4,201 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
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
Crustal Characteristics in the Subduction Zone of Mexico: Implication of the Tectonostratigraphic Terranes on Slab Tearing
During the past years, significant work has been done for studying the crustal anisotropy and state of stress of the Mexican subduction zone. At the same time, there is new evidence of the geometry of the subducted slab proposing subduction tearing. Here, we present a study of the Earth crust using three different methods: azimuthal anisotropy based on ambient noise, shear‐wave splitting of tectonic tremors, and moment tensor inversions of the earthquakes of 7 September 2017 M_w 8.2 Tehuantepec, Mexico. This earthquake initiated a seismic sequence that triggered shallow seismicity and aftershocks. The shallow earthquakes fall into a region where there were few published focal mechanism higher than M_w 4.5. Two slab tearings: in the Michoacán–Guerrero border and in central Oaxaca, best represent the slab geometry of the Mexican subduction zone. At the Michoacán–Guerrero, the subducted slab is subhorizontal, whereas in central Oaxaca the plate is characterized by northeast vergence. We interpret that the mantle’s flow in this part of the subducted slab produces multiple alignments in the crust and differentiates the tectonostratigraphic terranes of the southern region of Mexico
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
Editorial
A partir de este número de Anagramas intentaremos ofrecer un énfasis temático que, si bien no será excluyeme de otros tópicos, sí tendrá un peso mayor en cuanto a número de artículos dedicados a la reflexión respectiva, nuestro interés por ofrecer diferentes rumbos y sentidos de la comunicación nos obliga a especificar las búsquedas y fas reflexiones.Como revista naciente, tuvimos cierta apertura hacia ta variedad temática en los cuatro números anteriores; si bien predominan en ellos las reflexiones relacionadas contó comunicación corporativa, la comunicación gráfica publicitaria y los lenguajes audiovisuales, hemos de reconocer que la pluralidad de enfoques y asuntos posibles de abordar desde la comunicación, empezó a generar la necesidad de especializar cada edición. Creemos que es hora de afianzar el reconocimiento obtenido luego de tres años de presencia en la comunidad académica dando este paso hacia la especialización temátic
- …