Add non-linearity parameters for PMT simulation

Added parameters for PMT non-linearity simulation and on/off PMTs.

Author: asanchezcastillo

sbnd_calibration_database.md

@@ -133,12 +133,15 @@ This section displays a list of the variables in the database, as well as their
 | caen_digitizer | integer | CAEN digitizer to which the PMT is connected | N/A | 
 | caen_digitizer_channel | integer | CAEN digitizer channel to which the PMT is connected | N/A |
 | total_transit_time | real | Total transit time | ns |
+| on_pmt | bool | Whether the channel is powered on | N/A |
 | reconstruct_channel | bool | Whether the channel is used for reconstruction | N/A |
 | cosmic_timing_correction | real | Timing correction derived from cosmic muon calibration | ns |
 | spe_amp | real | Mean amplitude of SPE | ADC |
 | spe_amp_std | real | Std of the SPE amplitude | ADC |
 | gauss_w_wc_power | real | Power parameter for Gauss noise filter | N/A | 
 | gauss_wc | real | WC parameter for Gauss noise filter | GHz |
+| nonlinearity_pesat | real | Parameter PESat for PMT non linearity simulation | N/A |
+| nonlinearity_alpha | real | Parameter alpha for PMT non linearity simulation | N/A |
 | ser_vec_0 → ser_vec_550 | real | ADC count per bin (550 in total) for the Single Electron Response (SER) pulse (More info: [DocDB 38059](https://sbn-docdb.fnal.gov/cgi-bin/sso/ShowDocument?docid=38059)) | ADC |