M. Spurio, G. Carminati, A. Margiotta University of Bologna and INFN

1. MUons from PArametric formulas: a fast Generator of atmospheric m for neutrino telescopes (MUPAGE) M. Spurio, G. Carminati, A. Margiotta University of Bologna and INFN VLVnT08 - Toulon 22-24 April 2008 MUPAGE: A fast muon generator

2. Atmospheric muons in a VLVnT • Atmospheric muons represent an important tool for neutrino telescopes • Pointing capability (moon shadow) • Detector calibration, PMTs efficiency • … • They can also represent a background: • wrongly reconstructed tracks as upgoing events • high energy muon bundles (diffuse flux background) • Simultaneous muons from two different primary CR • Muons in bundle seem to be particularly “dangerous”. MUPAGE: A fast muon generator

3. An alternative way to a full Monte Carlo simulation • dedicated parameterization of the flux of single AND multiple atmospheric muons, based on a FULL MONTE CARLO simulation; see also VLVnT05 (Catania). • It reproduces the underwater (and underground: MACRO) measurement of the muon flux • This parameterization is now interfaced as a PHYSICS GENERATOR for detector-dependent simulation. MUPAGE: A fast muon generator

4. MUPAGE: Generator of underwater/ice muon bundles MUPAGE (C++ code) Parametric Formulas dNm/dEm=F(h,q;m,R) Muons on the “can” MUPAGE: A fast muon generator

5. Parametric Formulas dNm/dEm=F(h,q;m,R) Recipes: Primary CR flux + • Interaction model and shower propagation: HEMAS • Hadronic interactions:DPMJET • (no prompt muons) • Muon transport: MUSIC • Underwater muons MUPAGE: A fast muon generator

6. 1m ● 2m ■ 3m ▲ 4m ▼ Underwatermuons:data Multiplicity MUPAGE: A fast muon generator

7. MUPAGE (C++ code) Muons on the “can” MUPAGE: A fast muon generator

8. User input parameters CAN: cylinder surface surrounding detector active volume • Input: detector surface and physics information: • detector geometry, depth • Medium: water/ice • zenith angle range [0o,85o] • max distance of muons from the shower axis in a bundle [100m] • Range of muon energy [20,105] GeV • Range bundle multiplicity [0,1000] • Output: • ascii files in table format • Equivalent livetime of simulated run Example: Livetime=(8644 pm 12)s MUPAGE: A fast muon generator

9. Examples and application R,H ~ 300 m, 600 m Area =1.4 km2 depth ~ 2.5 km.w.e. Test on: SL3,SL4 2xIntel Xeon Quad Core, 2.33 GHz Sample 1 For data-MC comparison Sample 2 Diffuse n flux Background • Livetime = 1 year •  Em> 3000 GeV • 6 m ranges: m=1,2,3, 4÷10, 11÷100, 101÷1000 • 0.45109 bundles • 820 files • 500 GB (ascii) • CPU: 232 h • Livetime = 1 month • Em> 20 GeV • m=[0,100] • 3.6 109 bundles • 358 files (2h livetime) • 600 GB (ascii) • CPU: 360 h MUPAGE: A fast muon generator

10. Ex. 1: Data/MC Angular distribution of atmospheric muons • See talk of Margiotta (ANTARES) • See talk of Amore (NEMO-Fase 1) MUPAGE: A fast muon generator

11. Ex.2:“Simultaneous” muon bundles in ANTARES (Sample 1) • Atmospheric muon bundles from unrelated CRs can arrive on the detector simultaneously (Dt ≤ 4 ms) • Tracks cannot be distinguished • Strong dependence on detector depth • For ANTARES • Max Depth = 2450 m • Pre- trigger rate ~ 3x10-2 Hz • Post-trigger rate ~7x10-4 Hz • Mis-reco as “upgoing”:<1/month • For AMANDA~2-3 Hz (trigger) 1 2 MUPAGE: A fast muon generator

12. Ex. 3: Muon showers in ANTARES (Sample 1) Nucl.Instrum.Meth.A588:107-110,2008. e-Print: arXiv:0711.3158 [astro-ph] • Study H.E. muon energy loss (through e+e− pair production, bremsstrahlung, and photonuclear interactions) • The average dE/dx due to these effects is proportional to the muon energy. • Figure: number of E.M. showers in Data and MC (mupage) MUPAGE: A fast muon generator

13. Ex.4: Moon Shadow • Check the absolute orientation of the detector, i.e. the pointing • Check the angular resolution • A large data set is needed MUPAGE: A fast muon generator

14. Ex.5: Background for diffuse flux AMANDA-II:Phys.Rev.D76,042008(2007) • MUPAGE can easily produce a large set of events for the bck evaluation 807 d 63 d MUPAGE: A fast muon generator

15. Conclusions • Atmospheric muons are an important tool for nT • MUPAGE : • produce the event kinematics on the can with a CPU time (107 events/h) smaller than the one needed to produce the Cherenkov light inside the can • Easy and ready to use • Widely used in the ANTARES and NEMO coll. • Below the CR knee: • most of events in the nT are from CR below the knee • the parameterization was tuned to reproduce the underwater measured flux and the underground MACRO results (multiplicity, decoherence, energy spectrum) • Above the CR knee: • HE background events • maximum CR flux (no underestimate of the background) • (A KM3nT can give constraint on the CR flux?) MUPAGE: A fast muon generator

16. Output: Table format Event number & bundle multiplicity • - Track id • - Coordinates of the impact point on the can surface • - Direction cosines (vx, vy, vz) • - Energy (GeV) • - Arrival time in ns of the ith muon (0 for the first one) • - GEANT particle identification number For each muon in bundle: MUPAGE: A fast muon generator

17. Horandel APP19(2003)193 MUPAGE: A fast muon generator

18. Flux vs. zenith angle MUPAGE: A fast muon generator

19. Single muon energy spectrum MUPAGE: A fast muon generator

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