Answer
The spin angular momentum is not conserved.
Work Step by Step
The proton $p$ has spin $\frac{1}{2}$
The antiproton $\bar{p}$ has spin $\frac{1}{2}$
The $\Lambda^0$ has spin $\frac{1}{2}$
The $\Sigma^+$ has spin $\frac{1}{2}$
The $e^-$ has spin $\frac{1}{2}$
The left side of the proposed reaction can have net spin $0$ or $\pm 1$ while the right side of the proposed reaction can have net spin $\pm \frac{1}{2}$ or $\pm \frac{3}{2}$
Therefore, the spin angular momentum is not conserved.
