Electron(positron) pion separation for test run - pion background

Kinematics: Beam energy = 5.650 GeV, $\theta_e=45^O$
Target: 4 cm LH2 for electron runs, 15 cm LH2 for positron runs

$p_e$	run#	cuts	$e^-$	total	$\pi^-$/$e^-$	$\pi^-$/$e^-$
(GeV/c)			($e^+$)		(detected)	(real)
1.50	2773	$E_{preshower}>250-0.14\times E_{shower}$	29185	318337	9.91	17.00
	2774	0.65$<$ep-ratio$<$4.0	12780	139499	9.92	-
	2786		77	1572702	-	-
	2788		9	305428	-	-
	2789		46	818330	-	-
	2790		67	1579627	-	-
0.90	2775	$E_{preshower}>150-0.08\times E_{shower}$	9789	692503	69.74	206.54
	2776	0.65$<$ep-ratio$<$4.0	3980	274530	67.98	-
	2791		611	1288158	-	-
	2793		640	1290782	-	-
	2794		668	1291353	-	-
0.55	2777	$E_{preshower}>160-0.12\times E_{shower}$	14570	1159028	74.95	286.33
	2778	0.60$<$ep-ratio$<$4.0	10372	813698	73.67	-
	2814		1612	1118462	-	-
	2815		1679	1122901	-	-
	2816		1655	1130667	-	-
	2817		1627	1143697	-	-

$\bigstar$ positron runs are shown in color;
$\bigstar$ Cherenkov ADCs (48 channels) have been calibrated manually so the distribution of output of each channel is aligned to the same position;
$\bigstar$ global cuts applied: $0<E_{shower}<2000$ and $50<E_{preshower}<4000$;
$\bigstar$ $\pi^-$ ratio after decay (drift distance 23.4m from target to spectrometer):
25.95% for 0.55 GeV/c; 33.33% for 0.90 GeV/c; 41.70% for 1.50 GeV/c

Data analysis for run # 2773 (electron run, $p_e=1.50$ GeV/c) and run # 2786 (positron run, $p_e=1.50$ GeV/c) are shown in Figure

Figure: data analysis for run #2773 and #2786