850 research outputs found

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Does exercise intensity matter for fatigue during (neo‐)adjuvant cancer treatment? The Phys‐Can randomized clinical trial

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    Exercise during cancer treatment improves cancer‐related fatigue (CRF), but the importance of exercise intensity for CRF is unclear. We compared the effects of high‐ vs low‐to‐moderate‐intensity exercise with or without additional behavior change support (BCS) on CRF in patients undergoing (neo‐)adjuvant cancer treatment. This was a multicenter, 2x2 factorial design randomized controlled trial (Clinical Trials NCT02473003) in Sweden. Participants recently diagnosed with breast (n = 457), prostate (n = 97) or colorectal (n = 23) cancer undergoing (neo‐)adjuvant treatment were randomized to high intensity (n = 144), low‐to‐moderate intensity (n = 144), high intensity with BCS (n = 144) or low‐to‐moderate intensity with BCS (n = 145). The 6‐month exercise intervention included supervised resistance training and home‐based endurance training. CRF was assessed by Multidimensional Fatigue Inventory (MFI, five subscales score range 4‐20), and Functional Assessment of Chronic Illness Therapy‐Fatigue scale (FACIT‐F, score range 0‐52). Multiple linear regression for main factorial effects was performed according to intention‐to‐treat, with post‐intervention CRF as primary endpoint. Overall, 577 participants (mean age 58.7 years) were randomized. Participants randomized to high‐ vs low‐to‐moderate‐intensity exercise had lower physical fatigue (MFI Physical Fatigue subscale; mean difference −1.05 [95% CI: −1.85, −0.25]), but the difference was not clinically important (ie <2). We found no differences in other CRF dimensions and no effect of additional BCS. There were few minor adverse events. For CRF, patients undergoing (neo‐)adjuvant treatment for breast, prostate or colorectal cancer can safely exercise at high‐ or low‐to‐moderate intensity, according to their own preferences. Additional BCS does not provide extra benefit for CRF in supervised, well‐controlled exercise interventions

    In utero exposure to cigarette chemicals induces sex-specific disruption of one-carbon metabolism and DNA methylation in the human fetal liver

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    Background: Maternal smoking is one of the most important modifiable risk factors for low birthweight, which is strongly associated with increased cardiometabolic disease risk in adulthood. Maternal smoking reduces the levels of the methyl donor vitamin B12 and is associated with altered DNA methylation at birth. Altered DNA methylation may be an important mechanism underlying increased disease susceptibility; however, the extent to which this can be induced in the developing fetus is unknown. Methods: In this retrospective study, we measured concentrations of cobalt, vitamin B12, and mRNA transcripts encoding key enzymes in the 1-carbon cycle in 55 fetal human livers obtained from 11 to 21 weeks of gestation elective terminations and matched for gestation and maternal smoking. DNA methylation was measured at critical regions known to be susceptible to the in utero environment. Homocysteine concentrations were analyzed in plasma from 60 fetuses. Results: In addition to identifying baseline sex differences, we found that maternal smoking was associated with sex-specific alterations of fetal liver vitamin B12, plasma homocysteine and expression of enzymes in the 1-carbon cycle in fetal liver. In the majority of the measured parameters which showed a sex difference, maternal smoking reduced the magnitude of that difference. Maternal smoking also altered DNA methylation at the imprinted gene IGF2 and the glucocorticoid receptor (GR/NR3C1). Conclusions: Our unique data strengthen studies linking in utero exposures to altered DNA methylation by showing, for the first time, that such changes are present in fetal life and in a key metabolic target tissue, human fetal liver. Furthermore, these data propose a novel mechanism by which such changes are induced, namely through alterations in methyl donor availability and changes in 1-carbon metabolism

    Measurement of W ± -boson and Z -boson production cross-sections in pp collisions at s = 2.76 TeV with the ATLAS detector

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    Abstract: The production cross-sections for W± and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb-1 collected at a centre-of-mass energy s=2.76 TeV. The decay channels W→ℓν and Z→ℓℓ are used, where ℓ can be an electron or a muon. The cross-sections are presented for a fiducial region defined by the detector acceptance and are also extrapolated to the full phase space for the total inclusive production cross-section. The combined (average) total inclusive cross-sections for the electron and muon channels are: σW+→ℓνtot=2312±26(stat.)±27(syst.)±72(lumi.)±30(extr.)pb, σW-→ℓνtot=1399±21(stat.)±17(syst.)±43(lumi.)±21(extr.)pb, σZ→ℓℓtot=323.4±9.8(stat.)±5.0(syst.)±10.0(lumi.)±5.5(extr.)pb.Measured ratios and asymmetries constructed using these cross-sections are also presented. These observables benefit from full or partial cancellation of many systematic uncertainties that are correlated between the different measurements

    Measurement of the azimuthal anisotropy of charged-particle production in Xe+Xe collisions at sNN =5.44 TeV with the ATLAS detector

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    This paper describes the measurements of flow harmonics v2-v6 in 3μb-1 of Xe+Xe collisions at sNN=5.44 TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and pT dependence of the vn obtained using two-particle correlations and the scalar product technique are presented. The measurements are also performed using a template-fit procedure, which was developed to remove nonflow correlations in small collision systems. This nonflow removal is shown to have a significant influence on the measured vn at high pT, especially in peripheral events. Comparisons of the measured vn with measurements in Pb+Pb collisions and p+Pb collisions at sNN=5.02 TeV are also presented. The vn values in Xe+Xe collisions are observed to be larger than those in Pb+Pb collisions for n=2, 3, and 4 in the most central events. However, with decreasing centrality or increasing harmonic order n, the vn values in Xe+Xe collisions become smaller than those in Pb+Pb collisions. The vn in Xe+Xe and Pb+Pb collisions are also compared as a function of the mean number of participating nucleons, (Npart), and the measured charged-particle multiplicity in the detector. The v3 values in Xe+Xe and Pb+Pb collisions are observed to be similar at the same (Npart) or multiplicity, but the other harmonics are significantly different. The ratios of the measured vn in Xe+Xe and Pb+Pb collisions, as a function of centrality, are also compared to theoretical calculations

    Measurement of differential cross sections for single diffractive dissociation in √s = 8 TeV pp collisions using the ATLAS ALFA spectrometer

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    A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy √ s = 8 TeV is used to study inclusive single diffractive dissociation, pp → Xp. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are measured in the central detector components. The fiducial range of the measurement is −4.0 &lt; log10 ξ &lt; −1.6 and 0.016 &lt; |t| &lt; 0.43 GeV2 , where ξ is the proton fractional energy loss and t is the squared four-momentum transfer. The total cross section integrated across the fiducial range is 1.59 ± 0.13 mb. Cross sections are also measured differentially as functions of ξ, t, and ∆η, a variable that characterises the rapidity gap separating the proton and the system X. The data are consistent with an exponential t dependence, dσ/dt ∝ e Bt with slope parameter B = 7.65 ± 0.34 GeV−2 . Interpreted in the framework of triple Regge phenomenology, the ξ dependence leads to a pomeron intercept of α(0) = 1.07 ± 0.09

    Measurement of the inclusive cross-section for the production of jets in association with a Z boson in proton–proton collisions at 8 TeV using the ATLAS detector

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    Abstract: The inclusive cross-section for jet production in association with a Z boson decaying into an electron–positron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb-1 of s=8 TeV proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Z+ jets cross-section is unfolded to the particle level. The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects. The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations

    Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and pp collisions at √sNN = 5.02 TeV with the ATLAS detector

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    Studies of the fragmentation of jets into charged particles in heavy-ion collisions can provide information about the mechanism of jet quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. This paper presents a measurement of the angular distribution of charged particles around the jet axis in √ s N N = 5.02 TeV Pb + Pb and pp collisions, using the ATLAS detector at the LHC. The Pb + Pb and p p data sets have integrated luminosities of 0.49 nb − 1 and 25 pb − 1 , respectively. The measurement is performed for jets reconstructed with the anti- k t algorithm with radius parameter R = 0.4 and is extended to an angular distance of r = 0.8 from the jet axis. Results are presented as a function of Pb + Pb collision centrality and distance from the jet axis for charged particles with transverse momenta in the 1- to 63-GeV range, matched to jets with transverse momenta in the 126- to 316-GeV range and an absolute value of jet rapidity of less than 1.7. Modifications to the measured distributions are quantified by taking a ratio to the measurements in p p collisions. Yields of charged particles with transverse momenta below 4 GeV are observed to be increasingly enhanced as a function of angular distance from the jet axis, reaching a maximum at r = 0.6 . Charged particles with transverse momenta above 4 GeV have an enhanced yield in Pb + Pb collisions in the jet core for angular distances up to r = 0.05 from the jet axis, with a suppression at larger distances

    A search for the dimuon decay of the Standard Model Higgs boson with the ATLAS detector

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    A search for the dimuon decay of the Standard Model (SM) Higgs boson is performed using data corresponding to an integrated luminosity of 139 fb(-1) collected with the ATLAS detector in Run 2 pp collisions at root s = 13 TeV at the Large Hadron Collider. The observed (expected) significance over the background-only hypothesis for a Higgs boson with a mass of 125.09 GeV is 2.0 sigma (1.7 sigma). The observed upper limit on the cross section times branching ratio for pp -&gt; H -&gt; mu mu is 2.2 times the SM prediction at 95% confidence level, while the expected limit on a H -&gt; mu mu signal assuming the absence (presence) of a SM signal is 1.1(2.0). The best-fit value of the signal strength parameter, defined as the ratio of the observed signal yield to the one expected in the SM, is mu = 1.2 +/- 0.6. (C) 2020 The Author(s). Published by Elsevier B.V

    Identification of boosted Higgs bosons decaying into b -quark pairs with the ATLAS detector at 13 TeV

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    Abstract: This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H→bb¯, for proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy s=13 TeV. These decays are reconstructed from calorimeter jets found with the anti-ktR=1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R=0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb-1 of data collected in 2015 and 2016 using g→bb¯ and Z(→bb¯)γ event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties
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