1,440 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
Self-consistent description of multipole strength: systematic calculations
We use the quasiparticle random phase approximation with a few Skyrme density
functionals to calculate strength functions in the Jpi = 0+, 1-, and 2+
channels for even Ca, Ni, and Sn isotopes, from the proton drip line to the
neutron drip line. We show where and how low-lying strength begins to appear as
N increases. We also exhibit partial energy-weighted sums of the transition
strength as functions of N for all nuclei calculated, and transition densities
for many of the interesting peaks. We find that low-energy strength increases
with N in all multipoles, but with distinctive features in each. The low-lying
0+ strength near the neutron at large N barely involves protons at all, with
the strength coming primarily from a single two-quasineutron configuration with
very large spatial extent. The low-lying 1- strength is different, with protons
contributing to the transition density in the nuclear interior together with
neutrons at large radii. The low-lying 2+ transition strength goes largely to
more localized states. The three Skyrme interactions we test produce similar
results, differing most significantly in their predictions for the location of
the neutron drip line, the boundaries of deformed regions, energies of and
transition strengths to the lowest 2+ states between closed shells, and
isovector energy-weighted sum rules.Comment: 43 pages, 48 figures, 1 tabl
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
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
Magnetic susceptibility study of hydrated and non-hydrated NaxCoO2-yH2O single crystals
We have measured the magnetic susceptibility of single crystal samples of
non-hydrated NaxCoO2 (x ~ 0.75, 0.67, 0.5, and 0.3) and hydrated Na0.3CoO2-yH2O
(y ~ 0, 0.6, 1.3). Our measurements reveal considerable anisotropy between the
susceptibilities with H||c and H||ab. The derived anisotropic g-factor ratio
(g_ab/g_c) decreases significantly as the composition is changed from the
Curie-Weiss metal with x = 0.75 to the paramagnetic metal with x = 0.3. Fully
hydrated Na0.3CoO2-1.3H2O samples have a larger susceptibility than
non-hydrated Na0.3CoO2 samples, as well as a higher degree of anisotropy. In
addition, the fully hydrated compound contains a small additional fraction of
anisotropic localized spins.Comment: 6 pages, 5 figure
- …