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

Motivation  

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: 64% @ 680ns + 36% @3340ns LYSO: 41ns τ1 τ2

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

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

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