatter processes. Tracking information is used to distinguish contributions from the pileup interactions using their vertex separation along the beam axis. The performance of the $E_{\rm T}^{\rm miss}$ reconstruction algorithms, especially with respect to the amount of pileup, is evaluated using data collected in proton-proton collisions at a centre-of-mass energy of 8 TeV during 2012, and results are shown for a data sample corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The results of simulation modelling of $E_{\rm T}^{\rm miss}$ in events containing a $Z$ boson decaying to two charged leptons (electrons or muons) or a $W$ boson decaying to a charged lepton and a neutrino is compared to data. The acceptance for different event topologies, with and without high transverse momentum neutrinos, is shown for a range of threshold criteria for $E_{\rm T}^{\rm miss}$, and estimates of the systematic uncertainties in the $E_{\rm T}^{\rm miss}$ measurements are presented.

Measurements of ZZ production in the ℓ+ℓ−ℓ'+ℓ'− channel in proton–proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 fb−1 of collisions collected by the ATLAS experiment in 2015 and 2016. Here ℓ and ℓ′ stand for electrons or muons. Integrated and differential ZZ→ℓ+ℓ−ℓ'+ℓ'− cross sections with Z→ℓ+ℓ− candidate masses in the range of 66 GeV to 116 GeV are measured in a fiducial phase space corresponding to the detector acceptance and corrected for detector effects. The differential cross sections are presented in bins of twenty observables, including several that describe the jet activity. The integrated cross section is also extrapolated to a total phase space and to all standard model decays of Z bosons with mass between 66 GeV and 116 GeV, resulting in a value of 17.3±0.9[±0.6(stat)±0.5(syst)±0.6(lumi)] pb. The measurements are found to be in good agreement with the standard model. A search for neutral triple gauge couplings is performed using the transverse momentum distribution of the leading Z boson candidate. No evidence for such couplings is found and exclusion limits are set on their parameters.11 MoreReceived 22 September 2017DOI:https://doi.org/10.1103/PhysRevD.97.032005Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.© 2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)W & Z bosonsResearch AreasElectroweak interactionW & Z bosonsTechniquesParticle data analysisParticles & Fields

The production of $Z$ bosons with one or two isolated high-energy photons is studied using $pp$ collisions at $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$. The analyses use a data sample with an integrated luminosity of $20.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the ATLAS detector during the 2012 LHC data taking. The $Z\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}\ensuremath{\gamma}$ production cross sections are measured with leptonic (${e}^{+}{e}^{\ensuremath{-}}$, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, $\ensuremath{\nu}\overline{\ensuremath{\nu}}$) decays of the $Z$ boson, in extended fiducial regions defined in terms of the lepton and photon acceptance. They are then compared to cross-section predictions from the Standard Model, where the sources of the photons are radiation off initial-state quarks and radiative $Z$-boson decay to charged leptons, and from fragmentation of final-state quarks and gluons into photons. The yields of events with photon transverse energy ${E}_{\mathrm{T}}&gt;250\text{ }\text{ }\mathrm{GeV}$ from ${\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}\ensuremath{\gamma}$ events and with ${E}_{\mathrm{T}}&gt;400\text{ }\text{ }\mathrm{GeV}$ from $\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}$ events are used to search for anomalous triple gauge-boson couplings $ZZ\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}\ensuremath{\gamma}$. The yields of events with diphoton invariant mass ${m}_{\ensuremath{\gamma}\ensuremath{\gamma}}&gt;200\text{ }\text{ }\mathrm{GeV}$ from ${\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}\ensuremath{\gamma}\ensuremath{\gamma}$ events and with ${m}_{\ensuremath{\gamma}\ensuremath{\gamma}}&gt;300\text{ }\text{ }\mathrm{GeV}$ from $\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}\ensuremath{\gamma}$ events are used to search for anomalous quartic gauge-boson couplings $ZZ\ensuremath{\gamma}\ensuremath{\gamma}$ and $Z\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\gamma}$. No deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings.

This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high-pT photon or jet. The dataset consists of proton–proton collisions with an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z′ boson.

This paper describes a measurement of light-by-light scattering based on Pb+Pb collision data recorded by the ATLAS experiment during Run 2 of the LHC. The study uses $2.2$ nb$^{-1}$ of integrated luminosity collected in 2015 and 2018 at $\sqrt{s_\mathrm{NN}}=5.02$ TeV. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy $E_{\mathrm{T}}^{\gamma} > 2.5$ GeV, pseudorapidity $|\eta_{\gamma}| < 2.37$, diphoton invariant mass $m_{\gamma\gamma} > 5$ GeV, and with small diphoton transverse momentum and diphoton acoplanarity. The integrated and differential fiducial cross sections are measured and compared with theoretical predictions. The diphoton invariant mass distribution is used to set limits on the production of axion-like particles. This result provides the most stringent limits to date on axion-like particle production for masses in the range 6-100 GeV. Cross sections above 2 to 70 nb are excluded at the 95% CL in that mass interval.

A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) and for a heavy neutral $Z^{\prime}$ boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb$^{-1}$ from proton--proton collisions at $\sqrt{s} = 13$ TeV recorded by the ATLAS detector at the LHC. The heavy resonance is assumed to decay to a $\tau^+ \tau^-$ pair with at least one $\tau$ lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2--1.2 TeV for the MSSM neutral Higgs bosons and 0.5--2.5 TeV for the heavy neutral $Z^{\prime}$ boson. The data are in good agreement with the background predicted by the Standard Model and hence results are given as upper limits on the production cross section times branching fraction of the boson decay to $\tau^+\tau^-$ as a function of the boson mass. The results are interpreted in MSSM and $Z^{\prime}$ benchmark scenarios. The most stringent MSSM parameter space constraints for the Higgs boson search exclude at 95\% confidence level (CL) $\tan\beta > 7.6$ for $m_A = 200$ GeV in the $m_{h}^{\textrm{mod+}}$ MSSM scenario. This analysis extends the MSSM limits from previous searches for the mass range $m_A > 500$ GeV. For the Sequential Standard Model, a $Z^{\prime}_\mathrm{SSM}$ mass up to 1.90 TeV is excluded at 95% CL and masses up to 1.82--2.17 TeV are excluded for a $Z^{\prime}_{\mathrm{SFM}}$ of the Strong Flavour Model.

Narrow resonances decaying into WW, WZ or ZZ boson pairs are searched for in 36.7 fb−1 of proton–proton collision data at a centre-of-mass energy of s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The diboson system is reconstructed using pairs of large-radius jets with high transverse momentum and tagged as compatible with the hadronic decay of high-momentum W or Z bosons, using jet mass and substructure properties. The search is sensitive to diboson resonances with masses in the range 1.2–5.0 TeV. No significant excess is observed in any signal region. Exclusion limits are set at the 95% confidence level on the production cross section times branching ratio to dibosons for a range of theories beyond the Standard Model. Model-dependent lower limits on the mass of new gauge bosons are set, with the highest limit set at 3.5 TeV in the context of mass-degenerate resonances that couple predominantly to bosons.

Searches for the exclusive decays of the Higgs and Z bosons into a J/ψ, ψ(2S), or ϒ(nS) (n=1,2,3) meson and a photon are performed with a pp collision data sample corresponding to an integrated luminosity of 36.1fb−1 collected at s=13TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above the expected backgrounds, and 95% confidence-level upper limits on the branching fractions of the Higgs boson decays to J/ψγ, ψ(2S)γ, and ϒ(nS)γ of 3.5×10−4, 2.0×10−3, and (4.9,5.9,5.7)×10−4, respectively, are obtained assuming Standard Model production. The corresponding 95% confidence-level upper limits for the branching fractions of the Z boson decays are 2.3×10−6, 4.5×10−6 and (2.8,1.7,4.8)×10−6, respectively.

A search for high-mass resonances decaying to τν using proton-proton collisions at √s=13 TeV produced by the Large Hadron Collider is presented. Only τ-lepton decays with hadrons in the final state are considered. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 36.1 fb−1. No statistically significant excess above the standard model expectation is observed; model-independent upper limits are set on the visible τν production cross section. Heavy W′ bosons with masses less than 3.7 TeV in the sequential standard model and masses less than 2.2–3.8 TeV depending on the coupling in the nonuniversal G(221) model are excluded at the 95% credibility level.Received 22 January 2018DOI:https://doi.org/10.1103/PhysRevLett.120.161802Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasExtensions of gauge sectorParticle productionPhysical SystemsHypothetical gauge bosonsTechniquesHadron collidersParticles & Fields

The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable $B$-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity $\sqrt{s}=13$ TeV $pp$ collision sample corresponding to around $2.0\,\mathrm{nb}^{-1}$ collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation.

The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at √s=13 TeV using a data sample with an integrated luminosity of 150 pb−1 recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4–7 GeV and pseudorapidity range |η|<2.4. A significant nonzero elliptic anisotropy coefficient v2 is observed for muons from charm decays, while the v2 value for muons from bottom decays is consistent with zero within uncertainties.Received 5 September 2019Revised 29 November 2019Accepted 22 January 2020DOI:https://doi.org/10.1103/PhysRevLett.124.082301Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.© 2020 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Jets & heavy flavor physicsResearch AreasRelativistic heavy-ion collisionsJets & heavy flavor physicsResearch AreasCollective flowJets & heavy flavor physicsParticle correlations & fluctuationsRelativistic heavy-ion collisionsNuclear Physics

A search is presented for pair production of long-lived neutral particles using $33\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of $\sqrt{\mathrm{s}}=13\text{ }\text{ }\mathrm{TeV}$ proton--proton collision data, collected during 2016 by the ATLAS detector at the LHC. This search focuses on a topology in which one long-lived particle decays in the ATLAS inner detector and the other decays in the muon spectrometer. Special techniques are employed to reconstruct the displaced tracks and vertices in the inner detector and in the muon spectrometer. One event is observed that passes the full event selection, which is consistent with the estimated background. Limits are placed on scalar boson propagators with masses from 125 GeV to 1000 GeV decaying into pairs of long-lived hidden-sector scalars with masses from 8 GeV to 400 GeV. The limits placed on several low-mass scalars extend previous exclusion limits in the range of proper lifetimes $c\ensuremath{\tau}$ from 5 cm to 1 m.

Accurate screw placement is critical to avoid vascular or neurologic complications during spine surgery and to maximize fixation for fusion and deformity correction. Computer-assisted navigation, robotic-guided spine surgery, and augmented reality surgical navigation are currently available technologies that have been developed to improve screw placement accuracy. The advent of multiple generations of new technologies within the past 3 decades has presented surgeons with a diverse array of choices when it comes to pedicle screw placement. Considerations for patient safety and optimal outcomes must be paramount when selecting a technology.

A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to 20.2 fb−1 of √s=8 TeV pp collisions and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of WW or WZ boson pairs accompanied by a high-mass dijet system, with one W decaying leptonically and a W or Z decaying hadronically. The hadronically decaying W/Z is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters α4 and α5 are set by fitting the transverse mass of the diboson system, and the resulting 95% confidence intervals are −0.024<α4<0.030 and −0.028<α5<0.033.Received 19 September 2016DOI:https://doi.org/10.1103/PhysRevD.95.032001Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.© 2017 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasHypothetical particle physics modelsParticle interactionsParticles & Fields

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 bb¯ 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 Z′ 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.

This Letter presents a search for heavy charged long-lived particles produced in proton-proton collisions at $\sqrt{s} = 13$ TeV at the LHC using a data sample corresponding to an integrated luminosity of 36.1 fb$^{-1}$ collected by the ATLAS experiment in 2015 and 2016. These particles are expected to travel with a velocity significantly below the speed of light, and therefore have a specific ionisation higher than any high-momentum Standard Model particle of unit charge. The pixel subsystem of the ATLAS detector is used in this search to measure the ionisation energy loss of all reconstructed charged particles which traverse the pixel detector. Results are interpreted assuming the pair production of $R$-hadrons as composite colourless states of a long-lived gluino and Standard Model partons. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on $R$-hadron production cross-sections and gluino masses are set, assuming the gluino always decays in two quarks and a stable neutralino. $R$-hadrons with lifetimes above 1.0 ns are excluded at the 95% confidence level, with lower limits on the gluino mass ranging between 1290 GeV and 2060 GeV. In the case of stable $R$-hadrons, the lower limit on the gluino mass at the 95% confidence level is 1890 GeV.

Azimuthal anisotropies of muons from charm and bottom hadron decays are measured in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}= 5.02$ TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2018 with integrated luminosities of $0.5~\mathrm{nb}^{-1}$ and $1.4~\mathrm{nb^{-1}}$, respectively. The kinematic selection for heavy-flavor muons requires transverse momentum $4 < p_\mathrm{T} < 30$ GeV and pseudorapidity $|\eta|<2.0$. The dominant sources of muons in this $p_\mathrm{T}$ range are semi-leptonic decays of charm and bottom hadrons. These heavy-flavor muons are separated from light-hadron decay muons and punch-through hadrons using the momentum imbalance between the measurements in the tracking detector and in the muon spectrometers. Azimuthal anisotropies, quantified by flow coefficients, are measured via the event-plane method for inclusive heavy-flavor muons as a function of the muon $p_\mathrm{T}$ and in intervals of Pb+Pb collision centrality. Heavy-flavor muons are separated into contributions from charm and bottom hadron decays using the muon transverse impact parameter with respect to the event primary vertex. Non-zero elliptic ($v_{2}$) and triangular ($v_{3}$) flow coefficients are extracted for charm and bottom muons, with the charm muon coefficients larger than those for bottom muons for all Pb+Pb collision centralities. The results indicate substantial modification to the charm and bottom quark angular distributions through interactions in the quark-gluon plasma produced in these Pb+Pb collisions, with smaller modifications for the bottom quarks as expected theoretically due to their larger mass.

A measurement of the production of three isolated photons in proton-proton collisions at a centre-of-mass energy $\sqrt{s}$ = 8 TeV is reported. The results are based on an integrated luminosity of 20.2 fb$^{-1}$ collected with the ATLAS detector at the LHC. The differential cross sections are measured as functions of the transverse energy of each photon, the difference in azimuthal angle and in pseudorapidity between pairs of photons, the invariant mass of pairs of photons, and the invariant mass of the triphoton system. A measurement of the inclusive fiducial cross section is also reported. Next-to-leading-order perturbative QCD predictions are compared to the cross-section measurements. The predictions underestimate the measurement of the inclusive fiducial cross section and the differential measurements at low photon transverse energies and invariant masses. They provide adequate descriptions of the measurements at high values of the photon transverse energies, invariant mass of pairs of photons, and invariant mass of the triphoton system.

A measurement of the fragmentation functions of jets into charged particles in p+Pb collisions and pp collisions is presented. The analysis utilizes 28 nb−1 of p+Pb data and 26 pb−1 of pp data, both at sNN= 5.02 TeV, collected in 2013 and 2015, respectively, with the ATLAS detector at the LHC. The measurement is reported in the centre-of-mass frame of the nucleon–nucleon system for jets in the rapidity range |y⁎|<1.6 and with transverse momentum 45 <pT< 260 GeV. Results are presented both as a function of the charged-particle transverse momentum and as a function of the longitudinal momentum fraction of the particle with respect to the jet. The pp fragmentation functions are compared with results from Monte Carlo event generators and two theoretical models. The ratios of the p+Pb to pp fragmentation functions are found to be consistent with unity.

Searches for high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as b-jets are performed using an integrated luminosity of 3.2 fb−1 of proton–proton collisions with a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited ⁎b⁎ quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic Z′ bosons with masses from 1.1 TeV to 1.5 TeV. Contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass range 1.5–5.0 TeV.

The inclusive production of four isolated charged leptons in pp collisions is analysed for the presence of hard double-parton scattering, using 20.2 fb−1 of data recorded in the ATLAS detector at the LHC at centre-of-mass energy s=8 TeV. In the four-lepton invariant-mass range of 80<m4ℓ<1000 GeV, an artificial neural network is used to enhance the separation between single- and double-parton scattering based on the kinematics of the four leptons in the final state. An upper limit on the fraction of events originating from double-parton scattering is determined at 95% confidence level to be fDPS=0.042, which results in an estimated lower limit on the effective cross section at 95% confidence level of 1.0 mb.

This paper reports on a search for the electroweak diboson ($WW/WZ/ZZ$) production in association with a high-mass dijet system, using data from proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV. The data, corresponding to an integrated luminosity of 35.5 fb$^{-1}$, were recorded with the ATLAS detector in 2015 and 2016 at the Large Hadron Collider. The search is performed in final states in which one boson decays leptonically, and the other boson decays hadronically. The hadronically decaying $W/Z$ boson is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. The electroweak production of $WW/WZ/ZZ$ in association with two jets is measured with an observed (expected) significance of 2.7 (2.5) standard deviations, and the fiducial cross section is measured to be $45.1 \pm 8.6(\mathrm{stat.}) ^{+15.9} _{-14.6} (\mathrm{syst.})$ fb.

A search for non-resonant Higgs boson pair production, as predicted by the Standard Model, is presented, where one of the Higgs bosons decays via the $H\rightarrow bb$ channel and the other via one of the $H \rightarrow WW^*/ZZ^*/\tau\tau$ channels. The analysis selection requires events to have at least two $b$-tagged jets and exactly two leptons (electrons or muons) with opposite electric charge in the final state. Candidate events consistent with Higgs boson pair production are selected using a multi-class neural network discriminant. The analysis uses 139 fb$^{-1}$ of $pp$ collision data recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. An observed (expected) upper limit of 1.2 ($0.9^{+0.4}_{-0.3}$) pb is set on the non-resonant Higgs boson pair production cross-section at 95% confidence level, which is equivalent to 40 ($29^{+14}_{-9}$) times the value predicted in the Standard Model.

Two-particle pseudorapidity correlations are measured in √sNN=2.76TeVPb+Pb, √sNN=5.02TeVp+Pb, and √s=13TeVpp collisions at the Large Hadron Collider (LHC), with total integrated luminosities of approximately 7μb−1, 28 nb−1, and 65 nb−1, respectively. The correlation function CN(η1,η2) is measured as a function of event multiplicity using charged particles in the pseudorapidity range |η|<2.4. The correlation function contains a significant short-range component, which is estimated and subtracted. After removal of the short-range component, the shape of the correlation function is described approximately by 1+⟨a21⟩1/2η1η2 in all collision systems over the full multiplicity range. The values of ⟨a21⟩1/2 are consistent for the opposite-charge pairs and same-charge pairs, and for the three collision systems at similar multiplicity. The values of ⟨a21⟩1/2 and the magnitude of the short-range component both follow a power-law dependence on the event multiplicity. The short-range component in p + Pb collisions, after symmetrizing the proton and lead directions, is found to be smaller at a given η than in pp collisions with comparable multiplicity.10 MoreReceived 28 June 2016Revised 19 May 2017DOI:https://doi.org/10.1103/PhysRevC.95.064914Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2017 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasNucleon induced nuclear reactionsParticle correlations & fluctuationsRelativistic heavy-ion collisionsNuclear Physics

This paper reports a search for triboson [Formula: see text] production in two decay channels ([Formula: see text] and [Formula: see text] with [Formula: see text]) in proton-proton collision data corresponding to an integrated luminosity of 20.3 [Formula: see text] at a centre-of-mass energy of 8 [Formula: see text] with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95% confidence level upper limit on the SM [Formula: see text] production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM [Formula: see text] production. Limits are also set on WWWW anomalous quartic gauge couplings.

Measurements of dijet $p_{\mathrm{T}}$ correlations in Pb+Pb and $pp$ collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=2.76\textrm{ TeV}$ are presented. The measurements are performed with the ATLAS detector at the Large Hadron Collider using Pb+Pb and $pp$ data samples corresponding to integrated luminosities of 0.14 nb$^{-1}$ and 4.0 pb$^{-1}$, respectively. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameter values $R=0.3$ and $R=0.4$. A background subtraction procedure is applied to correct the jets for the large underlying event present in Pb+Pb collisions. The leading and sub-leading jet transverse momenta are denoted $p_{\mathrm{T_{\mathrm{1}}}}$ and $p_{\mathrm{T_{\mathrm{2}}}}$. An unfolding procedure is applied to the two-dimensional ($p_{\mathrm{T_{\mathrm{1}}}}$, $p_{\mathrm{T_{\mathrm{2}}}}$) distributions to account for experimental effects in the measurement of both jets. Distributions of $(1/N)\mbox{$\mathrm{d}$} N/\mbox{$\mathrm{d}$} x_{\mathrm{J}}$, where $x_{\mathrm{J}}=p_{\mathrm{T}_{2}}/p_{\mathrm{T}_{1}}$, are presented as a function of $p_{\mathrm{T_{\mathrm{1}}}}$ and collision centrality. The distributions are found to be similar in peripheral Pb+Pb collisions and $pp$ collisions, but highly modified in central Pb+Pb collisions. Similar features are present in both the $R=0.3$ and $R=0.4$ results, indicating that the effects of the underlying event are properly accounted for in the measurement. The results are qualitatively consistent with expectations from partonic energy loss models.

This paper presents a dedicated search for exotic decays of the Higgs boson to a pair of new spin-zero particles, $H \rightarrow aa$, where the particle $a$ decays to $b$-quarks and has a mass in the range of 20-60 GeV. The search is performed in events where the Higgs boson is produced in association with a $W$ boson, giving rise to a signature of a lepton (electron or muon), missing transverse momentum, and multiple jets from $b$-quark decays. The analysis is based on the full dataset of $pp$ collisions at $\sqrt{s} = 13$ TeV recorded in 2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb$^{-1}$. No significant excess of events above the Standard Model prediction is observed, and a $95\%$ confidence-level upper limit is derived for the product of the production cross section for $pp \rightarrow WH$ times the branching ratio for the decay $H \rightarrow aa \rightarrow 4b$. The upper limit ranges from 6.2 pb for an $a$-boson mass $m_a = 20$ GeV to 1.5 pb for $m_a = 60$ GeV.

Ratios of top-quark pair to $Z$-boson cross sections measured from proton--proton collisions at the LHC centre-of-mass energies of $\sqrt s=13$TeV, 8TeV, and 7TeV are presented by the ATLAS Collaboration. Single ratios, at a given $\sqrt s$ for the two processes and at different $\sqrt s$ for each process, as well as double ratios of the two processes at different $\sqrt s$, are evaluated. The ratios are constructed using previously published ATLAS measurements of the $t\overline{t}$ and $Z$-boson production cross sections, corrected to a common phase space where required, and a new analysis of $Z \rightarrow \ell^+ \ell^-$ where $\ell=e,\mu$ at $\sqrt s=13$TeV performed with data collected in 2015 with an integrated luminosity of $3.2$fb$^{-1}$. Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the $Z\rightarrow e^+e^-$ and the $Z\rightarrow \mu^+ \mu^-$ channels for each $\sqrt s$ value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-$x$ values near 0.1 and the light-quark sea for $x<0.02$.

A search is performed for a heavy particle decaying into different-flavor, dilepton pairs ($eμ$, $eτ$ or $μτ$), using 36.1 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV collected in 2015-2016 by the ATLAS detector at the Large Hadron Collider. No excesses over the Standard Model predictions are observed. Bayesian lower limits at the 95% credibility level are placed on the mass of a $Z^{\prime}$ boson, the mass of a supersymmetric $τ$-sneutrino, and on the threshold mass for quantum black-hole production. For the $Z^{\prime}$ and sneutrino models, upper cross-section limits are converted to upper limits on couplings, which are compared with similar limits from low-energy experiments and which are more stringent for the $eτ$ and $μτ$ modes

A search is performed for a heavy particle decaying into different flavour dilepton pairs ([Formula: see text], [Formula: see text] or [Formula: see text]), using 3.2 fb[Formula: see text] of proton-proton collision data at [Formula: see text] TeV collected in 2015 by the ATLAS detector at the Large Hadron Collider. No excess over the Standard Model prediction is observed. Limits at the 95 % credibility level are set on the mass of a [Formula: see text] boson with lepton-flavour-violating couplings at 3.0, 2.7 and 2.6 TeV, and on the mass of a supersymmetric [Formula: see text] sneutrino with R-parity-violating couplings at 2.3, 2.2 and 1.9 TeV, for [Formula: see text], [Formula: see text] and [Formula: see text] final states, respectively. The results are also interpreted as limits on the threshold mass for quantum black hole production.

A search for the production of three massive vector bosons in proton–proton collisions is performed using data at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in the years 2015–2017, corresponding to an integrated luminosity of 79.8 fb−1. Events with two same-sign leptons ℓ (electrons or muons) and at least two reconstructed jets are selected to search for WWW→ℓνℓνqq. Events with three leptons without any same-flavour opposite-sign lepton pairs are used to search for WWW→ℓνℓνℓν, while events with three leptons and at least one same-flavour opposite-sign lepton pair and one or more reconstructed jets are used to search for WWZ→ℓνqqℓℓ. Finally, events with four leptons are analysed to search for WWZ→ℓνℓνℓℓ and WZZ→qqℓℓℓℓ. Evidence for the joint production of three massive vector bosons is observed with a significance of 4.1 standard deviations, where the expectation is 3.1 standard deviations.

Introduction: Emergency Department Length of Stay (EDLOS) impacts outcomes of critically ill intracerebral hemorrhage (ICH) patients with the risk of dying while hospitalized increasing 40% when an intensive care unit (ICU) bed is delayed beyond 4h. The NINDS recommends admission to the destination unit within 3 hours of hospital arrival; however, EDLOS for ICH patients spans about 5 hours with a wide variation. To expedite patient admission, we developed a standardized triage pathway (NeuroICU-FastTrack). In this study, we evaluated whether NeuroICU-FastTrack decreased EDLOS and whether this decreased time reduced hospital length of stay or improved patient outcomes. Methods: ICH patients presenting to UFHealth Shands between 1/1/22-6/30/22 were evaluated to establish baseline EDLOS, length of hospitalization, and functional outcomes defined as modified Rankin Score (mRS). On 7/1/22 NeuroICU-FastTrack was implemented and patients admitted through 6/30/23 were evaluated to establish post-intervention characteristics. To avoid bias, data was extrapolated from medical records. Statistical analyses were performed on R (v4.3.1). Results: Compared to the pre-intervention group (n=48), the post-intervention group (n=129) had a significantly lower EDLOS (mean 7.3h vs 4.4h, p&lt;0.001), but no difference in functional outcomes. During the intervention period, there was a trend toward decreasing EDLOS (F(1,126)=3.91, p=0.050) and a significant decrease in the length of hospitalization by two days (F(1,123)= 4.38, p=0.038). Based on correlation analysis, the success of the NeuroICU-FastTrack is due to expedited timing of the bed request order, allocation of a pre-assigned bed, and speed of the final bed assignment (Pearson’s r= 0.307, 0.493 and 0.645 respectively; p&lt;0.001). Conclusion: There is an urgent need for expedited disposition of patients with ICH to an ICU due to significant variability in stroke care provided in an ED. The NeuroICU-FastTrack process significantly decreased the EDLOS from a median time of 6.2h to 2.8h. With this decreased EDLOS, there is an associated overall decreased hospital length of stay by two days. Additional studies are being conducted to evaluate whether our intervention impacted long-term functional outcomes.

Bosonic quantum devices offer a novel approach to realize quantum computations, where the quantum two-level system (qubit) is replaced with the quantum (an)harmonic oscillator (qumode) as the fundamental building block of the quantum simulator. The simulation of chemical structure and dynamics can then be achieved by representing or mapping the system Hamiltonians in terms of bosonic operators. In this perspective, we review recent progress and future potential of using bosonic quantum devices for addressing a wide range of challenging chemical problems, including the calculation of molecular vibronic spectra, the simulation of gas-phase and solution-phase adiabatic and nonadiabatic chemical dynamics, the efficient solution of molecular graph theory problems, and the calculations of electronic structure.

This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton–proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb−1. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: |ηγ|<1.37 and 1.56<|ηγ|<2.37. The measurement covers photon transverse energies 25<ETγ<400 GeV and 25<ETγ<350 GeV respectively for the two |ηγ| regions. For each jet flavour, the ratio of the cross sections in the two |ηγ| regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central γ+b measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions.

ATLAS measurements of the production of muons from heavy-flavor decays in √sNN=2.76 TeV Pb+Pb collisions and √s=2.76 TeV pp collisions at the LHC are presented. Integrated luminosities of 0.14 nb−1 and 570 nb−1 are used for the Pb+Pb and pp measurements, respectively, which are performed over the muon transverse momentum range 4<pT<14 GeV and for five Pb+Pb centrality intervals. Backgrounds arising from in-flight pion and kaon decays, hadronic showers, and misreconstructed muons are statistically removed using a template-fitting procedure. The heavy-flavor muon differential cross sections and per-event yields are measured in pp and Pb+Pb collisions, respectively. The nuclear modification factor RAA obtained from these is observed to be independent of pT, within uncertainties, and to be less than unity, which indicates suppressed production of heavy-flavor muons in Pb+Pb collisions. For the 10% most central Pb+Pb events, the measured RAA is approximately 0.35. The azimuthal modulation of the heavy-flavor muon yields is also measured and the associated Fourier coefficients vn for n=2, 3, and 4 are given as a function of pT and centrality. They vary slowly with pT and show a systematic variation with centrality which is characteristic of other anisotropy measurements, such as that observed for inclusive hadrons. The measured RAA and vn values are also compared with theoretical calculations.9 MoreReceived 15 May 2018DOI:https://doi.org/10.1103/PhysRevC.98.044905Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.©2018 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasCollective flowJets & heavy flavor physicsPhoton, lepton & quark productionQuark-gluon plasmaNuclear Physics

Many extensions of the Standard Model predict new resonances decaying to a $Z$, $W$, or Higgs boson and a photon. This paper presents a search for such resonances produced in $pp$ collisions at $\sqrt{s} = 13$ $\mathrm{TeV}$ using a dataset with an integrated luminosity of 36.1 fb$^{-1}$ collected by the ATLAS detector at the Large Hadron Collider. The $Z/W/H$ bosons are identified through their decays to hadrons. The data are found to be consistent with the Standard Model expectation in the entire investigated mass range. Upper limits are set on the production cross section times branching fraction for resonance decays to $Z/W+\gamma$ in the mass range from 1.0 to 6.8 $\mathrm{TeV}$, and for the first time into $H+\gamma$ in the mass range from 1.0 to 3.0 $\mathrm{TeV}$.

Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias triggers by the ATLAS detector operating at the LHC during 2010 at centre-of-mass energy √s = 7 TeV, and correspond to an integrated luminosity of 19 nb−1. Kinematic properties of these secondary vertices are used to study the validity of the modelling of hadronic interactions in simulation. Secondary-vertex yields are compared between data and simulation over a volume of about 0.7 m3 around the interaction point, and agreement is found within overall uncertainties.

A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at s=13TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.

A measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations is presented, using the quantity ${R}_{\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}}$. The quantity ${R}_{\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}}$ specifies the fraction of the inclusive dijet events in which the azimuthal opening angle of the two jets with the highest transverse momenta is less than a given value of the parameter $\mathrm{\ensuremath{\Delta}}{\ensuremath{\phi}}_{\mathrm{max}}$. The quantity ${R}_{\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}}$ is measured in proton-proton collisions at $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ as a function of the dijet rapidity interval, the event total scalar transverse momentum, and $\mathrm{\ensuremath{\Delta}}{\ensuremath{\phi}}_{\mathrm{max}}$. The measurement uses an event sample corresponding to an integrated luminosity of $20.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected with the ATLAS detector at the CERN Large Hadron Collider. Predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for nonperturbative effects are compared to the data. The theoretical predictions describe the data in the whole kinematic region. The data are used to determine the strong coupling ${\ensuremath{\alpha}}_{\mathrm{S}}$ and to study its running for momentum transfers from 260 GeV to above 1.6 TeV. Analysis that combines data at all momentum transfers results in ${\ensuremath{\alpha}}_{\mathrm{S}}({m}_{Z})=0.112{7}_{\ensuremath{-}0.0027}^{+0.0063}$.

Abstract We introduce a family of variational quantum algorithms, which we coin as quantum iterative power algorithms (QIPAs), and demonstrate their capabilities as applied to global-optimization numerical experiments. Specifically, we demonstrate the QIPA based on a double exponential oracle as applied to ground state optimization of the H 2 molecule, search for the transmon qubit ground-state, and biprime factorization. Our results indicate that QIPA outperforms quantum imaginary time evolution (QITE) and requires a polynomial number of queries to reach convergence even with exponentially small overlap between an initial quantum state and the final desired quantum state, under some circumstances. We analytically show that there exists an exponential amplitude amplification at every step of the variational quantum algorithm, provided the initial wavefunction has non-vanishing probability with the desired state and that the unique maximum of the oracle is given by <?CDATA $\lambda_1\gt0$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mn>1</mml:mn> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:mn>0</mml:mn> </mml:math> , while all other values are given by the same value <?CDATA $0\lt\lambda_2\lt\lambda_1$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mo>&lt;</mml:mo> <mml:msub> <mml:mi>λ</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:msub> <mml:mi>λ</mml:mi> <mml:mn>1</mml:mn> </mml:msub> </mml:math> (here λ can be taken as eigenvalues of the problem Hamiltonian). The generality of the global-optimization method presented here invites further application to other problems that currently have not been explored with QITE-based near-term quantum computing algorithms. Such approaches could facilitate identification of reaction pathways and transition states in chemical physics, as well as optimization in a broad range of machine learning applications. The method also provides a general framework for adaptation of a class of classical optimization algorithms to quantum computers to further broaden the range of algorithms amenable to implementation on current noisy intermediate-scale quantum computers.

Measurements of jet activity in top-quark pair events produced in proton-proton collisions are presented, using 3.2 fb[Formula: see text] of pp collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiring an opposite-charge [Formula: see text] pair and two b-tagged jets in the final state. The normalised differential cross-sections of top-quark pair production are presented as functions of additional-jet multiplicity and transverse momentum, [Formula: see text]. The fraction of signal events that do not contain additional jet activity in a given rapidity region, the gap fraction, is measured as a function of the [Formula: see text] threshold for additional jets, and is also presented for different invariant mass regions of the [Formula: see text] system. All measurements are corrected for detector effects and presented as particle-level distributions compared to predictions with different theoretical approaches for QCD radiation. While the kinematics of the jets from top-quark decays are described well, the generators show differing levels of agreement with the measurements of observables that depend on the production of additional jets.

The fragmentation of high-energy gluons at small opening angles is largely unconstrained by present measurements. Gluon splitting to $b$-quark pairs is a unique probe into the properties of gluon fragmentation because identified $b$-tagged jets provide a proxy for the quark daughters of the initial gluon. In this study, key differential distributions related to the $g\rightarrow b\bar{b}$ process are measured using 33 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data recorded by the ATLAS experiment at the LHC in 2016. Jets constructed from charged-particle tracks, clustered with the anti-$k_t$ jet algorithm with radius parameter $R = 0.2$, are used to probe angular scales below the $R=0.4$ jet radius. The observables are unfolded to particle level in order to facilitate direct comparisons with predictions from present and future simulations. Multiple significant differences are observed between the data and parton shower Monte Carlo predictions, providing input to improve these predictions of the main source of background events in analyses involving boosted Higgs bosons decaying into $b$-quarks.

The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 inverse microbarns of minimum bias events collected with proton-proton collisions at a center-of-mass energy of 7 TeV in the early low-luminosity data taking with the ATLAS detector at the LHC.

A search for pair production of bottom squarks in events with hadronically decaying τ-leptons, b-tagged jets, and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at √s=13 TeV delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of 139 fb−1. The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutralino ˜χ02 and a bottom quark, with ˜χ02 decaying into a Higgs boson and the lightest neutralino ˜χ01. The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying τ-leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the ˜χ02, where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between ˜χ02 and ˜χ01. Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.1 MoreReceived 16 March 2021Accepted 9 July 2021DOI:https://doi.org/10.1103/PhysRevD.104.032014Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2021 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Physical SystemsHiggs bosonsTau leptonsPropertiesSupersymmetryParticles & Fields

Measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel, characterized by two high-${p}_{\mathrm{T}}$ leptons (electrons or muons), are presented using data corresponding to an integrated luminosity of $20.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ from $pp$ collisions at a center-of-mass energy $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the $t\overline{t}$ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: ${A}_{\mathrm{C}}^{\ensuremath{\ell}\ensuremath{\ell}}$ based on the selected leptons and ${A}_{\mathrm{C}}^{t\overline{t}}$ based on the reconstructed $t\overline{t}$ final state. The inclusive asymmetries are measured in the full phase space to be ${A}_{\mathrm{C}}^{\ensuremath{\ell}\ensuremath{\ell}}=0.008\ifmmode\pm\else\textpm\fi{}0.006$ and ${A}_{\mathrm{C}}^{t\overline{t}}=0.021\ifmmode\pm\else\textpm\fi{}0.016$, which are in agreement with the Standard Model predictions of ${A}_{\mathrm{C}}^{\ensuremath{\ell}\ensuremath{\ell}}=0.0064\ifmmode\pm\else\textpm\fi{}0.0003$ and ${A}_{\mathrm{C}}^{t\overline{t}}=0.0111\ifmmode\pm\else\textpm\fi{}0.0004$.

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Allostery is a fundamental process by which biological macromolecules transmit the effect of a local perturbation at one site to a distal, functional site, allowing for regulation of activity. The long-range coupling between residues that gives rise to allostery in a protein is built up from short-range electrostatic and hydrophobic interactions. These are arguably the largest determinants of protein structure and are essential regulators of protein function. We introduce an effective coulombic electrostatic coupling network obtained from the analysis of molecular dynamics simulations of Cas9 in its apo, DNA- and RNA-bound forms. We characterize key electrostatic events that determine its functional activity and targeting precision. We demonstrate the locality of the electrostatic-interaction network over other connectivity matrices as validated through direct comparisons to NMR measurements. We define an electrostatic-based centrality metric that allows us to pinpoint relevant donor-acceptor pairs that promote charge displacements that modulate the cross-interaction between the PAM-interacting region and catalytic domains. We determine key amino acid residues central to the network, allowing us to identify a circular allosteric pathway that channels perturbations from the PAM-interacting domain to the HNH and RuvCII domains, and then back to the PAM-contacting region. The connectivity around HNH is important for controlling the directionality of signal transfer from and towards the PAM-interacting domain. The effective coulombic electrostatic coupling network makes it possible to elucidate allosteric pathways and provides valuable interpretations of experimental measurements.

To describe the clinical impact and lessons learned through implementation of a high sensitivity troponin (hsTn) assay.hsTn assays have received regulatory approval for use in the United States, and healthcare facilities are beginning to adopt these new assays. Questions remain about how to implement them and what effect they may have on demand for cardiovascular services.We conducted a mixed-methods implementation science-based investigation of hsTn adoption at a single academic medical center. We designed the investigation based on the Consolidated Framework for Implementation Research, exploring clinicians' perspectives on intervention characteristics, inner setting, individual characteristics, and process of implementation domains. Focus groups were conducted with clinicians from multiple service lines.Participants reported that the new hsTn assay did not fundamentally change processes of care such as cardiology consultations or inpatient admissions. Implementation was facilitated by leveraging the electronic medical record to provide useful suggestions for hsTn management at the point-of-care. The use of case-based teaching was considered most effective. Areas of ongoing concern included management of high-risk patients, outpatient follow-up, and feasibility of accelerated diagnostic protocols for early discharge from the emergency department. A decrease in the number of hsTn assays ordered was observed; no change was noted for admissions, cardiology consultations, or noninvasive cardiac imaging.A comprehensive educational campaign, based on multidisciplinary collaboration can effectively prepare clinicians for implementation of hsTn. New hsTn assays may not have any substantial effect on acute management of patients with cardiac complaints.

We introduce a family of variational quantum algorithms called quantum iterative power algorithms (QIPA) that outperform existing hybrid near-term quantum algorithms of the same kind. We demonstrate the capabilities of QIPA as applied to three different global-optimization numerical experiments: the ground-state optimization of the $H_2$ molecular dissociation, search of the transmon qubit ground-state, and biprime factorization. Since our algorithm is hybrid, quantum/classical technologies such as error mitigation and adaptive variational ansatzes can easily be incorporated into the algorithm. Due to the shallow quantum circuit requirements, we anticipate large-scale implementation and adoption of the proposed algorithm across current major quantum hardware.

This case report describes long-term therapeutic management in a 33-year-old diagnosed with Candida vulvovaginitis and vulvar hidradenitis suppurativa 47 months previously. Candida spp. yeasts are part of many women's normal vaginal microflora, and the development of vulvovaginal candidiasis is typically a result of a disturbance in the patient's microbial ecosystem, which manifests itself by intense pruritus, erythema, swelling, and thick white vaginal discharge. Hidradenitis suppurativa is a chronic auto-inflammatory skin condition that causes painful weeping lesions in areas of dense apocrine glands. Although certain mechanisms underlying the pathogenesis of Hidradenitis Suppurativa (e.g., risk factors include smoking, obesity, and family history) have been investigated, a definitive explanation remains elusive. Nutritional intervention in the form of an all-meat ketogenic diet may be considered therapy in the management of both diseases, as successfully seen in this case report. The patient refused standard of care with oral fluconazole for Candida vulvovaginitis and surgical removal for Hidradenitis suppurativa, and instead consumed a zero-carbohydrate all-meat ketogenic diet mostly of beef with strict adherence to the diet for 43 days in which symptoms ceased.

Parameterizations of unresolved turbulent processes in the ocean compromise the fidelity of large-scale ocean models used in climate change projections. In this work, we use a Bayesian approach for evaluating and developing turbulence parameterizations by comparing parameterized models with observations or high-fidelity numerical simulations. The method obtains optimal parameter values, correlations, sensitivities, and, more generally, likely distributions of uncertain parameters. We demonstrate the approach by estimating the uncertainty of parameters in the popular ‘K-Profile Parameterization’, using an ensemble of large eddy simulations of turbulent penetrative convection in the ocean surface boundary layer. We uncover structural deficiencies and discuss their cause. We conclude by discussing the applicability of the approach to Earth system models.

Parameterizations of unresolved turbulent processes often compromise the fidelity of large-scale ocean models. In this work, we argue for a Bayesian approach to the refinement and evaluation of turbulence parameterizations. Using an ensemble of large eddy simulations of turbulent penetrative convection in the surface boundary layer, we demonstrate the method by estimating the uncertainty of parameters in the convective limit of the popular ‘K-Profile Parameterization’. We uncover structural deficiencies and propose an alternative scaling that overcomes them.