AMIGA – A direct measurement of muons in Pierre Auger Observatory

1. AMIGA – A direct measurement of muons in Pierre Auger Observatory PASC Winter School Sesimbra, 19th December, 2007 P. Gonçalves, M. Pimenta, E. Santos, B. Tomé

2. Contents: • Introduction • Science motivations • AMIGA Detector • Detector performance simulations at LIP • Conclusions and prospects 2 / 16

3. Introduction • AMIGA – Auger Muons and Infill for the Ground Array • It’s an enhancement of the Pierre Auger Observatory. • It will allow to: • study at full efficiency the region of the 1017 eV and up to the 1019 eV. • Perform a direct measurement of the muonic component of the showers. • Project still in development phase. Completion in 2009. 3 / 16

4. Science Motivation • Infer about the primary cosmic ray composition. • Improve the understanding of the physical origin of the second knee and ankle. • Determine the maximum energy attainable for our Galaxy. • Provide an independent measurement of the lateral distribution profiles of the several cosmic shower components (muonic vs. electromagnetic). • Study new physics unavailable at particle acelerators. 4 / 16

5. AMIGA layout • Small area with buried muon counters and nearby Surface Detectors (SD). • The detectors are placed into triangular grids of 750 m (and 433 m) spacing. • The 750 m array covers an area of 23.5 km2 and is fully efficient for E > 3.5 x 1017 eV (42 detectors). • The 433 m array covers an area of 5.9 km2 and is fully efficient for E > 1017 eV (24 detectors) (In study). 5 / 16

6. AMIGA layout (II) • Each muon detector will be deployed at a depth of 2.5 m to 3 m near a SD. • The trigger will be given by the SD array. 6 / 16

7. The Muon Detector • Area of 30 m2. • 64 polysterene slabs: • 4 m long • 4.1 cm large and • 1 cm thick. • Have a middle groove which lodge an optical fibre. • The slabs are co-extruded with a reflective coating. • The fibres are bundled and read by a 64 channel MAPMT. • Stores signals above a given threshold in 25 ns time bins. 7 / 16

8. Specific problem to access the multihit patterns from a muon 8 / 16

9. Muon Counter Simulations • Shower simulation with CORSIKA. • A Geant4 simulation to: • track down the particles from the Earth surface until a depth of 3m where the detectors were placed. • obtain the energy deposited in the scintillators. 9 / 16

10. CORSIKA simulation • Particles from the air shower which reach the Earth surface: 1 – photons 2- positrons 3 – electrons 5 – anti-muons 6 - muons 10 / 16

11. Background • Particles from the air shower which reach the buried detector: 1 – photons 2 - positrons 3 – electrons 5 – anti-muons 6 - muons Primary particles Secondary particles 11 / 16

12. Multi-hit events • Ideally we should have a slab with deposited energy per muon… • However, there are additional signals from secondary particles created by muons. Number of slabs with deposited energy per muon Pattern of multi-hit events caused by secondary particles 12 / 16

13. A study in energy • If we look at the deposited energy we can eliminate most of the background. 13 / 16

14. A study in signal • But when we look at the same plot in electronic signal… 14 / 16

15. Detector Efficiency • Estimated efficiency of 80% to 90% • ~ 10 % of multi-hits 15 / 16

16. Conclusions and prospects • AMIGA is on the final stage of R&D. • Conclusion foreseen in 2009. • A study of the signal induced by muons was performed. • Signal contamination of ~10%. • The physics potential of AMIGA will be pursued. 16 / 16