The unquenched quark models predict the new particle $Sigma^*$ with spin parity $J^P=1/2^-$ and its mass is around the well established $Sigma^*(1385)$ with $J^P=3/2^+$. Here by using the effective Lagrangian approach we study kp reaction at the rang
e of $Lambda^{*}(1520)$ peak, comparing the resulting total cross section, and $pi^+pi^-$, $Lambdapi^+$, $Lambdapi^-$ invariant squared mass distributions for various incident $K^-$ momenta, as well as the production angular distribution of the $Lambda$ with the data from the Lawrence Berkeley Laboratory 25-inch hydrogen bubble chamber, we find that, apart from the existing resonance $Sigma^{*}(1385)$ with $J^P=3/2^+$, there is a strong evidence for the existence of the new resonance $Sigma^{*}$ with $J^P=1/2^-$ around 1380 MeV. Higher statistic data on relevant reactions are needed to clarify the situation.
Distinctive patterns are predicted by quenched quark models and unquenched quark models for the lowest SU(3) baryon nonet with spin parity $J^P=1/2^-$. While the quenched quark models predict the lowest $1/2^-$ $Sigma^*$ resonance to be above 1600 Me
V, the unquenched quark models predict it to be around $Sigma^*(1385)$ energy. Here we re-examine some old data of the $kp to la$ reaction and find that besides the well established $Sigma^{*}(1385)$ with $J^P=3/2^+$, there is indeed some evidence for the possible existence of a new $Sigma^{*}$ resonance with $J^P=1/2^-$ around the same mass but with broader decay width. Higher statistic data on relevant reactions are needed to clarify the situation.
