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

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

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

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)

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

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

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

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

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/0211194

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

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

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

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

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

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/0310079

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

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

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?

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