Prepared by R.P.Kokoulin, February 1st, 2002
Brief report on G4em activity during the visit of R.Kokoulin (MEPhI), S.Kelner (MEPhI), and A.Rybin (IHEP), January 21st – February 1st, 2002
MCS model implemented in G4 has been tested with high-energy muons in thick targets. It has been found that at large layer thickness the model does not reproduce the shape of the angular distribution (even in the central region). Besides that, the present model does not account for nuclear size effect (especially important for high energy penetrating particles).
Formulae and description of algorithm of MCS simulation for high-energy particles in thick layers (taking into account atomic and nuclear formfactors and scattering on atomic electrons) have been prepared and agreed.
Formulae for the cross section of gamma-to-muon pair conversion have been derived on the basis of earlier results of MEPhI group for muon bremsstrahlung (used in G4). A scheme of the process simulation (mean free path calculation, energy sampling) has been elaborated and agreed, process and algorithm description has been prepared.
Simple formulae (accurate in the ultrarelativistic case) for the final state particle angular distributions in the process of muon pair creation by photons have been derived, and a corresponding sampling algorithm has been elaborated and agreed.
Formulae for radiative correction to muon ionization and knock-on electron production (related with target electron bremsstrahlung) have been clarified. Necessary changes in the existing scheme of simulation algorithm to introduce this correction have been refined and agreed.
Intensive discussions on some other processes and effects (implemented or planned for implementation) in G4 electromagnetic physics (LPM suppression of electron bremsstrahlug and electron pair production, angular distribution of final state particles in these processes, etc.) took place. It has been found that some of the approximate formulae need attentive theoretical verification and, probably, revision.
Prospects of further development of electromagnetic physics description in G4, of HE electromagnetic processes and phenomena in relation with various experimental projects have been discussed (see the attached table). The priority list of works on electromagnetic physics in G4 (tentatively, for the period of 2002 – 2003), and also the time schedule of nearest tasks, have been prepared, discussed and agreed (follows below).
ADDENDUM: Some kinds of experiments not covered by the attached table that are necessary to have in mind:
A1. Various detectors response simulation and electron/muon/hadron CALIBRATION, especially of various calorimeters (ionization – gaseous, liquid; scintillation –organic, inorganic; Cherenkov –water, crystal; etc.), also coordinate detectors, TRD, etc.
A2. Muon and neutrino beams – beam properties (energy spectra, angular distributions); ionization cooling for muon rings (energies, angles), etc. (muons 0.2 – 100 GeV and higher)
A3. Cosmic-ray lead-emulsion balloon-born and space-born chamber experiments (0.1 – 100 TeV and higher)
As accurate as possible description of ionization, bremsstrahlung, gamma conversion, MCS both of moderate energy (1 – 100 MeV) electrons and high-energy muons is required (in the latter case – p.A3 - also LPM effect is important).
29.01.2002. Prepared by S.Kelner, R.Kokoulin.
PRIORITY LIST OF ELECTROMAGNETIC INTERACTION PROCESSES/EFFECTS TO BE TESTED/IMPLEMENTED/PREPARED FOR G4 STANDARD EM PHYSICS
(for the period 2002-2003)
(Discussed and agreed during the meetings on January 28-30, 2002: M.Maire, R.Kokoulin, S.Kelner, A.Rybin, V.Ivantchenko, H.Burkhardt)
1. PROCESSES/EFFECTS ALREADY IMPLEMENTED, BUT TO BE CAREFULLY TESTED
Multiple Coulomb scattering (moderate energies): rms values, convolution property
- L.Urban, V.Ivantchenko, by February 28, 2002
Direct electron pair production by muon (energy sampling, threshold variation)
- A.Rybin, by April 30, 2002
Inelastic muon scattering on nuclei (energy sampling, muon angular distribution)
- A.Rybin, R.Kokoulin, by April 30, 2002
Gamma-to-electron pair conversion (approximation of the angular distributions)
- S.Kelner, R.Kokoulin, by February 28, 2002
Electron and muon bremsstrahlung (approximations of the angular distributions)
- S.Kelner, R.Kokoulin, by February 28, 2002
2. PROSESSES NEARLY UNDERSTOOD / TO BE IMPLEMENTED
Multiple scattering of HE muons (with nuclear form-factors)
- L.Urban, new class, by June 2002 release
Gamma-to-muon pair conversion
- H.Burkhardt, by June 2002 release
Radiative correction to muon ionization / knock-on electron production
- L.Urban, correction, Autumn 2002
Photoproduction of hadrons (high-energy extension)
- M.Kosov (already implemented in ‘hadronic’ !!!)
Electroproduction of hadrons (refinement, high-energy extension)
- M.Kosov, in WW-approximation has been implemented; possible refinement?
LPM effect for electron bremsstrahlung and gamma conversion (bulk matter)
- R.Kokoulin (formulae revision, by Summer 2002); implementation - M.Maire, L.Urban, Autumn 2002
3. PROCESSES THAT NEED ADDITIONAL THEORETICAL ANALYSIS / ALGORITHM ELABORATION
Gamma-to-tau pair conversion on the screened nucleus (including incoherent part)
- MEPhI group, 2002
Extension of photonuclear (electronuclear,…) processes into PeV (multi-PeV) energies
- M.Kossov (?), 2002 – 2003; some new data and new ideas may appear…
Direct production of muon pairs by muon
- MEPhI group, 2002 - 2003
Tau electromagnetic interactions with atom and electron:
- bremsstrahlung,
- electron pair production,
- inelastic interaction with nuclei,
- respective energy loss
- MEPhI group, 2002 - 2003
Diffractive bremsstrahlung of muons and taus
- MEPhI group, 2003
Gamma-to-muon pair and –to-tau pair conversion in the field of electron
- MEPhI group, 2002
Direct production of muon and tau pairs by electron on atom
- MEPhI group, 2003
Table1. Electromagnetic interaction processes and experiments
|
Field |
Hadron colliders |
Electron linacs |
VHE n - astronomy |
VHE g - astronomy |
UHE cosmic rays |
HE m n underground experiments |
Low background experiments |
|
Experiments |
CMS, ATLAS,… |
TESLA, CLIC,… |
AMANDA, ANTARES… |
(many) |
PAO, EUSO, … |
Multipurpose n -detectors |
DM search, solar n , b b |
|
Energy Process |
1 – 10 TeV |
0.1 – 3 TeV |
1014 - 1017 eV |
1012 – 1016 eV |
1017 – 1021 eV |
0.1 – 100 TeV |
10 - 1000 GeV |
|
1. MCS (e, m ) |
Momentum measure-ments |
Radiation protection |
Angular resolution, background |
EM showers pattern |
- |
Angular resolution, background |
- |
|
2. LPM effect for brems. and pair production |
- |
- |
EM showers in water, rock |
- |
EM showers in air |
- |
- |
|
3. g ® ee, conversion, (angular distr.) |
Calorimeter response |
EM showers |
- |
Detector response |
- |
- |
- |
|
4. g ® m m conversion |
Background events |
Radiation protection |
VHE m source |
- |
VHE m source |
Multi m events, VHE m source |
- |
|
5. g +Z® Z+t t |
Background events |
n t - beam |
- |
- |
- |
- |
- |
|
6. g +e® e+l l, l l = e, m , or t pair |
Correction to p. 3, 4, 5 |
- |
- |
- |
|||
|
7. Diffractive bremsstrahlung of m and t -lepton |
- |
- |
m , t energy loss |
- |
- |
m charge ratio, I(h) curve |
- |
|
8. t +Z® t +Z+ee t +Z® t +Z+g t +Z® t +hadrons |
- |
- |
Signature of AGN etc. Energy loss, transport t . |
- |
- |
- |
- |
|
9. e+Z® e+Z+m m e+Z® e+Z+t t |
Correction to p. 4, 5 |
- |
- |
- |
- |
||
|
10.g +A® hadrons (revision, refinement) |
Background events |
Radiation protection |
- |
- |
- |
- |
Hadron background |
|
11. e+A® e+hadrons (revision, refinement) |
Background events |
Radiation protection |
- |
- |
- |
- |
Hadron background |