The Λ(1405)

Lambda(1405,1/2^-) photoproduction from the gamma p -> K^+ Lambda(1405) reaction

“…The pole positions are 1398 − 74i MeV (lower one) and 1429 − 14i (higher one) in the dimensional regularization scheme [15]. The coupling strengths to these poles were obtained from the residue of the amplitude, resulting in g KN Λ * = 1.43 for the lower pole and g KN Λ * = 2.52 for the higher one in the dimensional regularization 1 . When the dipole-and monopole-type form factors are applied to the regularization of the loop integral, one has g KN Λ * = 2.00 and 3.64, whereas 2.65 and 3.39, respectively [15].…”

“…The Λ(1405, 1/2 − ) ≡ Λ * , an excited state of the Λ(1116, 1/2 + ) with negative parity, has been studied for decades (See Ref. [1] for the review until 1998). Its production has been mainly conducted in proton-proton scattering and meson-proton scattering.…”

The S01 − Λ(1405) and − Λ(1670) resonances in meson-baryon unitarized coupled channel chiral perturbation theory

“…[22]. Let us look at the Λ(1405) resonance, which nature is under much discussion [42,43]. Following the PDG it is placed at (in MeV)…”

Properties of the (1405) measured at CLAS

“…Past experiments have shown a distortion of the invariant mass distribution ("lineshape") of the Λ(1405) from a simple Breit-Wigner form. On the theoretical side, all analyses agree that the closeness of the nearby NK threshold plays a role in the distortion, there is no universally accepted explanation (see [1] for a review). For the constituent quark model, the Λ(1405) has the largest discrepancy between the model prediction and experimental mass [2].…”