26 research outputs found

    A search for prompt lepton-jets in pp collisions at root s=8 TeV with the ATLAS detector

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    A search is presented for a new, light boson with a mass of about 1 GeV and decaying promptly to jets of collimated electrons and/or muons (lepton-jets). The analysis is performed with 20.3 fb−1 of data collected by the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a centre-of-mass energy of 8 TeV. Events are required to contain at least two lepton-jets. This study finds no statistically significant deviation from predictions of the Standard Model and places 95% confidence-level upper limits on the contribution of new phenomena beyond the SM, incuding SUSY-portal and Higgs-portal models, on the number of events with lepton-jets.We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; IN2P3-CNRS, CEADSM/IRFU, France; GNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZ. S, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; the Royal Society and Leverhulme Trust, United Kingdom

    Search for the production of single vector-like and excited quarks in the Wt final state in pp collisions at √s=8 TeV with the ATLAS detector

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    A search for vector-like quarks and excited quarks in events containing a top quark and a W boson in the final state is reported here. The search is based on 20.3 fb−1 of proton-proton collision data taken at the LHC at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector. Events with one or two leptons, and one, two or three jets are selected with the additional requirement that at least one jet contains a b-quark. Single-lepton events are also required to contain at least one large-radius jet from the hadronic decay of a high-pTW boson or a top quark. No significant excess over the expected background is observed and upper limits on the cross-section times branching ratio for different vector-like quark and excited-quark model masses are derived. For the excited-quark production and decay to Wt with unit couplings, quarks with masses below 1500 GeV are excluded and coupling-dependent limits are set

    Measurement of jet charge in dijet events from √s = 8  TeV pp collisions with the ATLAS detector

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    The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum-weighted sums, called jet charge, in dijet events using 20.3 fb−¹ of data recorded with the ATLAS detector at √s = 8 TeV in pp collisions at the LHC. The jet charge distribution is unfolded to remove distortions from detector effects and the resulting particle-level distribution is compared with several models. The pT dependence of the jet charge distribution average and standard deviation are compared to predictions obtained with several leading-order and next-to-leading-order parton distribution functions. The data are also compared to different Monte Carlo simulations of QCD dijet production using various settings of the free parameters within these models. The chosen value of the strong coupling constant used to calculate gluon radiation is found to have a significant impact on the predicted jet charge. There is evidence for a pT dependence of the jet charge distribution for a given jet flavor. In agreement with perturbative QCD predictions, the data show that the average jet charge of quark-initiated jets decreases in magnitude as the energy of the jet increases

    Conservative versus invasive strategy in elderly patients with non-ST-elevation myocardial infarction: insights from the international POPular age registry

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    This registry assessed the impact of conservative and invasive strategies on major adverse clinical events (MACE) in elderly patients with non-ST-elevation myocardial infarction (NSTEMI). Patients aged ≥75 years with NSTEMI were prospectively registered from European centers and followed up for one year. Outcomes were compared between conservative and invasive groups in the overall population and a propensity score-matched (PSM) cohort. MACE included cardiovascular death, acute coronary syndrome, and stroke. The study included 1190 patients (median age 80 years, 43% female). CAG was performed in 67% (N = 798), with two-thirds undergoing revascularization. Conservatively treated patients had higher baseline risk. After propensity score matching, 319 patient pairs were successfully matched. MACE occurred more frequently in the conservative group (total population 20% vs. 12%, adjHR 0.53, 95% CI 0.37–0.77, p = 0.001), remaining significant in the PSM cohort (18% vs. 12%, adjHR 0.50, 95% CI 0.31–0.81, p = 0.004). In conclusion, an early invasive strategy was associated with benefits over conservative management in elderly patients with NSTEMI. Risk factors associated with ischemia and bleeding should guide strategy selection rather than solely relying on age

    Search for new phenomena with photon+jet events in proton-proton collisions at √s=13 TeV with the ATLAS detector

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    A search is performed for the production of high-mass resonances decaying into a photon and a jet in 3.2 fb−1 of proton-proton collisions at a centre-of-mass energy of √s=13 TeV collected by the ATLAS detector at the Large Hadron Collider. Selected events have an isolated photon and a jet, each with transverse momentum above 150 GeV. No significant deviation of the γ+jet invariant mass distribution from the background-only hypothesis is found. Limits are set at 95% confidence level on the cross sections of generic Gaussian-shaped signals and of a few benchmark phenomena beyond the Standard Model: excited quarks with vector-like couplings to the Standard Model particles, and non-thermal quantum black holes in two models of extra spatial dimensions. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 2% decrease from about 6 fb for a mass of 1.5 TeV to about 0.8 fb for a mass of 5 TeV. The minimum excluded visible cross sections for Gaussian-shaped resonances with width-to-mass ratios of 15% decrease from about 50 fb for a mass of 1.5 TeV to about 1.0 fb for a mass of 5 TeV. Excited quarks are excluded below masses of 4.4 TeV, and non-thermal quantum black holes are excluded below masses of 3.8 (6.2) TeV for Randall-Sundrum (Arkani-Hamed-Dimopoulous-Dvali) models with one (six) extra dimensions

    Search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state in pp collisions at s=13 TeV with the ATLAS detector

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    A search for heavy resonances decaying to a W or Z boson and a Higgs boson in the final state is described. The search uses of proton–proton collision data at collected by the ATLAS detector at the CERN Large Hadron Collider in 2015 and 2016. The data are in agreement with the Standard Model expectations, with the largest excess found at a resonance mass of 3.0 TeV with a local (global) significance of 3.3 (2.1) σ. The results are presented in terms of constraints on a simplified model with a heavy vector triplet. Upper limits are set on the production cross-section times branching ratio for resonances decaying to a W (Z) boson and a Higgs boson, itself decaying to , in the mass range between 1.1 and 3.8 TeV at 95% confidence level; the limits range between 83 and 1.6 fb (77 and 1.1 fb) at 95% confidence level.OIT -Ontario Innovation Trust(IN2P3-CNRS)info:eu-repo/semantics/publishedVersio

    Measurement of the W<sup>+</sup>W<sup>− </sup>production cross section in pp collisions at a centre-of-mass energy of  √s = 13 TeV with the ATLAS experiment

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    The production of opposite-charge W-boson pairs in proton–proton collisions at √s = 13 TeV is measured using data corresponding to 3.16 fb−1 of integrated luminosity collected by the ATLAS detector at the CERN Large Hadron Collider in 2015. Candidate W-boson pairs are selected by identifying their leptonic decays into an electron, a muon and neutrinos. Events with reconstructed jets are not included in the candidate event sample. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. Agreement is found between the measurement and the most accurate calculations available

    Promoting Research Activities and Management Reform in Universities : An Approach from Policy Sciences

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    Many commentators have insisted without empirical evidence that the heterogeneity of fuculty members promotes the research activities in universities. We have to examine whether or not this assertion would be valid and which element of heterogeneity may contribute to promoting research outputs. This article investigates the relationship between heterogeneity in educational background and research performance, then examines how the Science Research Grant has been allocated to faculties in economics. The result shows that the more heterogeneous faculty members are, the more the research outputs increase. The analysis also indicates that the research performance has been little considered in making decision for adoption while it has made significant effect on the amount of grant for the adopted subject

    Search for single production of vector-like quarks decaying into Wb in pp collisions at √s = 8 TeV with the ATLAS detector

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    A search for singly produced vector-like Q quarks, where Q can be either a T quark with charge + 2 / 3 or a Y quark with charge - 4 / 3 , is performed in proton–proton collisions recorded with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 20.3 fb- 1 and was produced with a centre-of-mass energy of s=8&nbsp;TeV. This analysis targets Q→ Wb decays where the W boson decays leptonically. A veto on massive large-radius jets is used to reject the dominant tt¯ background. The reconstructed Q-candidate mass, ranging from 0.4 to 1.2&nbsp;TeV, is used in the search to discriminate signal from background processes. No significant deviation from the Standard Model expectation is observed, and limits are set on the Q→ Wb cross-section times branching ratio. The results are also interpreted as limits on the QWb coupling and the mixing with the Standard Model sector for a singlet T quark or a Y quark from a doublet. T quarks with masses below 0.95&nbsp;TeV are excluded at 95&nbsp;% confidence level, assuming a unit coupling and a BR(T→ Wb) = 0.5 , whereas the expected limit is 1.10 TeV

    Search for dark matter in association with a Higgs boson decaying to b-quarks in pp collisions at root s=13 TeV with the ATLAS detector

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