1,721,511 research outputs found
Search for pair production of heavy vector-like quarks decaying to high-pT W bosons and b quarks in the lepton-plus-jets final state in pp collisions at sqrt(s) = 13 TeV with the ATLAS detector
Full text linkA search is presented for the pair production of heavy vector-like T quarks, primarily targeting the T quark decays to a W boson and a b-quark. The search is based on 36.1 fb−1 of pp collisions at sqrt(s) = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, including at least one b-tagged jet and a large-radius jet identified as originating from the hadronic decay of a high-momentum W boson. No significant deviation from the Standard Model expectation is observed in the reconstructed T mass distribution. The observed 95% confidence level lower limit on the T mass are 1350 GeV assuming 100% branching ratio to Wb. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. This search is also sensitive to a heavy vector-like B quark decaying to Wt and other final states. The results are thus reinterpreted to provide a 95% confidence level lower limit on the B quark mass at 1250 GeV assuming 100% branching ratio to Wt; in the SU(2) singlet scenario, the limit is 1080 GeV. Mass limits on both T and B production are also set as a function of the decay branching ratios. The 100% branching ratio limits are found to be applicable to heavy vector-like Y and X production that decay to Wb and Wt, respectively
Determination of the strong coupling constant alpha(s) from transverse energy-energy correlations in multijet events at root s=8 TeV using the ATLAS detector
No full textMeasurements of transverse energy-energy correlations and their
associated asymmetries in multi-jet events using the ATLAS detector at
the LHC are presented. The data used correspond to vs = 8 TeV
proton-proton collisions with an integrated luminosity of 20.2 fb(-1).
The results are presented in bins of the scalar sum of the transverse
momenta of the two leading jets, unfolded to the particle level and
compared to the predictions from Monte Carlo simulations. A comparison
with next-to-leading-order perturbative QCD is also performed, showing
excellent agreement within the uncertainties. From this comparison, the
value of the strong coupling constant is extracted for different energy
regimes, thus testing the running of alpha(s)(mu) predicted in QCD up to
scales over 1 TeV. A global fit to the transverse energy-energy
correlation distributions yields alpha(s)(m(Z)) = 0.1162 +/- 0.0011
(exp.)(-0.0070)(+0.0084) (theo.), while a global fit to the asymmetry
distributions yields a value of alpha(s)(m(Z)) = 0.1196 +/- 0.0013
(exp.)(-0.0045)(+0.0075) (theo.)
Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb−1 of sqrt(s) = 13 TeV pp collision data with the ATLAS detector
Full text linkA search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (e or μ), or at least three isolated leptons, is presented. The analysis relies on the identification of b-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at sqrt(s) = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb−1, is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring R-parity conservation or R-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields
Search for direct top squark pair production in final states with two leptons in root s=13 TeV pp collisions with the ATLAS detector
Full text linkThe results of a search for direct pair production of top squarks in
events with two opposite-charge leptons (electrons or muons) are
reported, using 36.1 fb(-1) of integrated luminosity from proton-proton
collisions at root s = 13 TeV collected by the ATLAS detector at the
Large Hadron Collider. To cover a range of mass differences between the
top squark (t) over tilde and lighter supersymmetric particles, four
possible decay modes of the top squark are targeted with dedicated
selections: the decay (t) over tilde -> b (chi) over tilde (+/-)(1) into
a b-quark and the lightest chargino with (chi) over tilde (+/-)(1) W
(chi) over tilde (0)(1),the decay (t) over tilde -> t (chi) over tilde
(0)(1) into an on-shell top quark and the lightest neutralino, the
three-body decay (t) over tilde -> bW (chi) over tilde (0)(1) and the
four-body decay (t) over tilde -> bl nu(chi) over tilde (0)(1). No
significant excess of events is observed above the Standard Model
background for any selection, and limits on top squarks are set as a
function of the (t) over tilde and (chi) over tilde (0)(1) masses. The
results exclude at 95\% confidence level (t) over tilde masses up to
about 720 GeV, extending the exclusion region of supersymmetric
parameter space covered by previous searches
Search for new phenomena in high-mass final states with a photon and a jet from pp collisions at sqrt(s) = 13 TeV with the ATLAS detector
Full text linkA search is performed for new phenomena in events having a photon with high transverse momentum and a jet collected in 36.7~\text {fb}^{-1} of proton–proton collisions at a centre-of-mass energy of sqrt(s) = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The invariant mass distribution of the leading photon and jet is examined to look for the resonant production of new particles or the presence of new high-mass states beyond the Standard Model. No significant deviation from the background-only hypothesis is observed and cross-section limits for generic Gaussian-shaped resonances are extracted. Excited quarks hypothesized in quark compositeness models and high-mass states predicted in quantum black hole models with extra dimensions are also examined in the analysis. The observed data exclude, at 95% confidence level, the mass range below 5.3 TeV for excited quarks and 7.1 TeV (4.4 TeV) for quantum black holes in the Arkani-Hamed–Dimopoulos–Dvali (Randall–Sundrum) model with six (one) extra dimensions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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