# F) noise subtraction and its effect on asymmetry and yield

Noise subtraction was implemented by adding up all the beam trips in a given run to calculate the noise rate for each strip and subtracting a time normalized noise counts from the beam-on counts for each strip. This is performed before any further processing to get asymmetry, yields , S/B etc

for plus helicity

N_plus_laserON_corrected = N_plus_laserON - N_beamtrip*(hplus_laserON_time/beam_trip_time) N_plus_laserOFF_corrected = N_plus_laserOFF - N_beamtrip*(hplus_laserOFF_time/beam_trip_time)

and similarly for minus helicity

N_minus_laserON_corrected = N_minus_laserON - N_beamtrip*(hminus_laserON_time/beam_trip_time) N_minus_laserOFF_corrected = N_minus_laserOFF - N_beamtrip*(hminus_laserOFF_time/beam_trip_time)

We do not expect changes in the asymmetry between with and out without this correction but yields and S/B should get cleaned up.

As an example the run 21939 is shown here.
the first plot for each set compared does not have the noise subtraction while the second plot in each set has the correction:

Conclusion: No significant changes in the asymmetry but significant changes in the yields/hits spectra