2,182 research outputs found
Multichannel calculation of the very narrow and the very broad
The narrow (2317) and broad (2300-2400) charmed
scalar mesons and their radial excitations are described in a coupled-channel
quark model that also reproduces the properties of the light scalar nonet. All
two-meson channels containing ground-state pseudoscalars and vectors are
included. The parameters are chosen fixed at published values, except for the
overall coupling constant , which is fine-tuned to reproduce the
(2317) mass, and a damping constant for subthreshold
contributions. Variations of and (2300-2400) pole
postions are studied for different values. Calculated cross sections
for -wave and scattering, as well as resonance pole positions,
are given for the value of that fits the light scalars. The thus
predicted radially excited state (2850), with a width of about 50
MeV, seems to have been observed already.Comment: 3 pages, EPJ LaTeX, 2 Postscript figures, 1 table; parallel talk at
the IVth International Conference on Quarks and Nuclear Physics (QNP06),
Madrid, 5-10 June 200
Towards Meson Spectroscopy Instead of Bump Hunting
Mesonic resonances are generally observed in data as narrow, moderately
broad, or wide peaks in scattering or production processes. In the eyes of
nearly all experimentalists, any suchlike bump is a true resonance as soon as
its statistical significance exceeds certain minimal values. However, this
simple point of view ignores possible effects from competing hadronic channels
and the opening of the corresponding thresholds. On the other hand, most
theoretical hadron-model builders consider mesons merely bound states of a
quark and an antiquark, or of more exotic combinations sometimes involving
valence gluons as well. Also the latter description is much too naive, since
considerable mass shifts or even the dynamical generation of extra states due
to unquenching are equally ignored.
In the present paper, a largely empirical yet very successful approach to
meson spectroscopy is revisited, in which all the above phenomena can be
accounted for non-perturbatively, with concrete examples of some enigmatic
mesonic states described in detail. First, the X(4260) charmonium enhancement
is argued to be a non-resonant structure resulting from depletion effects due
to competing channels and resonances. Then, the X(3872) charmonium-like meson
is described as a unitarised state. Also, the
unusual pattern of masses and widths of the open-charm axial-vector mesons
, , , and is shown to follow
from highly non-perturbative coupled-channel and mixing effects. Finally, first
indications of a very light scalar boson are presented, on the basis of
published BABAR data.Comment: Invited seminar given by G. Rupp at the International School of
Nuclear Physics, 33rd course: "From Quarks and Gluons to Hadrons and Nuclei",
Erice, Sicily, Italy, 16 - 24 September 2011; 7 pages, 5 figures (9 plots),
style of Progress in Particle and Nuclear Physic
Continuum bound states K-long, D_{1}(2420), D_{s1}(2536) and their partners K-short, D_{1}(2400), D*_{sJ}(2463)
The very recently observed meson is described as a
bound state in a unitarised meson model, owing its
existence to the strong OZI-allowed coupling to the nearby -wave
threshold. By the same non-perturbative mechanism, the narrow
axial-vector resonance shows up as a quasi-bound-state partner
embedded in the continuum. With the same model and parameters, it
is also shown that the preliminary broad resonance and
the established narrow may be similar
partners, as a result of the strong OZI-allowed coupling to the
nearby -wave threshold. The continuum bound states
(2420) and are found to be mixtures of 33%
and 67% , whereas their partners and
have more or less the opposite -state
content, but additionally with some or admixture,
respectively.
The employed mechanism also reproduces the ratio of the - mass
difference and the width, by describing as a bound state
embedded in the continuum. The model's results for
states containing one quark are also discussed.Comment: 11 pages, plain LaTeX, v2:relation to work of Kokoski and Godfrey in
conclusions and more references v3:B-states included. More reference
Multichannel calculation for Ds* vector states and the Ds(2632) resonance
We study bound states below threshold and resonances above threshold in the
D0-K+ and Ds-eta systems, using a many-coupled-channel model for non-exotic
meson-meson scattering applied to states with the quantum numbers of c-sbar
quark-antiquark vector mesons. We fit the ground state at 2.112 GeV, whence the
lowest resonances in D0-K+ come out at 2.61, 2.72, 3.03, and 3.08 GeV. The
resonance at 2.61 GeV acquires a width of about 8 MeV, while its partial P-wave
cross section is up to six times larger in Ds-eta than in D0-K+, provided a
mechanism accounting for Okubo-Zweig-Iizuka--forbidden decays is included. The
latter finding is in agreement with the observations of the SELEX collaboration
with respect to the recently reported DsJ(2632) resonance. Therefore, we
conclude that the DsJ(2632) is most probably the first recurrence excitation of
the Ds*(2112) meson.Comment: 11 pages, 6 figures; v2: Significant improvements for threshold
behavior, and for the hadronic widths by including additional two-meson
channels. Misprints in formulas correcte
Coupling constants and transition potentials for hadronic decay modes of a meson
Within the independent-harmonic-oscillator model for quarks inside a hadron,
a rigorous method is presented for the calculation of coupling constants and
transition potentials for hadronic decay, as needed in a multi-channel
description of mesons.Comment: 19 pages, 4 figure
A very broad X(4260) and the resonance parameters of the 3D vector charmonium state
We argue that the X(4260) enhancement contains a wealth of information on
vector c-cbar spectroscopy. We discuss the shape of the X(4260) observed in the
OZI-forbidden process "electron-positron into J/psi and a pair of charged
pions", in particular at and near vector charmonium resonances as well as
open-charm threshold enhancements. The resulting very broad X(4260) structure
does not seem to classify itself as a vector charmonium resonance, but its
detailed shape allows to identify new vector c-cbar states. Here, we estimate
the resonance parameters of the psi(3D) state.Comment: 4 pages, 5 figures; version 2: 2 figures replace
D_{sJ}(2860) as the first radial excitation of the D_{s0}^*(2317)
A coupled-channel model previously employed to describe the narrow
(2317) and broad (2400) charmed scalar mesons is generalized
so as to include all ground-state pseudoscalar-pseudoscalar and vector-vector
two-meson channels. All parameters are chosen fixed at published values, except
for the overall coupling constant, which is fine-tuned to reproduce the
(2317) mass. Thus, the radial excitations (2850) and
(2740) are predicted, both with a width of about 50 MeV. The former
state appears to correspond to the new (2860) resonance decaying to
announced by BABAR in the course of this work. Also the (2400)
resonance is roughly reproduced, though perhaps with a somewhat too low central
resonance peak.Comment: Plain LaTeX, 4 pages, 2 Postscript figures; v2: REVTeX, 4 pages,
introduction expanded, "Note added in proof" and references added, figures
with more detail and improved quality, version accepted for publication in
Physical Review Letter
Recoupling matrix elements and decay
Recoupling matrix elements are evaluated, in the harmonic oscillator
approximation, for all possible angular and radial excitations in processes
where quarks recombine. A diagrammatic representation is given. Their use is
demonstrated in calculating the transition potential for rho to two pions in a
pair creation model.Comment: 15 pages, 10 figure
Relating multichannel scattering and production amplitudes in a microscopic OZI-based model
Relations between scattering and production amplitudes are studied in a
microscopic multichannel model for meson-meson scattering, with coupling to
confined quark-antiquark channels. Overlapping resonances and a proper
threshold behaviour are treated exactly in the model. Under the spectator
assumption, it is found that the two-particle production amplitude shares a
common denominator with the elastic scattering amplitude, besides a numerator
consisting of a linear combination of all elastic and some inelastic matrix
elements. The coefficients in these linear combinations are shown to be
generally complex. Finally, the standard operator expressions relating
production and scattering amplitudes, viz. A=T/V and Im(A)=T*A, are fulfilled,
while in the small-coupling limit the usual isobar model is recovered.Comment: 16 pages, 3 figures, plain LaTeX
Relativistic Unitarized Quark/Meson Model in Momentum Space
An outline is given how to formulate a relativistic unitarized constituent
quark model of mesons in momentum space, employing harmonic quark confinement.
As a first step, the momentum-space harmonic-oscillator potential is solved in
a relativistically covariant, three-dimensional quasipotential framework for
scalar particles, using the spline technique. Then, an illustrative toy model
with the same dynamical equations but now one and one meson-meson
channel, coupled to one another through quark exchange describing the
mechanism, is solved in closed form on a spline basis. Conclusions are
presented on how to generalize the latter to a realistic multichannel
quark/meson model.Comment: Plain LaTeX, 12 pages, 2 EPS figures. Contribution to the Second
International Workshop on Hadron Physics, Effective Theories of Low Energy
QCD, 25-29 September, 2002 (Coimbra, Portugal
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