1,721,580 research outputs found
Λ + c production vs the event charged-particle multiplicity in pp collisions at 13 TeV with ALICE at the LHC
Full text link2020 - 2021The Quantum Chromo-Dynamics (QCD) theory predicts, in condition of very high
temperature and/or energy density, a phase transition from the ordinary nuclear
matter to a colour-deconfined medium called Quark–Gluon Plasma (QGP). The
ALICE experiment was designed and optimized for the investigation of this hot
and dense medium, produced via heavy-ion collisions at the Large Hadron Collider
(LHC). Due to the very short lifetime of the QGP, its properties cannot be directly
revealed and its characterization is done through indirect signals, obtained from
the observation of the ordinary particles that emerge from the interaction region.
In particular, charm quarks are effective probes used for the investigation of QGP.
Due to their large masses, they are produced in hard scattering processes on a
timescale shorter than the QGP formation time and therefore experience the whole
system evolution. The measurement of charm-baryon production, and in particular
the baryon-to-meson ratios, provides unique information to characterize novel
mechanisms of hadron formation beyond in-vacuum fragmentation, e.g. coalescence,
which are expected to be significant in presence of a medium characterized by
free colour charges. Measurements of charm-baryon production in pp collisions
are essential to establish a baseline for p-A and A-A collisions. In addition, they
provide critical tests of perturbative QCD (pQCD) calculations and models of charm
hadronisation in hadronic collisions.
The aim of the studies carried out in this thesis is the measurement of Λ
+
c
charmed baryon yield, employed for the estimation of the baryon-to-meson ratio
Λ
+
c
/D0
. The first measurements of the Λ
+
c production yields and of the Λ
+
c
/D0
baryon-to-meson ratios as a function of the charged-particle pseudorapidity density
are presented. The study allows the characterization of the evolution of the Λ
+
c
/D0
baryon-to-meson ratio from very low to high charged particle density and provides
new experimental constraints on the production mechanisms in pp collisions. The
analysed sample is collected in pp collisions at the energy in the centre-of-mass
system of √
s = 13 TeV with the ALICE detector. The measurement is performed
by reconstructing the hadronic decay channel Λ
+
c → pK0
s → pπ
+π
−, exploiting
selections on its decay topology and on the particle identification (PID) of the decay
products, extracting the signal via an invariant mass analysis and correcting for its
selection and reconstruction efficiency and for the detector acceptance. A machine
1
learning algorithm based on Boosted Decision Trees (BDT) has been developed
and is used in order to improve the signal extraction by optimally combining
topological and PID variables that allow discriminating signal candidates from the
combinatorial background. The results are compared with a theoretical model that
explains the multiplicity dependence by a canonical treatment of quantum charges
in the statistical hadronisation approach and with predictions from PYTHIA event
generators that implement colour reconnection mechanisms beyond the leading
colour approximation to model the hadronisation process. [edited by Author]XXXIV cicl
Λ+c production vs the event charged-particle multiplicity in pp collisions at 13 TeV with ALICE at the LHC
No full textThe Quantum Chromo-Dynamics (QCD) theory predicts, in condition of very high temperature and/or energy density, a phase transition from the ordinary nuclear matter to a colour-deconfined medium called Quark–Gluon Plasma (QGP). The ALICE experiment was designed and optimized for the investigation of this hot and dense medium, produced via heavy-ion collisions at the Large Hadron Collider (LHC). Due to the very short lifetime of the QGP, its properties cannot be directly revealed and its characterization is done through indirect signals, obtained from the observation of the ordinary particles that emerge from the interaction region. In particular, charm quarks are effective probes used for the investigation of QGP. Due to their large masses, they are produced in hard scattering processes on a timescale shorter than the QGP formation time and therefore experience the whole system evolution. The measurement of charm-baryon production, and in particular the baryon-to-meson ratios, provides unique information to characterize novel mechanisms of hadron formation beyond in-vacuum fragmentation, e.g. coalescence, which are expected to be significant in presence of a medium characterized by free colour charges. Measurements of charm-baryon production in pp collisions are essential to establish a baseline for p-A and A-A collisions. In addition, they provide critical tests of perturbative QCD (pQCD) calculations and models of charm hadronisation in hadronic collisions. The aim of the studies carried out in this thesis is the measurement of Λ+c charmed baryon yield, employed for the estimation of the baryon-to-meson ratio Λ+c /D0. The first measurements of the Λ+c production yields and of the Λ+c /D0 baryon-to-meson ratios as a function of the charged-particle pseudorapidity density are presented. The study allows the characterization of the evolution of the Λ+c /D0 baryon-to-meson ratio from very low to high charged particle density and provides new experimental constraints on the production mechanisms in pp collisions. The analysed sample is collected in pp collisions at the energy in the centre-of-mass system of √s = 13 TeV with the ALICE detector. The measurement is performed by reconstructing the hadronic decay channel Λ+c → pK0s→ pπ+π−, exploiting selections on its decay topology and on the particle identification (PID) of the decay products, extracting the signal via an invariant mass analysis and correcting for its selection and reconstruction efficiency and for the detector acceptance. A machine learning algorithm based on Boosted Decision Trees (BDT) has been developed and is used in order to improve the signal extraction by optimally combining topological and PID variables that allow discriminating signal candidates from the combinatorial background. The results are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach and with predictions from PYTHIA event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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