1,721,262 research outputs found
Measurement of radiative widths of a2(1320) and π2(1670)
No full textThe COMPASS Collaboration at CERN has investigated the reaction π̄γ → π̄π̄π+ embedded in the Primakoff reaction of 190 GeV pions scattering in the Coulomb field of a lead target, π̄Pb → π̄π̄π+ Pb. Exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at momentum transfer below 0.001 (GeV/c)2. Using a partial-wave analysis the amplitudes and relative phases of the a2(1320) and π2(1670) mesons have been extracted, and the Coulomb and the diffractive contributions have been disentangled. Measuring absolute production cross sections we have determined the radiative width of the a2(1320) to be Γ0(a2(1320) → πγ) = (358 ± 6stat ± 42syst) keV. As the first measurement, Γ0(π2(1670) → πγ) = (181 ± 11stat ± 27syst)keV · (BRf2π /BR/f2π) is obtained for the radiative width of the π2(1670), where in this analysis the branching ratio BRff2πPDG = 0.56 has been used. We compare these values to previous measurements and theoretical predictions
Multiplicities of charged kaons from deep-inelastic muon scattering off an isoscalar target
No full textPrecise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented in three-dimensional bins of the Bjorken scaling variable x, the relative virtual-photon energy y, and the fraction z of the virtual-photon energy carried by the produced hadron. The data were obtained by the COMPASS Collaboration by scattering muons off an isoscalar 6LiD target. They cover the kinematic domain in the photon virtuality, , , , and in the invariant mass of the hadronic system. The results from the sum of the z-integrated and multiplicities at high x point to a value of the non-strange quark fragmentation function larger than obtained by the earlier DSS fit
Measurement of P-T-weighted Sivers asymmetries in leptoproduction of hadrons
No full textThe transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron transverse momentum P-T, allow for the extraction of important transverse-momentum-dependent distribution functions. In particular, the weighted Sivers asymmetries provide direct information on the Sivers function, which is a leading-twist distribution that arises from a correlation between the transverse momentum of an unpolarised quark in a transversely polarised nucleon and the spin of the nucleon. Using the high-statistics data collected by the COMPASS Collaboration in 2010 with a transversely polarised proton target, we have evaluated two types of P-T-weighted Sivers asymmetries, which are both proportional to the product of the first transverse moment of the Sivers function and of the fragmentation function. The results are compared to the standard unweighted Sivers asymmetries and used to extract the first transverse moments of the Sivers distributions for u and d quarks
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
Spin alignment and violation of the OZI rule in exclusive ω and φ production in pp collisions
No full textExclusive production of the isoscalar vector mesons ω and φ is measured with a 190GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable xF of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass M p V of the system formed by fast proton pfast and vector meson V is discussed in terms of diffractive production of pfastV resonances in competition with central production. The measurement of the spin density matrix element ρ00 of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on xF and on M p V are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to ω production which are absent in the case of the φ meson. Removing the low-mass M p V resonant region, the OZI rule is found to be violated by a factor of eight, independently of xF
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