1,449 research outputs found
Final State Interactions in Hadronic D decays
We show that the large corrections due to final state interactions (FSI) in
the D^+\to \pi^-\pi^+\pi^+, D^+_s\to \pi^-\pi^+\pi^+, and D^+\to K^-\pi^+\pi^+
decays can be accounted for by invoking scattering amplitudes in agreement with
those derived from phase shifts studies. In this way, broad/overlapping
resonances in S-waves are properly treated and the phase motions of the
transition amplitudes are driven by the corresponding scattering matrix
elements determined in many other experiments. This is an important step
forward in resolving the puzzle of the FSI in these decays. We also discuss why
the \sigma and \kappa resonances, hardly visible in scattering experiments, are
much more prominent and clearly visible in these decays without destroying the
agreement with the experimental \pi\pi and K\pi low energy S-wave phase shifts.Comment: 22 pages, 6 figures, 5 tables. Minor changes. We extend the discusion
when quoting a reference and we include a new one. Some typos are fixe
Hidden charm dynamically generated resonances and the , reactions
We analyze two recent reactions of Belle, producing and
states that have an enhancement of the invariant , mass
distribution close to threshold, from the point of view that they might be
indicative of the existence of a hidden charm scalar and an axial vector meson
states below or thresholds, respectively. We conclude
that the data is compatible with the existing prediction of a hidden charm
scalar meson with mass around 3700 MeV, though other possibilities cannot be
discarded. The peak seen in the spectrum above threshold is,
however, unlikely to be due to a threshold enhancement produced by the
presence, below threshold, of the hidden charm axial vector meson X(3872).Comment: 5 pages, 5 figures, 2 table
Dynamical Generation of Hyperon Resonances
In this talk we report on how, using a chiral unitary approach for the
meson--baryon interactions, two octets of baryon states and a
singlet are generated dynamically, resulting in the case of strangeness
in two poles of the scattering matrix close to the nominal
resonance. We suggest experiments which could show evidence for the existence
of these states.Comment: Invited talk in the VIII International Conference on Hypernuclei and
Strange Particle Physic
A chiral covariant approach to scattering
We analyze vector meson - vector meson scattering in a unitarized chiral
theory based on a chiral covariant framework. We show that a pole assigned to
the the scalar meson can be dynamically generated from the
interaction, while this is not the case for the tensor meson
as found in earlier works. We show that the generation of the
tensor state is untenable due to an artefact of the extreme non-relativistic
kinematics used before. We further consider the effects arising from the
coupling of channels with different orbital angular momenta. We suggest to use
the formalism outlined here to obtain more reliable results for the dynamical
generation of resonances in the vector-vector interaction.Comment: 31 pages, 10 figures, extended version, new section with an improved
solution method, results and conclusions unchange
Nucleon-Nucleon Interactions from Dispersion Relations: Coupled Partial Waves
We consider nucleon-nucleon interactions from chiral effective field theory
applying the N/D method. The case of coupled partial waves is now treated,
extending Ref. [1] where the uncoupled case was studied. As a result three N/D
elastic-like equations have to be solved for every set of three independent
partial waves coupled. As in the previous reference the input for this method
is the discontinuity along the left-hand cut of the nucleon-nucleon partial
wave amplitudes. It can be calculated perturbatively in chiral perturbation
theory because it involves only irreducible two-nucleon intermediate states. We
apply here our method to the leading order result consisting of one-pion
exchange as the source for the discontinuity along the left-hand cut. The
linear integral equations for the N/D method must be solved in the presence of
L - 1 constraints, with L the orbital angular momentum, in order to satisfy the
proper threshold behavior for L>= 2. We dedicate special attention to satisfy
the requirements of unitarity in coupled channels. We also focus on the
specific issue of the deuteron pole position in the 3S1-3D1 scattering. Our
final amplitudes are based on dispersion relations and chiral effective field
theory, being independent of any explicit regulator. They are amenable to a
systematic improvement order by order in the chiral expansion.Comment: 11 pages. Extends the work of uncoupled partial waves of M.
Albaladejo and J. A. Oller, Phys. Rev. C 84, 054009 (2011) to the case of
coupled partial waves. This version matches the published version. Discussion
about the deuteron enlarged. Some references adde
Scalar resonances: scattering and production amplitudes
Scattering and production amplitudes involving scalar resonances are known,
according to Watson's theorem, to share the same phase . We show
that, at low energies, the production amplitude is fully determined by the
combination of with another phase , which describes
intermediate two-meson propagation and is theoretically unambiguous. Our main
result is a simple and almost model independent expression, which generalizes
the usual -matrix unitarization procedure and is suited to be used in
analyses of production data involving scalar resonances.Comment: 10 pages, 4 figures. Minor changes, references added, version to
appear in Phys. Rev.
decay within unitarized chiral perturbation theory
We improve the calculations of the decay
within the context of meson chiral lagrangians. We use a chiral unitary
approach for the meson-meson interaction, thus generating the
resonance and fixing the longstanding sign ambiguity on its contribution. This
also allows us to calculate the loops with one vector meson exchange, thus
removing a former source of uncertainty. In addition we ensure the consistency
of the approach with other processes. First, by using vector meson dominance
couplings normalized to agree with radiative vector meson decays. And, second,
by checking the consistency of the calculations with the related reaction. We find an decay width
of eV, in clear disagreement with published data but in
remarkable agreement with the most recent measurement.Comment: 15 pages, 10 figures, published versio
Chiral approach to the rho meson in nuclear matter
In this work, the properties of the meson at rest in cold symmetric
nuclear matter are studied. We make use of a chiral unitary approach to
pion-pion scattering in the vector-isovector channel, calculated from the
lowest order Chiral Perturbation Theory () lagrangian including
explicit resonance fields. Low energy chiral constraints are considered by
matching our expressions to those of one loop . To account for the
medium corrections, the couples to pairs which are properly
renormalized in the nuclear medium, accounting for both and
excitations. The terms where the couples directly to the hadrons in the
or excitations are also accounted for. In addition, the
is also allowed to couple to components.Comment: 30 pages, 20 figures, revised version. Additional sources of the rho
selfenergy considered. Some references adde
Recommended from our members
Gating Walls and Bridging Gaps: Validity in Language Teaching, Learning, and Assessment
Theoreticians and practitioners often speak as though classrooms and clinics were located outside the real world, but this is not so. The demand for the teaching, learning, and assessment of English language proficiency for international pilots and air traffic controllers is just one practical example touching almost everyone in the world that shows that contexts of actual language use are invariably in the real world just as learners and teachers are. From actual instances of discourse processing, in some cases with life or death consequences, it follows that judgments of validity, like those of ordinary truth, involve the dynamic interactions of persons, sign systems, and variable content in real contexts. Studies of so-called task-based performance assessment (in various forms and by other names) afford many ways to connect teaching, learning, and assessment. The authenticity, representativeness, and consequent generalizability of teaching, learning, and assessment tasks depends on their incorporation of the sign systems, social actions, and realia found in actual contexts of discourse. While codes, contexts, and interactions must be distinguished in theory, in practice they interact holistically. Our theories need to accommodate and account for the synergistic interactions
- …