6 Calorimetry
235
– in modern calorimeter facilities the energy deposits are usually distributed over
several systems of different geometries and materials. Simulation codes are
pushed to their limits in translating the recorded signal into a 1% precision energy
measurement;
– at LHC and in particular in the study of the UHE Cosmic Ray Frontier simulation
codes are used to extrapolate measured detector response by one to eight (!)
orders of magnitude;
– particle physics MC codes are applied to areas outside particle physics, such as of
radiation shielding, nuclear waste incineration and medical radiation treatment.
First, we will describe the general approach to these simulation issues before
addressing some specific points. Regular conferences on this subject provide a good
overview [55].
Electromagnetic Shower Simulation
For decades EGS4 [17] has been the standard to simulate electromagnetic phenomena. A modern extended incarnation has been developed by the GEANT4
Collaboration [18]. It includes the full panoply of radiation effects, including photons from scintillation, Cherenkov and Transition radiation up to electromagnetic
phenomena relevant at 10 PeV.
Hadronic Shower Simulation
The simulation must cover the physics and the corresponding cross-sections from
thermal energies (neutrons) up to (in principle) the 10 20 eV frontier, requiring many
different physics models; program suites, ‘toolkits’, such as GEANT4 [18], provide
the user with choices of physics interaction models to select the physics interactions
and particle types appropriate to a given experimental situation.
At high energies (~15 GeV to ~100 TeV)—in addition to measured cross
sections—models describing the hadron physics are used, such as the ‘Quark Gluon
String’ model [18], Fritiof or Dual Parton Models [56]. Such models are coupled
to descriptions of the fragmentation and de-excitation of the damaged nucleus. At
the highest energies other models, such as ‘relativistic Quark Molecular Dynamics’
models are being developed [57].
In the intermediate energy range (<10 GeV) Bertini-style cascade models [58]
are employed to describe the intra-nuclear cascade phenomena. These models use
measured cross-sections and angular distributions.
For the very low energy (<20 MeV) domain neutron transport codes have been
developed, using experimental cross-sections.
The different energy regimes covered by these models are connected with
parametric descriptions, in which cross-sections are parameterized and extrapolated
over the full range of hadronic shower energies. Well-known examples are Geisha
[59] and to a certain extent GCalor (or GEANTCalor) [60].
Applications: Illustrative Examples
We present comparisons of simulation with experiment to illustrate the quality of
shower modelling.
235
– in modern calorimeter facilities the energy deposits are usually distributed over
several systems of different geometries and materials. Simulation codes are
pushed to their limits in translating the recorded signal into a 1% precision energy
measurement;
– at LHC and in particular in the study of the UHE Cosmic Ray Frontier simulation
codes are used to extrapolate measured detector response by one to eight (!)
orders of magnitude;
– particle physics MC codes are applied to areas outside particle physics, such as of
radiation shielding, nuclear waste incineration and medical radiation treatment.
First, we will describe the general approach to these simulation issues before
addressing some specific points. Regular conferences on this subject provide a good
overview [55].
Electromagnetic Shower Simulation
For decades EGS4 [17] has been the standard to simulate electromagnetic phenomena. A modern extended incarnation has been developed by the GEANT4
Collaboration [18]. It includes the full panoply of radiation effects, including photons from scintillation, Cherenkov and Transition radiation up to electromagnetic
phenomena relevant at 10 PeV.
Hadronic Shower Simulation
The simulation must cover the physics and the corresponding cross-sections from
thermal energies (neutrons) up to (in principle) the 10 20 eV frontier, requiring many
different physics models; program suites, ‘toolkits’, such as GEANT4 [18], provide
the user with choices of physics interaction models to select the physics interactions
and particle types appropriate to a given experimental situation.
At high energies (~15 GeV to ~100 TeV)—in addition to measured cross
sections—models describing the hadron physics are used, such as the ‘Quark Gluon
String’ model [18], Fritiof or Dual Parton Models [56]. Such models are coupled
to descriptions of the fragmentation and de-excitation of the damaged nucleus. At
the highest energies other models, such as ‘relativistic Quark Molecular Dynamics’
models are being developed [57].
In the intermediate energy range (<10 GeV) Bertini-style cascade models [58]
are employed to describe the intra-nuclear cascade phenomena. These models use
measured cross-sections and angular distributions.
For the very low energy (<20 MeV) domain neutron transport codes have been
developed, using experimental cross-sections.
The different energy regimes covered by these models are connected with
parametric descriptions, in which cross-sections are parameterized and extrapolated
over the full range of hadronic shower energies. Well-known examples are Geisha
[59] and to a certain extent GCalor (or GEANTCalor) [60].
Applications: Illustrative Examples
We present comparisons of simulation with experiment to illustrate the quality of
shower modelling.