carla distefano for the nemo collaboration
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Carla Distefano for the NEMO Collaboration. THE MULTI-MESSENGER APPROACH TO UNIDENTIFIED GAMMA-RAY SOURCES Barcelona July 4 – 7, 2006. LNS. Detection of point-like neutrino sources with the NEMO-km 3 telescope. Outline of the talk. The NEMO project - PowerPoint PPT PresentationTRANSCRIPT
C.Distefano Barcelona July 4 – 7, 2006
LNS
Detection of point-like neutrino sources with the NEMO-km3 telescope
THE MULTI-MESSENGER APPROACH TO UNIDENTIFIED GAMMA-RAY SOURCESBarcelona July 4 – 7, 2006
Carla Distefanofor the NEMO Collaboration LNS
C.Distefano Barcelona July 4 – 7, 2006
LNSOutline of the talk
• The NEMO project
• Simulation of the km3 neutrino telescope performance
• Pointing accuracy
• Sensitivity to point-like neutrino sources
• Physics cases
• Microquasar LS 5039
• SNR RXJ1713.7-3946
• The NEMO project
• Simulation of the km3 neutrino telescope performance
• Pointing accuracy
• Sensitivity to point-like neutrino sources
• Physics cases
• Microquasar LS 5039
• SNR RXJ1713.7-3946
C.Distefano Barcelona July 4 – 7, 2006
LNSNeutrino telescope projectsBAIKAL, AMANDA: taking dataNESTOR, ANTARES, NEMO R&D: under constructionICECUBE: completion expected in 2010KM3NET – Mediterranean: EU Design Study 2006-2008
AMANDAICECUBE
BAIKAL
ANTARES
2400 m
NESTOR
3800 m
NEMO
3500 m
• In order to obtain the whole sky coverage 2 telescopes must be built
• The Galactic Centre is observable only from the Northern Hemisphere
Small scale detectors and demonstrators
km3 scale telescopes
C.Distefano Barcelona July 4 – 7, 2006
LNSNEMO
The NEMO Collaboration is dedicating a special effort in:
• search, characterization and monitoring of a deep sea site adequate
for the installation of the Mediterranean km3;
• development of technologies for the km3 (technical solutions chosen
by small scale demonstrators are not directly scalable to a km3).
• test of prototypes in deep sea: NEMO Phase-1 in Catania
• realization of a marine infrastructure for the km3: NEMO Phase-2 in
Capo Passero
The NEMO Collaboration is dedicating a special effort in:
• search, characterization and monitoring of a deep sea site adequate
for the installation of the Mediterranean km3;
• development of technologies for the km3 (technical solutions chosen
by small scale demonstrators are not directly scalable to a km3).
• test of prototypes in deep sea: NEMO Phase-1 in Catania
• realization of a marine infrastructure for the km3: NEMO Phase-2 in
Capo Passero
C.Distefano Barcelona July 4 – 7, 2006
LNSThe Capo Passero deep sea site
• The average depth is 3500 m, the distance from shore is 100 km.
• It is located in a wide abyssal plateau far from shelf breaks and geologically stable.
• Optical properties of deep sea water are the best measured among investigated sites (absorption length close to optically pure water astro-ph\0603701).
• Optical background is low (~30 kHz on 10’’ PMT at 0.5 s.p.e. threshold) and mainly due to 40K decay since the bioluminescence activity is extremely low.
• Underwater currents are very low (2.5 cm/s) and stable.
After eight years of activity in seeking and monitoring abyssal sites in the
Mediterranean Sea the NEMO Collaboration has selected a site close to Capo
Passero, Sicily (36° 16’ N, 16° 06’ E) .
The site has been proposed to ApPEC on January 2003 as candidate site for the
installation of the km3.
C.Distefano Barcelona July 4 – 7, 2006
LNSSeawater optical properties in Capo Passero
Average values 2850÷3250 m
• Light Absorption and Attenuation lengths measured in Capo Passero don’t show seasonal dependence.
• Absorption lengths measured in Capo Passero are close to the optically pure sea water data.
C.Distefano Barcelona July 4 – 7, 2006
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.
(mainly 40K decay, very few bioluminescence).
Optical data are consistent with biological measurements:
No luminescent bacteria have been observed in Capo Passero
below 2500 m
Optical background in Capo Passero
40K
Baseline rate~ 30 kHz
15
20
25
30
35
0 7 14 21 28 35 42 49
Co
un
tin
g r
ates
(kH
z)
0.0%
0.5%
1.0%
1.5%
2.0% Tim
e abo
ve 200 kHz
Days
30 kHz
C.Distefano Barcelona July 4 – 7, 2006
LNSFeasibility study for the km3 telescope
• 1 main Junction Box
• 8 10 secondary Junction Boxes
• 60 80 towers
• 140 200 m between each tower
• 16 18 floors for each tower
• 64 72 PMT for each tower
• 4000 6000 PMTs
Parameters to optimize: distances, number of towers, tower height, …
Electro-optical cable from shore
Primary Junction Box
Secondary Junction Boxes
towers
electro-optical cables network
Detector architecture issues
• Reduce the number of structures to
reduce the number of underwater
connections and allow operation with
a ROV;
• Detector modularity.
C.Distefano Barcelona July 4 – 7, 2006
LNSNEMO Phase-1
300
m
Mini-Tower compacted
Mini-Tower unfurled
15 m
Deployment of JB and mini-tower Sept. 2006
Junction Box
NEMO mini-tower(4 floors, 16 OMs)
TSS FrameDeployedJanuary 2005
• Realization of the key elements of
the km3
• Validation of the technological
solutions proposed
• Installation at 2000 m offshore
Catania (LNS Underwater Test Site)
C.Distefano Barcelona July 4 – 7, 2006
LNSSimulated NEMO-km3 detector
20 m
40 m
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
- optical background 30 kHz
- optical properties of the
NEMO site of Capo Passero
- ANTARES s/w tools used
PMT location and orientation
C.Distefano Barcelona July 4 – 7, 2006
LNSDetector pointing accuracy: observation of the Moon shadow
Moon rest frame
Moon disk
Event density
(1 year of data
taking)
Detection of the deficit (The Moon
Shadow) provides a measurement of:
• the detector angular resolution;
• the detector absolute orientation.
The Moon absorbs Cosmic Rays a lack of atmospheric muons is expected.
2659 8deg
0.19 0.02deg
k
2
222 2
12moon
dNk e
d
100 days needed to observe a 3 effect
C.Distefano Barcelona July 4 – 7, 2006
LNSDetector sensitivity to muon neutrino fluxes
We compute the detector sensitivity to muon neutrinos from point-like sources:
minimum muon neutrino flux detectable with respect to the background.
90% c.l.
Calculation of the sensitivity spectrum:
- we simulate the expected background b (atm. and ) and we estimate the 90% c.l.
sensitivity in counts <90(b)> (Feldman & Cousins);
- we simulate a reference source spectrum
(d/d)0 which produces ns counts;
- we calculate the sensitivity spectrum as:
- we apply the event selection in order to minimize the sensitivity.
Feldman & Cousins define the sensitivity as the average upper limits for no true signal. It is the maximum number of events that can be excluded at a given confidence level.
0s
90
90dd
n)b(
dd
C.Distefano Barcelona July 4 – 7, 2006
LNSAtmospheric muon and neutrino background
Atmospheric neutrinos:
• upward tracks are good neutrino candidates;
• event direction and energy criteria can be used to
discriminate background from astrophysical signals.
Atmospheric muons:
• down-going muons are several orders of magnitude
more than neutrino-induced muons;
• up-going background events are due to mis-
reconstructed (fake) tracks;
• quality cuts applied to reject mis-reconstructed
tracks.
ANTARES
C.Distefano Barcelona July 4 – 7, 2006
LNSEvent simulation
exp. events/year
1 7.1·107
1.5 5.7·104
2 163.5
2.5 1.29
Atm. (1°) 1.06
Atm. (1°) 7.9·103
NBartol+RQPM 4·104 expected events/year
NOkada 4·108 expected events/year
Atmospheric neutrinos are generated according to the Bartol + RQPM (highest prediction) flux
Atmospheric muons are generated according to the Okada parameterization, taking into
account the depth of the NEMO Capo Passero site (3500 m) and the flux variation inside the
detector sensitive height (~ 900 m):
Astrophysical neutrinos: source declination: = - 60˚
- 24 hours of diurnal visibility
- large up-going angular range covered by the
source (24 – 84)
Neutrino energy range: 102 - 108 GeV
s cmGeV /10 2GeV,
7
0
dd
C.Distefano Barcelona July 4 – 7, 2006
LNSSensitivity for a point-like ( = -60˚) neutrino source (3 years)
Search bin:
NEMO 0.5˚
IceCube 1˚
=2
IceCube sensitivity values from
Ahrens et al. Astrop. Phys. 20 (2004) 507
Neutrino energy range:
102 - 108 GeV
(d/d)90 expressed
in GeV-1/cm2 s
C.Distefano Barcelona July 4 – 7, 2006
LNSSensitivity for a point-like ( = -60˚) neutrino source (3 years)
Detector sensitivity as a function of
the high energy neutrino cut-off max
Hard spectrum sources: the detector
sensitivity is better and gets better if
the spectrum extends to VHE.
Soft spectrum sources: the detector
sensitivity doesn’t vary much with max.
C.Distefano Barcelona July 4 – 7, 2006
LNSSensitivity for a point-like neutrino source (3 years)
=2
Diurnal visibility:
Time per day spent by the source
below the Astronomical Horizon
with respect to the latitude of the
Capo Passero site.
The detector sensitivity gets worse
with increasing declination due to the
decrease of the diurnal visibility.
Equatorial coordinates
Detector sensitivity as a function of the source declination
Average search bin: <rbin> = 0.5°
C.Distefano CRIS 2006 – Catania May 29 – June 2
LNSMicroquasar: LS 5039
HESS observed TeV -rays from LS 5039
Observed gamma-ray spectrum:
(0.25 TeV) = 5.1 0.8·10-12 ph/cm2 s
= 2.12 0.15
Aharonian et al. astro-ph/0508658
Aharonian et al. Science 309, 746, 2005
Neutrino energy flux:
f(0.1 TeV) ~ 10-10 erg/cm2 s
Sensitivity:
f,90 is expressed in erg/cm2 s
Selected events:
Ns: source events;
Nb: bkg events.
Expected neutrino events in 3 years of data taking:
C.Distefano CRIS 2006 – Catania May 29 – June 2
LNSSNR: RX J1713.7-3946
Aharonian et al. Nature 432, 75, 2004
Expected neutrino flux:
Alvarez-Muñiz & Halzen (ApJ 576, L33, 2002):
d/d ~ 4 ·10-8 -2 cm-2 s-1 GeV-1
max = 10 TeV
Costantini & Vissani (Astrop. Phys. 23, 477, 2005):
d/d ~ 3 ·10-8 -2.2 cm-2 s-1 GeV-1
= 50 GeV1 PeV
Expected neutrino events in 3 years of data taking: Sensitivity:
(d/d)90 is expressed in
GeV-1/cm2 s
Selected events:
Ns: source events;
Nb: bkg events.
C.Distefano Barcelona July 4 – 7, 2006
LNSOutlook
The NEMO project:
R&D study for the realization of the Mediterranean km3 neutrino telescope:
Search, characterization and monitoring of an adequate deep sea site;
Development of technologies for the km3 ;
Test of prototypes in deep sea: NEMO Phase-1 in Catania;
Realization of a marine infrastructure for the km3: NEMO Phase-2 in Capo Passero.
Angular Resolution and Pointing Accuracy:
Detection of the Moon shadow in 100 days;
Estimated angular resolution 0.2°;
Absolute pointing can be recovered looking at the Moon Shadow.
Detector Sensitivity to point sources (3 years):
NEMO (=2,102-108 GeV, =-60°) 1.2·10-9 E-2/(GeV cm2 s) search-bin 0.5°
ICECUBE 2.4·10-9 search-bin 1°
Discussed physics cases:
QSO LS 5039 and SNR RXJ1713.7-3946: both sources could be detected in 3 years;
a survey of TeV gamma-ray sources is under analysis.
C.Distefano Barcelona July 4 – 7, 2006
LNS
C.Distefano Barcelona July 4 – 7, 2006
LNS
We
igh
ted
Ev
en
ts
Simulation of atmospheric neutrino background
We use the ANTARES event generation code (weighted generation);
We simulated a power law interacting neutrino spectrum:
X=2 for 102 GeV < < 108 GeV ; Ngen= 7·109 interacting neutrinos
4 isotropic angular distribution
The atmospheric neutrino events
are weighted to the Bartol + RQPM
(highest prediction) flux
Nrec 3.7·105 reconstructed events Bartol+RQPM
1 year
NBartol+RQPM 4·104 expected events/year
Events at the detector
C.Distefano Barcelona July 4 – 7, 2006
LNSSimulation of atmospheric muon background
The events are generated at the detector, applying a weighted generation technique. We
simulate a broken power law spectrum (compromise between the requirement of high statistics
and CPU time consumption):
The atmospheric muon events are weighted to the
Okada parameterization (Okada, 1994), taking into
account the depth of the NEMO Capo Passero site
and the flux variation inside the detector sensitive
height (~ 900 m):
X=1 for < 1 TeV; Ngen= 3·107 events
X=3 for > 1 TeV; Ngen= 2.5·107 events
Nrec 3.8·106 reconstructed events
NOkada 4·108 expected events/year
tgen 4 days
We
igh
ted
Ev
en
ts
Okada1 year
Events at the detector
We
igh
ted
Ev
en
ts
Okada1 year
Events at the detector
C.Distefano Barcelona July 4 – 7, 2006
LNSSimulation of atmospheric muon background
The events are generated at the detector, applying a weighted generation technique. We
simulate a broken power law spectrum (compromise between the requirement of high statistics
and CPU time consumption):
The atmospheric muon events are weighted to the
Klimushin, Bugaev & Sokalski parameterization (PRD,
64, 014016, 2001), taking into account the depth of the
NEMO Capo Passero site and the flux variation inside
the detector sensitive height (~ 900 m):
X=1 for < 1 TeV; Ngen= 3·107 events
X=3 for > 1 TeV; Ngen= 2.5·107 events
Nrec 3.8·106 reconstructed events
NOkada 5·108 expected events/year
tgen 4 days
1 year
Events at the detector
1 year
Events at the detector
C.Distefano Barcelona July 4 – 7, 2006
LNSAtmospheric muon background for a point-like source
• The statistics of generated events
corresponds to a few days.
• Reconstructed events have a RA flat
distribution.
• We can project the full sample of
simulated events in a few degrees bin RA,
centered in the source position.
• We get statistics of atmospheric muons
corresponding to a time of ~1 year for each
microquasar.
Distribution of equatorial coordinates of the reconstructed atmospheric muons.
We
igh
ted
Co
un
tsW
eig
hte
d C
ou
nts
C.Distefano CRIS 2006 – Catania May 29 – June 2
LNS
=1
Event detection for a point-like ( = -60˚) neutrino source
reconstructionselection
Energy spectra of reconstructed and selected neutrino events (3 years)neutrino energy range 102-108 GeV
=2
=1.5
=2.5
C.Distefano Barcelona July 4 – 7, 2006
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
C.Distefano Barcelona July 4 – 7, 2006
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 may 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
C.Distefano Barcelona July 4 – 7, 2006
LNSThe km3 telescope: a downward looking detector
Neutrino telescopes search for muon tracks induced by neutrino interactions
The downgoing atmospheric flux overcomes by several orders of
magnitude the expected fluxes induced by interactions.
On the other hand, muons cannot
travel in rock or water more than
50 km at any energy
Upgoing and horizontal muon
tracks are neutrino signatures
C.Distefano Barcelona July 4 – 7, 2006
LNSAtmospheric muon background vs depth
Downgoing muon background is
strongly reduced as a function of
detector installation depth.
Depth >3000 m (1 km rock) is
suggested for detector installation
NEMO
NESTOR
ANTARESAMANDA
Bugaev
BAIKAL
C.Distefano Barcelona July 4 – 7, 2006
LNSCherenkov track reconstruction
pseudo vertex
j 0 j j cc(t - t ) = l + d tg( )
ANTARES
Cherenkov photons emitted by the
muon track are correlated by the
causality relation:
The track can be reconstructed
during offline analysis of space-
time correlated PMT signals (hits).
Fit yields muon track parameters
(, ) and number of hit PMTs
C.Distefano Barcelona July 4 – 7, 2006
LNSEvent selection
• quality cut:
The used reconstruction algorithm is a robust track fitting procedure based on a maximization
likelihood method. The reconstruction may give more than one possible solutions:
- > cut - log(L)/NDOF+0.1(Ncomp-1)
log(L)/NDOF log-likelihood per degrees of freedom
Ncomp number of compatible solutions (within 1)
• energy cut:
- Nfit>Nfitmin Nfit number of hits in the reconstructed event
• angular cuts:
- rejection of down-going tracks
- rec<max rec reconstructed event direction
- choice of the search bin size
- r<rmin r angular distance from source positionThe optimal values of cut, Nfitmin, max and rmin are chosen optimizing the detector sensitivity.
C.Distefano Barcelona July 4 – 7, 2006
LNSSensitivity for a point-like ( = -60˚) neutrino source (3 years)
Search bin:
NEMO 0.5˚
IceCube 1˚
=2
IceCube sensitivity values from
Ahrens et al. Astrop. Phys. 20 (2004) 507
(d/d)90 is expressed in GeV-1/cm2 sNeutrino energy range:102 - 108 GeV
C.Distefano Barcelona July 4 – 7, 2006
LNSSensitivity for a point-like neutrino source (3 years)
=2
Diurnal visibility:
Time per day spent by the source
below the Astronomical Horizon
with respect to the latitude of the
Capo Passero site.
The detector sensitivity gets worse
with increasing declination due to the
decrease of the diurnal visibility.
Equatorial coordinates
Detector sensitivity as a function of the source declination
<cut> = -7.3 no selection in Nfit
max = 90°-101° <rbin> = 0.5°
C.Distefano Barcelona July 4 – 7, 2006
LNSMicroquasar: LS 5039
HESS observed TeV -rays from LS 5039
(0.25 TeV) = 5.1 0.8·10-12 ph/cm2 s
= 2.12 0.15
Aharonian et al. astro-ph/0508658
Aharonian et al. Science 309, 746, 2005
f(0.1 TeV) ~ 10-10 erg/cm2 s
f,90 is expressed in erg/cm2 s
Expected neutrino events in 3 years of data taking:
Ns: source events; N
b: bkg events.
C.Distefano Barcelona July 4 – 7, 2006
LNSSNR: RX J1713.7-3946
Aharonian et al. Nature 432, 75, 2004
Expected neutrino flux:
Alvarez-Muñiz & Halzen (ApJ 576, L33, 2002):
d/d ~ 4 ·10-8 -2 cm-2 s-1 GeV-1
max = 10 TeV
Costantini & Vissani (Astrop. Phys. 23, 477, 2005):
d/d ~ 3 ·10-8 -2.2 cm-2 s-1 GeV-1
= 50 GeV1 PeV
(d/d)90 is expressed in GeV-1/cm2 sNs: source events; N
b: bkg events.
Expected neutrino events in 3 years of data taking: