1,720,968 research outputs found
Hadronic Jets: flavour and substructure
No full textHadronic jets, collimated sprays of particles produced in high-energy particle collisions, play a crucial role in the study of particle physics. In this PhD thesis, the focus is on two aspects of hadronic jets: flavour and substructure. The flavour of a jet refers to the identity of the initiating quark or gluon, and can provide information about the underlying physics processes that produced the jet. The substructure of a jet refers to its internal structure and is sensitive to the properties of the partons within the jet. The thesis presents a comprehensive study of the flavour and substructure of hadronic jets, including the development of new analysis techniques. Additionally, this thesis discusses the advancement of existing techniques for performing high-accuracy calculations for jet substructure observables, critical for comparing theoretical predictions with experimental measurements.
Recently, there has been a growing interest in machine learning and quantum computing techniques applied to jet physics or other close-related subjects. Machine learning algorithms are increasingly being used to identify and classify jets, while quantum computers have the potential to revolutionize high-precision calculations in jet physics. This thesis discusses a novel method to calculate the gradient of a function on quantum computers, further advancing the use of quantum computing in jet physics. The results of this study are ready for further phenomenological applications, contributing to a better understanding of the properties of hadronic jets and the physics of high-energy particle collisions
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
On heavy-flavour jets with Soft Drop
No full textWe study hadronic jets that are tagged as heavy-flavoured, i.e. they contain either beauty or charm. In particular, we consider heavy-flavour jets that have been groomed with the Soft Drop algorithm. In order to achieve a deeper understanding of these objects, we apply resummed perturbation theory to jets initiated by a massive quark and we perform analytic calculations for two variables that characterise Soft Drop jets, namely the opening angle and the momentum fraction of the splitting that passes Soft Drop. We compare our findings to Monte Carlo simulations. Furthermore, we investigate the correlation between the Soft Drop energy fraction and alternative observables that aim to probe heavy-quark fragmentation functions
Quantum gradient evaluation through quantum non-demolition measurements
Full text linkWe discuss a Quantum Non-Demolition Measurement (QNDM) protocol to estimate
the derivatives of a cost function with a quantum computer. %This is a key step
for the implementation of variational quantum circuits. The cost function,
which is supposed to be classically hard to evaluate, is associated with the
average value of a quantum operator. Then a quantum computer is used to
efficiently extract information about the function and its derivative by
evolving the system with a so-called variational quantum circuit. To this aim,
we propose to use a quantum detector that allows us to directly estimate the
derivatives of an observable, i.e., the derivative of the cost function. With
respect to the standard direct measurement approach, this leads to a reduction
of the number of circuit iterations needed to run the variational quantum
circuits. The advantage increases if we want to estimate the higher-order
derivatives. We also show that the presented approach can lead to a further
advantage in terms of the number of total logical gates needed to run the
variational quantum circuits. These results make the QNDM a valuable
alternative to implementing the variational quantum circuits
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
Practical Jet Flavour Through NNLO
Full text linkAn infrared and collinear (IRC) safe definition of the partonic flavour of a
jet is vital for precision predictions of quantum chromodynamics at colliders.
Jet flavour definitions have been presented in the literature, but they are
typically defined through modification of the jet algorithm to be sensitive to
partonic flavour at every stage of the clustering. While this does ensure that
the sum of flavours in a jet is IRC safe, a flavour-sensitive clustering
procedure is difficult to apply to realistic data. We introduce a distinct and
novel approach to jet flavour that can be applied to any collection of partons
defined by any algorithm. Our definition of jet flavour is the sum of flavours
of all partons that remain after Soft Drop grooming, reclustered with the Jade
algorithm. We prove that this prescription is IRC safe through
next-to-next-to-leading order (NNLO), and so can interface with the most
precise fixed-order calculations for jets available at present. We validate the
IRC safety of this definition with numeric fixed-order codes and further show
that jet flavour with Soft Drop reclustered with a generalised kT algorithm
fails to be IRC safe at NNLO.Comment: 19 pages, 4 figures; version accepted for publicatio
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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