2,523 research outputs found
Non-factorizable contribution in nonleptonic weak interactions of K mesons
Two pion decays of K mesons, K_L-K_S mass difference, two photon and the
Dalitz decays of K_L are studied systematically by assuming that their
amplitude is given by a sum of factorizable and non-factorizable ones. The
former is estimated by using a naive factorization while the latter is assumed
to be dominated by dynamical contributions of various hadron states.Comment: 23 pages,1 figur
Non-factorizable long distance contributions in color suppressed decays of B mesons
, , and decays are
studied. Their amplitude is given by a sum of factorized and non-factorizable
ones. The latter which is estimated by using a hard pion approximation is
rather small in color favored and decays but still
can efficiently interfere with the main amplitude given by the factorization.
In the color suppressed and decays, the
non-factorizable contribution is very important. The sum of the factorized and
non-factorizable amplitudes can reproduce well the existing experimental data
on the branching ratios for the color favored and
and the color suppressed and decays by
taking reasonable values of unknown parameters involved.Comment: 19 pages, Revte
Newly observed two-body decays of B mesons in a hybrid perspective
In consistency with the b --> c type of (quasi) two body decays, recently
observed two body decays of B mesons are studied in a hybrid perspective in
which their amplitude is given by a sum of factorizable and non-factorizable
ones, and a role of the latter in these decays are discussed.Comment: 7 page
Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4
Metal-insulator transition in Ca_{1-x}Li_xPd_3O_4 has been studied through
charge transport measurements. The resistivity, the Seebeck coefficient, and
the Hall coefficient are consistently explained in terms of a simple one-band
picture, where a hole with a moderately enhanced mass is itinerant
three-dimensionally. Contrary to the theoretical prediction [Phys. Rev. B62,
13426 (2000)], CaPd_3O_4 is unlikely to be an excitonic insulator, and holds a
finite carrier concentration down to 4.2 K. Thus the metal-insulator transition
in this system is basically driven by localization effects.Comment: RevTeX4 format, 4 pages, 5 eps figure
CaCu_3Ti_4O_12/CaTiO_3 Composite Dielectrics: A Ba/Pb-free Ceramics with High Dielectric Constants
We have measured dielectric properties of CaCuTiO
( = 0, 0.1, 0.5, 1, 1.5, 2, 2.9 and 3), and have found that
CaCuTiO (a composite of CaCuTiO and
CaTiO) exhibits a high dielectric constant of 1800 with a low dissipation
factor of 0.02 below 100 kHz from 220 to 300 K. These are comparable to (or
even better than) those of the Pb/Ba-based ceramics, which could be attributed
to a barrier layer of CaTiO on the surface of the CaCuTiO
grains. The composite dielectric ceramics reported here are environmentally
benign as they do not contain Ba/Pb.Comment: 4 pages, 4 figures, Appl. Phys. Lett. (scheduled on July 25, 2005
Magnetic and transport properties of the spin-state disordered oxide La0.8Sr0.2Co_{1-x}Rh_xO_{3-\delta}
We report measurements and analysis of magnetization, resistivity and
thermopower of polycrystalline samples of the perovskite-type Co/Rh oxide
LaSrCoRhO. This system constitutes a
solid solution for a full range of ,in which the crystal structure changes
from rhombohedral to orthorhombic symmetry with increasing Rh content . The
magnetization data reveal that the magnetic ground state immediately changes
upon Rh substitution from ferromagnetic to paramagnetic with increasing
near 0.25, which is close to the structural phase boundary. We find that one
substituted Rh ion diminishes the saturation moment by 9 , which implies
that one Rh ion makes a few magnetic Co ions nonmagnetic (the low
spin state), and causes disorder in the spin state and the highest occupied
orbital. In this disordered composition (), we find that
the thermopower is anomalously enhanced below 50 K. In particular, the
thermopower of =0.5 is larger by a factor of 10 than those of =0 and 1,
and the temperature coefficient reaches 4 V/K which is as large as
that of heavy-fermion materials such as CeRuSi.Comment: 8 pages, 6 figures, accepted to Phys. Rev.
Two-Staged Magnetoresistance Driven by Ising-like Spin Sublattice in SrCo6O11
A two-staged, uniaxial magnetoresistive effect has been discovered in
SrCo6O11 having a layered hexagonal structure. Conduction electrons and
localized Ising spins are in different sublattices but their interpenetration
makes the conduction electrons sensitively pick up the stepwise
field-dependence of magnetization. The stepwise field-dependence suggests two
competitive interlayer interactions between ferromagnetic Ising-spin layers,
i.e., a ferromagnetic nearest-layer interaction and an antiferromagnetic
next-nearest-layer interaction. This oxide offers a unique opportunity to study
nontrivial interplay between conduction electrons and Ising spins, the coupling
of which can be finely controlled by a magnetic field of a few Tesla.Comment: 14 pages, 4 figures, accepted for publication in Phys. Rev. Let
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