44,120 research outputs found
Inclusive Decays of Bottom Hadrons in New Formulation of Heavy Quark Effective Field Theory
We apply the new formulation of heavy quark effective field theory (HQEFT) to
the inclusive decays of bottom hadrons. The long-term ambiguity of using heavy
quark mass or heavy hadron mass for inclusive decays is clarified within the
framework of the new formulation of HQEFT. The order corrections are
absent and contributions from terms are calculated in detail. This
enables us to reliably extract the important CKM matrix element from
the inclusive semileptonic decay rates. The resulting lifetime ratios
and are found to well agree
with the experimental data. We also calculate in detail the inclusive
semileptonic branching ratios and the ratios of the and decay
rates as well as the charm countings in the , and
systems. For decays, all the observables are found to be consistent with
the experimental data. More precise data for the decays and further
experimental measurements for the and systems will be very
useful for testing the framework of new formulation of HQEFT at the level of
higher order corrections.Comment: 20 pages, RevTex, 8 figures, 3 tables, revised version with `dressed
heavy quark' being addressed, to be published in Int. J. Mod. Phys.
Notch effects in tensile behavior of AM60 magnesium alloys
The deformation and failure behavior of an AM60 magnesium alloy was investigated using tensile test on circumferentially notched specimens with different notch radii. The strain and stress triaxiality corresponding to the failure point were evaluated using both analytical and finite element analyses. Combining with systematical observations of the fracture surfaces, it is concluded that deformation and failure of AM60 magnesium alloy are notch (constraint) sensitive. The failure mechanisms change from ductile tearing to quasi cleavage with the increase of constraint
|V_ub| and |V_cb|, Charm Counting and Lifetime Differences in Inclusive Bottom Hadron Decays
Inclusive bottom hadron decays are analyzed based on the heavy quark
effective field theory (HQEFT). Special attentions in this paper are paid to
the b\to u transitions and nonspectator effects. As a consequence, the CKM
quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the
inclusive semileptonic decays B\to X_u e \nu and B\to X_c e \nu. Various
observables, such as the semileptonic branch ratio B_SL, the lifetime
differences among B^-, B^0, B_s and \Lambda_b hadrons, the charm counting n_c,
are predicted and found to be consistent with the present experimental data.Comment: 20 pages, Revtex, 4 figures and 2 table
Generalized Darboux transformations for the KP equation with self-consistent sources
The KP equation with self-consistent sources (KPESCS) is treated in the
framework of the constrained KP equation. This offers a natural way to obtain
the Lax representation for the KPESCS. Based on the conjugate Lax pairs, we
construct the generalized binary Darboux transformation with arbitrary
functions in time for the KPESCS which, in contrast with the binary Darboux
transformation of the KP equation, provides a non-auto-B\"{a}cklund
transformation between two KPESCSs with different degrees. The formula for
N-times repeated generalized binary Darboux transformation is proposed and
enables us to find the N-soliton solution and lump solution as well as some
other solutions of the KPESCS.Comment: 20 pages, no figure
Quantization of a Friedmann-Robertson-Walker model in N=1 Supergravity with Gauged Supermatter
The theory of N = 1 supergravity with gauged supermatter is studied in the
context of a k = + 1 Friedmann minisuperspace model. It is found by imposing
the Lorentz and supersymmetry constraints that there are {\seveni no} physical
states in the particular SU(2) model studied.Comment: 5 pages, Talk at the 1st Mexican School in Gravitation and
mathematical physics, Guanajuato, Mexico, December 12-16 199
Nonperturbative Determination of Heavy Meson Bound States
In this paper we obtain a heavy meson bound state equation from the heavy
quark equation of motion in heavy quark effective theory (HQET) and the heavy
meson effective field theory we developed very recently. The bound state
equation is a covariant extention of the light-front bound state equation for
heavy mesons derived from light-front QCD and HQET. We determine the covariant
heavy meson wave function variationally by minimizing the binding energy
. Subsequently the other basic HQET parameters and
, and the heavy quark masses and can also be
consistently determined.Comment: 15 pages, 1 figur
QCD factorization for B -> PP
In this work, we give a detailed discussion for QCD factorization involved
the complete chirally enhanced power corrections for B decays to two light
pseudoscalar mesons, and present some detailed calculations of radiative
corrections at the order of alpha_s. We point out that the infrared finiteness
of the vertex corrections in the chirally enhanced power corrections requires
twist-3 light-cone distribution amplitudes (LCDAs) of the light pseudoscalar
symmetric. However, even in the symmetric condition, there is also logarithmic
divergence from the endpoints of the twist-3 LCDAs in the hard spectator
scattering. We point out that the decay amplitudes of B --> PP predicted by QCD
factorization are really free of the renormalization scale dependence, at least
at the order of alpha_s. At last, we briefly compare the QCD factorization with
the generalized factorization and PQCD method.Comment: 31 pages, 3 eps figure
The Fundamental Plane of Gamma-ray Globular Clusters
We have investigated the properties of a group of -ray emitting
globular clusters (GCs) which have recently been uncovered in our Galaxy. By
correlating the observed -ray luminosities with various
cluster properties, we probe the origin of the high energy photons from these
GCs. We report is positively correlated with the encounter rate
and the metalicity which place an
intimate link between the gamma-ray emission and the millisecond pulsar
population. We also find a tendency that increase with the energy
densities of the soft photon at the cluster location. Furthermore, the
two-dimensional regression analysis suggests that , soft photon
densities, and / possibly span fundamental
planes which potentially provide better predictions for the -ray
properties of GCs.Comment: 17 pages, 4 figures, 3 tables, published in Ap
Transport properties for a Luttinger liquid wire with Rashba spin-orbit coupling and Zeeman splitting
We study the transport properties for a Luttinger-liquid (LL) quantum wire in
the presence of both Rashba spin-orbit coupling (SOC) and a weak external
in-plane magnetic field. The bosonized Hamiltonian of the system with an
externally applied longitudinal electric field is established. And then the
equations of motion for the bosonic phase fields are solved in the Fourier
space, with which the both charge and spin conductivities for the system are
calculated analytically based on the linear response theory. Generally, the ac
conductivity is an oscillation function of the strengths of electron-electron
interaction, Rashba SOC and magnetic field, as well as the driving frequency
and the measurement position in the wire. Through analysis with some examples
it is demonstrated that the modification on the conductivity due to
electron-electron interactions is more remarkable than that due to SOC, while
the effects of SOC and Zeeman splitting on the conductivity are very similar.
The spin-polarized conductivities for the system in the absence of Zeeman
effect or SOC are also discussed, respectively. The ratio of the spin-polarized
conductivities is dependent of the
electron-electron interactions for the system without SOC, while it is
independent of the electron-electron interactions for the system without Zeeman
splitting.Comment: 10 pages, 8 figure
Vertical Diffusivities of Active and Passive Tracers
The climate models that include a carbon-cycle need the vertical diffusivity of a passive tracer. Since an expression for the latter is not available, it has been common practice to identify it with that of salt. The identification is questionable since T, S are active, not passive tracers. We present the first derivation of the diffusivity of a passive tracer in terms of Ri (Richardson number) and Rq (density ratio, ratio of salinity over temperature z-gradients). The following results have emerged: (a) The passive tracer diffusivity is an algebraic function of Ri, Rq. (b) In doubly stable regimes (DS, partial derivative of T with respect to z > 0, partial derivative of S with respect to z 0. (c) In DC regimes (diffusive convection, partial derivative of T with respect to z 1), the passive scalar diffusivity is larger than that of salt. At Ri = O(1), it can be more than twice as large. (d) In SF regimes (salt fingers, partial derivative of T with respect to z > 0, partial derivative of S with respect to z > 0, Rq < 1), the passive scalar diffusivity is smaller than that of salt. At Ri = O(1), it can be less than half of it. (e) The passive tracer diffusivity predicted at the location of NATRE (North Atlantic Tracer Release Experiment) is discussed. (f) Perhaps the most relevant conclusion is that the common identification of the tracer diffusivity with that of salt is valid only in DS regimes. In the Southern Ocean, where there is the largest CO2 absorption, the dominant regime is diffusive convection discussed in (c) above
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