Monte Carlo codes: MUSIC, MUSUN, SOURCES

1. Monte Carlo codes: MUSIC, MUSUN, SOURCES Vitaly Kudryavtsev Department of Physics and Astronomy University of Sheffield v.kudryavtsev@sheffield.ac.uk Vitaly Kudryavtsev

2. MUSIC • MUon SImulation Code - a code to transport muons through large thickness of matter (P. Antonioli et al., Astroparticle Physics, 7, 357 (1997); V. A. Kudryavtsev et al., Phys. Lett. B, 471, 251 (1999): • Fortran-77, a set of subroutines; two subroutines should be called from the user’s ‘main’ programme: • initialization: initialiaze_music • propagation: muon_transport (a loop should be arranged in the main programme to transport many muons - only one initialization is required) • Inputs: muon coordinates, direction, energy, distance to transport muons; • Outputs: final muon coordinates, direction, energy; • A specific version for each type of the rock should be generated by me; • All processes are treated stochastically if an energy transfer to secondary particles exceeds 10-3E. • Uses most recent and accurate cross-sections of muon interactions with matter. • 3D code: takes into account muon deflection due to multiple Coulomb scattering and stochastic processes; Vitaly Kudryavtsev

3. MUSIC • Simple and fast (a few seconds to transport 1000 muons to 1 km w. e.); • Accurate - agrees with GEANT4 and FLUKA (only a few tests have been done, however); if a difference is found, I would trust MUSIC. • Tested against experimental data (V. A. Kudryavtsev et al., Phys. Lett. B, 494, 175 (2000); V. A. Kudryavtsev et al. Nuclear Instrum. and Meth. in Phys. Res. A, 505, 688 (2003); also references therein). • Used by many groups across the world (LVD, MACRO, SNO, KamLAND, ANTARES etc.) Vitaly Kudryavtsev

4. MUSIC vs experimental data MUSIC vs LVD data, from M. Aglietta et al. (LVD Collaboration), Phys. Rev. D, 58, 092005 (1998). MUSIC vs LVD data, from M. Aglietta et al. (LVD Collaboration), Phys. Rev. D, 60, 112001 (1999). Vitaly Kudryavtsev

5. MUSIC vs experimental data C. Waltham (SNO Collaboration). Proc. ICRC 2001, p. 991. Vitaly Kudryavtsev

6. MUSIC vs experimental data Filled circles - AMANDA Open circles - Baikal From V. A. Kudryavtsev et al., Phys. Lett. B, 494, 175 (2000). Vitaly Kudryavtsev

7. MUSIC vs experimental data A. Tang (Chinese University of Hong Kong), personal communication Vitaly Kudryavtsev

8. MUSUN • You may not need to propagate muons each time you want to simulate neutrons. Muon propagation can be done once and muon energy spectra and angular distributions stored to be used in future. • MUon Simulations UNderground - a code to generate muons underground (V. A. Kudryavtsev et al., Phys. Lett. B, 494, 175 (2000); V. A. Kudryavtsev et al. Nuclear Instrum. and Meth. in Phys. Res. A, 505, 688 (2003)). The code uses the results from MUSIC: • Fortran-77, a set of subroutines; two subroutines should be called from the user’s ‘main’ programme: • initialization: initialiaze • sampling muons: sampling (a loop should be arranged in the main programme to sample many muons - only one initialization is required) • Inputs: vertical depth (simple version of MUSUN assumes flat surface above the lab; more complex mountain profile is also possible on request - LNGS version exists), range of energies, angles; • Outputs: muon direction, energy (also sampling on a surface of a parallelepiped is possible - muon coordinates); Vitaly Kudryavtsev

9. SOURCES • Neutron production via spontaneous fission and (,n) reactions: SOURCES-4A (Wilson et al. SOURCES4A, Technical Report LA-13639-MS, Los Alamos, 1999) - neutron flux and energy spectrum from U/Th; the latest version SOURCES-4C. • Features: • Input - radioactive isotope concentrations, material; • Output - neutron energy spectra from each radioactive isotope in each material; • In addition to thick target neutron yields also interface problems, alpha-particle beams etc. • Watt spectrum for spontaneous fission; • Measured or calculated (GNASH) (,n) cross-sections (library - can be modified); • Transition probabilities to the excited states (nuclide level branching ratios) - mainly GNASH calculations (library - can be modified); • Stopping power for alphas. Vitaly Kudryavtsev

10. SOURCES-4A • Problems: • Alphas below 6.5 MeV only; • Some cross-sections are missing (energy threshold for these reactions is higher than 6.5 MeV); • Cross-sections needed updating; • Transition probabilities to the excited states are present up to 6.5 MeV only. • Modifications to SOURCES: • 6.5 MeV upper limit removed (now 10 MeV limit for alphas); • Some cross-sections already present in the code library extended to higher energies using available experimental data; • Some cross-section updated according to recent experimental results (Na); • New cross-sections added (35Cl, 54Fe, Cu); • Probability of transitions to the excited states at high energies of alphas are as at 6.5 MeV (this overestimates the neutron energy); • For new cross-sections - all transitions to the ground state only. Vitaly Kudryavtsev

11. SOURCES-4A • Cross-sections on heavy (Fe) targets - too few measurements: for example Fe - only 54Fe cross-section has been measured. • Calculated cross-sections should be used; where to find them? • GNASH-FKK code (www.nea.fr/abs/html/psr-0125.html)? • Recipe can also be found in: Estimation of Unknown Excitation Functions and Thick Target Yields for p, d, 3He and alpha Reactions. Series: Landolt-Börnstein: Numerical Data and Functional Relationships in Science and Technology - New Series; Group 1: Elementary Particles, Nuclei and Atoms Vol. 5: Q-Values and Excitation Functions of Nuclear Reactions. Part c; Keller, K.A., Lange, J., Münzel, H. 1974, VI, 257 pp. 506 figs., Hardcover, ISBN: 3-540-06723-X (Springer). • Rachid Lemrani (Saclay) found a code EMPIRE, which calculates the cross-sections. • Note that Coulomb barrier suppress significantly the cross-sections for high-Z elements even if the energy threshold (calculated from the Q-value of the reaction is small); for Fe-Cu the Coulomb barrier is about 7.0-7.2 MeV. • Transition probabilities are absent for E > 6.5 MeV and for all heavy targets. • Accuracy: 50-70% for Fe and stainless steel if compared to the Heaton’s estimates. • Updated library of the cross-sections and transition probabilities will be kept in the code repository. Please, put your updates there marking clearly the date and name and summary of the update!!! Vitaly Kudryavtsev

12. Neutron production spectra • Neutron production spectrum in NaCl (from modified SOURCES-4A): 60 ppb U, 300 ppb Th - mainly (,n). • Neutron production rate in NaCl - 1.0510-7 cm-3 s-1 agrees with other calculations. • Major problem: neutron energy spectrum in the laboratory (after propagation) is softer than measured at Modane (Chazal et al. Astropart. Phys. 9 (1998) 163; revised recently - Gerbier et al. TAUP2003), Gran Sasso (Arneodo et al. Nuovo Cimento A112 (1999) 819) and CPL (Korea) (Kim et al. Astropart. Phys. 20 (2004) 549) and also softer than other simulations. Vitaly Kudryavtsev

13. Neutron production spectra 5.5 MeV alphas - Mg (natural) 5.0 MeV alphas - Al2O3 Energy spectrum of neutrons from 5.0 MeV alphas incident on aluminum oxide slab (left) and from 5.5 MeV alphas incident on magnesium slab (right) as calculated by SOURCES 4A (from SOURCES manual) and compared to measured data (Jacobs and Liskien, Annals of Nuclear Energy, 10 (1983) 541). Vitaly Kudryavtsev