1,722,835 research outputs found
Decay of entangled fermion pairs with post-selection
No full textWe consider a pair of unstable fermions in a spin-entangled state. After the decay of one fermion, a spin measurement is performed on the surviving partner, with a Stern-Gerlach experiment or similar. The measurement not only projects the spin of the surviving fermion, but is also physically equivalent to a spin projection for the decayed one — even when it no longer exists. This post-selection effect would be experimentally accessible using muon pairs in a maximally-entangled state, produced either in the decay of a scalar particle, or in e+e− collisions at wide angles. © 2023 The Author(s)This work of has been supported by MICINN projects PID2019-
110058 GB-C21, PID2022-142545NB-C21 and CEX2020-001007-S
funded by MCIN/AEI/10.13039/501100011033 and by ERDF, and by
Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the
project CERN/FIS-PAR/0019/2021.Peer reviewe
Closer look at postdecay t t ¯ entanglement
No full textTop pair production is ideally suited to observe postdecay entanglement, thus providing a novel test of quantum mechanics. We provide top polarized decay amplitudes that can be used to compute semianalytical predictions and, in particular, to better understand why the postdecay entanglement arises. We obtain predictions for the LHC, identifying general phase space regions where experimental measurements of tW entanglement are feasible. We also give predictions for polarized e+e- collisions, focusing on the possibility that the postdecay tW entanglement is larger than the tt¯ one. © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.I thank J. A. Casas for many discussions and previous collaboration. This work has been supported by the Spanish Research Agency (Agencia Estatal de Investigación) through Projects No. PID2019–110058 GB-C21,
No. PID2022-142545NB-C21, and No. CEX2020- 001007-S funded by MCIN/AEI/10.13039/ 501100011033, and by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the Project No. CERN/FIS-PAR/0019/2021.Peer reviewe
Full quantum tomography of top quark decays
No full textQuantum tomography in high-energy physics processes has usually been restricted to the spin degrees of freedom. We address the case of top quark decays t→Wb, in which the orbital angular momentum (L) and the spins of W and b are intertwined into a 54-dimensional LWb density operator. The entanglement between L and the W or b spin is large and could be determined for decays of single top quarks produced at the Large Hadron Collider with Run 2 data. With the foreseen statistical and systematic uncertainties, the significance is well above 5σ from the separability hypothesis for L-W entanglement, and 3.2σ for L-b. These would be the first entanglement measurements between orbital and spin angular momenta in high-energy physics. Likewise, the genuine tripartite entanglement between L and the two spins could be established with more than 5σ. The method presented paves the way for similar measurements in other processes. © 2024 The Author(s)This work of has been supported by the Spanish Research Agency (Agencia Estatal de Investigación) through projects PID2019-110058GBC21, PID2022-142545NB-C21 and CEX2020-001007-S funded by MCIN/AEI/10.13039/501100011033, and by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the project CERN/FIS-PAR/0019/2021.Peer reviewe
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
Novel signatures for vector-like quarks
Full text linkWe consider supersymmetric extensions of the standard model with a vector-like doublet (T B) of quarks with charge 2/3 and −1/3, respectively. Compared to non-supersymmetric models, there is a variety of new decay modes for the vector-like quarks, involving the extra scalars present in supersymmetry. The importance of these new modes, yielding multi-top, multi-bottom and also multi-Higgs signals, is highlighted by the analysis of several benchmark scenarios. We show how the triangles commonly used to represent the branching ratios of the ‘standard’ decay modes of the vector-like quarks involving W, Z or Higgs bosons can be generalised to include additional channels. We give an example by recasting the limits of a recent heavy quark search for this more general case.Fil: Aguilar Saavedra, J. A.. Universidad Autónoma de Madrid; EspañaFil: Lopez, Daniel Elbio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Muñoz, C.. Universidad Autónoma de Madrid. Facultad de Ciencias. Departamento de Biología; España. Universidad Autónoma de Madrid; Españ
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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