1,871 research outputs found
Bound States of the Heavy Flavor Vector Mesons and Y(4008) and
The and systems are studied dynamically
in the one boson exchange model, where , , , and
exchanges are taken into account. Ten allowed states with low spin
parity are considered. We suggest that the , , and
molecules should exist, and the
bound states with the same quantum numbers very likely exist as well. However,
the CP exotic (, ) and
states may not be bound by the one boson exchange potential. We find that the
I=0 configuration is more deeply bound than the I=1 configuration, hence
may not be a molecule. Although Y(4008) is
close to the threshold, the interpretation of Y(4008) as a
molecule is not favored by its huge width.
and states can be produced copiously in
annihilation, detailed scanning of the annihilation
data near the and threshold is an
important check to our predictions.Comment: 17 pages,6 figur
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Dopaminergic neurons inhibit striatal output via non-canonical release of GABA
The substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) contain the two largest populations of dopamine (DA)-releasing neurons in the mammalian brain. These neurons extend elaborate projections in striatum, a large subcortical structure implicated in motor planning and reward-based learning. Phasic activation of dopaminergic neurons in response to salient or reward-predicting stimuli is thought to modulate striatal output via the release of DA to promote and reinforce motor action1–4. Here we show that activation of DA neurons in striatal slices rapidly inhibits action potential firing in both direct-and indirect-pathway striatal projection neurons (SPNs) through vesicular release of the inhibitory transmitter γ-aminobutyric acid (GABA). GABA is released directly from dopaminergic axons but in a manner that is independent of the vesicular GABA transporter VGAT. Instead GABA release requires activity of the vesicular monoamine transporter VMAT2, which is the vesicular transporter for DA. Furthermore, VMAT2 expression in GABAergic neurons lacking VGAT is sufficient to sustain GABA release. Thus, these findings expand the repertoire of synaptic mechanisms employed by DA neurons to influence basal ganglia circuits, reveal a novel substrate whose transport is dependent on VMAT2, and demonstrate that GABA can function as a bona fide co-transmitter in monoaminergic neurons
Are Y(4260) and {\rm Z(4250)} or Hadronic Molecules?
In this work, we have investigated whether Y(4260) and
could be or molecules in the framework of meson
exchange model. The off-diagonal interaction induced by exchange plays a
dominant role. The exchange has been taken into account, which leads
to diagonal interaction. The contribution of exchange is not favorable
to the formation of molecular state ,
however, it is beneficial to the binding of molecule . Light vector meson exchange leads to diagonal
interaction as well. For , the contribution from
and exchange almost cancels each other. For the currently allowed
values of the effective coupling constants and a reasonable cutoff in
the range 1-2 GeV, We find that Y(4260) could be accommodated as a
and molecule, whereas the interpretation of as a or molecule is disfavored.
The bottom analog of Y(4260) and may exist, and the most
promising channels to discovery them are and
respectively.Comment: 21 pages, 3 figures and 7 table
Possible Molecular States of System and Y(4140)
The interpretation of Y(4140) as a molecule is studied
dynamically in the one boson exchange approach, where , and
exchange are included. Ten allowed states with
low spin parity are considered, we find that the , ,
, and configurations are most
tightly bound. We suggest the most favorable quantum numbers are
for Y(4140) as a molecule, however,
and can not be excluded. We propose to search for the
and partners in the and final
states, which is an important test of the molecular hypothesis of Y(4140) and
the reasonability of our model. The molecule is
deeply bound, experimental search in the channel at Tevatron
and LHC is suggested.Comment: 13 pages,2 figure
and Analogous Heavy Flavor States
The proximity of to the threshold
suggests that it may be a molecular state. The system has been studied dynamically from quark model, and
state mixing effect is taken into account by solving the multichannel
Schrdinger equation numerically. We suggest the most favorable
quantum number is , if future experiments confirm as a loosely bound molecule state. More precise measurements of
mass and width, partial wave analysis are helpful to
understand its structure. The analogous heavy flavor mesons
and are studied as well, and the masses predicted in our
model are in agreement with the predictions from potential model and QCD sum
rule. We further apply our model to the and
system. We find the exotic bound molecule doesn't exist, while
the bound state solution can be found only if the
screening mass is smaller than 0.17 GeV. The state mixing effect between
the molecular state and the conventional charmonium should be considered to
understand the nature of X(3872).Comment: 27 pages, 6 figure
Dynamics of Hadronic Molecule in One-Boson Exchange Approach and Possible Heavy Flavor Molecules
We extend the one pion exchange model at quark level to include the short
distance contributions coming from , , and
exchange. This formalism is applied to discuss the possible molecular states of
, , , ,
the pseudoscalar-vector systems with and respectively. The
" function" term contribution and the S-D mixing effects have been
taken into account. We find the conclusions reached after including the heavier
mesons exchange are qualitatively the same as those in the one pion exchange
model. The previous suggestion that
molecule should exist, is confirmed in the one boson exchange model, whereas
bound state should not exist. The system
can accomodate a molecule close to the threshold, the mixing between
the molecule and the conventional charmonium has to be considered to identify
this state with X(3872). For the system, the pseudoscalar-vector
systems with and , near threshold molecular states may exist.
These bound states should be rather narrow, isospin is violated and the I=0
component is dominant. Experimental search channels for these states are
suggested.Comment: 21 pages, 11 figures, 8 table
Free field realization of the exceptional current superalgebra \hat{D(2,1;\a)}_k
The free-field representations of the D(2,1;\a) current superalgebra and
the corresponding energy-momentum tensor are constructed. The related screening
currents of the first kind are also presented.Comment: Latex file, 10 page
Symbolic Dynamics Analysis of the Lorenz Equations
Recent progress of symbolic dynamics of one- and especially two-dimensional
maps has enabled us to construct symbolic dynamics for systems of ordinary
differential equations (ODEs). Numerical study under the guidance of symbolic
dynamics is capable to yield global results on chaotic and periodic regimes in
systems of dissipative ODEs which cannot be obtained neither by purely
analytical means nor by numerical work alone. By constructing symbolic dynamics
of 1D and 2D maps from the Poincare sections all unstable periodic orbits up to
a given length at a fixed parameter set may be located and all stable periodic
orbits up to a given length may be found in a wide parameter range. This
knowledge, in turn, tells much about the nature of the chaotic limits. Applied
to the Lorenz equations, this approach has led to a nomenclature, i.e.,
absolute periods and symbolic names, of stable and unstable periodic orbits for
an autonomous system. Symmetry breakings and restorations as well as
coexistence of different regimes are also analyzed by using symbolic dynamics.Comment: 35 pages, LaTeX, 13 Postscript figures, uses psfig.tex. The revision
concerns a bug at the end of hlzfig12.ps which prevented the printing of the
whole .ps file from page 2
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