1. MUPAGE: A fast muon generator
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 April 2008
M. Spurio - VLVnT08
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”.
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

3. MUPAGE: A fast muon generator
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.
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

4. MUPAGE: Generator of underwater/ice muon bundles
(C++ code)
Parametric Formulas
dNm/dEm=F(h,q;m,R)
Muons
on the “can”
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

5. Recipes: Primary CR flux +
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
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

6. Underwater muons:data
Multiplicity
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

7. MUPAGE: A fast muon generator
(C++ code)
Muons
on the “can”
Single Muons
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 E(h,q)
sampling energy according to E(h,q,m,R)
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

8. User input parameters Input: detector surface and physics information:
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
M. Spurio - VLVnT08
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 month
Em> 20 GeV
m=[0,100]
3.6 109 bundles
358 files (2h livetime)
600 GB (ascii)
CPU: 360 h
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
M. Spurio - VLVnT08
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)
M. Spurio - VLVnT08
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
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

12. Ex. 3: Muon showers in ANTARES (Sample 1)
Nucl.Instrum.Meth.A588: , e-Print: arXiv:  [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)
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

13. MUPAGE: A fast muon generator
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
M. Spurio - VLVnT08
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
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

15. MUPAGE: A fast muon generator
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?)
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

16. MUPAGE: A fast muon generator
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:
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

17. MUPAGE: A fast muon generator
Horandel
APP19(2003)193
4,75E-13
2,51E-13
1,31E-13
6,79E-14
3,47E-14
1,76E-14
8,80E-15
4,39E-15
2,19E-15
1,08E-15
5,33E-16
2,65E-16
1,31E-16
6,42E-17
3,10E-17
1,48E-17
6,81E-18
3,05E-18
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

18. MUPAGE: A fast muon generator
Flux vs. zenith angle
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

19. Single muon energy spectrum
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

20. MUPAGE: A fast muon generator
M. Spurio - VLVnT08
MUPAGE: A fast muon generator

21. MUPAGE: A fast muon generator
M. Spurio - VLVnT08
MUPAGE: A fast muon generator