Variables

The following is a list of the variable used to steer the simulation. The default values are given in square brackets.

• id0 [1120]
  primary type in ISAJET ids.
• id1-id15 [0]
  additional primaries can be defined. If more than one primary is defined, one is chosen by random at the start of each shower.
• e0 [1e5]
  primary energy
• e1,e2 [1e5,1e5]
  if e2>e1 the primary energy is chosen as a function $\sim E^{-egamma}$
• egamma [1]
  spectrum-index $\gamma$, energies are chosen in the limits ]e1,e2[ with a distribution $dn/dE\sim E^{-\gamma}$. The default value gives a constant distribution on a log-scale.
• eran [0]
  the primary energy spectrum can be discretized, with the variable eran. In general $\textrm{abs(eran)}$ discrete values will be generated between e1 and e2. Choosing eran=1 or -1 does not make sense. According to the sign of eran, the values will be chosen randomly or sequentially.
  • eran>1
    The random number chosen to generate the primary energy is calculated as rengy=int(r*eran)/(eran-1). This way one can discretize the random primary energy. For example, egamma=1, e1=1e6, e2=1e11, eran=6, will chose randomly among the discrete primary energies 1e6,1e7,1e8,1e9, 1e10, and 1e11 GeV.
  • eran<-1
    
    rengy=mod(int(ishow-1/imodan),-eran)/(-eran-1)
    
    computes a series of primary energies. Following the above example, eran=-6 all energies 1e6 to 1e11  GeV will be chosen sequentially. the imodan makes each discrete value repeat imodan times.
    

• theta [0]
  zenith angle
• phi [0]
  azimuth angle
• theta1,theta2 [0,0]
  if theta2>theta1 theta is chosen randomly in this range.
• tran [2]
  tran=1 chooses theta in a $d\cos(\theta)$ distribution
  tran=2 chooses theta in $\cos(\theta)d\cos(\theta)$ distribution, which is the realistic scenario for a surface detector array.
  tran=3 user defined theta distribution. See file theta.F for definition.
• phi1,phi2 [0,0]
  if phi2>phi1, phi is chosen uniformly in this range.
• hinj [100000]
  height of injection of the primary cosmic ray.
• dinj [0]
  injection distance from coordinate system origin (0,0,hcore). This variable is only considered if given a value greater then zero, in which case hinj is ignored.
• haxmax [0]
  if haxmax>0, this is the maximal longitudinal distance (in meters) over which the shower will be evolved. This can be used as a condition for the computation to stop in the case of horizontal showers.
• nshow [1]
  number of showers to compute.
• icasan [1]
  predefined analysis-level.
• imodan [0]
  if not zero, analysis output happens every imodanth shower.
• dzana [10]
  step width for depth in longitudinal analysis.
• izvertical [1]
  take vertical depth (1) or slant depth (0) for longitudinal analysis.
• iocask [1]
  switch for hadronic cascade equations:
  • [iocask=0] no hadronic cascade equations.
  • [iocask=1] use cascade equations in each shower.
  • [iocask=2] use cascade equations after the initial part of imodan showers has been calculated. I.e. the initial condition is the average of the high energy part from imodan showers.
• iecask [1]
  switch for electromagnetic cascading.
  • [iecask=0] off.
  • [iecask=1] on.
  • [iecask=2] same as iocask=2, takes initial condition from imodan showers (average).
  By switching these last two options off, the program runs in full Monte-Carlo mode.

• fbase [seneca]
  base name for current run. Usually the name of the options-file without the extension. Used for the predefined analysis, for example.
• chkfile [seneca.check]
  file name of the check file in which one finds the information about a specific simulation.
• ioegs4 [1]
  • [EGS4 mode:] 
  • [ioegs4=1] calculates with internal EGS4 stack
  • [ioegs4=2] gives particles back to main stack in the first part of a run (i.e. the Monte-Carlo part) before switching to cascade equations
  • [ioegs4=3] gives always particles back to the main stack
• seed,seed0 [0]
  initial seed of the random number generator.
• seed1 [0]
  if not zero, seed1 is set at the start of each shower. Useful only to study artificial fluctuations.
• seed2 [0]
  optional seed, activated as first particle falls below Seed2Engy.
• seed3 [1234]
  initial seed for EGS4. The EGS4 random number generator is very simple but fast. Do not initialize to zero!
• Seed2Engy,fSeed2Engy [1e30,1]
  The first particles below this energy threshold activates the seed2. Useful in combination with Stack2Engy. If fSeed2Engy is given, Seed2Engy will be calculated relative to the primary energy.
• Stack2Engy,fStack2Engy [1e30,1]
  Two different stacks for particles in Monte-Carlo mode can be chosen: a high energy stack and a low energy stack. First all high energy particles will be treated with stack 1 accumulating all low energy particles in stack 2. Once the stack 1 is empty, stack 2 is processed. In combination with Seed2Engy, this can be used to generate showers which have identical high energy part, but different low energy evolution. To do so you have to set seed0 and seed3 to some value, since the hadronic part and EGS4 have different random number generators. Furthermore, set ioegs4 to 2, so that EGS4 does not use its internal stack, and ipthin to 0 , such that thinning does not disturb the random number sequence. (See use of 'fseed' command below.)
• ElowH [1e6]
  Amount of energy to be processed in the low energy hadronic source function.
• fElowH [1]
  Fraction of energy to produce low energy particles. The weight of produced hadrons will be 1/fElowH. The actual value chosen is min(ElowH,fElowH*etot), etot=total energy of hadrons in the source function.
• ElowE [1e5]
  Amount of energy to produce low energy electrons and photons from the source function.
• fElowE [1]
  fractional energy. Weight of particles will be 1/fElowE. The actual value is min(ElowE,fElowE*etot), with etot being the integrated energy in the source function.
• hground [100]
  Ground level altitude.
• hobs [hground]
  observation level altitude. Concerns the radial analysis. This variable is initialized to the value of hground, but can be modified after setting hground.
• hcore [hobs]
  altitude where the shower goes through (0,0,hcore). Initialized to hobs.
• zmax [1023.9]
  max vertical depth of shower. Same as hground, but lets you specify in $g/cm^{2}$.
• EmaxH [1e30]
  upper bound for hadronic cascade equations. This value controls the amount of natural fluctuations in the shower. Setting it to the primary energy will give no fluctuations and calculate an average shower.
• fEmaxH [1e-3]
  determine EmaxH as fEmaxH*e0.
• EminH [1e4]
  minimum energy for hadronic CE. Most important if one wants to compute lateral distribution functions. The value should not be below 1e3 GeV.
• EmaxE [1e30]
  upper bound for electromagnetic cascade equations. Equivalent to EmaxH.
• fEmaxE [1e-3]
  determine eemax as fEmaxE*e0
• Emax
  set both EmaxH and EmaxE to the same value.
• fEmax
  set both fEmaxH and fEmaxE to the same value.
• EminE [10]
  lower energy-cutoff for ECE. Should not be lower than 10 GeV.
  Remark: there is no Emin variable, because it does not make any sense to set EminE and EminH to the same value.
• EcutE [0.001]
  kinetic energy-cutoff for electrons/positrons.
• EcutP [0.001]
  kinetic energy-cutoff for photons.
• EcutM [0.050]
  kinetic energy-cutoff for muons.
• EcutH [0.050]
  kinetic energy-cutoff for hadrons.
• thinH [0]
  thinning level as fraction of primary energy.
• thinE [0]
  thinning level for electromagnetic interactions.
• thin [0]
  sets both values, thinH and thinE.
• iothin [1]
  thinning option:
  • [iothin=1] original thinning following Hillas
  • [iothin=2] statistical thinning with a weight-limit
  • [iothin=3] statistical thinning with weight-limit, but not beyond the distance rthmax from shower-axis
  Thinning is only relevant if the program is used in pure Monte-Carlo mode. In cascade mode, the fractional amount of low energy particles is controlled by ElowH and ElowE, so no thinning should be used there.

• ipthin [1]
  partial thinning option:
  • [ipthin=0] no partial thinning
  • [iothin=1] partial thinning allowed
  Partial thinning means to thin all particles below the treshold, even when a part of the particles are still above. When switched off, thinning is only done when the primary is below the treshold. Only relevant for keeping track of the seed.

• wtmax,wtmaxH,wtmaxE [1e30]
  maximum weight for statistical thinning. Setting ths value defaults iothin to 2.
• rthmax [100]
  max radius for thinning option 3. Particles with a radius larger than rthmax from the shower axis will not be thinned any more.
• dlhmax [1e30]
  maximum propagation step for charged particles (except electrons, they are treated in EGS4). This is important for low energy protons, if of any interest. A low value (like 10 m) ensures that the diverging energy loss is properly considered, but increases computing time.
• ngener [-1]
  maximum number of generations of interactions in MC-mode. -1 means off. ngener=1 means do only the first interaction.
• iogmag [2]
  deflect particles in the geomagnetic field:
  • [iogmag=0] off
  • [iogmag=1] hadrons and muons only
  • [iogmag=2] all particles.
• geoBx, geoBy, geoBz [ $20\times10^{-6}$,0, $40\times10^{-6}$]
  the three components of the geomagnetic field.
• upkill [0]
  • [upkill=0] do not kill upwards going particles.
  • [upkill=1] kill upwards going particles.
• iopnuc [2]
  switch on/off photo-nuclear effect
  • [iopnuc=0] off
  • [iopnuc=1] creates hadrons from CE with weight of other hadrons
  • [iopnuc=2] creates hadrons from CE with weight of EM particles (which is usually larger )
  the latter two values make no difference for the MC part.

• theminH,theminE [0.1,0.1] 
  minimum angle with respect to the shower axis for particles to be stored in the initial condition function for CEs. This is important for lateral distributions to be right. At lower energies, this value should be decreased (Compare to pure MC).
• iolpm [1]
  switch on/off LPM effect.
• ionkg [1]

  Option to control the treatment of low energy EM particles.

  • [ionkg=0] off, means do MC mode.
  • [ionkg=1] computation of longitudinal profile with NKG formula (deprecated)
  • [ionkg=2] takes precomputed low energy sub-showers for the low-energy EM-stuff. This is very precise for the longitudinal profile, but note that no lateral information is provided.
    If you do Xmax only this is the way to go. You can even set EminH to 100GeV, ElowH to 1e5 GeV, so the low energy hadronic part does not take up too much time.
• elowhi [100]
  transition energy from low to high energy model.

• home [$HOME/share/seneca]
  specifies the directory of all data-files
• nex2home [home]
  directory of the nexus2 ini-files.
• nex397home [home]
  directory of the nexus397-ini files.