1. Neutrino astrophysics
Detection methods
Radiochemical
Scintillator
Čerenkov
Heavy water
Sources
Solar neutrinos
Supernova neutrinos
Atmospheric (cosmogenic) neutrinos
Neutrinos from neutralino annihilation
High energy astrophysical neutrinos

2. Detection methods Basic theory:
need to detect a charged particle (or γ)
CC (W exchange)
inverse β decay
neutrino “converted” to charged lepton
NC (Z exchange)
neutrino scattering
detect charged recoil product

3. Radiochemical detectors
Detection by inverse β decay
ν + n  e- + p
e.g. 37Cl  37Ar, 71Ga  71Ge
Low energy threshold
electron-neutrinos only
Not real-time
No pointing

4. Scintillators Detection by Energy measurement Not pointing
ν-e scattering
inverse β+ decay
Energy measurement
Not pointing
Also used as active element in detectors with high Z target (e.g. OMNIS)

5. Čerenkov radiation Refractive index of water is 1.34
threshold for Čerenkov radiation 0.77 MeV (e), 159 MeV (μ)
Flavour sensitivity varies with energy (mainly e at solar neutrino energies, mainly μ at very high energies)
Pointing capability
Not much energy resolution

6. Heavy water For solar neutrinos
ν + d  e + p + p (electron only)
ν + d  ν + p + n (flavour blind)
ν + e  ν + e (e dominates)
Also potentially an excellent supernova neutrino detector

7. Sources Neutrino production mechanisms
nuclear physics (e.g. p + p  d + e + ν)
keV - MeV
thermal (e.g. e+ + e-  ν + ν)
MeV
beam dump + pion decay (pX  np + X)
GeV - EeV
neutralino annihilation?
GeV

8. Solar neutrinos Main channel: pp  d + e+ + ne (E ≤ 420 keV)
see Physics of Massive Neutrinos
Main channel: pp  d + e+ + ne (E ≤ 420 keV)
Some rare side chains up to 20 MeV
Detectors:
radiochemical
Homestake
Gallex and SAGE
Čerenkov
Kamiokande et seq.
Heavy water
SNO

9. Supernova neutrinos
About 99% of the energy release from a core collapse supernova is in neutrinos
initial pulse from neutronisation: p + e-  n + ne
most neutrinos from thermal production
seem to be critical to get SN to explode!
energies of different flavours differ owing to different opacities
Thompson, Burrows, Pinto, astro-ph/

10. Oscillation in solar and supernova neutrinos
Well studied in solar neutrinos
MSW effect
do distinguish n from n
don’t distinguish μ from τ
should also happen in SNe
affects observed energy spectrum and rate

11. Atmospheric neutrinos
Beam dump: cosmic ray protons on air
produces two nμ for each ne
deficit in upgoing nμ is oscillation signal
background for astrophysical and dark matter neutrinos

12. Neutrinos from neutralino annihilation
SUSY neutralino χ is a Majorana particle
χχWW, ZZ, tt, ττ, bb,…
W, Z, t, τ, b  n + X
energy of neutrino typically ~½Mχ in favourable cases
need high number densities
gravitational capture in Sun or Earth
halo response to SBH?
SOHO, 4/3/04, 284 Å

13. Indirect detection of dark matter via neutrinos
Rate is model dependent
many CMSSM models accessible to ANTARES or larger detector
these models have decays into WW, ZZ or tt
lower Ω gives larger signal (higher cross sections)
complementary to direct searches
different systematics
slightly different reach

14. High energy neutrino astrophysics
Cosmic ray data  astrophysical sources of high energy protons
must produce high energy neutrinos
but sources unknown
magnetic fields scramble proton direction

15. Energetics To accelerate protons to Ep, require BR > ΓEp/eβ
Produced proton spectrum ~ 1/E 2
result of acceleration in shocks
To produce Δ need EpEγ = 0.2 GeV2Γ2
produced neutrinos ~5% of proton energy
nμ produced, but may oscillate to nτ
E. Waxman, astro-ph/

16. GRBs as neutrino sources
“Fireball” model of gamma-ray burst
highly relativistic (Γ=300) outflow
variable source produces variation in Γ
internal shocks
shock acceleration
order of magnitude estimate of proton production in line with observed UHECR

17. Neutrinos from GRB In burst: In afterglow: In collapsar models:
protons produce pions on fireball photons
energies ~100 TeV
around 20 μ/km3/yr (4p)
In afterglow:
protons accelerated by shock as fireball ejecta hit surrounding gas
neutrino energies ~1017 eV
0.2 – 20 μ/km3/yr (4p) depending on gas
In collapsar models:
termination shock of jet emerging from stellar envelope
energies ~5 TeV
~0.1 μ/km3/burst

18. Neutrinos from microquasars
Accreting binary systems with neutron star/black hole and relativistic jet outflow
transient radio outbursts may be due to ejection of inner accretion disc
if jets contain protons, good chance of neutrino production
burst of 1 – 100 TeV neutrinos preceding radio flares?

19. Conclusions Detectors Sources need to consider
energy threshold
flavour response
pointing
useful to have several different technologies active
Sources
low energy (Sun, SNe)
useful oscillation lab
potentially good astrophysics
medium energy
more oscillations, cf. terrestrial LBL
high energy
if found, valuable astrophysical diagnostic