BCAL Beam Test Plots, November 20, 2006

First go

• Gain Correction:
  1. Establish the means of each cell in the Monte Carlo and find the ratio wrt MC Cell 8 over whole tagger spectra
  2. Find the current ratio of each ADC in the beamtest data wrt to North 8
  3. Correct the ADC ratio to match the Monte Carlo Ratios
     • The ratio of MC Cell 8 to North 8 defines the MeV/Channel

North 7

North 8

North 9

North 12

${\frac {MC8}{North8}}=0.018{\frac {MeV}{Channel}}$

How does this look over the entire tagger spectrum?

The 0.151 MeV/Ch is for a tagger photon (digregard this). The others are for energy deposit in the scintillator.

What if we look at MC 8 vs North 8 with Tagger Energy cuts?

North8 300<Ephoton<400

MC8 300<Ephoton<400

$({\frac {MC8}{North8}})_{{300<Ephoton<400}}=0.0177{\frac {MeV}{Channel}}$

North8 500<Ephoton<600

MC8 500<Ephoton<600

$({\frac {MC8}{North8}})_{{500<Ephoton<600}}=0.0165{\frac {MeV}{Channel}}$

• Very Strange: Apparent Energy Dependence

How do we see what's going on?

1. Cuts: Trig==8 (MOR and BCal OR), Nphotons==1
   • Possibly there are e+e-, maybe. Need to check the veto but it doesn't seem to be in the Root Trees
   1. Cut out the lower hump from the ADC sum.

ADCsum South 200<Ephoton<300

ADCsum South 300<Ephoton<400

ADCsum South 500<Ephoton<600

• This seems to remove the "junk" from the left of the spectra, and will flatten out the MC8/North8 ratio. But what is the "junk?

• -This has a 2% or more effect on the mean for 300<Ephoton<400. Probably much larger effect for the lower energies.

• Compare North 8 over all spectra when cutting on adcsumN > Ch1000 ~ 140MeV to previous

${\frac {MC8}{North8}}=0.0167{\frac {MeV}{Channel}}$

Using the new gain factors and scale factors. Looks reasonably closer except for the excess at the front of the spectra. I expect this is the contribution of the electrons or whatnot, the "junk", that we need to cut out.

It was suggested I start looking at tdc information for making cuts.

The veto almost has no information for run 2334

Can anyone explain why Ephoton vs tphoton has this pattern? Is it uncertainty in the timing offsets for the tagger t-counters? Is this fixable or something we have to live with? The tphoton scale is blown up but it's still curious.

And if you cut on 500<Ephoton<550 you get