The following steps have to be done to produce digitized Monte Carlo for the AHCAL. Up to date steerings for each step can be found in calice_sim/digitization/digihcal/steerings (currently only in pro test and only for 2007 hcal only runs).
- Monte Carlo production - Mokka
- Preparation of the real detector geometry - Ganging
- Simulation of detector effects (from energy to ADC) - Digitizing
- 3^(-1) - Reconstruction (from ADC to energy)
in addition there is the possibility to overlay noise extracted from random trigger events.
Mokka produces the "raw" Monte Carlo. The outcome is the deposited energy in the scintillator stored into a grid of 90x90 1x1 cm^2 cells. (detailedShowerMode to be explained).
Ganging is the step where the 1x1 cm^2 cells are combined to the real cell's sizes (Geometry).
In a first step the geometrical position is converted to hardware information (module/chip/channel) and stored in addition in the cellid.
The deposited energy is then converted to pedestal subtracted ADC counts. Pixel statistics, saturation and dead cell simulation is included (implicitly because for dead cells there are no calibration constants.) The optical crosstalk to neighboring cells is included as well.
The digitization does the following:
- Distributing the deposited energy of every hit to its direct neighbors.
- Converting energy to pixel accounting for the SiPM specific saturation curve
- Statistically smearing the number of pixel of step 2 (Binomial statistics)
- Converting from pixel to ADC channel
- Adding noise
The outcome of the digitization step can be feed into the reconstruction just like real data. The only difference is that pedestal subtraction is not necessary. (And stuff like triggers are missing, but this is not only an AHCAL specific problem.)
Random trigger events are used to create electronic noise. A pedestal subtracted random trigger event has for every channel an entry in ADC channels reflecting its characteristic noise spectrum.
In order to produce noise you need to have access to real data!