28 research outputs found
Effects of pseudoscalar-baryon channels in the dynamically generated vector-baryon resonances
We study the interaction of vector mesons with the octet of stable baryons in
the framework of the local hidden gauge formalism using a coupled channels
unitary approach, including also the pseudoscalar-baryon channels which couple
to the same quantum numbers. We examine the scattering amplitudes and their
poles, which can be associated to known baryon resonances,
and determine the role of the pseudoscalar-baryon channels, changing the width
and eventually the mass of the resonances generated with only the basis of
vector-baryon states
Searching for exotic states in the system
We study the system in order to investigate the possibility of
existence of strangeness +1 resonance(s). The formalism consists of solving the
Faddeev equations with the , and -matrices obtained
from chiral dynamics. The same formalism, which leads to the finding of several
resonances in the corresponding three-body = -1 channels in the
1400-2000 MeV energy region, results into only one broad bump around 1700 MeV
with isospin 0. The amplitudes in isospin 1 and 2 configuration do not have any
resonant structure
Magnetic moments of the low-lying , resonances within the framework of the chiral quark model
The magnetic moments of the low-lying spin-parity ,
resonances, like, for example, ,
, as well as their transition magnetic moments, are
calculated using the chiral quark model. The results found are compared with
those obtained from the nonrelativistic quark model and those of unitary chiral
theories, where some of these states are generated through the dynamics of two
hadron coupled channels and their unitarization
A new perspective on the Faddeev equations and the system from chiral dynamics and unitarity in coupled channels
We review recent work concerning the interaction and Faddeev
equations with chiral dynamics which allow us to look at the from a
different perspective and pay attention to problems that have been posed in
previous studies on the subject. We show results which provide extra
experimental evidence on the existence of two states. We then
show the findings of a recent approach to Faddeev equations using chiral
unitary dynamics, where an explicit cancellation of the two body off shell
amplitude with three body forces stemming from the same chiral Lagrangians
takes place. This removal of the unphysical off shell part of the amplitudes is
most welcome and renders the approach unambiguous, showing that only on shell
two body amplitudes need to be used. With this information in mind we use an
approximation to the Faddeev equations within the fixed center approximation to
study the system, providing answers within this approximation to
questions that have been brought before and evaluating binding energies and
widths of this three body system. As a novelty with respect to recent work on
the topic we find a bound state of the system with spin S=1, like a bound state
of -deuteron, less bound that the one of S=0, where all recent efforts
have been devoted. The width is relatively large in this case, suggesting
problems in a possible experimental observation.Comment: 18 pages, 7 figures, one misprint corrected, Nuclear Physics A in
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Delta rho pi interaction leading to N* and Delta* resonances
We have performed a calculation for the three body system
by using the fixed center approximation to Faddeev equations, taking the
interaction between and , and, and and
from the chiral unitary approach. We find several peaks in the modulus
squared of the three-body scattering amplitude, indicating the existence of
resonances, which can be associated to known and and baryon states.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
Two, three, many body systems involving mesons
In this talk we show recent developments on few body systems involving
mesons.
We report on an approach to Faddeev equations using chiral unitary dynamics,
where an explicit cancellation of the two body off shell amplitude with three
body forces stemming from the same chiral Lagrangians takes place. This removal
of the unphysical off shell part of the amplitudes is most welcome and renders
the approach unambiguous, showing that only on shell two body amplitudes need
to be used. Within this approach, systems of two mesons and one baryon are
studied, reproducing properties of the low lying states. On the other
hand we also report on multirho and multirho states which can be
associated to known meson resonances of high spin.Comment: Talk given in the International School of Nuclear Physics, Erice 201
Hidden beauty baryon states in the local hidden gauge approach with heavy quark spin symmetry
Using a coupled-channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-baryon interaction with hidden beauty and obtain several new states of N around 11 GeV. We consider the basis of states eta (b) N, I'N, BI > (b) , BI pound (b) , B (*) I > (b) , B (*) I pound (b) , B (*) I pound (b) (*) and find four basic bound states which correspond to BI pound (b) , BI pound (b) (*) , B (*) I pound (b) and B (*) I pound (b) (*) , decaying mostly into eta (b) N and I'N and with a binding energy about 50-130 MeV with respect to the thresholds of the corresponding channel. All of them have isospin I = 1/2 , and we find no bound states or resonances in I = 3/2 . The BI pound (b) state appears in J = 1/2 , the BI pound (b) (*) in J = 3/2 , the B (*) I pound (b) appears nearly degenerate in J = 1/2 , 3/2 and the B (*) I pound (b) (*) appears nearly degenerate in J = 1/2 , 3/2, 5/2. These states have a width from 2-110 MeV, with conservative estimates of uncertainties, except for the one in J = 5/2 which has zero width since it cannot decay into any of the states of the basis chosen. We make generous estimates of the uncertainties and find that within very large margins these states appear bound
Magnetic moments of the low-lying {1/2}^- octet baryon resonances
The magnetic moments of the negative parity octet resonances with spin {1/2}:
(1535), (1650), (1620), and (1690) have been
calculated within the framework of the chiral constituent quark model. In this
approach, the presence of the polarized pairs (or the meson cloud,
in other words) is considered by using the Lagrangian for Goldstone boson
emission from the constituent quarks. Further, the explicit contributions
coming from the spin and orbital angular momentum, including the effects of the
configurations mixing between the states with different spins, are obtained.
The motivation for these calculations comes from the recent interest in
experimental measurement of the magnetic moment of the
resonance and of similar calculations being done within lattice quantum
chromodynamics approaches. Our results can be compared with those expected to
come from these sources.Comment: 17 pages, 2 table
Collision times in pi-pi and pi-K scattering and spectroscopy of meson resonances
Using the concept of collision time (time delay) introduced by Eisenbud and
Wigner and its connection to on-shell intermediate unstable states, we study
mesonic resonances in pi-pi and pi-K scattering. The time-delay method proves
its usefulness by revealing the spectrum of the well-known rho- and K*-mesons
and by supporting some speculations on rho-mesons in the 1200 MeV region. We
use this method further to shed some light on more speculative meson
resonances, among others the enigmatic scalars. We confirm the existence of
chiralons below 1 GeV in the unflavoured and strange meson sector.Comment: 22 pages LaTex, 8 figure
Prediction of a Z(c)(4000) state and relationship with the claimed Z(c)(4025)
After discussing the OZI suppression of one light meson exchange in the interaction of with isospin I = 1 , we study the contribution of the two-pion exchange to the interaction and the exchange of heavy vectors, J/psi for diagonal transitions and D-* for transitions of to J/psi rho. We find these latter mechanisms to be weak, but enough to barely bind the system in J = 2 with a mass around 4000 MeV, while the effect of the two-pion exchange is a net attraction, though weaker than that from heavy-vector exchange. We discuss this state and try to relate it to the Z (c) (4025) state, above the threshold, claimed in an experiment at BES from an enhancement of the distribution close to threshold. Together with the results from a recent reanalysis of the BES experiment showing that it is compatible with a J = 2 state below threshold around 3990 MeV, we conclude that the BES experiment could show the existence of the state that we find in our approach