LHEP Physics ListsThe LHEP Physics lists are based on a parametrised modeling for all hadronic interactions for all particles. The parametrised model is an improved version of the Gheisha model. These lists combine the high energy parameterised (HEP) and low energy parameterised (LEP) models describing inelastic interactions for all hadrons. The modeling of elastic scattering off a nucleus and of capture of negative stopped particles and neutrons proceeds via parameterised models.
Cross sections used are based on Gheisha parameterisations.
There are several variants adding specific model variants:
This is the main LHEP based physics list, using exclusively parameterised modeling. In addition to the above, standard electromagnetic physics options are used.
This physics list is in use in high energy experiments for shower simulations.
Similar to LHEP, with the exception of parameters of electromagnetic processes tuned to yield better cpu performance with only slightly less precision. In addition, the nuclear capture of negative particles and neutrons at rest is modeled using the modeling of the Chiral Invariant Phase Space (CHIPS) model.
For shower simulation is high energy physics experiments, this list provides similar physics results as LHEP.
- LHEP_BERT and LHEP_BERT_HP
- LHEP_PRECO and LHEP_PRECO_HP
String model based physics listsThese Physics lists apply a string models for the modeling of interactions of high energy hadrons, i.e. for protons, neutrons, pions and Kaons above ~(5-25) GeV depending on the exact physics list. Interactions at lower energies are modeled by the low energy parameterised (LEP) model. Depending on the physics list, the LEP model can in part be replaced by a cascade model for a subset of particles with energies below 10 GeV. Nuclear capture of negative particles and neutrons at rest is modeled using the modeling of the Chiral Invariant Phase Space (CHIPS) model. Coherent elastic scattering is modeled with improved models. Proton and neutron coherent elastic scattering uses the CHIPS parameterization, and for pion and Kaons an Compared to LHEP physics lists, improved cross sections for hadronic inelastic interactions are used:
- Pion cross sections use a tabulation based on evaluation by Barachenko.
- proton and neutron cross sections use a parameterisation based on the Axen and Wellisch systematic.
- QGSP and QGSP_EMV
QGSP is the basic physics list applying the quark gluon string model for high energy interactions of protons, neutrons, pions, and Kaons and nuclei. The high energy interaction creates an exited nucleus, which is passed to the precompound model modeling the nuclear de-excitation.
QGSP_EMV is identical to QGSP, but parameters of electromagnetic processes tuned to yield better cpu performance with only slightly less precision.
- QGSC and QGSC_EMV
As QGSP except applying CHIPS modeling for the nuclear de-excitation. In comparison to thin target experiments, this improves simulation of the nuclear de-excitation part of the interaction, resulting in slightly increased production of relatively low energy secondary protons (and neutrons).
QGSC_EMV is identical to QGSC, but parameters of electromagnetic processes tuned to yield better cpu performance with only slightly less precision.
This variant of QGSC uses a different algorithm setting up the excited nucleus created by the high energy interaction resulting in a good description of target fragmentation products; comparisons to thin target data well reproduce the proton production rate in the nuclear fragmentation region.
- QGSP_BERT and QGSP_BERT_EMV
Like QGSP, but using Geant4 Bertini cascade for primary protons, neutrons, pions and Kaons below ~10GeV. In comparison to experimental data we find improved agreement to data compared to QGSP which uses the low energy parameterised (LEP) model for all particles at these energies. The Bertini model produces more secondary neutrons and protons than the LEP model, yielding a better agreement to experimental data.
QGSP_BERT_EMV is like QGSP_BERT, but parameters of electromagnetic processes tuned to yield better cpu performance with only slightly less precision.
Both QGSP_BERT and QGSP_BERT_EMV are less CPU performant as QGSP.
This list is similar to QGSP_BERT and in addition uses the data driven high precision neutron package (NeutronHP) to transport neutrons below 20 MeV down to thermal energies.
This is a variant of QGSP_BERT where the Geant4 Bertini cascade is only used for particles below ~5.5 GeV.
- QGSP_BIC and QGSP_BIC_HP
Like QGSP, but using Geant4 Binary cascade for primary protons and neutrons with energies below ~10GeV, thus replacing the use of the LEP model for protons and neutrons In comparison to teh LEP model, Binary cascade better describes production of secondary particles produced in interactions of protons and neutrons with nuclei.
Both lists, QGSP_BIC and QGSP_BIC_HP, also use the binary light ion cascade to model inelastic interaction of ions up to few GeV/nucleon with matter.
The list QGSP_BIC_HP is like QGSP_BIC with the addition to use the data driven high precision neutron package (NeutronHP) to transport neutrons below 20 MeV down to thermal energies.
- QGSP_NEQ, QGSP_EMV_NQE, and QGSP_BERT_NQE
These lists correspond to teh lists without the trailing _NQE, except that here the quasi-elastic channel for high energy inelastic reactions is ignored. This quasi-elastic channel was missing from string model based physics lists prior to release 8.3. To allow comparison to results obtained with older releases of Geant4, i.e. 8.2 and before, these lists are provided for a transisition period.
- FTFP, FTFP_EMV, and FTFC
In FTF physics lists, a different string model is used. The FTF model is based on the FRITIOF description of string excitation and fragmentation. This model is currently (releases 8.3, and 9.0) being improved with further refinements forseen for the next release of Geant4.