Constants to Review

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These are constants whose values need to be revisited


Description Variable Value File Line Action to take
fADC counts -> physical units a_scale 1.0E6/1.3E5
Energy conversion factor for dE calc. w_eff 29.5E-9 109
Gain factor for dE calc. gas_gain 1.0E5 110
initial time -> drift conversion 55.0E-4 113 Remove

CCDB table - CDC/cdc_parms

Name Value Description Action
CDC_TDRIFT_SIGMA 2.8181818181818e-9 The error on the drift time in the CDC, used to gaussianly smear actual CDC hits.
CDC_TIME_WINDOW 1000.0E-9 The time window for which CDC hits are accumulated (in sec), used for background determination
CDC_PEDESTAL_SIGMA 0.00000006 The error in the energy deposition measurement in the CDC due to pedestal noise
CDC_DRIFT_SPEED 0.0055 CDC drift speed (unit?)
CDC_TWO_HIT_RESOL 25. time window for two hit resolution (in ns)
CDC_MAX_HITS 100 number of hit per readout channel
CDC_THRESH_KEV 1. threshold applied (in KeV)
CDC_STRAW_RADIUS 0.8 straw radius (in cm)


Description Variable Value File Line
fADC counts -> physical units a_scale 2.4E4/1.3E5
Time range used to cluster cathode hits (ns) TIME_SLICE 10 10
Energy conversion factor for dE calc. W_EFF 30.2e-9 26
Gain factor for dE calc. GAS_GAIN 8e4 27

CCDB table - FDC/fdc_parms

Name Value Description Action
FDC_DRIFT_SPEED 0.0055 electron drift velocity
FDC_WIRE_DEAD_ZONE_RADIUS 3.5 dead wire radius
FDC_STRIP_DEAD_ZONE_RADIUS 5.0 other dead wire radius
FDC_K2 1.15
FDC_THRESH_KEV 1. threshold in keV
FDC_THRESH_STRIPS 5. threshold in pC
FDC_ELECTRON_CHARGE 1.6022e-4 electron charge in fC
FDC_DIFFUSION_COEFF 1.1e-6 diffusion speed cm^2/s --> 200 microns at 1 cm
FDC_TDRIFT_SIGMA 3.6363636e-9 The error on the drift time in the FDC, used to gaussianly smear incoming hits
FDC_CATHODE_SIGMA 150.0 The error in the distance along the wire as measured by the cathodes (NOT including Lorentz effect, but including fluctuations due to ion trail density, in microns)
FDC_PED_NOISE 0.0 The FDC pedestal noise is used to smear the cathode ADC values such that the position along the wire has the resolution specified by FDC_CATHODE_SIGMA, units in pC (calculated from FDC_CATHODE_SIGMA in SmearFDC)
FDC_TIME_WINDOW 1000.0E-9 Time window for acceptance of FDC hits units in seconds
FDC_HIT_DROP_FRACTION 0.0 Fraction of FDC hits to randomly drop (0=drop nothing 1=drop everything)


Description Variable Value File Line/Function
fADC counts -> physical units a_scale 1.0E6/1.3E5 53
shower profile parameters? DFCALCluster shower_profile()
mcsmear gaussian time resolution (ps) 200. mcsmear/ 869

CCDB table - FCAL/fcal_parms

Name Value Description Action
FCAL_PHOT_STAT_COEF 0.035 Photon-statistics factor for smearing hit energy
FCAL_BLOCK_THRESHOLD 0.02 Single block energy threshold (applied after smearing, units of GeV)
FCAL_ATTEN_LENGTH1 100. Attenuation length for Outer Glass (in cm)
FCAL_ATTEN_LENGTH2 73.1 Attenuation length for Inner Glass (in cm)
FCAL_RHG_RADIUS 30. Radius of inner lead glass blocks in cm
FCAL_C_EFFECTIVE 15. effective speed of light in glass in cm/ns
FCAL_WIDTH_OF_BLOCK 4. block width in cm
FCAL_LENGTH_OF_BLOCK 45. block length in cm
FCAL_TWO_HIT_RESOL 75. time window for two hit separation in ns
FCAL_MAX_HITS 100 maximum number of hits in a single block
FCAL_THRESH_MEV 5. threshold applied in a block (in hdgeant) Note: different unit than for smeared-blocks threshold (see above)
FCAL_ACTIVE_RADIUS 120. radius of the calorimeter
FCAL_CENTRAL_ROW 29 number of blocks in central row
FCAL_CENTRAL_COLUMN 29 number of blocks in central column


Description Variable Value File Line
fADC counts -> physical units, 100 keV/count (?) a_scale 0.0001 38
non-linear shower energy corrections 23-46
sigma(z) estimation, cm (with TDC info, from NIM article) m_sig_z 1.1 / sqrt(E) 96
sigma(z) estimation, cm (without TDC info, from NIM article) m_sig_z 30. 104

In DBCALUnifiedHit_factory::brun():34-119 - Need to revisit timewalk corrections.

Various clusterizing parameters/calculations:

  // The method below for determining sig_theta works better than the one
  // above. sigma_z is determined using errors when reconstructing MC data.
  double sigma_z = sqrt(1.394*1.394/m_E + 0.859*0.859);
  m_sig_theta = sigma_z*sin(m_theta)*sin(m_theta)/DBCALGeometry::BCALINNERRAD;

  In DBCALCluster_factory::evnt(), energy threshold is 5*k_MeV

  In DBCALCluster_factory::clusterize()
    float seedThresh = 1*k_GeV;
    float minSeed = 10*k_MeV;

  In DBCALCluster_factory::overlap( const DBCALCluster& highEClust,
                                    const DBCALCluster& lowEClust )
  //deltaPhi_force_merge and delta_z_force_merge were determined by looking
  //at the separation of decay photons from pi0's from a pythia sample.
  //There are no events where the decay photons have separation
  //(delta_phi < 0.2 && delta_z < 25 cm), so in most cases it should be safe
  //to merge clusters together if they are so close.
  const double deltaPhi_force_merge = 0.1; //radians
  const double delta_z_force_merge = 15.0*k_cm;

  //A major cause of extra clusters are lower energy hits, which have poor
  //z-resolution and so are not properly merged. Treat low energy
  //clusters (< 40 MeV) as a special case. Again, hopefully this is only
  //a temporary fix until we have a more comprehensive solution.
  const double delta_z_force_merge_low_E = 40.0*k_cm;
  const double low_E = .04*k_GeV;

CCDB table - BCAL/bcal_parms

Name Value Description Action
BCAL_DARKRATE_GHZ 0.0176 Silicon PMT dark rate (from GlueX-doc-1754-v3)
BCAL_SIGMA_SIG_RELATIVE 0.105 Single PE width to amplitude ratio 6.489/61.67 = 0.105 (from GlueX-doc-1754-v3)
BCAL_SIGMA_PED_RELATIVE 0.139 Pedestal width to single PE amplitude ratio 8.585/61.67 = 0.139 (from GlueX-doc-1754-v3)
BCAL_SIPM_GAIN_VARIATION 0.04 Variation of gains between individual SiPM tiles. Yi measured a value of ~4% and indicated this in private communication.
BCAL_XTALK_FRACT 0.10 This factor includes both the cross-talk and after-pulse probability for a 100ns window.
BCAL_INTWINDOW_NS 100. integration widnows in [ns]
BCAL_DEVICEPDE 0.21 Photon detection efficiency (from GlueX-doc-1754-v3)
BCAL_SAMPLING_FRACT 0.095 Sampling Fraction
BCAL_AVG_DARK_DIGI_VALS_PER_EVENT 240 Digitized values due to dark pulses only: Inner region has 3 digitized values/event, Outer region has 2 digitized values/event
BCAL_PHOTONSPERSIDEPERMEV_INFIBER 75 try to extract from GlueX-doc-1069 back to photons per side per MeV in fiber
BCAL_SAMPLINGCOEFA 0.042 Set the sampling smearing coefficients ( from GlueX-doc 827 v3 Figure 13 )
BCAL_TIMEDIFFCOEFA 0.098994949 time smearing comes from beam test time difference resolution with beam incident on the center of the module
BCAL_TIMEDIFFCOEFB 0 no floor term, but leave the option here
BCAL_THRESH_MEV 1. Threshold applied to energy deposition in MeV (HDGeant)
BCAL_TWO_HIT_RESOL 50. time window for two hit resolution in ns
BCAL_MAX_HITS 100 maximum number of hits per readout channels

CCDB table - BCAL/mc_parms

Name Value Description Action
SiPM_tbin_width 0.100

CCDB table - BCAL/cluster_merging

Name Value Description Action
MIN_CLUSTER_SEPARATION_XY 15.0 Minimum separation between 2 clusters for them NOT to be merged (cm)


Description Variable Value File Line
fADC counts -> physical units a_scale 0.2/5.2E5 48
fADC time resolution (ns) hit->sigma_t 4.0 49
TDC time resolution (ns) hit->sigma_t 0.160 50

CCDB table - TOF/tof_parms

Name Value Description Action
TOF_C_EFFECTIVE 15.0 effective light speed in the plastic scintillator paddles units [ns]
TOF_ATTEN_LENGTH 150. attenuation legth of paddle units [cm]
TOF_POS_RES 3.0 TOF position resolution in the transvers direction of the paddle [cm]
TOF_ADC_TO_E 1.0 conversion of ADC to energy
TOF_TDC_MC_RES 0.06 TDC resolution as in the MC units [ns]
TOF_PHOTONS_PERMEV 8000. scintillation photon generated per MeV energy
TOF_THETA_MAX 50.74 total internal reflection
TOF_PMT_SURFACE 19.63 PMT surface in cm^2
TOF_ADC_RES_MC 50. adc resolution pC/count in MC
TOF_TDC_RES_MC 0.06 TDC resolution in ns
TOF_PMT_GAIN_MC 40000000. PMT gain factor in MC
TOF_PHE_EFF 0.2 PMT quantum efficiency
TOF_REFLECT_EFF 0.5 reflection efficiency of scintillation light
TOF_CENT_TRES -0.698970004 timing resolution in the center of the paddle log10(0.2ns)
TOF_ADC_TO_E 1.0 ADC to energy conversion factor in MC
TOF_HALFPADDLE 126. half the length of a TOF paddle in cm
TOF_PADDLE_LENGTH 252. half the length of a TOF paddle in cm
TOF_PADDLEWIDTH 6. with of a TOF paddle in cm
TOF_E_THRESHOLD 0.001 Energy threshold in GeV
TOF_SIGMA 0.1 Timing resolution in [ns]
TOF_TWO_HIT_RESOL 25. two hit resolution in tof [ns]
TOF_THRESH_MEV 0. threshold applied to deposited energy in MC
TOF_MAX_HITS 25 maximum merged hits per paddle
TOF_MAX_PAD_HITS 25 maximum total hits per paddle

Start Counter

Description Variable Value File Line
fADC counts -> physical units a_scale 2.0E-2/5.2E-5 36
fADC time resolution (ns) hit->sigma_t 4.0 37
TDC time resolution (ns) hit->sigma_t 0.160 38

CCDB table - START_COUNTER/start_parms

Name Value Description Action
START_SIGMA 0.3 Start counter timing resolution 300ps
START_PHOTONS_PERMEV 200. Start counter number of photons per MeV
START_ATTEN_LENGTH 150. attenuation length in cm
START_C_EFFECTIVE 15. effective speed of light in cm/ns
START_TWO_HIT_RESOL 25. time window for two hit resolution in ns
START_MAX_HITS 100 maximum number of hits per readout channel
START_THRESH_MEV 0.150 threshold in MeV
START_LIGHT_GUIDE 140. light guid length in cm

Geometry constants



FDC/DFDCGeometry.h has a bunch of constants that need to be reconciled with HDGeant/hitFDC.c Note that HDGeant/hitFDC.c actually reads these out of the CCDB (!)

//----- These were cut from HDGeant/hitFDC.c -----
#define DRIFT_SPEED           .0055
#define CATHODE_ROT_ANGLE     1.309  // 75 degrees
//#define CATHODE_ROT_ANGLE     0.7854 // 45 degrees
#define TWO_HIT_RESOL         250.
#define WIRES_PER_PLANE       96
#define WIRE_SPACING          1.0
#define STRIPS_PER_PLANE      192 
#define STRIP_SPACING         0.5
#define U_OF_STRIP_ZERO            (-((STRIPS_PER_PLANE-1)*STRIP_SPACING)/2)
#define STRIP_GAP             0.1
#define MAX_HITS             100
//#define K2                  1.15
#define STRIP_NODES           3
#define THRESH_KEV           1.
#define THRESH_STRIPS        5.   /* mV */
#define ELECTRON_CHARGE 1.6022e-4 /* fC */