M. Doring

Clues to the nature of the Δ∗(1700) resonance from pion- and photon-induced reactions

Abstract We make a study of the π − p → K 0 π 0 Λ , π + p → K + π + Λ , K + K ¯ 0 p , K + π + Σ 0 , K + π 0 Σ + , and η π + p reactions, in which the basic dynamics is given by the excitation of the Δ ∗ ( 1700 ) resonance which subsequently decays into K Σ ∗ ( 1385 ) or Δ ( 1232 ) η . In a similar way we also study the γ p → K 0 π + Λ , K + π − Σ + , K + π + Σ − , K 0 π 0 Σ + , and η π 0 p related reactions. The cross sections are proportional to the square of the coupling of Δ ∗ ( 1700 ) to Σ ∗ K ( Δη ) for which there is no experimental information but which is provided in the context of coupled channels chiral unitary theory where the Δ ∗ ( 1700 ) is dynamically generated. Within present theoretical and experimental uncertainties one can claim a global qualitative agreement between theory and experiment. We provide a list of items which need to be improved in order to make further progress along these lines.

Radiative decay of the {lambda}*(1520)

A recently developed nonperturbative chiral approach to dynamically generate the 3/2{sup -} baryon resonances has been extended to investigate the radiative decays {lambda}*(1520){yields}{gamma}{lambda}(1116) and {lambda}*(1520){yields}{gamma}{sigma}{sup 0}(1193). We show that the {lambda}*(1520) decay into {gamma}{lambda} is an ideal test for the need of extra components of the resonance beyond those provided by the chiral approach since the largest meson-baryon components give no contribution to this decay. The case is different for {gamma}{sigma} decay, where the theory agrees with experiment, though the large uncertainties of these data call for more precise measurements. Some estimates of the weight of the needed genuine resonance component are made.

s-wave pion-nucleus optical potential

We calculate the

Role of theN*(1535)in theJ/ψ→p¯ηpandJ/ψ→p¯K+Λreactions

s

Radiative decays of the Δ*(1700) and the Λ*(1520)

-wave part of the pion-nucleus optical potential using a unitarized chiral approach that has been previously used to simultaneously describe pionic hydrogen and deuterium data as well as low-energy

Chiral dynamics in theγp→π0ηpandγp→π0K0Σ+reactions

ensuremath{pi}N

The γp → π0ηp and related reactions in a chiral dynamical approach

scattering in vacuum. This energy-dependent model allows for additional isoscalar parts in the potential from multiple rescattering. We consider Pauli blocking and pion polarization in an asymmetric nuclear matter environment. Also, higher order corrections of the

Radiative decay of the Λ*(1520)

ensuremath{pi}N

Radiative decay of the ?*(1520)

amplitude are included. The model can accommodate the repulsion required by phenomenological fits, though the theoretical uncertainties are bigger than previously thought. We also find an enhancement of the isovector part compatible with empirical determinations.

Chiral dynamics in the γp → π0ηp and γp → π0K0Σ+ reactions

We study the