1,720,974 research outputs found
Measurement of η meson production in γγ interactions and Γ(η → γγ) with the KLOE detector
No full textWe present a measurement of η meson production in photon-photon interactions produced by electron-positron beams colliding with √s = 1 GeV. The measurement is done with the KLOE detector at the φ-factory DAΦNE with an integrated luminosity of 0.24 fb−1. The e+e− → e+e−η cross section is measured without detecting the out-going electron and positron, selecting the decays η → π+π−π0 and η → π0π0π0. The most relevant background is due to e+e− → ηγ when the monochromatic photon escapes detection. The cross section for this process is measured as σ(e+e− → ηγ) = (856 ± 8stat ± 16syst) pb. The combined result for the e+e− → e+e−η cross section is σ(e+e− → e+e−η) = (32.72 ± 1.27stat ± 0.70syst) pb. From this we derive the partial width Γ(η → γγ) = (520 ± 20stat ± 13syst) eV. This is in agreement with the world average and is the most precise measurement to date
Measurement of Γ(η → π+ π− γ)/Γ(η → π+ π− π0) with the KLOE detector
No full textThe ratio Rη=Γ(η→π+π−γ)/Γ(η→π+π−π0) has been measured by analysing 22 million φ→ηγ decays collected by the KLOE experiment at DAΦNE, corresponding to an integrated luminosity of 558 pb−1. The η→π+π−γ proceeds both via the ρ resonant contribution, and possibly a non-resonant direct term, connected to the box anomaly. Our result, Rη=0.1856±0.0005stat±0.0028syst, points out a sizable contribution of the direct term to the total width. The di-pion invariant mass for the η→π+π−γ decay could be described in a model-independent approach in terms of a single free parameter, α. The determined value of the parameter α is α = (1.32 ± 0.08stat(+0.1 -0.09, syst) ± 0.02theo) GeV-2
Constraints on a Minimal Hidden Photon with Kaluza-Klein Excitations in Large Extra Dimensions
Full text linkThe major purpose of this work is to combine the minimal-hidden-photon model with Large Extra Dimensions (LED). This involves confining the Standard- Model photon to a 3-brane, whilst allowing the hidden photon and graviton to occupy the higher-dimensional bulk. After integrating out the extra dimensions both the hidden photon and graviton obtain a tower of massive Kaluza-Klein (KK) modes. The Standard-Model photon obtains no KK modes, in accordance with experiment. The work begins with a discussion of the minimal hidden photon with-out KK modes, including the current constraints. In most cases existing constraints are simply quoted or rederived, but for some experiments original constraints are produced. For example new constraints from atomic spectra are produced. Significant modifications are also made to the published constraint
from the SN1987a energy-loss experiment. This means properly accounting for the plasma mass of the electron, and also accounting for the modification of the kinetic-mixing parameter in a plasma. Finally constraints are produced for the minimal-hidden-photon model with KK modes
Latest results in kaon physics on the KLOE data and status of analysis of the KLOE-2 data
No full textMeasurements of the Form Factor in VP Transitions and Study of the Dalitz Plot at KLOE
No full textThe VectorPseudoscalar decays and have been measured based on 1.7 pb of data collected with the KLOE experiment, for extracting the branching ratios and transistion form factors. With 1.6 pb of data from the same experiment, we measure the Dalitz plot distribution of the decay. Preliminary values are given for the Dalitz plot parameters
Direct tests of T, CP, CPT symmetries in transitions of neutral K mesons with the KLOE experiment
No full textTests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in and out states required for a genuine test involving an antiunitary transformation implied by time-reversal is implemented exploiting the entanglement of KK‾ pairs produced at a ϕ-factory. A data sample collected by the KLOE experiment at DAΦNE corresponding to an integrated luminosity of about 1.7 fb is analysed to study the Δt distributions of the ϕ→KK→πππeν and ϕ→KK→πeν3π processes, with Δt the difference of the kaon decay times. A comparison of the measured Δt distributions in the asymptotic region Δt≫τ allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method
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
- …
