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La La rivelazione rivelazione di di neutrini astrofisici neutrini astrofisici

T. MontaruliT. Montaruli Università

Università di Bari di Bari & INFN& INFN

• Neutrino Astrophysics Motivations

• Physics Issues

• Current Neutrino Telescopes and Experimental Results

• Future Outlook



Lecce, 23-, 23-26 Aprile 26 Aprile 20032003


Probes of the Universe Probes

Probes of the of the Universe Universe

Photons: straight-line propagation but reprocessed in sources and extragalactic backgrounds absorb Eγ > TeV (pair production on IR, CMBR, radio)

Protons: directions scrambled by magnetic fields (deflection<1° E>50 EeV) Neutrons:


∼10kpc for E ~EeV Absorption length of photons and protons

Mrk 501 γ+IR


p photopion pγ→e+e-

UHE particles (γ, p, n, …) have small path-lengths respect to Hubble scale (GZK cut-off)

Survey of remote regions and engines inside sources through neutrinos: small


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 3 Kinetic energy per nucleus (eV)

knee ~3000 TeV

New component

with hard spectrum?

ankle~10 EeV 1 par km-2 yr-1


~E-2.7 10% of SN power is enough to feed CRs: 1051 erg per SN + ~3 SN per century in disk ~ 10-25 erg/cm3s

Power spectrum for diffusive shock acceleration with differential index α ~ -2; but


observed ~ -2.7 due to propagation effects and escape time from Galaxy

Ankle: extragalactic sources (Galaxy cannot contain EHECR, no such

powerful galactic source candidates, no evident anisotropy correlated with galactic plane

The cosmic ray connection

The The cosmic ray cosmic ray connection connection

Cosmic ν’s can provide an answer to the debated question:

Which are the sources of the HE cosmic rays (E> 1014 eV) ?

Cosmic ray spectrum: 106 eV to ~1020 eV


The ankle and the GZK cut-off

The The ankle ankle and the GZK cut and the GZK cut - - off off

[Greisen 66;

Zatsepin & Kuzmin66]

1 event/km2/century

GZK cut-off due to interactions of CRs (E> 5 1019 eV) on CMBR EHECR data: light composition favored


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 5

Top-down: decays of unstable or meta-stable particles produced by radiation, interaction or collapse of topological defects or decay of relic particles

Z decays due to UHE ν interaction on relic ν’s (Weiler, 1982)

ν production and sources ν ν production and production and sources sources

Bottom-up (beam-dump model): cosmic accelerator + interaction on matter or γ’s: π0 → γ-astronomy π± → ν-astronomy

Cosmogenic ν’s: UHE ν interactions on CMB (Engel Seckel, Stanev, 2001)

Proton acceleration: Emax~ ΓBR and if collapsed objects Emax~ ΓBM

• Jets of AGN, GRB fireballs

• Accretion shocks in galaxy clusters , Galaxy mergers

• Young supernova remnants (p or heavy ion accelaration)

• Pulsars, Magnetars (large magnetic fields)

• Micro-quasars (binaries with jets seen in radio)


The link with γ astronomy The The link with link with γ γ astronomy astronomy

Neglecting γ absorption (large uncertainty)



∼ Φ


1st order Fermi acceleration mechanism: harder spectra than atmospheric ν’s Observations consistent with em mechanisms BUT first evidence in a SNR of hadronic mechanism? RXJ1713-39 CANGAROO, Nature 416 2002

Syncrotron IC



Reimer et al, A&A 390, L43 (2002): any GeV emission should be

compatible with EGRET measured flux 3EG

J1714-3857 (even if not coincident with

CANGAROO source)


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 7

Detected Sources emitting γs with E>TeV Detected Sources emitting

Detected Sources emitting γ γ s with s with E> E> TeV TeV

AMANDA location ANTARES location 11 visible 100% of day 3 visible 100% of day 8 never visible 8 visible >50% of day

3 visible 20-50% of day 8 visible <20% of day RXJ1713-39 not visible

BL Lacs, Pulsars and SNRs

Cygnus OB2: association of stars

Earth shadowing not considered, only visibility

AMANDA location: sources always at same elevation, constant sensitivity with time possible advantage for



Detection principle Detection

Detection principle principle

ν interaction cross-section very low ⇒ huge detectors (km3) not feasible


Markov/ Greisen idea (1960) ν + N → µ + X

Target is surrounding matter M = ρ Rµ S (Eµ = 1 TeV : Rµ = 2.5 km)

3d PMT array reconstructs µ tracks and cascades. Also νe and ντcan be detected (better energy resolution but worse

angular resolution)


µ ν


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 9

Cosmic νs Oscillations

ν interaction length ~Earth diameter @40 TeV ντ undergoes regeneration through CC + τ decay

cosmic ν’s at surce: νeµτ= 1:2:0 (if µ’s decay) ⇒ oscillations with atm ν’s parameters and L ~ Mpc ⇒ νeµτ = 1:1:1

ντµ: 2.85, 1.29 (reduced to 1.11, 1.07 for E-2) νeµ secondaries/ντ: 37%,6% (reduced to 2.2%,0.2% for E-2)

E-1 diff. spectrum


Cosmic ν ν s Oscillations s Oscillations


The backgrounds The The backgrounds backgrounds

•Environment (40K, bioluminescence) and electronics

•Atmospheric ν’s

•Atmospheric µ’s (sea/ice shielding)

Rejection: direction and energy,

time for bursters

Problem: 2 orders of magnitude uncertainty on current predictions of prompt νs

E2.5 /dE (GeV1.5 cm-2 s-1 sr-1 )

ANTARES Atmospheric νs


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 11

Neutrino telescope parameters Neutrino

Neutrino telescope parameters telescope parameters

‘Background free’ region: direction and/or time constraint, energy cut ⇒ upper limits scale with 1/exposure

‘Background limited’ region: upper limits scale with 1/sqrt(exposure)

Sensitivity: N are events from ν source and B events from atm ν background number of sigmas=N/sqrt(B) ∝ √(AT) / ∆θ

∆θ = angular resolution AT = exposure

Discovery potential at 100 TeV: source luminosity to have 10 events/km2/yr with Pν --> µ ~ 10-4 and N = fν/Eν Pν →µ AT





∼ 4πd


5 ·10


/[AT (km


yr)] in erg/s

Pulsars/SNRs/magnetars/µquasars ⇒ 1035 erg/s (5 kpc) AGN/BL Lacs/GRBs ⇒ > 6 ·1043 erg/s (>100 Mpc)

~200 ev/yr/km2 W&B limit (4.5 10-8 E-2 GeV cm-2 s-1 sr-1)




Effective areas Effective areas Effective areas

Event rates ⇔ Effective area (volume): includes reconstruction efficiencies, affected by absorption length and coincidence requests to suppress

backgrounds, strongly dependent on spectrum


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 13

Angular and energy resolutions Angular

Angular and and energy resolutions energy resolutions

Resolution dominated by reconstructon

Limiting value ~0.15°



Resolution dominated by kinematic angle θνµ

Energy resolution log(Erec/EMC)

Factor 3 Factor 2

Reconstruction resolution limited by phototube TTS and light diffusion in water


4 years Super-Kamiokande

5.6 years MACRO

170 days


10-15 10-14

µ ⋅cm




southern sky

northern sky

Point-like sources Point

Point - - like sources like sources



Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 15

AMANDA II (νe)[3](prelim) [2]

All flavors

Diffuse fluxes Diffuse

Diffuse fluxes fluxes


µ limits for E-2

AMANDA Cascades (νeµτ) 130 d (PRD67, 2003): 9.8 10-6 GeV cm-2 s-1 sr-1 AMANDAII 197d: 6 10-7 GeV cm-2 s-1 sr-1

AMANDA (νµ) 130 d (astro-ph/030328): 8.4 10-7 GeV cm-2 s-1 sr-1 AMANDA UHE >1016eV: 2 (no sys)/4.8 (sys) 10-6 GeV cm-2 s-1 sr-1

Baikal (νe+2νµ) 234 d NT200+70d NT96 (Neutrino02): 1.3-1.9 10-6 GeVcm-2 s-1 sr-1


Search for Dark Matter

Neutralinos from the Sun Relativistic Monopoles


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 17

AMANDA B-10:302 OM’s/10 strings Results recently published on atm

ν’s (

30% sys), diffuse muon fluxes &

cascades (6-1000 TeV), UHE


(>10-5000 PeV), WIMPs, SNs

Ang. resolution 3.9° (EAS check) E resolution ~30-60%

Effective area


µ > 10 TeV > 104 m2 AMANDA II: about factor of 10

120 m

400 m

Absorption length (480 nm): 110 m Effective scatter length ~ 25 m


Baikal Neutrino Telescope

1100 m depth in Siberian Lake 3.6 km off-shore 51°N 104°E

deployment+EAS on ice platform Ang. res 4° 192 OMs on 8 strings

Absorption length (480 nm): 28 m Effective scatter length > 200 m


Planned upgrade 2003-4 Future 1300 OMs/91 strings


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 19 2475m


350m350m active active

Electro-optical submarine cable


Junction box Junction box Readout cables

Readout cables

anchor anchor

float float

Electronics containers Electronics containers


Compass, Compass, tilt meter tilt meter Optical module Optical module

Acoustic beacon Acoustic beacon


12 equipped strings 90 OMs/line

Shore station

Absorption length (460 nm): 55-65 m Effective scatter length > 100 m

ANTARES http://

ANTARES http:// antares antares .in2p3. .in2p3. fr fr


Detector Deployment:

Detector Deployment: achievemets achievemets and planning and planning

Jun 00:

Jun 00:

implosion test implosion test Collaboration formed

Collaboration formed

Deployment of 12 lines Deployment of 12 lines RR&D and Site evaluation &D and Site evaluation

programme to select a suitable site programme to select a suitable site

Nov 99

Nov 99-- Jun 00: “demonstrator” line Jun 00: “demonstrator” line deployment + operation

deployment + operation ⇒⇒ atmospheric µatmospheric µss

1616-17/03/03 Connections by submarine -17/03/03 Connections by submarine 12/02/03 Instrumentation line deployed

12/02/03 Instrumentation line deployed 24/12/02: Prototype line deployed

24/12/02: Prototype line deployed


Teresa Montaruli, IFAE, Lecce, 24 Aprile 2003 21

•n. 64 towers, 16 storeys/tower, 600 m implemented

• 4096 PMTs

main electro optical cable

main JB 200 m

200 m

1400 m


NEMO.RD Issues:

•selection of the optimal site for

km3 site in Mediterranean (Capo Passero)

•R&D on materials and mechanical structures suited for long-term

measurements in sea water and on low power consumption electronics

•feasibility study and physics simulations

•Test site off-shore Catania: first multi-purpose underwater Lab connected to shore in real time

Shore station 25 km Electro-25 km Electro-OpticalOptical Cable

Cable (installed Sep01) to JB splits for 2 sites GEOSTAR (seismologic monitoring),...


Actual proposal of general layout for Km

Actual proposal of general layout for Km33 detectordetector


Conclusions Conclusions

• Cosmic neutrinos are reasonably expected but fluxes are low

• AMANDA and Baikal are already producing results at the level of SK and MACRO, AMANDA II 1 order of magnitude better, BUT all flavors

•Towards a km3 detector:

ICE/sea water have complementary optical properties

ICE: larger scattering but longer absorption lengths (better calorimeter but worse angular resolution) deployment from ice platform but no recovery EAS to check pointing capabilities, no 40K and bioluminescence

2 detectors in upper and lower emisphere are needed to ensure full sky coverage ICECUBE: 4800 OM’s/80 strings construction in austral summer 2004-5

Funding request: $295 M

ANTARES 2 lines taking data at 2500 m




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