The radiative decay of the $\Lambda (1405)$ and its two-pole structure

Abstract

We evaluate theoretically the radiative decay widths into $\gamma \Lambda$ and $\gamma {\Sigma }^0$ of the two poles of the $\Lambda (1405)$ found in chiral unitary theories and we find quite different results for each of the two poles. We show that, depending on which reaction is used to measure the $\Lambda (1405)$ radiative decays, one gives more weight to one or the other pole, resulting in quite different shapes in the $\gamma \Lambda ({\Sigma }^0)$ invariant mass distributions. Our results for the high-energy pole agree with those of the empirical determination of the $\gamma \Lambda$ and $\gamma {\Sigma }^0$ radiative widths (based on an isobar model fitting of the $K^{-}p$ atom data), which are sometimes referred to as ``experimental data''. We have made a detailed study of the $K^{-}p\to {\pi }^0\gamma \Lambda ({\Sigma }^0)$ and ${\pi }^{-}p\to K^0\gamma \Lambda ({\Sigma }^0)$ reactions and have shown that they, indeed, lead to different shapes for the $\gamma \Lambda ({\Sigma }^0)$ invariant mass distributions.

Version to appear in European Physical Journal A; a brief description of the chiral unitary coupled-channel approach added

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• Transition form factors of the N*(1535) as a dynamically generated resonance
• Internal structure of resonant Lambda(1405) state in chiral dynamics
• Electromagnetic mean squared radii of Lambda(1405) in chiral dynamics
• The pole structure of the Lambda(1405) in a recent QCD simulation
• On the nature of the $\Lambda (1405)$ and $\Lambda (1670)$ from their $N_c$ behavior in chiral dynamics
• The role of the $\Lambda (1405)$ in the $pp\to p{K}^{+}\Lambda (1405)$ reaction
• Regge phenomenology of pion photoproduction off the nucleon at forward angles
• Light-quark contributions to the magnetic form factor of the Lambda(1405)
• Helicity Amplitudes of the Lambda(1670) and two Lambda(1405) as dynamically generated resonances
• Role of five-quark components in radiative and strong decays of the Lambda(1405) resonance
• The $K^{-}p\to {\Sigma }^0{\pi }^0$ reaction at low energies in a chiral quark model
• Production of hyperon resonances induced by kaon on a deuteron target
• Radiative decays of dynamically generated charmed baryons
• The $\Xi (1620)$ and $\Xi (1690)$ molecular states from $S=-2$ meson-baryon interaction up to next-to-leading order
• Determination of compositeness of the Lambda(1405) resonance from its radiative decay
• Structure of the $\mathbf{\Lambda }(1670)$ resonance
• Low energy reaction $K^{-}p\to \Lambda \eta$ and the negative parity $\Lambda$ resonances
• Singlet baryons in the graded symmetry approach to partially quenched QCD
• Radiative decay into gamma-baryon of dynamically generated resonances from the vector-baryon interaction
• Determining Compositeness of Hadronic Resonances: the $\Lambda (1405)$ Radiative Decay and the $a_0(980)$-$f_0(980)$ Mixing
• The nature of the Lambda(1405)
• Electromagnetic transition form factors and Dalitz decays of hyperons