Carla Distefano for the NEMO Collaboration

C.Distefano KM3NET ‘Physics and Simulation (WP2)’ Oct 24 – 25, 2006

LNS

NEMO software

Carla Distefanofor the NEMO Collaboration

KM3NET ‘Physics and Simulation (WP2)’ Oct 24 – 25, 2006


LNS

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)

The NEMO Software


LNS

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.)

NEMO Simulations


LNSThe ANTARES Software

Detector generator

gendet

Geomety file

GentraGenneu

Muon tracks

km3

modk40

Hits on PMs

Hits on PMs + back hits

reco

Reconstructed tracks

Muon Generatoror

Neutrino Generator

Light simulator and propagator

Track reconstructor

Background and electronicssimulator

code

I/O


LNSSimulated NEMO-km3 detector

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”)

DETECTOR LAY-OUTThe ANTARES code gentra v1r2

has been used to generate the

detector geometry file.



Detector generator

gendet

Geomety file

GentraGenneu

Muon tracks

km3

modk40

Hits on PMs


reco


Muon Generatoror

Neutrino Generator


Track reconstructor


code

I/O


LNSMuon tracking and light generation

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).

The ANTARES simulation package km3 v2r1 is used to simulate the

passage of muons inside the detector and to generate the PMT hits



Detector generator

gendet

Geomety file

GentraGenneu

Muon tracks

km3

modk40

Hits on PMs


reco


Muon Generatoror

Neutrino Generator


Track reconstructor


code

I/O


LNS

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.

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 output

RAWH 2 25 250 -1



Detector generator

gendet

Geomety file

GentraGenneu

Muon tracks

km3

modk40

Hits on PMs


reco


Muon Generatoror

Neutrino Generator


Track reconstructor


code

I/O


LNSMain modifications by Zaborov for a km3

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.

Some parameters in include files has been changed in order to take into account the high number of PMTs, clusters,strings…


LNSMain modifications by LNS in RECO

Recov4r4km3 (LNS version)Same as v4r3km3 (Zaborov version) with:• Some internal conditions in AartStrategy.cc have been relaxedIf(mest_hits[0].size() <15) continue; modified intoIf(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

Recov4r5km3Same 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)


LNSComparison between different RECO versions

Nemo detector(5832 PMT81 Towers 140m distant)

20kHz background

Median vs E

Aeff vs E

vs Ev4r3km3 (Zaborov Version)

v4r4km3 (LNS version with coinc)

v4r4km3 (LNS version with coinc)+quality cuts


LNS

log10E(GeV)

Main modification by LNS

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

v4r6km3v4r4km3 (LNS version with coinc)Nemo detector(5832 PMT 81 Towers 140m distant)35kHz background

ratio

Aeff(v4r6km3)/Aeff(v4r4km3)

quality cuts

reconstruction


LNS

Detection of the Moon shadow


LNSDetection of the Moon shadow

The detection of the deficit (The Moon Shadow) and of its

position in the sky provides a measurement of:

• the detector angular resolution;

• the detector absolute orientation.

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.

This approach has been already adopted in several cosmic ray

detectors as MACRO, SOUDAN, MILAGRO….


LNSSimulation 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


LNSObservation of the Moon shadow

(simulation normalized to 1 year of data taking)

2

2

2

D

2

2moon

2 e2

1kdD

dN k= 659 ± 8 deg-2

= 0.19 ± 0.02 deg

Event Selection*:

Nhitmin= 20

cut= -7.6

S1year=5.5

days 100~)3(2

minminmin

S

StSt gen

Minimum time needed for observation:

Moon rest frame

Moon disk

Event density

* Events selection criteria will be discussed tomorrow.


LNSEstimate of the detector angular resolution

= 0.19 ± 0.02 deg

Event Selection:

Nhitmin= 20

cut= -7.6

S1year=5.5

median angle of selected events:

estimated angular resolution:

= 0.22 deg

Reconstructed

Selected


LNS

0.2

0.4

0.6

Study of the telescope absolute pointing

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.

Moon rest frame Moon rest frame

Moon rest frame


LNSMoon shadow: CORSIKA-Music muon generation

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).

Study of the effect of multi-muons events in the detection of the

Moon Shadow a full simulation of atmospheric muons.


LNS

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

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


LNSCosmic Ray Primary Spectrum

0 00 0

0

1ˆ

c z

c c

z

HorandelZ

Z

z

EdE E

dE E

The generated events are weighed to the Cosmic Ray Primary Spectra

provided by J.R. Horandel Astr. Phys. 19 (2003) 193.

Total numbers of

Generated Primaries: 2.7 109

Muons reachingthe detector can: 1.9 108

Reconstructed Events: 3.4 106

Present statistics


LNSCORSIKA-Music generation: preliminary results

Corsika + Music

Events statistics too poor: preliminary results

Okada

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

PRELIMINARY

Documents

Carla Distefano for the NEMO Collaboration