120098329
Reciprocal consistency of the dressed electromagnetic nucleon current
A field-theory-based approach to pion photoproduction off the nucleon is used to derive a microscopically consistent formulation of the fully dressed electromagnetic nucleon current in a Lorentz-covariant effective Lagrangian formalism. It is shown how the rigorous implementation of local gauge invariance at all levels of the reaction dynamics provides equations that lend them-selves to practically manageable truncations of the underlying nonlinearities of the problem. The requirement of consistency also suggests a novel way of treating the pion photoproduction problem. Preliminary applications to pion photoproduction show very good agreement with the experimantal data.
204016596
Meson baryon interaction in the hadron exchange picture
Elastic πN scattering and the reaction π+p→K+Σ+ are described simultaneously in a unitary coupled‐channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t‐ and u‐ channel exchanges that drive the meson‐baryon interaction in the different channels. Angular distributions, polarizations, and spin‐rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic continuation.
53708602
Scalar mesons moving in a finite volume and the role of partial wave mixing
Phase shifts and resonance parameters can be obtained from finite-volume lattice spectra for interacting pairs of particles, moving with non-zero total momentum. We present a simple derivation of the method that is subsequently applied to obtain the ππ and πK phase shifts in the sectors with total isospin I = 0 and I = 1/2 , respectively. Considering different total momenta, one obtains extra data points for a given volume that allow for a very efficient extraction of the resonance parameters in the infinite-volume limit. Corrections due to the mixing of partial waves are provided. We expect that our results will help to optimize the strategies in lattice simulations, which aim at an accurate determination of the scattering and resonance properties.
119190125
Finite volume effects in pion-kaon scattering and reconstruction of the κ(800) resonance
A bstractSimulating the κ(800) on the lattice is a challenging task that starts to become feasible due to the rapid progress in recent-years lattice QCD calculations. As the reso- nance is broad, special attention to finite-volume effects has to be paid, because no sharp resonance signal as from avoided level crossing can be expected. In the present article, we investigate the finite volume effects in the framework of unitarized chiral perturbation theory using next-to-leading order terms. After a fit to meson-meson partial wave data, lattice levels for πK scattering are predicted. In addition, levels are shown for the quantum numbers in which the σ(600), f0(980), a0(980), φ(1020), K*(892), and ρ(770) appear, as well as the repulsive channels. Methods to extract the κ(800) signal from the lattice spec- trum are presented. Using pseudo-data, we estimate the precision that lattice data should have to allow for a clear-cut extraction of this resonance. To put the results into con- text, in particular the required high precision on the lattice data, the σ(600), the P -wave resonances K*(892) and ρ(770), and the repulsive πK, ππ phases are analyzed as well.
46785821
Chiral dynamics and S-wave contributions in semileptonic B decays
A bstractThe flavor-changing neutral current process b → sl+l− is beneficial to testing the standard model and hunting for new physics scenarios. In exclusive decay modes like B → K*(892)l+l−, the S-wave effects may not be negligible and thus have to be reliably estimated. Using the scalar form factors derived from dispersion relations in two channels and matched to Chiral Perturbation Theory, we investigate the S-wave contributions in $ {{\overline{B}}^0}\to {K^{-}}{\pi^{+}}{l^{+}}{l^{-}} $, with the Kπ invariant mass lying in the vicinity of the mass of K*(892), and Bs → K−K+l+l− with mKK ~ mϕ. We find that the S-wave will modify differential decay widths by about 10% in the process of $ {{\overline{B}}^0}\to {K^{-}}{\pi^{+}}{l^{+}}{l^{-}} $ and about 5% in Bs → K−K+l+l−. A forward-backward asymmetry for the charged kaon in the final state arises from the interference between the S-wave and P-wave contributions. The measurement of this asymmetry offers a new way to determine the variation of the Kπ S-wave phase versus the invariant mass.
16407243
Kaon–nucleon scattering lengths from kaonic deuterium experiments revisited
Abstract We analyse the impact of the recent measurement of kaonic hydrogen X rays by the SIDDHARTA collaboration on the allowed ranges for the kaon–deuteron scattering length in the framework of non-relativistic effective field theory. Based on data from K ¯ N scattering only, we predict the kaon–deuteron scattering length A K d = ( − 1.46 + i 1.08 ) fm , with an estimated uncertainty of about 25% in both the real and the imaginary part.
10205186
Simultaneous photoproduction of eta and pi0 mesons on the proton.
The analysis of the gammap-->etapi(0)p reaction has been performed using data from the GRAAL experiment. The total and differential cross sections and the beam asymmetry have been obtained from threshold up to 1.5 GeV of beam energy. The two resonances S11(1535) and Delta(1700) are expected to be excited in the intermediate states of this reaction. The results are used to test predictions based on the assumption that both resonances are dynamically generated from the meson-baryon interaction provided by chiral Lagrangians. The term involving the Delta(1700) excitation, followed by the decay into etaDelta(1232), is found to be dominant.