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Carla Distefano for the NEMO Collaboration

Carla Distefano for the NEMO Collaboration. KM3NET ‘Physics and Simulation (WP2)’ Oct 24 – 25, 2006. NEMO software. The NEMO Software. The simulations performed by the NEMO Collaboration are carried out using the OPNEMO and ANTARES software.

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Carla Distefano for the NEMO Collaboration

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  1. Carla Distefanofor the NEMO Collaboration KM3NET ‘Physics and Simulation (WP2)’ Oct 24 – 25, 2006 NEMO software

  2. The NEMO Software The simulations performed by the NEMO Collaboration are carried out using the OPNEMO and ANTARES software. By the end of 2002, ANTARES software modified for a km3 detector by D. Zaborov was installed in Catania In parallel: development of simulation software OPNEMO with new track and energy reconstruction algorithms (work mainly conducted in Rome)

  3. NEMO Simulations • Using the ANTARES software several issues important for the km3 detector feasibility and performance were addressed: • Dependence on environmental parameters (depth, optical background, optical proprieties …) (see talk by R. Coniglione) • Dependence on detector structures (towers, strings, lattice ….) and geometries (distance between towers, storeys, PMT orientation …) (see talk by R. Coniglione) • Effect of directional-sensitive optical modules (see talk by K. Fratini) • - Detection of the Moon Shadow (this talk) • -Detector sensitivity for diffuse and point sources (see tomorrow talk by C.D.)

  4. The ANTARES Software Detector generator Gentra Genneu Muon Generator or Neutrino Generator gendet Muon tracks Geomety file km3 Light simulator and propagator Hits on PMs modk40 Background and electronics simulator Hits on PMs + back hits Track reconstructor reco code Reconstructed tracks I/O

  5. Simulated NEMO-km3 detector The ANTARES code gentra v1r2 has been used to generate the detector geometry file. DETECTOR LAY-OUT • Simulated Detector Geometry: • square array of 81 NEMO towers • 140 m between each tower • 18 floors for each tower • vertical distance 40 m • storey length 20 m • 4 PMTs for each storey • 5832 PMTs • Depth = 3500 m (Capo Passero site) PMT location and orientation (PMT=10”)

  6. The ANTARES Software Detector generator Gentra Genneu Muon Generator or Neutrino Generator gendet Muon tracks Geomety file km3 Light simulator and propagator Hits on PMs modk40 Background and electronics simulator Hits on PMs + back hits Track reconstructor reco code Reconstructed tracks I/O

  7. Muon tracking and light generation The ANTARES simulation package km3 v2r1 is used to simulate the passage of muons inside the detector and to generate the PMT hits The same package (codes gen and hit) has been used to generate new photon tables simulating the absorption length profile measured in the Capo Passero site by the NEMO and ANTARES Collaborations. Light scattering has been simulated according to the –partic-0.0075- model, with Lb~50 m @440 nm (see the ANTARES documentation).

  8. The ANTARES Software Detector generator Gentra Genneu Muon Generator or Neutrino Generator gendet Muon tracks Geomety file km3 Light simulator and propagator Hits on PMs modk40 Background and electronics simulator Hits on PMs + back hits Track reconstructor reco code Reconstructed tracks I/O

  9. Optical background in Capo Passero The ANTARES code modk40 v4r8 is used to add optical background hits and to simulate the electronics. ** gain randomisation (0-off, 1-on)GAIN 1 ** K40 frequency (Hz) and time offset (ns)FK40 30000 1000** raw hit production from SPE integration with 2 ARS, 25 nsec integration, 250 nsec ** dead time chosing the last number negative, the 'hit' tag can be suppressed from outputRAWH 2 25 250 -1 Optical background was measured in Capo Passero @ 3000 m depth. Data are consistent with 30 kHz background on 10”PMT at 0.5 s.p.e.

  10. The ANTARES Software Detector generator Gentra Genneu Muon Generator or Neutrino Generator gendet Muon tracks Geomety file km3 Light simulator and propagator Hits on PMs modk40 Background and electronics simulator Hits on PMs + back hits Track reconstructor reco code Reconstructed tracks I/O

  11. Main modifications by Zaborov for a km3 Some parameters in include files has been changed in order to take into account the high number of PMTs, clusters,strings… • Reco V4r3 modified by Zaborov (AartStrategy) • Causality filter respect to the hit with the highest charge • (|dt|<dr/vlight + 20ns) AND (||dt|-dr/c|<500ns) • Hit selection for prefit-> at least 3 hits with charge > 2.5 p.e.

  12. Main modifications by LNS in RECO • Recov4r4km3 (LNS version) • Same as v4r3km3 (Zaborov version) with: • Some internal conditions in AartStrategy.cc have been relaxed • If(mest_hits[0].size() <15) continue; modified into • If(mest_hits[0].size() <6) continue; • If(ndof<5) continue; modified into • If(ndof<1) continue; • Hit selection for prefit-> at least 3 hits with charge higher than 2.5 p.e. or in concidence (at least two hits with Dt<20ns in a LCM) • Modifications for gcc3.X • Recov4r5km3 • Same as v4r4km3 with: • Hit selection for prefit-> at least 3 hits with charge higher than 2.5 p.e. or in concidence (at least three hits with Dt<20ns+dr/vlight in a LCM)

  13. Comparison between different RECO versions Nemo detector (5832 PMT 81 Towers 140m distant) 20kHz background Median vs E Aeff vs E q n-m vs Em v4r3km3 (Zaborov Version) v4r4km3 (LNS version with coinc) v4r4km3 (LNS version with coinc)+quality cuts

  14. Main modification by LNS log10Em(GeV) Recov4r6km3: Starting from v4r6 ANTARES version we applied the same modifications of v4r4km3 version Documentation for v4r6 improvements in antares.in2p3.fr/users/stolar/internal/recoco v4r6km3 v4r4km3 (LNS version with coinc) Nemo detector (5832 PMT 81 Towers 140m distant) 35kHz background reconstruction Aeff(v4r6km3)/Aeff(v4r4km3) ratio quality cuts

  15. Detection of the Moon shadow

  16. Detection of the Moon shadow The Moon is opaque to Cosmic Rays and thus causes a deficit in the CRs and therefore in the atmospheric muon flux reaching the detector. • The detection of the deficit (TheMoon Shadow) and of its position in the sky provides a measurement of: • the detector angular resolution; • the detector absolute orientation. This approach has been already adopted in several cosmic ray detectors as MACRO, SOUDAN, MILAGRO….

  17. Simulation of the Moon shadow: OkadaMoon code • The code OkadaMoon (C++ gcc3.X): • calculates the Moon position in the sky at a given time and transforms the Moon astronomical coordinates in the detector frame; • generates the muons in a circular window around the Moon position with radius R=10°; • simulates the lack of atmospheric muons in correspondence to the Moon disk; • weights the muons to the Okada parameterization but any other parameterizations could be easily implemented. L. Ferrari, Diploma Thesis Moon below the Horizon

  18. Observation of the Moon shadow Moon rest frame Moon disk (simulation normalized to 1 year of data taking) Event density Event Selection*: Nhitmin= 20 cut= -7.6 S1year=5.5 k= 659 ± 8 deg-2 = 0.19 ± 0.02 deg Minimum time needed for observation: * Events selection criteria will be discussed tomorrow.

  19. Estimate of the detector angular resolution Event Selection: Nhitmin= 20 cut= -7.6 S1year=5.5 estimated angular resolution: = 0.19 ± 0.02 deg median angle of selected events: Reconstructed Selected = 0.22 deg

  20. Study of the telescope absolute pointing Moon rest frame Moon rest frame Moon rest frame We introduce a rotation  around the Z axis to simulate a possible systematic error in the absolute azimuthal orientation of tracks. (1 year of data taking) • for   0.2 (expected accuracy), the shadow is still observable at the Moon position; • for   0.2 (pessimistic case), systematic errors could be corrected; • the presence of possible systematic errors in the absolute zenithal orientation is still under analysis.

  21. Moon shadow: CORSIKA-Music muon generation Study of the effect of multi-muons events in the detection of the Moon Shadow  a full simulation of atmospheric muons. • Corsika (http://www-ik.fzk.de/corsika) has been modified to simulate the Moon Shadow: • We implemented the calculation of Moon position in the sky; • We restricted the generation of primaries in a circular window around the Moon position with radius R=10°; • The lack of primaries in correspondence to the Moon disk is simulated; • The produced muons are propagated up to the detector using the MUSIC code (Antonioli et al, 1997).

  22. CORSIKA input • Corsika version: CORSIKA version 6.2 (http://www-ik.fzk.de/corsika) + Sheffield modifications to get output files in the ANTARES format + modifications to simulate the Moon Shadow • Hadronic interaction model -> QGSJET and GHEISHA • “curved” version for horizontal showers and “flat” for vertical showers Simulation input • Primary ions -> p, He, N, Mg, Fe • Primary energy -> 10-105 TeV/nucleon • Primary zenith angles –> 0° 85° • Energy threshold for muons at sea level -> 0.5 TeV for ions between 0° and 60° and 1 TeV for ions between 60° and 85° • Slope primary spectrum  E-2 • Isotropic angular primary distribution

  23. Cosmic Ray Primary Spectrum The generated events are weighed to the Cosmic Ray Primary Spectra provided by J.R. Horandel Astr. Phys. 19 (2003) 193. Present statistics Total numbers of Generated Primaries: 2.7 109 Muons reaching the detector can: 1.9 108 Reconstructed Events: 3.4 106

  24. CORSIKA-Music generation: preliminary results Events statistics too poor: preliminary results PRELIMINARY Okada Corsika + Music Event Selection: Nhitmin= 20 cut= -7.6 Fit results: = 0.19 ± 0.02 deg k= 659 ± 8 deg-2 Event Selection: Nhitmin= 26 cut= -7.1 Fit results: = 0.26 ± 0.04 deg k= 230 ± 2 deg-2

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