1,870 research outputs found
The nature of the resonances from a coupled-channels approach
The positive parity charmonium states are expected to lie
around the 3.9 GeV/ energy region, according to the predictions of quark
models. However, a plethora of states with difficult assignment and
unconventional properties have been discovered over the years, i.e., the
, , , , and the
resonances, which complicates the description of this intriguing region.
In this work we analyze the and sectors, employing a
coupled-channels formalism successfully applied to the sector, where
the was described as a molecule with a sizable
component. This coupled-channels formalism is based on a
widely-used Constituent Quark Model, which describes the quark-quark
interactions, and the quark pair creation mechanism, used to couple the
two and four quark sectors.
The recent controversy about the quantum numbers of the state, the
properties of the one and the nature of the new resonance
are analyzed in a unified theoretical framework, being all the parameters
completely constrained from previous calculations in the low-lying heavy
quarkonium phenomenology.Comment: 6 pages, 2 tables. XVII International Conference on Hadron
Spectroscopy and Structure - Hadron201
Heavy mesons in the Quark Model
Since the discovery of the , the quark model was very successful in
describing the spectrum and properties of heavy mesons including only
components. However since 2003, with the discovery of the , many
states that can not be accommodated on the naive quark model have been
discovered, and they made unavoidable to include higher Fock components on the
heavy meson states. We will give an overview of the success of the quark model
for heavy mesons and point some of the states that are likely to be more
complicated structures such as meson-meson molecules.Comment: Contribution to the Proceedings of the 15th International Workshop on
Meson Physics - MESON201
Puzzles in quarkonium hadronic transitions with two pion emission
The anomalously large rates of some hadronic transitions from quarkonium are
studied using QCD multipole expansion (QCDME) in the framework of a constituent
quark model which has been successful in describing hadronic phenomenology. The
hybrid intermediate states needed in the QCDME method are calculated in a
natural extension of our constituent quark model based on the Quark Confining
String (QCS) scheme. Some of the anomalies are explained due to the presence of
an hybrid state with a mass near the mass of the decaying resonance whereas
other are justified by the presence of molecular components in the wave
function. Some unexpected results are pointed out.Comment: Conference proceedings of the XI Quark Confinement and the Hadron
Spectrum (CONFINEMENT XI). Saint Petersburg (Russia) from 8 to 12 September
201
Charmonium resonances in the 3.9 GeV/ energy region and the puzzle
An interesting controversy has emerged challenging the widely accepted nature
of the and the resonances, which had initially been
assigned to the and states,
respectively. To unveil their inner structure, the properties of the
and charmonium states in the energy
region of these resonances are analyzed in the framework of a constituent quark
model. Together with the bare states, threshold effects due to the
opening of nearby meson-meson channels are included in a coupled-channels
scheme calculation. We find that the structure of both states is dominantly
molecular with a probability of bare states lower than . Our
results favor the hypothesis that and resonances arise as
different decay mechanisms of the same state. Moreover we
found an explanation for the recently discovered MeV as a
state and rediscovery the lost as an
additional state in the family.Comment: 6 pages, 3 table
Molecular components in P-wave charmed-strange mesons
Results obtained by various experiments show that the
and mesons are very narrow states located below the and
thresholds, respectively. This is markedly in contrast with the
expectations of naive quark models and heavy quark symmetry. Motivated by a
recent lattice study which addresses the mass shifts of the ground
states with quantum numbers () and
() due to their coupling with -wave
thresholds, we perform a similar analysis within a
nonrelativistic constituent quark model in which quark-antiquark and
meson-meson degrees of freedom are incorporated. The quark model has been
applied to a wide range of hadronic observables and thus the model parameters
are completely constrained. The coupling between quark-antiquark and
meson-meson Fock components is done using a model in which its only
free parameter has been elucidated performing a global fit to the
decay widths of mesons that belong to different quark sectors, from light to
heavy. We observe that the coupling of the meson sector to
the threshold is the key feature to simultaneously lower the
masses of the corresponding and states
predicted by the naive quark model and describe the meson as the
state of the doublet predicted by heavy quark
symmetry, reproducing its strong decay properties. Our calculation allows to
introduce the coupling with the -wave channel and the
computation of the probabilities associated with the different Fock components
of the physical state.Comment: 11 pages, 3 figures, 7 table
The X(3872) and other possible molecular states
We perform a coupled channel calculation of the and sectors
in the framework of a constituent quark model. The interaction for the
states is obtained using the Resonant Group Method (RGM) and the underlying
quark interaction model. The coupling with the two quark system is performed
using the model. The X(3872) is found as a molecular state with a
sizable component. A comparison with Belle and BaBar data has been
done, finding a good agreement. Other possible molecular molecular states are
discussed.Comment: 5 pages, 5 figures, Proceedings to the Hadron 2009 - XIII
International Conference on Hadron Spectroscopy, Florida State University
(USA
Molecular components in and mesons
Different experiments have confirmed that the and
mesons are very narrow states located, respectively, below the
and thresholds. This is markedly in contrast with the
expectations of naive quark models and heavy quark symmetry. We address the
mass shifts of the ground states with quantum numbers
() and () using a
nonrelativistic constituent quark model in which quark-antiquark and
meson-meson degrees of freedom are incorporated. The quark model has been
applied to a wide range of hadronic observables and thus the model parameters
are completely constrained. We observe that the coupling of the
meson sector to the threshold is a key feature in
lowering the masses of the corresponding and
states predicted by the naive quark model, but also in
describing the meson as the state of the
doublet predicted by heavy quark symmetry and thus
reproducing its strong decay properties. Two features of our formalism cannot
be address nowadays by other approaches: the coupling of the -wave
threshold in the channel and the
computation of the probabilities associated with different Fock components in
the physical state.Comment: Contribution to the proceedings of the 14th International Workshop on
Meson Production, Properties and Interaction (MESON2016). June 2-7, 2016.
Krakow, Polan
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