Update on the background and preshower analysis


A few weeks back I spoke about investigating a different background method. This was described in Background investigation. Breifly, I was paring across events rather then using the like-sign pairs in an event to make background. This means that any correlations between the paired track within an event are removed, however, the method of normalisation is not a funcition of 2srt(N++*N--) as usual but rather uncertain.

Signal vs. Background overlay

Sig. Like Sign Background

To comapre the background fairly the like-sign pairs have been normalised with the same method as the cross event paring method

Here, we see like-sign paring, the background has been normalised by taking the integral outside the peak region, 6-8 and 10-12 Gev. This is an estimate and may be cutting into the signal peak. This has to be looked at in more detail

Sig. Cross Event Background paring

And for cross event paring with the same normalisation

Background for cross event scaled to background from like sign

Signal Background subtracted

Signal minus Like Sign background

Signal minus Cross Event Background

With the preshower

The effect of the preshower was not great with the PID cuts applied, similar to what we have seen before with the like sign background

Gaussian fits and Integral under peak:

Fit for like sign background

  1. Constant 24.3 +/- 9.9
  2. Mean 8.8 +/- 0.3
  3. Sigma 0.7 +/- 0.4
  4. Integral under peak == 68 +/-11.0

Histogram for cross event background

Fit for Cross Event Bg.

  1. Constant 20.2 +/- 5.6
  2. Mean 8.7 +/- 0.2
  3. Sigma .6 +/- 0.1
  4. Integral under peak == 64 +/- 7.0

Histogram for cross event background with preshower

Fit for cross event background with the preshower

  1. Constant 16.4 +/- 4.8
  2. Mean 8.9 +/- 0.2
  3. Sigma 0.4 +/- 0.1
  4. Integral under peak == 37 +/- 4.4