1,721,047 research outputs found
Effects of finite volume on the KL-KS mass difference
Get PDFPhenomena that involve two or more on-shell particles are particularly sensitive to the effects of finite volume and require special treatment when computed using lattice QCD. In this paper we generalize the results of Lüscher and Lellouch and Lüscher, which determine the leading-order effects of finite volume on the two-particle spectrum and two-particle decay amplitudes to determine the finite-volume effects in the second-order mixing of the K0 and K0 ̄ states. We extend the methods of Kim, Sachrajda, and Sharpe to provide a direct, uniform treatment of these three, related, finite-volume corrections. In particular, the leading, finite-volume corrections to the KL-KS mass difference ΔMK and the CP-violating parameter εK are determined, including the potentially large effects which can arise from the near degeneracy of the kaon mass and the energy of a finite-volume, two-pion state
A High-Statistics Lattice Calculation of and in the meson
No full textWe present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found ~GeV, which is interesting for phenomenological applications. We also find GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy of the heavy quark inside the -meson and of the chromo-magnetic term , related to the -- mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at , on a lattice volume and using, for the meson correlators, the results obtained with the SW-Clover improved lattice action for the light quarks. For the kinetic energy we found GeV, which is interesting for phenomenological applications. We also find GeV, corresponding to GeV, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.We present a high-statistics lattice calculation of the kinetic energy − λ 1 /2 m b of the heavy quark inside the B -meson and of the chromo-magnetic term A2, related to the B ∗ −B mass splitting, performed in the HQET Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at β = 6.0, on a lattice volume 24 3 × 40 and using, for the meson correlators, the results obtained with the SW-Clover O ( a ) improved lattice action for the light quarks. For the kinetic energy we found −λ 1 = 〈B| h ̄ (iD) 2 h|B〉/(2M B ) = −(0.09 ± 0.14) GeV 2 , which is interesting for phenomenological applications. We also found λ 2 = 0.07 ± 0.01 GeV 2 , corresponding to M B∗ 2 − M B 2 = 4λ 2 = 0.280 ± 0.060 GeV 2 , which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified
Light-meson leptonic decay rates in lattice QCD+QED
Get PDFThe leading electromagnetic (e.m.) and strong isospin-breaking corrections to the pi(+ )-> mu(+) nu[gamma] and K+ -> mu(+)nu[gamma] leptonic decay rates are evaluated for the first time on the lattice. The results are obtained using gauge ensembles produced by the European Twisted Mass Collaboration with N-f = 2 + 1 + 1 dynamical quarks. The relative leading-order e.m. and strong isospin-breaking corrections to the decay rates are 1.53(19)% for pi(mu 2) decays and 0.24(10)% for K-mu 2 decays. Using the experimental values of the pi(mu 2) and K-mu 2 decay rates and updated lattice QCD results for the pion and kaon decay constants in isosymmetric QCD, we find that the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-us vertical bar = 0.22538(46), reducing by a factor of about 1.8 the corresponding uncertainty in the particle data group review. Our calculation of vertical bar V-us vertical bar allows also an accurate determination of the first-row Cabibbo-Kobayashi-Maskawa unitarity relation vertical bar V-ud vertical bar(2) + vertical bar V-us vertical bar(2) + vertical bar V-ub vertical bar(2) = 0.99988(46). Theoretical developments in this paper include a detailed discussion of how QCD can be defined in the full QCD + QED theory and an improved renormalization procedure in which the bare lattice operators are renommlized nonperturbatively into the regularization independent momentum subtraction (RI'-MOM) scheme and subsequently matched perturbatively at O(alpha(em)alpha(s) (M-W)) into the W-regularization scheme appropriate for these calculations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
A high statistics lattice calculation of the b-meson binding energy
No full textWe present a high statistics lattice calculation of the B--meson binding energy \overline{\Lambda} of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at \beta=6.0, 6.2 and 6.4 and using, for the meson correlators, the results obtained by the APE group at the same values of \beta. Our best estimate, obtained by combining results at different values of \beta, is \overline{\Lambda}=180^{+30}_{-20} MeV. For the \overline{MS} running mass, we obtain \overline{m}_{b}(\overline{m}_{b})=4.15 \pm 0.05 \pm 0.20 GeV, in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory.We present a high statistics lattice calculation of the B -meson binding energy Λ of the heavy-quark inside the pseudoscalar B -meson. Our numerical results have been obtained from several independent numerical simulations at β = 6.0, 6.2 and 6.4, and using, for the meson correlators, the results obtained by the APE group at the same values of β. Our best estimate, obtained by combining results at different values of β, is Λ = 180 −20 +30 MeV. For the MS running mass, we obtain m b ( m b ) = 4.15 ± 0.05 ± 0.20 GeV , in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory.We present a high statistics lattice calculation of the B--meson binding energy of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at , and , and using, for the meson correlators, the results obtained by the APE group at the same values of . Our best estimate, obtained by combining results at different values of , is MeV. For the running mass, we obtain GeV, in reasonable agreement with previous determinations. The systematic error is the truncation of the perturbative series in the matching condition of the relevant operator of the Heavy Quark Effective Theory
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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