1,149 research outputs found
The B Meson Decay Constant from Unquenched Lattice QCD
We present determinations of the B meson decay constant f_B and of the ratio
f_{B_s}/f_B using the MILC collaboration unquenched gauge configurations which
include three flavors of light sea quarks. The mass of one of the sea quarks is
kept around the strange quark mass, and we explore a range in masses for the
two lighter sea quarks down to m_s/8.
The heavy b quark is simulated using Nonrelativistic QCD, and both the
valence and sea light quarks are represented by the highly improved (AsqTad)
staggered quark action.
The good chiral properties of the latter action allow for a much smoother
chiral extrapolation to physical up and down quarks than has been possible in
the past. We find f_B = 216(9)(19)(4) (6) MeV and f_{B_s} /f_B = 1.20(3)(1).Comment: 4 pages, 2 figure
Precision lattice QCD calculations and predictions of fundamental physics in heavy quark systems
I describe the recent success in performing accurate calculations of the
effects of the strong force on particles containing bottom and charm quarks.
Since quarks are never seen in isolation, and so cannot be studied directly,
numerical simulations are key to understanding the properties of these
particles and extracting information about the quarks. The results have direct
impact on the worldwide experimental programme that is aiming to determine the
parameters of the Standard Model of particle physics precisely and thereby
uncover or constrain the possibilities for physics beyond the Standard Model.
The numerical simulation of the strong force is a huge computational task and
the recent success is the result of international collaboration in developing
techniques that are fast enough to do the calculations on powerful
supercomputers.Comment: Invited talk at SCIDAC 2006, Denver, June 2006. 15 page
Recent results from lattice calculations
Recent results from lattice QCD calculations relevant to particle physics
phenomenology are reviewed. They include the calculations of strong coupling
constant, quark masses, kaon matrix elements, and D and B meson matrix
elements. Special emphasis is on the recent progress in the simulations
including dynamical quarks.Comment: 13 pages, 8 figures, plenary talk at the 32nd International
Conference on High-Energy Physics (ICHEP 2004), August 16-22, 2004, Beijing,
Chin
Leptonic decay constants f_Ds and f_D in three flavor lattice QCD
We determine the leptonic decay constants in three flavor unquenched lattice
QCD. We use O(a^2)-improved staggered light quarks and O(a)-improved charm
quarks in the Fermilab heavy quark formalism. Our preliminary results, based
upon an analysis at a single lattice spacing, are f_Ds = 263(+5-9)(+/-24) MeV
and f_D = 225(+11-13)(+/-21) MeV. In each case, the first reported error is
statistical while the is the combined systematic uncertainty.Comment: Talk presented at Lattice2004(heavy), Fermilab, June 21-26, 2004. 3
pages, 2 figure
Topographic Evolution in the Atomic Scale Growth and Erosion Continuum
This review gives a detailed survey of the range of fascinating surface features which develop under growth or erosion conditions under the combined influence of thermal and more energetic atomic particle fluxes. Collisionally induced atomic ejection and migration, and thermally and radiation induced atom and defect diffusion processes are outlined and their relevance to topographic initiation and evolution explored. A range of experimental observations of surface feature elaboration is discussed from net growth to net erosion conditions and models for their explanation are considered. It is concluded that while much data have been accumulated, much of these have been in so diverse experimental conditions that precise modelling in atomic terms is difficult and generalisations are treacherous. A clear need for structured, extensive studies exists with very precise parameter definition and control
Charm as a domain wall fermion in quenched lattice QCD
We report a study describing the charm quark by a domain-wall fermion (DWF)
in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge
ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of
GeV. We calculate masses of heavy-light (charmed) and
heavy-heavy (charmonium) mesons with spin-parity and ,
leptonic decay constants of the charmed pseudoscalar mesons ( and ),
and the - mixing parameter. The charm quark mass is found to be
GeV. The mass splittings in
charmed-meson parity partners and are
degenerate within statistical errors, in accord with experiment, and they
satisfy a relation , also consistent with
experiment. A C-odd axial vector charmonium state, \chi_{c1}m_{h_{c}} = 3533(11)_{\rm stat.}\chi_{c1}) mass. However, in this regard, we emphasize
significant discrepancies in the calculation of hyperfine splittings on the
lattice. The leptonic decay constants of and mesons are found to be
MeV and
,
where the first error is statistical, the second a systematic due to chiral
extrapolation and the third error combination of other known systematics. The
- mixing bag parameter, which enters the
transition amplitude, is found to be .Comment: 49 pages, 15 figure
Branching ratios of Bc Meson Decaying to Pseudoscalar and Axial-Vector Mesons
We study Cabibbo-Kobayashi-Maskawa (CKM) favored weak decays of Bc mesons in
the Isgur-Scora-Grinstein-Wise (ISGW) quark model. We present a detailed
analysis of the Bc meson decaying to a pseudoscalar meson (P) and an
axial-vector meson (A). We also give the form factors involving transition in
the ISGW II framework and consequently, predict the branching ratios of decays.Comment: 19 pages,7 table
Bc Meson Formfactors and Bc-->PV Decays Involving Flavor Dependence of Transverse Quark Momentum
We present a detailed analysis of the Bc form factors in the BSW framework,
by investigating the effects of the flavor dependence on the average transverse
quark momentum inside a meson. Branching ratios of two body decays of Bc meson
to pseudoscalar and vector mesons are predicted.Comment: 18 pages, 5 figure
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