文摘
We determine the helicity amplitudes A 1/2 and radiative decay widths in the transition L \Lambda(1670) ? \rightarrow g \gamma Y (Y = L \Lambda or S0 \Sigma^{{0}}_{} . The L \Lambda(1670) is treated as a dynamically generated resonance in meson-baryon chiral dynamics. We obtain the radiative decay widths of the L \Lambda(1670) to g \gamma L \Lambda as 2¡À1 keV and to g \gamma S0 \Sigma^{{0}}_{} as 120¡À50 keV. Also, the Q2-dependence of the helicity amplitudes A 1/2 is calculated. We find that the K X \Xi component in the L \Lambda(1670) structure, mainly responsible for the dynamical generation of this resonance, is also responsible for the significant suppression of the decay ratio GgL \Gamma_{{\gamma\Lambda}}^{}/GgS0 \Gamma_{{\gamma \Sigma^{0}}}^{} . A measurement of the ratio would, thus, provide direct access to the nature of the L \Lambda(1670) . To compare the result for the L \Lambda(1670) , we calculate the helicity amplitudes A 1/2 for the two states of the L \Lambda(1405) . Also, the analytic continuation of Feynman parameterized integrals of more complicated loop amplitudes to the complex plane is developed which allows for an internally consistent evaluation of A 1/2 .
