11,770 research outputs found
Nucleon-Meson Coupling Constants and Form Factors in the Quark Model
We demonstrate the calculation of the coupling constants and form factors
required by effective hadron lagrangians using the quark model. These relations
follow from equating expressions for strong transition amplitudes in the two
approaches. As examples we derive the NNm nucleon-meson coupling constants and
form factors for m = pi, eta, eta', sigma, a_0, omega and rho, using harmonic
oscillator quark model meson and baryon wavefunctions and the 3P0 decay model;
this is a first step towards deriving a quark-based model of the NN force at
all separations. This technique should be useful in the application of
effective lagrangians to processes in which the lack of data precludes the
direct determination of coupling constants and form factors from experiment.Comment: 7 pages, 4 figures, 1 tabl
Y(2175): Distinguish Hybrid State from Higher Quarkonium
The possibility of Y(2175) as a meson is studied. We
study the decay of from both the model and the
flux tube model, and the results are similar in the two models. We show that
the decay patterns of strangeonium hybrid and
are very different. The experimental search of the decay modes ,
, , is suggested to distinguish the two
pictures. Measuring the partial width ratios is crucial to
discriminate the from the assignment.Comment: 13 pages, 8 figure
The decay of the observed (1400) and (1600) hybrid candidates
We study the possible interpretation of the two exotic resonances at 1400 and 1600 MeV, claimed to be observed by BNL, decaying
respectively into , , and . These
objects are interpreted as hybrid mesons, in the quark-gluon constituent model
using a chromoharmonic confining potentiel.
The quantum numbers can be considered in a
constituent model as an hybrid meson (). The lowest states may be built in two ways : =1 (gluon-excited)
corresponding to an angular momentum between the gluon and () system,
while (quarks-excited) corresponds to an angular momentum
between and . For the gluon-excited mode hybrids, we find
the decay dominated by the channel, and by the channel
for the quark-excited mode. In our model, neither the quark-excited nor the
gluon-excited (1400 MeV) hybrids can decay into and
, in contradiction with experiment. Hence, the 1400 MeV resonance
seems unlikely to be an hybrid state. The (1600 MeV) gluon-excited
hybrid is predicted with too large a total decay width, to be considered as an
hybrid candidate. On the contrary the quark-excited mode has a total decay
width around 165 MeV, with a preferred decay channel, in agreement
with BNL. Our conclusion is that {\it{this resonance may be considered as a
hybrid meson in the quark-excited mode}}Comment: 13 pages, 1 figur
Distinguishing Among Strong Decay Models
Two competing models for strong hadronic decays, the and
models, are currently in use.
Attempts to rule out one or the other have been hindered by a poor
understanding of final state interactions and by ambiguities in the treatment
of relativistic effects.
In this article we study meson decays in both models, focussing on certain
amplitude ratios for which the relativistic uncertainties largely cancel out
(notably the ratios in and
), and using a Quark Born Formalism to estimate the
final state interactions.
We find that the model is strongly favoured.
In addition, we predict a amplitude ratio of for the decay
.
We also study the parameter-dependence of some individual amplitudes (as
opposed to amplitude ratios), in an attempt to identify a ``best'' version of
the model.Comment: 20 pages, uuencoded postscript file with 7 figures, MIT-CTP-2295;
CMU-HEP94-1
Scaling of the 3P0 strength in heavy meson strong decays
The phenomenological 3P0 decay model has been extensively applied to
calculate meson strong decays. The strength \gamma\ of the decay interaction is
regarded as a free flavor independent constant and is fitted to the data. We
calculate through the 3P0 model the total strong decay widths of the mesons
which belong to charmed, charmed-strange, hidden charm and hidden bottom
sectors. The wave function of the mesons involved in the strong decays are
given by a constituent quark model that describes well the meson phenomenology
from the light to the heavy quark sector. A global fit of the experimental data
shows that, contrarily to the usual wisdom, the \gamma\ depends on the reduced
mass of the quark-antiquark pair in the decaying meson. With this
scale-dependent strength \gamma, we are able to predict the decay width of
orbitally excited B mesons not included in the fit.Comment: 7 pages, 5 tables, 2 figure
D mesons in matter and the in-medium properties of charmonium
We study the changes in the partial decay widths of excited charmonium states
into , when the D meson mass decreases in nuclear matter, taking the
internal structure of the hadrons into account. Calculations within the 3P0
model for and imply that naive estimates of the
in-medium widths based only on phase space are grossly exaggerated. Due to
nodes in the wave functions, these states may even become narrow at high
densities, if the D meson mass is decreased by about 200 MeV. For the
states, we generally expect stronger modifications of the widths. The relevance
of the widths for suppression in heavy ion collision is
discussed. These phenomena could be explored in experiments at the future
accelerator facility at GSI.Comment: 12 pages, 3 figures; allowed for two independent oscillator
parameters for the charmonium states and D mesons, results are not
significantly modified and conclusions remains unaltere
J/Psi mass shift in nuclear matter
The mass shift in cold nuclear matter is computed using an effective
Lagrangian approach. The mass shift is computed by evaluating and
meson loop contributions to the self-energy employing medium-modified
meson masses. The modification of the and masses in nuclear matter is
obtained using the quark-meson coupling model. The loop integrals are
regularized with dipole form factors and the sensitivity of the results to the
values of form-factor cutoff masses is investigated. The mass shift
arising from the modification of the and loops at normal nuclear
matter density is found to range from -16 MeV to -24 MeV under a wide variation
of values of the cutoff masses. Experimental perspectives for the formation of
a bound state of to a nucleus are investigated.Comment: 9 pages, latex file, 6 figures. Version published in Phys. Lett.
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