2,659 research outputs found
Semileptonic Decay Scalar Form Factor and from Lattice QCD
We present a new study of D semileptonic decays on the lattice which employs
the Highly Improved Staggered Quark (HISQ) action for both the charm and the
light valence quarks. We work with MILC unquenched lattices and
determine the scalar form factor for
semileptonic decays. The form factor is obtained from a scalar current matrix
element that does not require any operator matching. We develop a new approach
to carrying out chiral/continuum extrapolations of . The method uses
the kinematic "" variable instead of or the kaon energy and is
applicable over the entire physical range. We find in the chiral plus
continuum limit and hereby improve the theory error on this quantity by a
factor of 4 compared to previous lattice determinations. Combining the
new theory result with recent experimental measurements of the product from BaBar and CLEO-c leads to the most
precise direct determination of the CKM matrix element to date,
, where the first error comes from experiment and the
second is the lattice QCD theory error. We calculate the ratio and find GeV and show
that this agrees with experiment.Comment: 23 pages, 31 figures, 11 tables. Added a paragraph in sction VII, and
updated with PDG 2010 instead of PDG 200
form factors from lattice QCD
We report the first lattice QCD calculation of the form factors for the
standard model tree-level decay . In combination with future
measurement, this calculation will provide an alternative exclusive
semileptonic determination of . We compare our results with previous
model calculations, make predictions for differential decay rates and branching
fractions, and predict the ratio of differential branching fractions between
and . We also present standard model
predictions for differential decay rate forward-backward asymmetries,
polarization fractions, and calculate potentially useful ratios of
form factors with those of the fictitious decay. Our lattice
simulations utilize NRQCD and HISQ light quarks on a subset of the MILC
Collaboration's asqtad gauge configurations, including two lattice
spacings and a range of light quark masses.Comment: 24 pages, 21 figures; Ver. 2 matches published versio
B→Dlν form factors at nonzero recoil and extraction of |Vcb|
We present a lattice QCD calculation of the B→Dlν semileptonic decay form factors f+(q2) and f0(q2) for the entire physical q2 range. Nonrelativistic QCD bottom quarks and highly improved staggered quark charm and light quarks are employed together with Nf=2+1 MILC gauge configurations. A joint fit to our lattice and BABAR experimental data allows an extraction of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|. We also determine the phenomenologically interesting ratio R(D)=B(B→Dτντ)/B(B→Dlνl) (l=e,μ). We find |Vcb|B→Dexcl=0.0402(17)(13), where the first error consists of the lattice simulation errors and the experimental statistical error and the second error is the experimental systematic error. For the branching fraction ratio we find R(D)=0.300(8)
Manual on application of molecular tools in aquaculture and inland fisheries management. Part 2. Laboratory protocols and data analysis
The aim of this manual is to provide a comprehensive practical tool for the generation and analysis of genetic data for subsequent application in aquatic resources management in relation to genetic stock identification in inland fisheries and aquaculture.
The material only covers general background on genetics in relation to aquaculture and fisheries resource management, the techniques and relevant methods of data analysis that are commonly used to address questions relating to genetic resource characterisation and population genetic analyses. No attempt is made to include applications of genetic improvement techniques e.g. selective breeding or producing genetically modified organisms (GMOs). The manual includes two ‘stand-alone’ parts, of which this is the second volume:
Part 1 – Conceptual basis of population genetic approaches: will provide a basic foundation on genetics in general, and concepts of population genetics. Issues on the choices of molecular markers and project design are also discussed.
Part 2 – Laboratory protocols, data management and analysis: will provide step-by-step protocols of the most commonly used molecular genetic techniques utilised in population genetics and systematic studies. In addition, a brief discussion and explanation of how these data are managed and analysed is also included.
This manual is expected to enable NACA member country personnel to be trained to undertake molecular genetic studies in their own institutions, and as such is aimed at middle and higher level technical grades. The manual can also provide useful teaching material for specialised advanced level university courses in the region and postgraduate students. The manual has gone through two development/improvement stages. The initial material was tested at a regional workshop and at the second stage feedback from participants was used to improve the contents
B and Bs semileptonic decay form factors with NRQCD/HISQ quarks
We discuss our ongoing effort to calculate form factors for several B and Bs
semileptonic decays. We have recently completed the first unquenched
calculation of the form factors for the rare decay B -> K ll. Extrapolated over
the full kinematic range of q^2 via model-independent z expansion, these form
factor results allow us to calculate several Standard Model observables. We
compare with experiment (Belle, BABAR, CDF, and LHCb) where possible and make
predictions elsewhere. We discuss preliminary results for Bs -> K l nu which,
when combined with anticipated experimental results, will provide an
alternative exclusive determination of |Vub|. We are exploring the possibility
of using ratios of form factors for this decay with those for the unphysical
decay Bs -> eta_s as a means of significantly reducing form factor errors. We
are also studying B -> pi l nu, form factors for which are combined with
experiment in the standard exclusive determination of |Vub|. Our simulations
use NRQCD heavy and HISQ light valence quarks on the MILC 2+1 dynamical asqtad
configurations.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Form Factors and the Fragmentation Fraction Ratio
We present a lattice quantum chromodynamics determination of the scalar and
vector form factors for the decay over the full
physical range of momentum transfer. In conjunction with future experimental
data, our results will provide a new method to extract , which may
elucidate the current tension between exclusive and inclusive determinations of
this parameter. Combining the form factor results at non-zero recoil with
recent HPQCD results for the form factors, we
determine the ratios and . These results give the fragmentation
fraction ratios and ,
respectively. The fragmentation fraction ratio is an important ingredient in
experimental determinations of meson branching fractions at hadron
colliders, in particular for the rare decay . In addition to the form factor results, we make the first prediction
of the branching fraction ratio , where is an electron or muon. Current
experimental measurements of the corresponding ratio for the semileptonic
decays of mesons disagree with Standard Model expectations at the level of
nearly four standard deviations. Future experimental measurements of
may help understand this discrepancy.Comment: 21 pages, 15 figure
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