MUons from PArametric formulas a fast Generator of

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 VLVn. T 08 - Toulon 2224 April 2008 M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 1

Atmospheric muons in a VLVn. T o Atmospheric muons represent an important tool for neutrino telescopes n n n o They can also represent a background: n n n o Pointing capability (moon shadow) Detector calibration, PMTs efficiency … 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”. M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 2

o An alternative way to a full Monte Carlo simulation n n o dedicated parameterization of the flux of single AND multiple atmospheric muons, based on a FULL MONTE CARLO simulation; see also VLVn. T 05 (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. M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 3

MUPAGE: Generator of underwater/ice muon bundles Parametric Formulas d. Nm/d. Em=F(h, q; m, R) M. Spurio - VLVn. T 08 MUPAGE (C++ code) MUPAGE: A fast muon generator Muons on the “can” 4

Parametric Formulas d. Nm/d. Em=F(h, q; m, R) Recipes: Primary CR flux + o o o M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator Interaction model and shower propagation: HEMAS Hadronic interactions: DPMJET (no prompt muons) Muon transport: MUSIC Underwater muons 5

Underwater muons: data 1 m ● 2 m ■ 3 m 4 m M. Spurio - VLVn. T 08 Multiplicity ▲ ▼ MUPAGE: A fast muon generator 6

MUPAGE (C++ code) Muons on the “can” Single Muons Impact point on the can P=P(h, q) Bundles (for each m) Impact point on the can P=P(h, q) sampling lateral spread R(h, q) w. r. t. bundle axis muon coincident with bundle axis impact point according to R sampling energy according to E(h, q) E(h, q, m, R) M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 7

User input parameters o Input: detector surface and physics information: n detector geometry, depth n Medium: water/ice n zenith angle range [0 o, 85 o] n o CAN: cylinder surface surrounding detector active volume max distance of muons from the shower axis in a bundle [100 m] n Range of muon energy [20, 105] Ge. V n Range bundle multiplicity [0, 1000] Output: n ascii files in table format n Equivalent livetime of simulated run Example: Livetime=(8644 pm 12)s M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 8

Examples and application Test on: SL 3, SL 4 2 x. Intel Xeon Quad Core, 2. 33 GHz R, H ~ 300 m, 600 m Area =1. 4 km 2 depth ~ 2. 5 km. w. e. Sample 1 For data-MC comparison • Livetime = 1 month • Em> 20 Ge. V • m=[0, 100] • 3. 6 109 bundles • 358 files (2 h livetime) • 600 GB (ascii) • CPU: 360 h M. Spurio - VLVn. T 08 Sample 2 Diffuse n flux Background • Livetime = 1 year • Em> 3000 Ge. V • 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 MUPAGE: A fast muon generator 9

Ex. 1: Data/MC Angular distribution of atmospheric muons o o See talk of Margiotta (ANTARES) See talk of Amore (NEMO-Fase 1) M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 10

Ex. 2: “Simultaneous” muon bundles in ANTARES (Sample 1) o o Atmospheric muon bundles from unrelated CRs can arrive on the detector simultaneously (Dt ≤ 4 ms) Tracks cannot be distinguished Strong dependence on detector 2 depth For ANTARES n n o 1 Max Depth = 2450 m Pre- trigger rate ~ 3 x 10 -2 Hz Post-trigger rate ~7 x 10 -4 Hz Mis-reco as “upgoing”: <1/month For AMANDA~2 -3 Hz (trigger) M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 11

Ex. 3: Muon showers in ANTARES (Sample 1) o Study H. E. muon energy loss (through e+e− pair Nucl. Instrum. Meth. A 588: 107 -110, 2008. e-Print: ar. Xiv: 0711. 3158 [astro-ph] production, bremsstrahlung, and photonuclear interactions) o o The average d. E/dx due to these effects is proportional to the muon energy. Figure: number of E. M. showers in Data and MC (mupage) M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 12

Ex. 4: Moon Shadow o o o Check the absolute orientation of the detector, i. e. the pointing Check the angular resolution A large data set is needed M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 13

Ex. 5: Background for diffuse flux AMANDA-II: Phys. Rev. D 76, 042008(2007) o MUPAGE can easily produce a large set of events for the bck evaluation M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 807 d 63 d 14

Conclusions o o Atmospheric muons are an important tool for n. T MUPAGE : n n n o Below the CR knee: n n o most of events in the n. T 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: n n o 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. HE background events maximum CR flux (no underestimate of the background) (A KM 3 n. T can give constraint on the CR flux? ) M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 15

Output: Table format Event number & bundle multiplicity - Track id For each - Coordinates of the impact point on the can surface muon in - Direction cosines (vx, vy, vz) bundle: - Energy (Ge. V) - Arrival time in ns of the ith muon (0 for the first one) - GEANT particle identification number M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 16

Horandel APP 19(2003)193 4, 75 E-13 2, 51 E-13 1, 31 E-13 6, 79 E-14 3, 47 E-14 1, 76 E-14 8, 80 E-15 4, 39 E-15 2, 19 E-15 1, 08 E-15 5, 33 E-16 2, 65 E-16 1, 31 E-16 6, 42 E-17 3, 10 E-17 1, 48 E-17 6, 81 E-18 3, 05 E-18 M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 17

Flux vs. zenith angle M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 18

Single muon energy spectrum M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 19

M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 20

M. Spurio - VLVn. T 08 MUPAGE: A fast muon generator 21