1,721,012 research outputs found
A Fragmentation Approach to Jet Flavor
Full text linkAn intuitive definition of the partonic flavor of a jet in quantum
chromodynamics is often only well-defined in the deep ultraviolet, where the
strong force becomes a free theory and a jet consists of a single parton.
However, measurements are performed in the infrared, where a jet consists of
numerous particles and requires an algorithmic procedure to define their phase
space boundaries. To connect these two regimes, we introduce a novel and simple
partonic jet flavor definition in the infrared. We define the jet flavor to be
the net flavor of the partons that lie exactly along the direction of the
Winner-Take-All recombination scheme axis of the jet, which is safe to all
orders under emissions of soft particles, but is not collinear safe. Collinear
divergences can be absorbed into a perturbative fragmentation function that
describes the evolution of the jet flavor from the ultraviolet to the infrared.
The evolution equations are linear and a small modification to traditional
DGLAP and we solve them to leading-logarithmic accuracy. The evolution
equations exhibit fixed points in the deep infrared, we demonstrate
quantitative agreement with parton shower simulations, and we present various
infrared and collinear safe observables that are sensitive to this flavor
definition.Comment: 29 pages, 7 figures; version submitted to the journa
(N)NLO+NLL’ accurate predictions for plain and groomed 1-jettiness in neutral current DIS
No full textAbstract The possibility to reanalyse data taken by the HERA experiments offers the chance to study modern QCD jet and event-shape observables in deep-inelastic scattering. To address this, we compute resummed and matched predictions for the 1-jettiness distribution in neutral current DIS with and without grooming the hadronic final state using the soft-drop technique. Our theoretical predictions also account for non-perturbative corrections from hadronisation through parton-to-hadron level transfer matrices extracted from dedicated Monte Carlo simulations with Sherpa. To estimate parameter uncertainties in particular for the beam-fragmentation modelling we derive a family of replica tunes to data from the HERA experiments. While NNLO QCD normalisation corrections to the NLO+NLL’ prediction are numerically small, hadronisation corrections turn out to be quite sizeable. However, soft-drop grooming significantly reduces the impact of non-perturbative contributions. We supplement our study with hadron-level predictions from Sherpa based on the matching of NLO QCD matrix elements with the parton shower. Good agreement between the predictions from the two calculational methods is observed
Resummed predictions for jet-resolution scales in multijet production in ee annihilation
No full textA bstract We present for the first time resummed predictions at NLO + NLL′ accuracy for the Durham jet-resolution scales y n,n +1 in multijet production in e + e − collisions. Results are obtained using an implementation of the well known Caesar formalism within the Sherpa framework. For the 4-, 5- and 6-jet resolutions we discuss in particular the impact of subleading colour contributions and compare to matrix-element plus parton-shower predictions from Sherpa and Vincia
Measuring hadronic Higgs boson branching ratios at future lepton colliders
Full text linkWe present a novel strategy for the simultaneous measurement of Higgs-boson branching ratios into gluons and light quarks at a future lepton collider operating in the Higgs-factory mode. Our method is based on template fits to global event-shape observables, and in particular fractional energy correlations, thereby exploiting differences in the QCD radiation patterns of quarks and gluons. In a constrained fit of the deviations of the light-flavour hadronic Higgs-boson branching ratios from their Standard Model expectations, based on an integrated luminosity of 5ab-1, we obtain 68% confidence level limits of μgg=1±0.05 and μqq¯<21
Tagging the initial-state gluon
No full textWe study the production of an electroweak boson in association with jets, in processes where the jet with the highest transverse momentum is identified as quark-initiated. The quark/gluon tagging procedure is realised by a cut on a jet angularity and it is therefore theoretically well-defined and exhibits infrared and collinear safety. In this context, exploiting resummed perturbation theory, we are able to provide theoretical predictions for transverse momentum distributions at a well-defined and, in principle, systematically improvable accuracy. In particular, tagging the leading jet as quark-initiated allows us to enhance the initial-state gluon contribution. Thus these novel transverse momentum distributions are potentially interesting observables to probe the gluonic degrees of freedom of the colliding protons
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
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