Recent publications
Phenotypic plasticity in body growth enables organisms to cope with unpredictable paucities in resource availability. Growth traits influence survival and reproductive success, and thereby, population persistence, and early‐life resource availability may govern lifetime patterns in growth, reproductive success, and survival. The influence of early‐life environment is decidedly consequential for indeterminately growing ectotherms, which rely on available resources and ambient temperatures to maximize fitness throughout life. Using 17 years of mark–recapture data, we evaluate the effects of resource availability on patterns in growth for populations of western terrestrial garter snakes (Thamnophis elegans), which differ along pace‐of‐life continuums into fast‐ and slow‐living ecotypes. We use an adaptation of the von Bertalanffy estimator to fit structural growth models and linear predictors for body condition to analyze the consequences of annual and early‐life prey availability. Snakes from resource‐poor early‐life environments are primed to exploit conditions in high‐prey environments later in life. Slow pace‐of‐live animals exhibit a greater capacity for compensatory strategies in structural growth, while body condition was best explained by a complex interaction across males and non‐gravid females between prey availability and ecotype. Our findings highlight the importance of accounting for context‐dependent early‐life environments as well as sex‐specific reproductive demands when evaluating population traits.
The ATLAS tile calorimeter (TileCal) is the hadronic sampling calorimeter covering the central region of the ATLAS detector at the Large Hadron Collider (LHC). This paper gives an overview of the calorimeter’s operation and performance during the years 2015–2018 (Run 2). In this period, ATLAS collected proton–proton collision data at a centre-of-mass energy of 13 TeV and the TileCal was 99.65% efficient for data-taking. The signal reconstruction, the calibration procedures, and the detector operational status are presented. The performance of two ATLAS trigger systems making use of TileCal information, the minimum-bias trigger scintillators and the tile muon trigger, is discussed. Studies of radiation effects allow the degradation of the output signals at the end of the LHC and HL-LHC operations to be estimated. Finally, the TileCal response to isolated muons, hadrons and jets from proton–proton collisions is presented. The energy and time calibration methods performed excellently, resulting in good stability and uniformity of the calorimeter response during Run 2. The setting of the energy scale was performed with an uncertainty of 2%. The results demonstrate that the performance is in accordance with specifications defined in the Technical Design Report.
Proton–proton collision data recorded by the ATLAS detector in 2011, at a centre-of-mass energy of 7 TeV, have been used for an improved determination of the W -boson mass and a first measurement of the W -boson width at the LHC. Recent fits to the proton parton distribution functions are incorporated in the measurement procedure and an improved statistical method is used to increase the measurement precision. The measurement of the W -boson mass yields a value of m W = 80 , 366.5 ± 9.8 ( stat. ) ± 12.5 ( syst. ) MeV = 80 , 366.5 ± 15.9 MeV, and the width is measured as Γ W = 2202 ± 32 ( stat. ) ± 34 ( syst. ) MeV = 2202 ± 47 MeV. The first uncertainty components are statistical and the second correspond to the experimental and physics-modelling systematic uncertainties. Both results are consistent with the expectation from fits to electroweak precision data. The present measurement of m W is compatible with and supersedes the previous measurement performed using the same data.
Background Ectothermic arthropods, like ticks, are sensitive indicators of environmental changes, and their seasonality plays a critical role in tick-borne disease dynamics in a warming world. Juvenile tick phenology, which influences pathogen transmission, may vary across climates, with longer tick seasons in cooler climates potentially amplifying transmission. However, assessing juvenile tick phenology is challenging in climates where desiccation pressures reduce the time ticks spend seeking blood meals. To improve our understanding of juvenile tick seasonality across a latitudinal gradient, we examine Ixodes pacificus phenology on lizards, the primary juvenile tick host in California, and explore how climate factors influence phenological patterns. Methods Between 2013 and 2022, ticks were removed from 1,527 lizards at 45 locations during peak tick season (March-June). Tick counts were categorized by life stage (larvae and nymphs) and linked with remotely sensed climate data. Juvenile phenology metrics, including abundance, date of peak abundance, and temporal overlap between larval and nymphal populations, were analyzed along a latitudinal gradient, including tick abundances on lizards, Julian date of peak mean abundance. Generalized Additive Models (GAMs) were applied to assess climate-associated variation in juvenile abundance on lizards. Results Mean tick abundance per lizard ranged from 0.17 to 47.21 across locations, with the highest in the San Francisco Bay Area and lowest in Los Angeles, where more lizards had zero ticks attached. In the San Francisco Bay Area, peak nymphal abundance occurred 25 days earlier than peak larval abundance. Temporal overlap between larval and nymphal stages at a given location varied regionally, with northern areas showing higher overlap. We found that locations with higher temperatures and increased drought stress were linked to lower tick abundances, though the magnitude of these effects depended on regional location. Conclusion Our study, which compiled 10 years of data, reveals significant regional variation in juvenile I. pacificus phenology across California, including differences in the abundance, peak timing, and temporal overlap. These findings highlight the influence of local climate on tick seasonality, with implications for tick-borne disease dynamics in a changing climate.
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During the 2015–2018 data-taking period, the Large Hadron Collider delivered proton-proton bunch crossings at a centre-of-mass energy of 13 TeV to the ATLAS experiment at a rate of roughly 30 MHz, where each bunch crossing contained an average of 34 independent inelastic proton-proton collisions. The ATLAS trigger system selected roughly 1 kHz of these bunch crossings to be recorded to disk. Offline algorithms then identify one of the recorded collisions as the collision of interest for subsequent data analysis, and the remaining collisions are referred to as pile-up.
Pile-up collisions represent a trigger-unbiased dataset, which is evaluated to have an integrated luminosity of 1.33 pb − 1 in 2015–2018. This is small compared with the normal trigger-based ATLAS dataset, but when combined with vertex-by-vertex jet reconstruction it provides up to 50 times more dijet events than the conventional single-jet-trigger-based approach, and does so without adding any additional cost or requirements on the trigger system, readout, or storage. The pile-up dataset is validated through comparisons with a special trigger-unbiased dataset recorded by ATLAS, and its utility is demonstrated by means of a measurement of the jet energy resolution in dijet events, where the statistical uncertainty is significantly reduced for jet transverse momenta below 65 GeV.
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A search is presented for new particles produced in proton-proton collisions at a centre-of-mass energy of 13 TeV that result in final states comprising a massive vector ( W or Z ) boson that decays hadronically and large missing transverse momentum. The data sample was collected with the ATLAS experiment at the Large Hadron Collider from 2015 to 2018 and corresponds to an integrated luminosity of 140 fb − 1 . No significant excess over the Standard Model expectation is observed. Model-independent 95% confidence-level limits on the visible cross-section that range from 0.3 fb to 79.5 fb are obtained for non-Standard-Model processes. Exclusion limits are also presented for models with axion-like particles, for two-Higgs-doublet models with a pseudo-scalar mediator between the Standard Model and the dark sector, for the invisible decay of the Higgs boson and for pair-produced weakly interacting dark matter candidates.
While much bias and discrimination research has focused on individual identity analysis, for example, gender, race, or ethnicity, what is not fully understood is how other social categories of difference influence discrimination. Using qualitative content analysis, this study examines facets of women leaders' identity that influence their experiences of bias. Respondents were 913 women in four United States industries in which top leadership roles are male dominated but the industries overall are female dominated or gender balanced. The findings revealed 30 distinct identity factors that were used as the basis for discrimination. The variety of the factors and the variation of stigma within each factor show that women leaders are considered “never quite right” as almost any facet of their identity can be declared problematic for a specific woman in a specific context. Human resource leaders should create inclusive policies so that women can express their authentic selves at work. Leadership teams and supervisors should be trained to recognize identity factors that may be the focus of criticism and, thus, serve as veiled bases for discrimination.
A bstract
This paper reports the observation of top-quark pair production in proton-lead collisions in the ATLAS experiment at the Large Hadron Collider. The measurement is performed using 165 nb − 1 of p +Pb data collected at s NN = 8 . 16 TeV in 2016. Events are categorised in two analysis channels, consisting of either events with exactly one lepton (electron or muon) and at least four jets, or events with two opposite-charge leptons and at least two jets. In both channels at least one b -tagged jet is also required. Top-quark pair production is observed with a significance over five standard deviations in each channel. The top-quark pair production cross-section is measured to be σ t t ¯ = 58.1 ± 2.0 stat . − 4.4 + 4.8 syst . nb, with a total uncertainty of 9%. In addition, the nuclear modification factor is measured to be R p A = 1.090 ± 0.039 stat . − 0.087 + 0.094 syst . . The measurements are found to be in good agreement with theory predictions involving nuclear parton distribution functions.
A bstract
Measurements of the Higgs boson production times decay rates and differential cross-sections have recently been performed by the ATLAS experiment in several decay channels using up to 139 fb − 1 of proton-proton collision data at s = 13 TeV recorded at the Large Hadron Collider. This paper presents multiple interpretations of these Higgs boson measurements. Measurements of production-mode cross-sections, simplified template cross-sections and fiducial differential cross-sections in different decay channels are reparameterised in terms of the impact of Standard Model effective field theory operators, and constraints are reported on the corresponding Wilson coefficients. Production and decay rate measurements are interpreted in UV-complete extensions of the Standard Model, namely the two-Higgs-doublet model (2HDM) near the alignment limit and the Minimal Supersymmetric Standard Model (MSSM) for various MSSM benchmark scenarios. The constraints on the 2HDM parameters (cos( β − α ), tan β ) and the MSSM parameters ( m A , tan β ) are complementary to those obtained from direct searches for additional Higgs bosons.
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A search for the resonant production of a heavy scalar X decaying into a Higgs boson and a new lighter scalar S , through the process X → S (→ b b ¯ ) H (→ γγ ), where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using an integrated luminosity of 140 fb − 1 of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed over the mass range 170 ≤ m X ≤ 1000 GeV and 15 ≤ m S ≤ 500 GeV. Parameterised neural networks are used to enhance the signal purity and to achieve continuous sensitivity in a domain of the ( m X , m S ) plane. No significant excess above the expected background is found and 95% CL upper limits are set on the cross section times branching ratio, ranging from 39 fb to 0.09 fb. The largest deviation from the background-only expectation occurs for ( m X , m S ) = (575, 200) GeV with a local (global) significance of 3.5 (2.0) standard deviations.
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A search for neutral long-lived particles (LLPs) decaying in the ATLAS hadronic calorimeter using 140 fb − 1 of proton-proton collisions at s = 13 TeV delivered by the LHC is presented. The analysis is composed of three channels. The first targets pair-produced LLPs, where at least one LLP is produced with sufficiently low boost that its decay products can be resolved as separate jets. The second and third channels target LLPs respectively produced in association with a W or Z boson that decays leptonically. In each channel, different search regions target different kinematic regimes, to cover a broad range of LLP mass hypotheses and models. No excesses of events relative to the background predictions are observed. Higgs boson branching fractions to pairs of hadronically decaying neutral LLPs larger than 1% are excluded at 95% confidence level for proper decay lengths in the range of 30 cm to 4.5 m depending on the LLP mass, a factor of three improvement on previous searches in the hadronic calorimeter. The production of long-lived dark photons in association with a Z boson with cross-sections above 0.1 pb is excluded for dark photon mean proper decay lengths in the range of 20 cm to 50 m, improving previous ATLAS results by an order of magnitude. Finally, long-lived photo-phobic axion-like particle models are probed for the first time by ATLAS, with production cross-sections above 0.1 pb excluded in the 0.1 mm to 10 m range.
This paper describes measurements of the transverse momentum spectra of W and Z bosons produced in proton–proton collisions at centre-of-mass energies of s = 5.02 TeV and s = 13 TeV with the ATLAS experiment at the Large Hadron Collider. Measurements are performed in the electron and muon channels, W → ℓ ν and Z → ℓ ℓ ( ℓ = e or μ ), and for W events further separated by charge. The data were collected in 2017 and 2018, in dedicated runs with reduced instantaneous luminosity, and correspond to 255 and 338 pb - 1 at s = 5.02 TeV and 13 TeV, respectively. These conditions optimise the reconstruction of the W -boson transverse momentum. The distributions observed in the electron and muon channels are unfolded, combined, and compared to QCD calculations based on parton shower Monte Carlo event generators and analytical resummation. The description of the transverse momentum distributions by Monte Carlo event generators is imperfect and shows significant differences largely common to W - , W + and Z production. The agreement is better at s = 5.02 TeV, especially for predictions that were tuned to Z production data at s = 7 TeV. Higher-order, resummed predictions based on DYTurbo generally match the data best across the spectra. Distribution ratios are also presented and test the understanding of differences between the production processes.
A bstract
Inclusive and differential cross-sections are measured at particle level for the associated production of a top quark pair and a photon ( t t ¯ γ ). The analysis is performed using an integrated luminosity of 140 fb − 1 of proton-proton collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector. The measurements are performed in the single-lepton and dilepton top quark pair decay channels focusing on t t ¯ γ topologies where the photon is radiated from an initial-state parton or one of the top quarks. The absolute and normalised differential cross-sections are measured for several variables characterising the photon, lepton and jet kinematics as well as the angular separation between those objects. The observables are found to be in good agreement with the Monte Carlo predictions. The photon transverse momentum differential distribution is used to set limits on effective field theory parameters related to the electroweak dipole moments of the top quark. The combined limits using the photon and the Z boson transverse momentum measured in t t ¯ production in associations with a Z boson are also set.
This paper reports a summary of searches for a fermionic dark matter candidate in the context of theoretical models characterised by a mediator particle exchange in the s -channel. The data sample considered consists of pp collisions delivered by the Large Hadron Collider during its Run 2 at a centre-of-mass energy of s = 13 TeV and recorded by the ATLAS detector, corresponding to up to 140 fb - 1 . The interpretations of the results are based on simplified models where the new mediator particles can be spin-0, with scalar or pseudo-scalar couplings to fermions, or spin-1, with vector or axial-vector couplings to fermions. Exclusion limits are obtained from various searches characterised by final states with resonant production of Standard Model particles, or production of Standard Model particles in association with large missing transverse momentum.
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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 − 1 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: R → SH and A → ZH , where R is a CP-even boson, A is a CP-odd boson, H is a CP-even boson, and S is considered to decay into invisible particles that are candidates for dark matter. In these processes, S → invisible and H → ZZ . The Z boson associated with the heavy scalar boson H decays into all decay channels of the Z boson. The mass range under consideration is 390–1300 (320–1300) GeV for the R ( A ) boson and 220–1000 GeV for the H 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.
The observation of the electroweak production of a W boson and a photon in association with two jets, using pp collision data at the Large Hadron Collider at a centre of mass energy of s = 13 TeV, is reported. The data were recorded by the ATLAS experiment from 2015 to 2018 and correspond to an integrated luminosity of 140 fb - 1 . This process is sensitive to the quartic gauge boson couplings via the vector boson scattering mechanism and provides a stringent test of the electroweak sector of the Standard Model. Events are selected if they contain one electron or muon, missing transverse momentum, at least one photon, and two jets. Multivariate techniques are used to distinguish the electroweak W γ j j process from irreducible background processes. The observed significance of the electroweak W γ j j process is well above six standard deviations, compared to an expected significance of 6.3 standard deviations. Fiducial and differential cross sections are measured in a fiducial phase space close to the detector acceptance, which are in reasonable agreement with leading order Standard Model predictions from MadGraph5+Pythia8 and Sherpa . The results are used to constrain new physics effects in the context of an effective field theory.
Sprayed liquid flap (SLF) is a novel powered-lift concept that utilizes an atomized liquid spray as a jet flap. Similar to a jet flap, SLFs modulate the flow and aerodynamics using a jet expelled on the pressure surface. However, SLFs differ through two mechanisms: 1) the liquid density is two orders of magnitude larger than the ambient air, and 2) the SLF medium has a porous-like character. The present effort explores SLFs using computational fluid dynamics at a state before experiments and therefore relies on benchmarks of underlying physics associated with a liquid-jet in crossflow. The studies evaluate flow rates, SLF positioning, and configurations spanning a range of flow conditions. The present investigation shows that SLFs can provide lift control combined with drag reduction with potential for application in aircraft. Additionally, the present study demonstrates that SLFs operate as a flow control device, not propulsion. Besides two-dimensional analysis, the SLF concept was investigated in three dimensions, which showed good consistency in potential applications despite three-dimensional effects on the SLF. Overall, this effort indicates the clear potential of a novel flow powered-lift control device useful for a range of aerodynamic applications.
In this chapter, we identify the two typical visions humans have developed for how to attain worldwide peace, neither of which has worked, and in their place, we argue for a barrierless world that encompasses global human belonging while also enabling people to retain and treasure their local identities. The two prototypical, failed notions are that (1) nations should not go to war even though each retains its power to deter aggression from others—consistent with the principles of the Peace of Westphalia and (2) all countries unite and become one big country encompassing all of humanity—a lofty idea that implies that people must give up their historic national social identities, which history shows they do not easily do. Therefore, we propose a third model that shows promise of working. In it, people achieve a sense of global identity and citizenship, and simultaneously sustain and treasure their national and ethnic identity. In doing so, they develop both a local and a global sense of belonging. Thus, the territorial imperative may be mitigated through the development and fostering of character strengths in individuals and leaders such as creativity, teamwork, fairness, compassion, and a perspective encompassing a world-minded value orientation. This would involve, over time and perhaps several generations, a sense of interdependence by the engagement of global institutions and entities such as the United Nations, NGOs, and other transnational entities to promote and strengthen global human belonging with active and purposeful engagement by all.
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