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Pad Chamber in the trigger

In the NA44 design upgraded for the $Pb$ beam running, the PC is an essential tracking device of limiting acceptance. In 1995, a PC hit was required in the multiplicity trigger. This increases the rate of useful events, but reduces the efficiency due to inherent inefficiency of the chamber and the coincidence inefficiency. The following algorithm was used to find PC-related trigger inefficiency component:

1. Count good tracks in the run with PC in the trigger and normalize to the live beam.
2. Same in the run with no PC in the trigger, the rest of the trigger being the same
3. Take the ratio; apply as a multiplier to the particle yield.

If a couple of data sets with the trigger conditions required for the comparison could not be found, we used the one with the closest settings.

Table 4.6: Corrections for the PC in the trigger. "1" is used when PC was not part of the trigger. See section  4.3.3.

momentum	4 GeV		8 GeV
$p_T$ setting	low	high	low	high
$\pi^+$	1	1	$1.13 \pm 0.01$	1
$K^{+}$	8$\pi^+$low	8$\pi^+$high	8$\pi^+$low	8$\pi^-$high
$\pi^-$	$1.128$	1	$1.096\pm 0.009$	$1.219\pm 0.011$
$K^{-}$	4$\pi^-$low	8$\pi^-$high	8$\pi^-$low	8$\pi^-$high

Table 4.6 summarizes the corrections.