1. FLUKA as a new high energy cosmic ray generator G. Battistoni 2, A. Margiotta 1, S. Muraro 2, M. Sioli 1 University and INFN of 1) Bologna and 2) Milano for the FLUKA Collaboration Very Large Volume Telescope Workshop 2009, Athens

2. Outline Main features of FLUKA Motivations Code structure Geometry setup First results Conclusions A. Margiotta, Athens 2009 2

3. 3 FLUKA - Interaction and Transport Monte Carlo code FLUKA is a general purpose tool for calculations of particle transport and interactions with matter, covering an extended range of applications (Shielding, Radiobiology, High energy physics, Cosmic Ray physics, Nuclear and reactor physics). Built and maintained with the aim of including the best possible physical models in terms of completeness and precision. Continuously benchmarked with a wide set of experimental data from well controlled accelerator experiments. More than 2000 users all over the world Physics models (e.g. hadronic interaction models) built according to a theoretical microscopic point of view (no parameterizations) => High predictivity also in regions where experimental data are not available Cosmic Ray physics with FLUKA “triggered” by:  HEP physics (e.g. atmospheric neutrino flux calculations)  radioprotection in space FLUKA authors: A. Fasso 1, A. Ferrari 2, J. Ranft 3, P.R. Sala 4 1 SLAC Stanford, 2 CERN, 3 Siegen University, 4 INFN Milan http://www.fluka.org

5. A. Margiotta, Athens 2009 5 Motivations extension of the existing FLUKA cosmic-ray library to high energy region (primaries at the knee of the spectrum)  use in underground and underwater sites use of a unique framework with high quality physics models (FLUKA) for the whole simulation, from primary interaction in the upper atmosphere to the detector level (and through the detector itself, in principle) creation of a prediction data set (muons and muon- related secondaries) for some topic sites: presently LNGS, ANTARES and Capo Passero sites

6. A. Margiotta, Athens 2009 6 Code structure Geometry description Generation of the kinematics (i.e. the source particles) ↔ primary cosmic ray composition model 2 hadronic interaction models can be used:  DPMJET-II.53  FLUKA Output file on an event by event basis – interface between standard and user output (presently ASCII “ANTARES-like” and root output)  information on primary cosmic ray generating the shower  for each particle reaching the detector level, stores all the relevant parameters (particle ID, 3-momenta, vertex coordinates, momentum in atmosphere, information on the parent mesons etc) N.B. With FLUKA, shower generation, transport in the sea/rock, and particle folding in the detector is performed inside the same framework

7. Geometry setup (e.g. LNGS site)  100 atmospheric shells  1 spherical body for the mountain, whose radius is dynamically changed, according to primary direction and to the Gran Sasso mountain map (direction  rock depth)  1 rock box surrounding the experimental underground halls, where muon-induced secondary are activated (e.m. and hadron showers from photo-nuclear interactions)  Underground halls: one box + one semi-cylinder  Possibility to include simultaneously more than one experimental Hall to study large transverse momentum secondaries with detector coincidences) A. Margiotta, Athens 2009

8. Earth Geometry for underground sites Spherical mountain whose radius is dynamically changed using a detailed topographical map Atmosphere Primary injection point R d R0R0 z A. Margiotta, Athens 2009

9. Geometry setup: LNGS halls LNGS underground halls External (rock) volume to propagate all particles down to 100 MeV  muon-produced secondaries A. Margiotta, Athens 2009

10. Some results from the simulation For a given site (e.g. Hall C at LNGS), possibility to parameterize all particle components reaching the underground level muons photons electrons log10 E kin (GeV) events/year Vertexes of particles entering the Hall C at LNGS A. Margiotta, Athens 2009

11. 11 Geometry setup (underwater) Underwater case (e.g. ANTARES/KM3NeT)  Earth ≡ sphere of perfectly absorbing medium  sea ≡ spherical shell of water  atmosphere ≡ 100 concentric atmospheric shells  Can ≡ virtual cylindrical surface bounding the active volume (instrumented volume + 2-3 abs )

12. M. Sioli, Blois 2008 12 Atmosphere Earth Sea Can  Geometry for underwater sites

13. A. Margiotta, Athens 2009 13 Primary sampling Primary energy spectrum has the form: Possibility to choose among different spectra (now MACRO- fit is implemented) Sampling done re-adapting some HEMAS routines E E cut  ~2.7 ÷ 3 E cut ~3000 TeV

14. A. Margiotta, Athens 2009 14 Technical issues (biasing)–underwater case ■ initialize minimum energy for primary cosmic rays: lower bound evaluated according to muon survival probabilities  2* E thr  recompute “on the fly” energy thresholds: muon survival probabilities for various depths in sea water and various muon energies at surface, evaluated with MUSIC (V. Kudryatsev) muon energy at sea level  survival probability < 10 -5 function obtained with a fit  multiplied by 0.9 underground case : thresholds are evaluated according to the rock map ■ kill in atmosphere all particles with energy lower than this threshold. ■ only muons with E> 20/100 GeV at the can are stored. ■ CPU time request optimized : FULL MC !!!

15. A. Margiotta, Athens 2009 15 Some results from the simulation -1 Vertexes of particles entering a KM3 detector can at 3500 m under sea level Sea bottom = 3500 m Can radius = 1000 m height = 1000 m primaries sampled on a circle with R= 2000 m perpendicular to their direction and centered in the origin of the can muons propagated from the sea level to their geometrical intercept with the detector surface

16. A. Margiotta, Athens 2009 16 Some results from the simulation -2 multiplicity Log (energy/TeV) primary energy multiplicity @ can meters muon decoherence

17. A. Margiotta, Athens 2009 17 Conclusions FLUKA can be used as a new high energy cosmic ray generator for underground and underwater physics. Package developed using LNGS and neutrino telescope sites as examples. It cannot substitute MUPAGE for fast simulation of atmospheric muon background. Unique framework  significant simplification of the FULL MC chain Next steps:  Introduce other primary cosmic ray composition models  Extensive studies with FLUKA hadronic model in progress: very encouraging results!  Some space for code optimization.  Sea level sampling Further information: send me an e-mail.

19. spare slides

20. A. Margiotta, Athens 2009 20   (ordinary) meson decay: dN  /d cos  ~ 1/ cos  Primary C.R. proton/nucleus: A,E,isotropic   hadronic interaction: multiparticle production  (A,E), dN/dx(A,E)  extensive air shower  short-lifetime meson production and prompt decay (e.g. charmed mesons) Isotropic ang. distr. detection: N  (A,E), dN  /dr transverse size of bundle  P t (A,E) (TeV) muon propagation in water : radiative processes and fluctuations Multi-TeV muon transport Primary p, He,..., Fe nuclei with lab. energy from 1 TeV/nucleon up to >10000 TeV/nucleon The physics of CR TeV muons

21. The FLUKA hadronic interaction models (for a detailed study of their validity for CR studies :hep-ph/0612075 and 0711.2044) Hadron-Hadron Elastic,exchange Phase shifts data, eikonal P<3-5GeV/c Resonance prod and decay low E π,K Special High Energy DPM hadronization Hadron-NucleusNucleus-Nucleus E < 5 GeV PEANUT Sophisticated GINC Preequilibrium Coalescence High Energy Glauber-Gribov multiple interaction s Coarser GINC Coalescence E< 0.1GeV/u BME Complete fusion+ peripheral 0.1< E< 5 GeV/u rQMD-2.4 modified new QMD E> 5 GeV/u DPMJET DPM+ Glauber+ GINC Evaporation/Fission/Fermi break-up  deexcitation > 5 GeV Elab DPM: soft physics based on (multi)Pomeron exchange DPMJET: soft physics of DPM plus 2+2 processes from pQCD Relevant for HE C.R. physics

22. 22 MINOS Charge Ratio at the Surface = 1.374 ± 0.004 (stat.) (sys.) Phys. Rev. D 76, 052003 (2007) R FLUKA μ + /μ − = 1.333 ± 0.007 Agreement between FLUKA simulation and MINOS data within 3%Agreement between FLUKA simulation and MINOS data within 3% Discrepancy systematically remarkableDiscrepancy systematically remarkable No dependence on muon momentum in the atmosphere in the range consideredNo dependence on muon momentum in the atmosphere in the range considered L3 + COSMIC ( (hep-ex/0408114). R FLUKA = 1.29  0.05 R exp = 1.285  0.003 (stat.) ± 0.019 (sys.)