Maxim Mai

New insights into antikaon–nucleon scattering and the structure of the

We perform a combined analysis of antikaon–nucleon scattering cross sections and the recent SIDDHARTA kaonic hydrogen data in the framework of a K¯N–πY coupled-channel Bethe–Salpeter approach at next-to-leading order in the chiral expansion of the effective potential. We find a precise description of the antikaon–proton scattering amplitudes and are able to extract accurate values of the scattering lengths, a0=−1.81−0.28+0.30+i0.92−0.23+0.29fm and a1=+0.48−0.11+0.12+i0.87−0.20+0.26fm. We also discuss the two-pole structure of the Λ(1405).

Constraints on the chiral unitary \(\bar KN\) amplitude from πΣK+ photoproduction data

A chiral unitary approach for antikaon-nucleon scattering in on-shell factorization is studied. We find multiple sets of parameters for which the model describes all existing hadronic data similarly well. We confirm the two-pole structure of the Λ(1405). The narrow Λ(1405) pole appears at comparable positions in the complex energy plane, whereas the location of the broad pole suffers from a large uncertainty. In the second step, we use a simple model for photoproduction of K+πΣ off the proton and confront it with the experimental data from the CLAS Collaboration. It is found that only a few of the hadronic solutions allow for a consistent description of the CLAS data within the assumed reaction mechanism.

Weak decays of heavy hadrons into dynamically generated resonances

In this paper, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.

Chiral dynamics of the S11(1535) and S11(1650) resonances revisited

Abstract We analyze s-wave pion–nucleon scattering in a unitarized chiral effective Lagrangian including all dimension two contact terms. We find that both the S 11 ( 1535 ) and the S 11 ( 1650 ) are dynamically generated, but the S 31 ( 1620 ) is not. We further discuss the structure of these dynamically generated resonances.

Pion photoproduction off the proton in a gauge-invariant chiral unitary framework

We investigate pion photoproduction off the proton in a manifestly gauge-invariant chiral unitary extension of chiral perturbation theory. In a first step, we consider meson-baryon scattering taking into account all next-to-leading order contact interactions. The resulting low-energy constants are determined by a fit to s-wave pion-nucleon scattering and the low-energy data for the reaction pi- p --> eta n. To assess the theoretical uncertainty, we perform two different fit strategies. Having determined the low-energy constants, we then analyse the data on the s-wave multipole amplitudes E0+ of pion and eta photoproduction. These are parameter-free predictions, as the two new low-energy constants are determined by the neutron and proton magnetic moments.

Aspects of meson-baryon scattering in three- and two-flavor chiral perturbation theory

We analyze meson-baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one-loop order. We compute the complete set of matching relations between the dimension-two low-energy constants in the two- and three-flavor formulations of the theory. We derive new two-flavor low-energy theorems for pion-hyperon scattering that can be tested in lattice simulations.

Finite volume effects and quark mass dependence of the N(1535) and N(1650)

Abstract For resonances decaying in a finite volume, the simple identification of state and eigenvalue is lost. The extraction of the scattering amplitude is a major challenge as we demonstrate by extrapolating the physical S 11 amplitude of pion–nucleon scattering to the finite volume and unphysical quark masses, using a unitarized chiral framework including all next-to-leading order contact terms. We show that the pole movement of the resonances N ( 1535 ) 1 / 2 − and N ( 1650 ) 1 / 2 − with varying quark masses is non-trivial. In addition, there are several strongly coupled S -wave thresholds that induce a similar avoided level crossing as narrow resonances. The level spectrum is predicted for two typical lattice setups, and ways to extract the amplitude from upcoming lattice data are discussed.

Predictions for the \({\varvec{\Lambda }_b \rightarrow J/\psi ~ \Lambda (1405)}\) decay

We calculate the shape of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

The optical potential on the lattice

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