PID Efficiency of Left Arm

Run e94104-2218, a coincidence run with He4 target was selected to analyze the PID performance for the left arm. It is at kinematics 13, e.g.

$E_{beam}=4234.99$ GeV, $p_L=3.489$ GeV/c, $\theta_R=16.809^o$;

It is expected to have high electron rates so is not good for pion contamination analysis. But this is the only kinematics with negative polarity on the left arm after the latest high voltage change for PRs. Other runs with H2 or D2 targets are low in pion rates in principle, also show strong correlation in x vs. y so cannot cover the full area of the detectors.