9,868 research outputs found
Long distance contribution to decay and terms in CHPT
The long distance contribution to is
calculated using chiral perturbation theory. The leading contribution comes
from tree terms. The branching ratio of the long distance
contribution is found to be of order smaller than the short distance
contributions.Comment: 12 pages, 1 figure (available upon request
Study of Long Distance Contributions to
We calculate long distance contributions to $K\to\pi\nu\bar{\nu}\,,\
\pi\pi\nu\bar{\nu}\pi\pi\pi\nu\bar{\nu}K\to \pi\nu\bar{\nu}K\to \pi\pi\nu\bar{\nu}$ in the chiral logarithmic
approximation are at least seven orders of magnitude suppressed relative to
those from the short distance parts. The long distance effects in this class of
decays are therefore negligible.Comment: 13 pages, LaTeX fil
Low-lying even parity meson resonances and spin-flavor symmetry
A study is presented of the wave meson-meson interactions involving
members of the nonet and of the octet. The starting point is an
SU(6) spin-flavor extension of the SU(3) flavor Weinberg-Tomozawa Lagrangian.
SU(6) symmetry breaking terms are then included to account for the physical
meson masses and decay constants, while preserving partial conservation of the
axial current in the light pseudoscalar sector. Next, the matrix amplitudes
are obtained by solving the Bethe Salpeter equation in coupled-channel with the
kernel built from the above interactions. The poles found on the first and
second Riemann sheets of the amplitudes are identified with their possible
Particle Data Group (PDG) counterparts. It is shown that most of the low-lying
even parity PDG meson resonances, specially in the and sectors,
can be classified according to multiplets of the spin-flavor symmetry group
SU(6). The , and some resonances cannot be
accommodated within this SU(6) scheme and thus they would be clear candidates
to be glueballs or hybrids. Finally, we predict the existence of five exotic
resonances ( and/or ) with masses in the range 1.4--1.6 GeV,
which would complete the , , and multiplets of
SU(3)SU(2).Comment: 43 pages, 2 figures, 61 tables. Improved discussion of Section II. To
appear in Physical Review
The stability and the shape of the heaviest nuclei
In this paper, we report a systematic study of the heaviest nuclei within the
relativistic mean field (RMF) model. By comparing our results with those of the
Hartree-Fock-Bogoliubov method (HFB) and the finite range droplet model (FRDM),
the stability and the shape of the heaviest nuclei are discussed. The
theoretical predictions as well as the existing experimental data indicate that
the experimentally synthesized superheavy nuclei are in between the fission
stability line, the line connecting the nucleus with maximum binding energy per
nucleon in each isotopic chain, and the -stability line, the line
connecting the nucleus with maximum binding energy per nucleon in each isobaric
chain. It is shown that both the fission stability line and the
-stability line tend to be more proton rich in the superheavy region.
Meanwhile, all the three theoretical models predict most synthesized superheavy
nuclei to be deformed.Comment: 6 pages, 7 figures, to appear in Journal of Physics
Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell
A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via
A Study on the Critical Thickness of the Inner Tube for Magnetic Pulse Welding Using FEM and BEM
Due to high efficiency and quality in welding dissimilar metals, Magnetic Pulse Welding
(MPW) has attracted much attention. In this study, 3A21 aluminium alloy used as outer
tube was welded to 20Fe tube by MPW. In order to investigate the critical thickness of the
inner tube (20Fe) which is subjected to huge impact pressure from the outer tube (3A21),
both numerical simulations and experiments were carried out.
For the purpose of investigating the critical thickness of the inner tube under various
impact velocities, four discharge voltages (9 kV, 11 kV, 13 kV and 14 kV) were employed
in the MPW experiment. The diameters of inner tube at different locations were measured
to obtain its plastic deformation at various discharge voltages. The simulations
considering the coupled effects of the mechanical, thermal and electromagnetic process
were performed to research the impact velocity and deformation of tubular fittings in the
electromagnetic module (EM) in LS-DYNA. An inverse method was proposed to find the
dynamic yield stress of inner tube, and the predicted yield stress was then employed in
models with critical thickness. Both of the impact velocity and deformation were verified
experimentally
Spurious Shell Closures in the Relativistic Mean Field Model
Following a systematic theoretical study of the ground-state properties of
over 7000 nuclei from the proton drip line to the neutron drip line in the
relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in
fair agreement with existing experimental data, we observe a few spurious shell
closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell
closures are found to persist in all the effective forces of the relativistic
mean field model, e.g. TMA, NL3, PKDD and DD-ME2.Comment: 3 pages, to appear in Chinese Physics Letter
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