The A - dependence of $K^{0}$ and $Lambda$ neutrinoproduction on nuclei

For the first time, the A- dependence of the production of $K^0$, $Lambda$ and, for comparison, $pi^-$ mesons is investigated in neutrinonuclear reactions, using the data obtained with SKAT bubble chamber. An exponential parametrization ($sim A^{beta}$) of the particle yields results in ${beta}_{V^0} = 0.20 pm 0.05$ for $V^0$ particles (combined $K^0$ and $Lambda$), while for $pi^-$ mesons the A- dependence is much weaker, ${beta}_{pi^-} = 0.068 pm 0.007$. A nuclear enhancement of the ratio $K^0/pi^-$ is found; this ratio increases from $0.055 pm 0.013$ for $ u N$- interactions up to $0.070 pm 0.011$ at $A approx 21$ and $0.099 pm 0.011$ at $A approx 45$. It is observed, that the multiplicity rise of $V^0$s occures predominantely in the backward hemisphere of the hadronic c.m.s. It is shown, that the A- dependence of the nuclear enhancement of the ${Lambda}^0$ and $pi^-$ yields can be reproduced in the framework of a model, incorporating the secondary intranuclear interactions of pions originating from the primary $ u N$- interactions, while only (29$pm$9)% of that for $K^0$ at $A approx 45$ can be attributed to intranuclear interactions.