The program SIMDET simulates the response of an LC detector for e+ e- physics in a fast and flexible manner. The main objectives of the program are threefold:
The basic components of the detector are assumed to be:
The program applies Gaussian smearing to charged particle momenta. The calorimetric response is treated in a way using a parametrisation of results from the ab initio Monte Carlo program BRAHMS. Pattern recognition is emulated by means of cross reference tables between generated particles and detector response. An energy flow algorithm defines the output of the program. Impact informations for charged particles are also provided.
SIMDET offers for event input either to use a built in interface to PYTHIA for internal event generation or to read events generated by other programs and written by subroutine LCWRITE. Also, reading of events generated by CompHEP can be enabled.
After simulation and for the purpose of physics analysis, particles are classified as
Tracking efficiencies, charge mismeasurement and threshold energies for detector response are also taken into account either by default or with user adjustable values. Low energy muons are interpreted as pions.
The output of the program can be directed to a file using the standard output structure or a restricted form. Also, output of 'reconstructed' events can be completely suppressed or, if requested, the best estimates for the energy flow objects are stored such that the physics analysis package VECSUB can be directly used.
The program runs under the control of free format data cards with the possibility of overriding the default options.
A lot of changes and improvements were made with respect to version 2 of SIMDET September 1998; hence the old version should be considered as obsolete. This document describes SIMDET V3.1.
The code of SIMDET V3.1 is found here. A PATCHY/CMZ CAR file as well as straight Fortran source is supplied.
SIMDET has a built in an interface to PYTHIA for internal event generation via subroutine SIPYTH. Alternatively, events generated by other programs can be used for detector simulation; subroutine SIEVTI provides an input interface to events written by subroutine LCWRITE whereas subroutine SICOMP is reserved for events generated by the program package CompHEP. If the structure of the generated events does not coincide with common /LUJETS/ of PYTHIA, subroutine SIPREP should fill the arrays K(I,...), P(I,...) and V(I,...). In all cases, NEVENT specifies the number of events to be processed.
The detector parameters used are defined in subroutine SIDETR. The naming convention is self explanatory. It should be noted, however, that the CDR does not specify the resolution parameters for all of the detector components assumed to exist. Hence, the corresponding numbers given in SIDETR should be considered as a first trial. The results of possible further detector improvements and appropriate detailed simulations by means of the ab initio Monte Carlo program BRAHMS should update these numbers.
Four options exist for the vertex detector (subroutine SIVTXD):
Subroutine SIFFRE reads the set of data cards with the FFREAD package. Default settings in subroutine SIINIT and/or in subroutine SIDETR might be overwritten.
Booking of histograms is provided in subroutine SIBOOK. A few standard histograms are provided to monitor detector response.
After selection of all particles which might give a response in the detector (subroutine SIPART), charged particle tracking and impact parameter estimations are steered by subroutine SICHPA.
The calorimetric response is based on detector studies using the simulation package BRAHMS. The energy distributions of electrons and charged pions in adjacent cells were fitted and the parameters obtained are used for appropriate energy deposits simulations in the electromagnetic and hadronic calorimeters (subroutine SILEGO and subroutine SIDEPO). Afterwards, a cluster search algorithm (with some idealized assumptions) provides clusters (subroutine SICLUS_I) in the ECAL as well as the HCAL. Finally, an energy flow algorithm (subroutine SIFLOW_I) joins tracker and calorimeter informations such that as many single particles as possible are resolved. Particle identification on the basis of shower shapes and matching between tracker and calorimeter information in space and momentum is emulated. Finally, best estimates of the energy flow objects are established.
The simulation finishes by providing all measured objects in the proposed common output structure in subroutine SISTOR. If requested, the program allows to write (unformatted/formatted) all objects in either the standard structure or in a restricted structure (best estimates only) to an external file in subroutine SIWDST so that analysis can follow externally. If no external file should be written, the array VECP(I,K) is optionally filled in subroutine SIBEST which allows to use directly the physics analysis package VECSUB (a product from SLAC/DELPHI).
The user subroutine SIUSER (IFLAG) has been added and given as an independent card file. It is called during inititialization (IFLAG=1), for each event before writing to output file (IFLAG=2) and during termination of the job (IFLAG=3).
The program exist as Fortran as well as a PATCHY/CMZ CAR file. If the CAR file is used, the 'use' selection SIMDET selects the simulation material, while NOSIMU selects the code without any detector response. This enables physics studies at the parton level or generator level.
Please note that in the FORTRAN code error handling routines are inserted. These are of relevance for HP platforms only. If the CAR file is used, the 'use' selection HPUX includes this material.
Please link the CERN libraries and the lund/jetset74 libraries.
| Logical unit number | Default file name | Contents |
|---|---|---|
| 6 | simdetv3.res | debugging information like the history of a few events and histograms |
| 7 | user-defined | input events generated by an external program |
| 8 | simdetv3.dat | free format data card file |
| 11 | user-defined | simulated and reconstructed objects for further analysis |
| 12 | simdetv3.hist | PAW histogram file |
Note that the names of input and reconstructed event files should be enclosed in single quotes, start with a point and end with a blank when specified on the respective data cards. The length of all file names is restriced to 80 characters.
This describes the SIMDET V3.1 standard output structure. The output file starts with a single file header of 10 words. Each event starts with the number of generated particles NGENPA, which is followed by a record of 13 words for each particle. According to the user's choice, the whole event history or only the stable particles which might give a response in the detector are covered.
The number of the energy flow objects, NENFLO, then follows. For each object, blocks of records follow, describing status information, best estimates, generator information, charged particles, calorimetric clusters and muons from the muon system, in this order.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | INSTATE | INTEGER | ISR flag, PYTHIA default: |
| 0 = no radiation, 1 = ISR & Beamstrahlung, 2 = ISR only, 3 = Beamstrahlung | |||
| 2 | SQRTS | REAL | nominal collider cms energy [GeV] |
| 3 | SIGMA | REAL | Cross section [fb] |
| 4 | IDCLASS | INTEGER | Reaction identifier, user defined |
| 5 | dummy | INTEGER | not used |
| 6 | dummy | REAL | not used |
| 7 | FIELD | REAL | Magnetic field [T] |
| 8 | dummy | INTEGER | not used |
| 9 | dummy | INTEGER | not used |
| 10 | dummy | INTEGER | not used |
This record is written once per file.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | STATUS | INTEGER | 0 = no detector response, 1 = detector response |
| 2 | ID | INTEGER | particle code according to LUND convention |
| 3 | line | INTEGER | line number of mother in the LUND record |
| 4 | Px | REAL | x-component of momentum [GeV] |
| 5 | Py | REAL | y-component of momentum [GeV] |
| 6 | Pz | REAL | z-component of momentum [GeV] |
| 7 | E | REAL | Energy [GeV] |
| 8 | m | REAL | mass of particle [GeV] |
| 9 | Q | REAL | charge of particle |
| 10 | x | REAL | x-component of vertex [mm] |
| 11 | y | REAL | y-component of vertex [mm] |
| 12 | z | REAL | z-component of vertex [mm] |
| 13 | Time | REAL | time of production [mm/c] |
This record is repeated NGENPA times.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | STATUS | INTEGER | < 0: invalid object; 1=charged object; 2=neutral object; 3=composite object |
| 2 | Type | INTEGER | particle code according to LUND convention, 999 = cluster of unresolvable particles |
| 3 | NGEN | INTEGER | number of generator particles contributing to the energy flow object |
| 4 | NTRK | INTEGER | number of charged particles contributing to the energy flow object |
| 5 | NCAL | INTEGER | number of clusters contributing to the energy flow object |
| 6 | NMUS | INTEGER | number of muons contributing to the energy flow object |
This record and the following blocks are repeated NENFLO times.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | Px | REAL | x-component of momentum [GeV] |
| 2 | Py | REAL | y-component of momentum [GeV] |
| 3 | Pz | REAL | z-component of momentum [GeV] |
| 4 | E | REAL | Energy [GeV] |
| 5 | m | REAL | mass of particle [GeV] |
| 6 | Q | REAL | charge of particle |
This record is written once per energy flow object.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | link | INTEGER | line number of particle in the LUND record |
| 2 | Efrac | REAL | energy fraction |
This record is repeated NGEN times.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | P | REAL | absolute value of momentum [GeV] |
| 2 | Theta | REAL | polar angle [radian] |
| 3 | Phi | REAL | azimuth angle [radian] |
| 4 | Q | REAL | charge of particle |
| 5 | Imp(R,phi) | REAL | transverse impact parameter, in units of sigma |
| 6 | Imp(R,z) | REAL | Longitudinal impact parameter, in units of sigma |
| 7 | cov. matrix | REAL | element of the cov. matrix |
| 8 | cov. matrix | REAL | element of the cov. matrix |
| 9 | cov. matrix | REAL | element of the cov. matrix |
| 10 | cov. matrix | REAL | element of the cov. matrix |
| 11 | cov. matrix | REAL | element of the cov. matrix |
| 12 | cov. matrix | REAL | element of the cov. matrix |
| 13 | cov. matrix | REAL | element of the cov. matrix |
| 14 | cov. matrix | REAL | element of the cov. matrix |
| 15 | cov. matrix | REAL | element of the cov. matrix |
This record is repeated NTRK times.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | E | REAL | energy [GeV] |
| 2 | Theta | REAL | polar angle [radian] |
| 3 | Phi | REAL | azimuth angle [radian] |
| 4 | Time | REAL | timing information |
| 5 | C(em) | REAL | probability of being consistent with an electromagnetic particle |
| 6 | E | REAL | energy [GeV] |
| 7 | Theta | REAL | polar angle [radian] |
| 8 | Phi | REAL | azimuth angle [radian] |
| 9 | Time | REAL | timing information |
| 10 | C(mip) | REAL | probability of being consistent with a minimum ionizing particle |
This record is repeated NCAL times.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | E | REAL | energy [GeV] |
| 2 | Theta | REAL | polar angle [radian] |
| 3 | Phi | REAL | azimuth angle [radian] |
| 4 | Q | REAL | charge of particle |
| 5 | Time | REAL | timing information |
| 6 | C(punch) | REAL | probability of being consistent with an punch-through object |
This record is repeated NMUS times.
This describes the SIMDET V3.1 restricted output structure, mainly intended to save disc space for reconstructed events. The output file starts with a single file header of 10 words. Each event starts with the number of energy flow objects, NENFLO. This is followed by a series of records for each energy flow object, which describe only the best estimate of the object's energy and direction, in analogy to energy flow record 2 from the full data format, supplementerd by impact parameter information.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | INSTATE | INTEGER | ISR flag, PYTHIA default: |
| 0 = no radiation, 1 = ISR & Beamstrahlung, 2 = ISR only, 3 = Beamstrahlung | |||
| 2 | SQRTS | REAL | nominal collider cms energy [GeV] |
| 3 | SIGMA | REAL | Cross section [fb] |
| 4 | IDCLASS | INTEGER | Reaction identifier, user defined |
| 5 | dummy | INTEGER | not used |
| 6 | SQSACT | REAL | Event related cms energy |
| 7 | FIELD | REAL | Magnetic field [T] |
| 8 | dummy | INTEGER | not used |
| 9 | dummy | INTEGER | not used |
| 10 | dummy | INTEGER | not used |
This record is written once per file.
| Offset | Variable name | Data type | Meaning |
|---|---|---|---|
| 1 | Px | REAL | best estimate for x-component of momentum [GeV] |
| 2 | Py | REAL | best estimate for y-component of momentum [GeV] |
| 3 | Pz | REAL | best estimate for z-component of momentum [GeV] |
| 4 | E | REAL | best estimate for energy [GeV] |
| 5 | m | REAL | mass of particle [GeV] |
| 6 | Q | REAL | charge of particle |
| 7 | Imp(R,phi) | REAL | transverse impact parameter, in units of sigma |
| 8 | Imp(R,z) | REAL | Longitudinal impact parameter, in units of sigma |
| 9 | NTRK | INTEGER | number of charged particles contributing to the energy flow object |
| 10 | type | INTEGER | particle code according to LUND convention, 999 = cluster of unresolvable particles |
In cases of NTRK > 1, the largest impact parameters are recorded. This record is repeated NENFLO times.
This describes the SIMDET V3.1 free format data cards. The initialized default values are given in parentheses. Note that file names should be enclosed in single quotes, start with a point and end with a blank. The length of all file names is restriced to 80 characters. The sample data card file simdet_301.dat delivered with the program causes the simulation of events from the reaction e+e- -> H(80 GeV) Z -> bb qq at a center of mass energy of 500 GeV, generated using PYTHIA.
Certain obvious logical restrictions apply to the proper combination of options. For example, option 'HIST 1' only works in connection with option 'BEST 0'.
| Key | Variable | Data type | Meaning |
|---|---|---|---|
| NEVT | NEVENT | INTEGER | total number of events to process (D=10) |
| PYTH | IFPYTH | INTEGER | 1 = event generation by PYTHIA, 0 = no PYTHIA event generation (D=1) |
| EVTI | IFEVTI | INTEGER | 1 = event reading from an external file, written by sr LCWRITE, 0 = no event reading (D=0) |
| GENF | LUNGENF | INTEGER | input file name of generated events, user defined |
| WDST | IFWDST | INTEGER | 1 = event writing to an external file, 0 = no event writing (D=1) |
| RECF | LUNRECF | INTEGER | output file name of processed events, user defined |
| FORM | IFFORM | INTEGER | 1 = formatted output structure, 0 = unformatted output structure (D=0) |
| BEST | IFBEST | INTEGER | 1 = best estimates are enabled, 0 = no best estimates (D=0) |
| VECS | IFVECS | INTEGER | 1 = filling of the array VECP(I,K) for VECSUB, 0 = no filling of this array (D=0) |
| HIST | IFHIST | INTEGER | 1 = history of the generated event to output file, 0 = only stable generated particles to output file (D=0) |
| COMP | IFCOMP | INTEGER | 1 = event reading from an external file, written by CompHEP, 0 = no event reading (D=0) |
| APS2 | IFAPS2 | INTEGER | 1 = pixel detector (for 2 cm beam pipe) is enabled, 0 = no pixel detector (D=1) |
| APS1 | IFAPS1 | INTEGER | 1 = pixel detector (for 1 cm beam pipe) is enabled, 0 = no pixel detector (D=0) |
| CCD2 | IFCCD2 | INTEGER | 1 = CCD detector (for 2 cm beam pipe) is enabled, 0 = no CCD (2cm) detector (D=0) |
| CCD1 | IFCCD1 | INTEGER | 1 = CCD detector (for 1 cm beam pipe) is enabled, 0 = no CCD (1cm) detector (D=0) |
| FWTR | IFFWTR | INTEGER | 1 = additional forward tracker is enabled, 0 = no additional forward tracker (D=0) |
| FWMU | IFFWMU | INTEGER | 1 = forward muon detector is enabled, 0 = no forward muon detector (D=0) |
| LUMI | IFLUMI | INTEGER | 1 = luminosity detector is enabled, 0 = no luminosity detector (D=0) |
| MASK | IFMASK | INTEGER | 1 = instrumented mask is enabled, 0 = no instrumented mask (D=0) |
| EFTR | TRKEFF | REAL | measurement track efficiency (D=0.99) |
| PTTR | PTMINP | REAL | minimum transverse momentum required (D=0.050 [GeV]) |
| QMTR | QTRKMIS | REAL | charge misinterpretation probability (D=0.005) |
| EMPH | EMINPH | REAL | minimum energy required for photon detection (D=0.100 [GeV]) |
| AEMR | AEMRES | REAL | first energy resolution parameter for ECAL (D=0.102) |
| BEMR | BEMRES | REAL | second (constant) energy resolution parameter for ECAL (D=0.006) |
| EMHA | EMINHAS | REAL | minimum energy required for hadron detection in HCAL (D=0.200 [GeV]) |
| AHAR | AHARES | REAL | first energy resolution parameter for HCAL (D=0.405) |
| BHAR | BHARES | REAL | second (constant) energy resolution parameter for HCAL (D=0.042) |
| EMLU | EMINLU | REAL | minimum energy required for electron detection in LUMI detector (D=30.0 [GeV]) |
| EFLU | ELEFLU | REAL | measurement efficiency for electrons in LUMI detector (D=0.999) |
| CSLU | SIZLUM | REAL | cell size of LUMI detector (D=1.0 [degrees]) |
| ARLU | ALURESS | REAL | first energy resolution parameter for LUMI detector (D=0.10) |
| BRLU | BLURES | REAL | second (constant) energy resolution parameter for LUMI detector (D=0.01) |
| EMMU | EMINFWM | REAL | minimum energy required for muon detection in forward muon detector (D=5.0 [GeV]) |
| EFMU | EFFFWMU | REAL | measurement efficiency for muons in forward muon detector (D=0.95) |
| QMMU | QMISFWM | REAL | charge misinterpretation probability for muons in forward muon detector (D=0.003) |
| PFWT | PMINFTR | REAL | minimum transverse momentum in forward tracker (D=0.200 [GeV]) |
| EMSK | EMINMSK | REAL | minimum energy required for particle measurement in the mask (D=10.0 [GeV]) |
Further information