35,569 research outputs found
Transition Form Factors and Decay Rates with Extraction of the CKM parameters , ,
A systematic calculation for the transition form factors of heavy to light
mesons () is carried out
by using light-cone sum rules in the framework of heavy quark effective field
theory. The heavy quark symmetry at the leading order of expansion
enables us to reduce the independent wave functions and establish interesting
relations among form factors. Some relations hold for the whole region of
momentum transfer. The meson distribution amplitudes up to twist-4 including
the contributions from higher conformal spin partial waves and light meson mass
corrections are considered. The CKM matrix elements , and
are extracted from some relatively well-measured decay channels. A
detailed prediction for the branching ratios of heavy to light meson decays is
then presented. The resulting predictions for the semileptonic and radiative
decay rates of heavy to light mesons () are found to be compatible with the current experimental data
and can be tested by more precise experiments at B-factory, LHCb, BEPCII and
CLEOc.Comment: 23 pages, 32 figures, 25 tables,published version, minor corrections
and references adde
Large Component QCD and Theoretical Framework of Heavy Quark Effective Field Theory
Based on a large component QCD derived directly from full QCD by integrating
over the small components of quark fields with , an
alternative quantization procedure is adopted to establish a basic theoretical
framework of heavy quark effective field theory (HQEFT) in the sense of
effective quantum field theory. The procedure concerns quantum generators of
Poincare group, Hilbert and Fock space, anticommutations and velocity
super-selection rule, propagator and Feynman rules, finite mass corrections,
trivialization of gluon couplings and renormalization of Wilson loop. The
Lorentz invariance and discrete symmetries in HQEFT are explicitly illustrated.
Some new symmetries in the infinite mass limit are discussed. Weak transition
matrix elements and masses of hadrons in HQEFT are well defined to display a
manifest spin-flavor symmetry and corrections. A simple trace
formulation approach is explicitly demonstrated by using LSZ reduction formula
in HQEFT, and shown to be very useful for parameterizing the transition form
factors via expansion. As the heavy quark and antiquark fields in HQEFT
are treated on the same footing in a fully symmetric way, the quark-antiquark
coupling terms naturally appear and play important roles for simplifying the
structure of transition matrix elements, and for understanding the concept of
`dressed heavy quark' - hadron duality. In the case that the `longitudinal' and
`transverse' residual momenta of heavy quark are at the same order of power
counting, HQEFT provides a consistent approach for systematically analyzing
heavy quark expansion in terms of . Some interesting features in
applications of HQEFT to heavy hadron systems are briefly outlined.Comment: 59 pages, RevTex, no figures, published versio
Bose-Einstein Condensation of Sr Through Sympathetic Cooling with Sr
We report Bose-Einstein condensation of Sr, which has a small,
negative s-wave scattering length (\,). We overcome the poor
evaporative cooling characteristics of this isotope by sympathetic cooling with
Sr atoms. Sr is effective in this role in spite of the fact that
it is a fermion because of the large ground state degeneracy arising from a
nuclear spin of , which reduces the impact of Pauli blocking of
collisions. We observe a limited number of atoms in the condensate
() that is consistent with the value of and the
optical dipole trap parameters.Comment: 4 pages, 4 figure
Accurate Modelling of Left-Handed Metamaterials Using Finite-Difference Time-Domain Method with Spatial Averaging at the Boundaries
The accuracy of finite-difference time-domain (FDTD) modelling of left-handed
metamaterials (LHMs) is dramatically improved by using an averaging technique
along the boundaries of LHM slabs. The material frequency dispersion of LHMs is
taken into account using auxiliary differential equation (ADE) based dispersive
FDTD methods. The dispersive FDTD method with averaged permittivity along the
material boundaries is implemented for a two-dimensional (2-D) transverse
electric (TE) case. A mismatch between analytical and numerical material
parameters (e.g. permittivity and permeability) introduced by the time
discretisation in FDTD is demonstrated. The expression of numerical
permittivity is formulated and it is suggested to use corrected permittivity in
FDTD simulations in order to model LHM slabs with their desired parameters. The
influence of switching time of source on the oscillation of field intensity is
analysed. It is shown that there exists an optimum value which leads to fast
convergence in simulations.Comment: 17 pages, 7 figures, submitted to Journal of Optics A Nanometa
special issu
Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2 - (5s4d)3D2 transition
We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms
using the (5s5p)3P2 - (5s4d)3D2 transition. Atom number in a magneto-optical
trap is enhanced by driving this transition because Sr atoms that have decayed
into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state.
Spectroscopy of 84Sr, 86Sr, 87Sr, and 88Sr improves the value of the (5s5p)3P2
- (5s4d)3D2 transition frequency for 88Sr and determines the isotope shifts for
the transition.Comment: 4 pages, 5 figure
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