2,608 research outputs found
Spin alignment of vector meson in e+e- annihilation at Z0 pole
We calculate the spin density matrix of the vector meson produced in e+e-
annihilation at Z^0 pole. We show that the data imply a significant
polarization for the antiquark which is created in the fragmentation process of
the polarized initial quark and combines with the fragmenting quark to form the
vector meson. The direction of polarization is opposite to that of the
fragmenting quark and the magnitude is of the order of 0.5. A qualitative
explanation of this result based on the LUND string fragmentation model is
given.Comment: 15 pages, 2 fgiures; submitted to Phys. Rev.
Spin Alignment of Vector Meson in High Energy Reactions
The recent data on the polarization of vector meson at LEP show that the
vector mesons favor the helicity zero state. We calculate the helicity density
matrix of vector meson which contains a polarized fragmenting quark by adding
the spin of the fragmenting quark and that of the antiquark created in the
fragmentation. The data at LEP imply a significant polarization for the
antiquark in the opposite direction as that of the fragmenting quark. We extend
the calculations to other reactions and make predictions for vector mesons in
deeply inelastic lepton-nucleon scatterings and polarized collisions.Comment: 4 pages,3 figures, Talk given at 3rd Circum-Pan-Pacific Symposium on
"High Energy Spin Physics", Beijing, China, Oct.8-13, 200
Revisiting the as a hadronic molecule and its strong decays
Recently, the Belle collaboration measured the ratios of the branching
fractions of the newly observed excited state. They did not
observe significant signals for the decay, and reported an upper limit for the ratio of the three
body decay to the two body decay mode of . In
this work, we revisit the newly observed from the molecular
perspective where this resonance appears to be a dynamically generated state
with spin-parity from the coupled channels interactions of the and in -wave and in -wave. With
the model parameters for the -wave interaction, we show that the ratio of
these decay fractions reported recently by the Belle collaboration can be
easily accommodated.Comment: Published version. Published in Eur.\ Phys.\ J.\ C {\bf 80}, 361
(2020
Half Metallic Bilayer Graphene
Charge neutral bilayer graphene has a gapped ground state as transport
experiments demonstrate. One of the plausible such ground states is layered
antiferromagnetic spin density wave (LAF) state, where the spins in top and
bottom layers have same magnitude with opposite directions. We propose that
lightly charged bilayer graphene in an electric field perpendicular to the
graphene plane may be a half metal as a consequence of the inversion and
particle-hole symmetry broken in the LAF state. We show this explicitly by
using a mean field theory on a 2-layer Hubbard model for the bilayer graphene.Comment: 4+ pages, 4 figure
Electrical transport across metal/two-dimensional carbon junctions: Edge versus side contacts
Metal/two-dimensional carbon junctions are characterized by using a nanoprobe
in an ultrahigh vacuum environment. Significant differences were found in bias
voltage (V) dependence of differential conductance (dI/dV) between edge- and
side-contact; the former exhibits a clear linear relationship (i.e., dI/dV
\propto V), whereas the latter is characterized by a nonlinear dependence,
dI/dV \propto V3/2. Theoretical calculations confirm the experimental results,
which are due to the robust two-dimensional nature of the carbon materials
under study. Our work demonstrates the importance of contact geometry in
graphene-based electronic devices
- …