Xiaoyue Liu

Abstract

This paper describes a measurement of the jet radius dependence of the dijet momentum balance between leading back-to-back jets in Formula Presented of Formula Presented collisions collected in 2018 and Formula Presented of Formula Presented collisions collected in 2017 by the ATLAS detector at the LHC. Both datasets were collected at Formula Presented TeV. Jets are reconstructed using the anti-Formula Presented algorithm with jet radius parameters Formula Presented, 0.3, 0.4, 0.5, and 0.6. The dijet momentum balance distributions are constructed for leading jets with transverse momentum Formula Presented from 100 to 562 GeV for Formula Presented, 0.3, and 0.4 jets, and from 158 to 562 GeV for Formula Presented and 0.6 jets. The absolutely normalized dijet momentum balance distributions are constructed to compare measurements of the dijet yields in Formula Presented collisions directly to the dijet cross sections in Formula Presented collisions. For all jet radii considered here, there is a suppression of more balanced dijets in Formula Presented collisions compared with Formula Presented collisions, while for more imbalanced dijets there is an enhancement. There is a jet radius dependence to the dijet yields, being stronger for more imbalanced dijets than for more balanced dijets. Additionally, jet pair nuclear modification factors are measured. The subleading jet yields are found to be more suppressed than leading jet yields in dijets. A jet radius dependence of the pair nuclear modification factors is observed, with the suppression decreasing with increasing jet radius. These measurements provide new constraints on jet quenching scenarios in the quark-gluon plasma.

Abstract

The inclusive cross section for the production of a single top quark in association with a Formula Presented boson is measured using Formula Presented of proton-proton collision data collected with the ATLAS detector at Formula Presented. Events containing two charged leptons and at least one jet identified as originating from a Formula Presented-quark are selected. A multivariate discriminant is constructed to separate the Formula Presented signal from the Formula Presented background. The cross section is extracted using a profile likelihood fit to the signal and control regions and it is measured to be Formula Presented, in good agreement with the Standard Model prediction. The measured cross section is used to extract a value for the left-handed form factor at the Formula Presented vertex times the Cabibbo-Kobayashi-Maskawa matrix element Formula Presented of Formula Presented.

Abstract

Measurements of integrated and differential cross-sections for electroweak W±Z production in association with two jets (W±Zjj) in proton-proton collisions are presented. The data collected by the ATLAS detector at the Large Hadron Collider from 2015 to 2018 at a centre-of-mass energy of s = 13 TeV are used, corresponding to an integrated luminosity of 140 fb−1. The W±Zjj candidate events are reconstructed using leptonic decay modes of the gauge bosons. Events containing three identified leptons, either electrons or muons, and two jets are selected. Processes involving pure electroweak W±Zjj production at Born level are separated from W±Zjj production involving a strong coupling. The measured integrated fiducial cross-section of electroweak W±Zjj production per lepton flavour is σWZjj−EW→ℓ′νlljj = 0.368 ± 0.037 (stat.) ± 0.059 (syst.) ± 0.003 (lumi.) fb, where ℓ and ℓ′ are either an electron or a muon. Respective cross-sections of electroweak and strong W±Zjj production are measured separately for events with exactly two jets or with more than two jets, and in three bins of the invariant mass of the two jets. The inclusive W±Zjj production cross-section, without separating electroweak and strong production, is also measured to be σWZjj→ℓ′νlljj = 1.462 ± 0.063 (stat.) ± 0.118 (syst.) ± 0.012 (lumi.) fb, per lepton flavour. The inclusive W±Zjj production cross-section is measured differentially for several kinematic observables. Finally, the measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confidence level intervals on dimension-8 operators.

Abstract

This paper presents a measurement of the production cross-section of a Z boson in association with b- or c-jets, in proton–proton collisions at s=13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb-1. Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum pT>20 GeV and rapidity |y|<2.5. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z+≥1c-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

Abstract

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 sNN = 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 σtt¯=58.1±2.0stat.−4.4+4.8syst. nb, with a total uncertainty of 9%. In addition, the nuclear modification factor is measured to be RpA=1.090±0.039stat.−0.087+0.094syst. The measurements are found to be in good agreement with theory predictions involving nuclear parton distribution functions.

Abstract

Obstructive sleep apnea (OSA) and hypertension are two important modifiable risk factors for cardiovascular disease and mortality. Numerous studies have highlighted the interplay between these two conditions. We provide a critical review of the current literature on the role of the OSA as a risk factor for hypertension and its effect on blood pressure (BP). We discuss several key topics: the effect of OSA on nocturnal BP, BP response to continuous positive airway pressure (CPAP) treatment, CPAP effect on BP in refractory hypertension, the role of OSA in BP variability (BPV), and maladaptive cardiac remodeling mediated by OSA’s effect on BP. Finally, we discuss the unique aspects of ethnicity and social determinants of health on OSA with a focus on Asian populations and the disparity in BP control and cardiovascular outcomes.

Abstract

Background: High rates of physical inactivity persist in the United States, with higher rates among non-Hispanic Black adults than among their White peers. However, a comparison of physical activity engagement across nativity among Black adults in the United States has yet to be fully documented. The purpose of this cross-sectional study was to examine physical activity engagement rates among African immigrant and Afro-Caribbean immigrant adults compared with native-born African American adults using data from the 2010 to 2018 National Health Interview Survey. Methods: Using data from the 2010 to 2018 National Health Interview Survey, we used generalized linear models to compare levels of physical activity (meeting the moderate-to-vigorous physical activity [MVPA] recommendations) by ethnic subgroups of Black adults, sequentially adjusting for sociodemographic and health-related risk factors. Results: Data from 38,037 adults (58.8% female, 21% college/graduate degree, and 41.4% with obesity) were included. Only 41.9% of all participants met the MVPA recommendations. In the fully adjusted models across the 9 years, higher levels of MVPA were seen among African Americans (42%) than among African immigrants (38%) and Afro-Caribbean immigrants (41%). Compared with African Americans, African immigrants were less likely to engage in physical activity that met the MVPA guidelines (prevalence ratio: 0.90; 95% confidence interval: 0.85, 0.96), whereas there were no differences in meeting the guidelines between Afro-Caribbean immigrants (prevalence ratio: 0.96; 95% confidence interval:0.90, 1.02) and African Americans. Conclusion: Culturally tailored interventions addressing socioenvironmental barriers and facilitators of physical activity may have important impacts on physical activity promotion and long-term disease burden among Black adults across nativity.

Abstract

The ratio of branching ratios of the W boson to muons and electrons, RWμ/e=B(W→μν)/B(W→eν), has been measured using 140fb-1 of pp collision data at s=13 TeV collected with the ATLAS detector at the LHC, probing the universality of lepton couplings. The ratio is obtained from measurements of the tt¯ production cross-section in the ee, eμ and μμ dilepton final states. To reduce systematic uncertainties, it is normalised by the square root of the corresponding ratio RZμμ/ee for the Z boson measured in inclusive Z→ee and Z→μμ events. By using the precise value of RZμμ/ee determined from e+e- colliders, the ratio RWμ/e is determined to be (Formula presented.) The three uncertainties correspond to data statistics, experimental systematics and the external measurement of RZμμ/ee, giving a total uncertainty of 0.0045, and confirming the Standard Model assumption of lepton flavour universality in W-boson decays at the 0.5% level.

Abstract

Purpose of Review: Racial disparities in sleep health as well as the diagnosis and treatment of sleep disorders have emerged as a key driver of cardiovascular outcomes. Obstructive sleep apnea (OSA), is characterized by repeated airway obstructions during sleep and is associated with an increased risk of cardiovascular disease. While racial and ethnic minorities have disproportionately high OSA prevalence rates, diagnosis rates remain low. One explanation behind this phenomenon are structural environmental and lifestyle barriers that prevent access to OSA care. Additionally, there remains significantly limited understanding of OSA and its causes and symptoms within communities. Recent Findings: In general, minorities have poorer sleep health due to systemic and environmental racism, which also causes an increased in conditions such as obesity that increases OSA risk. Disparities also persist within various types of OSA treatment. The most common form of treatment, continuous positive airway pressure (CPAP) has lower adherence among African Americans, as well as those living in areas with low socioeconomic status (SES), primarily minorities. There have been a small number of studies that have shown some initial success of educational campaigns about OSA within minority communities in increasing screenings and diagnoses. Peer based education has been an effective technique, and there is a need for such programs to be expanded. Summary: Disparities persist, with minority groups having worse sleep health and lower rates of adherence to OSA treatment. Some grassroots, peer-led educational campaigns show promise in increasing adherence. In light of these disparities, there remains a need for the field of sleep medicine to continue addressing the systemic barriers that hinder the timely evaluation and treatment in racial minorities.

Abstract

A search for a hypothetical heavy scalar particle, X, decaying into a singlet scalar particle, S, and a Standard Model Higgs boson, H, using 140 fb−1 of proton-proton collision data at the centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the LHC is presented. The explored mass range is 300 ≤ mX ≤ 1000 GeV and 170 ≤ mS ≤ 500 GeV. The signature of this search is one or two leptons (e or μ) from the decay of vector bosons originating from the S particle, S → W±W∓/ZZ, and two photons from the Higgs boson decay, H → γγ. No significant excess is observed above the expected Standard Model background. The observed (expected) upper limits at the 95% confidence level on the cross- section for gg → X → SH, assuming the same S → WW/ZZ branching ratios as for a SM-like heavy Higgs boson, are between 530 (800) fb and 120 (170) fb.