Spin and parity measurement of the Lambda(1405) baryon

Abstract

A determination of the spin and parity of the $\Lambda (1405)$ is presented using photoproduction data from the CLAS detector at Jefferson Lab. The reaction $\gamma +p\to K^{+}+\Lambda (1405)$ is analyzed in the decay channel $\Lambda (1405)\to {\Sigma }^{+}+{\pi }^{-}$, where the decay distribution to ${\Sigma }^{+}{\pi }^{-}$ and the variation of the ${\Sigma }^{+}$ polarization with respect to the $\Lambda (1405)$ polarization direction determines the parity. The $\Lambda (1405)$ is produced, in the energy range $2.55<W<2.85$ GeV and for $0.6<\cos {\theta }_{K^{+}}<0.9$, with polarization $P=0.45\pm 0.02(\text{stat})\pm 0.07(\text{syst})$. The analysis shows that the decays are in $S$ wave, with the ${\Sigma }^{+}$ polarized such that the $\Lambda (1405)$ has spin-parity $J^P=1/2^{-}$, as expected by most theories.

6 pages, 4 figures, accepted by Phys. Rev. Lett

References in corpus (4)

• Chiral SU(3) theory of antikaon-nucleon interactions with improved threshold constraints
• Measurement of the Sigma pi photoproduction line shapes near the Lambda(1405)
• Differential Photoproduction Cross Sections of the Sigma0(1385), Lambda(1405), and Lambda(1520)
• Isospin Decomposition of the Photoproduced Σπ System Near the Λ(1405)

Cited by in corpus (35)

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• Hadron Physics at J-PARC
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• Hyperon I: Partial wave amplitudes for $K^{-}p$ scattering
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