1. The Effect of Filteringon
Pulse Height and Noise
David Hitlin
SuperB Workshop
Annecy
March 16, 2010 1 1

2. Motivation

3. Use CR-RC filter to model (BABAR CsI(Tl) actually uses CR-RC2)
Step function response
In our case the light has an exponential decay time (or two)
CsI: 680ns +
LYSO: 41ns τ1 τ2

4. Endcap – SuperB EC shaping (t1=40ns, t2=40ns)
LYSO readout
Endcap – SuperB EC shaping (t1=40ns, t2=40ns)
Scintillation light
Filter
Response

5. Barrel – SuperB EC shaping
CsI(Tl) readout
We can shorten the shaping time, with some loss of light
Still need to quantify loss of light
Barrel – BABAR shaping
(t1=680ns, t2=250ns)
Barrel – SuperB EC shaping
(t1=40ns, t2=40ns)
Scintillation light
Filter
Response

6. Conclusions
We must do something to ameliorate the effects of the long decay time of the CsI(Tl) crstals in the barrel calorimeter
Shortening the preamp shaping times can and the digitizer sampling time can help
There will, inevitably, be an effect on energy resolution
At high energies, we will begin to see the effect of photon statistics
At low energies, we will also begin to see the effect of electronic noise added in quadrature to photon statistics
For investigation:
Can we avoid reworking the barrel preamps by shortening the filter time in the front end of the digitizer?
This does not deal with preamp saturation due to pileup, as additional differentiation would happen after the preamp