1,721,001 research outputs found
Hadronic form factors for rare semileptonic <i>B</i> decays
No full textWe discuss first results for the computation of short distance contributions to semileptonic form factors for the rare decays and . Our simulations are based on RBC/UKQCD's ensembles with domain wall light quarks and the Iwasaki gauge action. For the valence -quark we chose the relativistic heavy quark action
Exclusive semileptonic decays on the lattice
Full text linkSemileptonic decays provide an alternative -decay
channel to determine the CKM matrix element , and to obtain a
-ratio to investigate lepton-flavor-universality violations. Results for the
CKM matrix element may also shed light on the discrepancies seen between
analyses of inclusive or exclusive decays. We calculate the decay form factors
using lattice QCD with domain-wall light quarks and a relativistic -quark.
We analyze data at three lattice spacings with unitary pion masses down to
. Our numerical results are interpolated/extrapolated to
physical quark masses and to the continuum to obtain the vector and scalar form
factors and with full error budgets at values
spanning the range accessible in our simulations. We provide a possible
explanation of tensions found between results for the form factor from
different lattice collaborations. Model- and truncation-independent
-parameterization fits following a recently proposed Bayesian-inference
approach extend our results to the entire allowed kinematic range. Our results
can be combined with experimental measurements of and
semileptonic decays to determine . The error is
currently dominated by experiment. We compute differential branching fractions
and two types of ratios, the one commonly used as well as a variant better
suited to test lepton-flavor universality.Comment: Version accepted and published (Phys. Rev. D 107, 114512) 30 pages,
13 Figures, supplementary data fil
Nonperturbative calculations of form factors for exclusive semileptonic decays
No full textPrecise theoretical predictions derived from the Standard Model are a key ingredient in searches for new physics in the flavor sector. The large mass and long lifetime of the quark make processes involving quarks of particular interest. We use lattice simulations to perform nonperturbative QCD calculations for semileptonic decays. We present results from our determinations of and semileptonic form factors and provide an outlook for our calculation. In addition we discuss the determination of -ratios testing lepton-flavor universality and suggest use of an improved ratio. Our calculations are based on the set of 2+1 flavor domain wall Iwasaki gauge field configurations generated by the RBC-UKQCD collaboration featuring three lattice spacings of , , and . Heavy -quarks are simulated using the relativistic heavy quark action
Heavy domain wall fermions: The RBC and UKQCD charm physics program
No full textWe review the domain wall charm physics program of the RBC and UKQCD collaborations based on simulations including ensembles with physical pion mass. We summarise our current set-up and present a status update on the decay constants fD, fD s, the charm quark mass, heavy-light and heavy-strange bag parameters and the ratio ξ</p
Semi-leptonic form factors for Bs→ K\ell ν and Bs → Ds \ell ν
No full textSemi-leptonic and decays provide an alternative -decay channel to determine the CKM matrix elements and or to obtain -ratios to investigate lepton flavor universality violations. In addition, these decays may shed further light on the discrepancies seen in the analysis of inclusive vs. exclusive decays. Using the nonperturbative methods of lattice QCD, theoretical results are obtained with good precision and full control over systematic uncertainties. This talk will highlight ongoing efforts of the -physics program by the RBC-UKQCD collaboration
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
Semileptonic D→πℓν, D→Kℓν and Ds→Kℓν decays with 2+1f domain wall fermions
No full textWe present the status of our project to calculate D→πℓν, D→Kℓν and Ds→Kℓν semileptonic form factors using domain wall fermions for both heavy and light quarks. Our computations are performed using RBC/UKQCD's set of 2+1 flavour domain wall fermion and Iwasaki gauge field ensembles. We plan to calculate three-point functions covering the full, physically allowed kinematic range. Given that the signal decays faster than the noise, unambiguously and reliably extracting the ground state is critical for success. We include an analysis of operator diagonalisation within several possible 2×2 operator bases and find an admixture of gauged fixed wall and Z(2) wall sources to be acceptable at both zero and non-zero momentum. Initial results for semileptonic form factors are presented for first ensembles
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