Neutrino Astronomy introduction the cosmic ray puzzle revisited

Neutrino Astronomy • introduction • the cosmic ray puzzle revisited • theory of high energy neutrino detection

Neutrino Sources • generic neutrino flux associated with the sources of the cosmic rays: 1. point 2. diffuse source • one example: gamma ray bursts • other science, one example: the search for dark matter

Neutrino Telescopes • First generation: AMANDA • Kilometer-scale neutrino observatory: Ice. Cube

Visible CMB 400 microwave photons per cm 3 1 Te. V = 1 Fermilab Ge. V -rays Flux Radio Energy (e. V)

With 103 Te. V energy, photons do not reach us from the edge of our galaxy because of their small mean free path in the microwave background. g + g CMB + e + e

/ / / Te. V sources! / / / cosmic / / rays / / /

Proton Astronomy? d. B d ____ ~ q = = E Rgyro ___ ~ 0. 1 o = [ d ______ 1 Mpc ][ B ______ 10 -9 G ] E _____ 3 x 1020 e. V B ~ 10 -6 Gauss in local cluster?

Interaction length of protons in microwave background p + g. CMB p+n l p = (�n. CMB ps+ CMB ) -1 @ 10 Mpc GZK cutoff above ~ 50 Ee. V

1000 Mpc 10 Mpc gamma ray bursts closest active galaxies local supecluster Virgo 1 pc ~ 3 ly ~ 1018 cm 1 Mpc 100 kpc halo 10 kpc 1 kpc 0. 1 kpc center of galaxy (scale height)

Multi-Messenger Astronomy Protons, -rays, neutrinos, [gravitational waves] as probes of the high-energy Universe 1. Protons: directions scrambled by magnetic fields n 2. -rays : straight-line propagation but reprocessed in the sources extragalactic backgrounds absorb E > Te. V 3. Neutrinos: straight-line propagation, unabsorbed, but difficult to detect

New Window on Universe? Expect Surprises

Knee of spectrum • Differential spectral index changes at ~ 3 x 1015 e. V – a = 2. 7 a = 3. 0 – Continues to 3 x 1018 e. V – Expect exp{-E / Z Emax} cutoff for each Z • Fine-tuning problem: – to match smoothly a new source with a steeper spectrum (Axford) – How serious is this? Knee

Transition to extragalactic origin? • Ankle new population of particles? • Suggestive evidence: Ankle New component with hard spectrum? – hardening of spectrum – change of composition • Measurements: – Energy – Depth of maximum (Xmax) – Nm / N e

Generic Spectrum with Cosmological Evolution sources evolve ~(1+z)3

Energy Spectrum by AGASA (θ< 45) 10 obs. / 1. 6 exp. 4. 0σ

Models of Cosmic Rays Bottom up – GRB fireballs – Jets in active galaxies – Accretion shocks in galaxy clusters – Galaxy mergers – Young supernova remnants – Pulsars, Magnetars – Mini-quasars – … • Observed showers either protons (or nuclei) Top-down – Radiation from topological defects – Decays of massive relic particles in Galactic halo – Resonant neutrino interactions on relic n’s (Zbursts) • Mostly pions (neutrinos, photons, not protons) Disfavored! • Highest energy cosmic rays are not gamma rays • Overproduce Te. V-neutrinos

Acceleration to 1021 e. V? ~102 Joules ~ 0. 01 MGUT dense regions with exceptional gravitational force creating relativistic flows of charged particles, e. g. • coalescing black holes/neutron stars • dense cores of exploding stars • supermassive black holes

Cas. A Supernova Remnant in X-rays Shock fronts Fermi acceleration John Hughes, Rutgers, NASA

Active Galaxies: Jets 20 Te. V gamma rays Higher energies obscured by IR light VLA image of Cygnus A

Jets Shock fronts Fermi acceleration Black Hole Accretion Disk

Challenge I: Acceleration shock velocity R B = boosted energy G from cosmic accelerator (V = e F; = v/c)

Superluminal motion: boosted accelerators 5 c 4 c 1 c 3 c telescope: 1 year later Eobs = G E' Dtobs = G-1 Dt' ' accelerator frame exp: G < ~ 10 3 ly light from blob is only 1 year behind that from agn!

Cosmic Accelerators E ~ Gc. BR R~ 2 GM/c energy magnetic field E ~ GBM boost factor mass

E (e. V) = B (Tesla) ms-pulsar 10 km 108 T 103 R B T-1 (#revs-1) E 1019 e. V R 2 2__p (m) T Fermilab few km few T 105 ~1012 e. V= 1 Te. V

E ~ G B M E > 1019 e. V ? • quasars • blasars • neutron stars black holes. . • grb G@1 > ~ 10 G@1 B @ 103 G M @� 109 Msun B @ 1012 G M @ Msun 2 > �� 10 ~ emit highest energy ’s!

cosmic neutrinos associated with cosmic rays

black hole radiation enveloping black hole p + -> n + p+ ~ cosmic ray + neutrino -> p + p 0 ~ cosmic ray + gamma

Irrespective of the cosmic-ray sources, some fraction will produce pions (and neutrinos) as they escape from the acceleration site • through hadronic collisions with gas • through photoproduction with ambient photons Cosmic rays interact with interstellar light/matter even if they escape the source Sources: • Transparent: protons (Ee. V cosmic-rays) ~ photons (Te. V point sources) ~neutrinos • Obscured sources • Hidden sources Unlike gammas, neutrinos provide unambiguous evidence for cosmic ray acceleration!

Requires kilometer-scale neutrino detectors

active galaxy Radiation field: Ask astronomers Produces cosmic ray beam?

Galactic Beam Dump

Modeling yields the same conclusion: • Line-emitting quasars such as 3 C 279 Beam: blazar jet with equal power in electrons and protons Target: external quasi-isotropic radiation • Supernova remnants such as RX 1713. 7 -3946 (? ) Beam: shock in interstellar medium Target: molecular cloud Nevents ~ 10 -2 -1 km year

neutrinos associated with the source of the cosmic rays? even neutrons do not escape neutrons escape

• Infrequently, a cosmic neutrino is captured in the ice, i. e. the neutrino interacts with an ice nucleus • In the crash a muon (or electron, or tau) is produced Cerenkov muon or tau light cone Detector • The muon radiates blue light in its wake • Optical sensors capture (and map) the light interaction neutrino

Optical Module

Use the phenomenon of Cherenkov light How to build a n detector?

Copyright © 2001 Purdue University

• Infrequently, a cosmic neutrino is captured in the ice, i. e. the neutrino interacts with an ice nucleus • In the crash a muon (or electron, or tau) is produced Cherenkov muon or tau light cone Detector • The muon radiates blue light in its wake • Optical sensors capture (and map) the light interaction neutrino

South Pole AMANDA– 1 mile deep

50 m Size perspective

• Construction began in 1995 (4 strings) • AMANDA-II completed in 2000 (19 strings total) • 677 optical modules • 200 m across • ~500 m tall (most densely instrumented volume) the AMANDA detector

AMANDA Event Signatures: Muons charged current muon neutrino interaction track nm + N m + X

Two events. . . 200 Te. V e candidate

Detection of e , , O(km) long muon tracks Electromagnetic and hadronic cascades 15 m direction determination by cherenkov light timing ~5 m

Optical Cherenkov Neutrino Telescope Projects ANTARES La-Seyne-sur-Mer, France NEMO Catania, Italy NESTOR BAIKAL Russia DUMAND Hawaii (cancelled 1995) Pylos, Greece AMANDA, South Pole, Antarctica

Northern hemisphere detectors Baikal NT 200 1100 m deep data taking since 1998 new: 3 distant strings Antares March 17, 2003 2 strings connected 2400 m deep completion: start 2006 Nestor March 29, 2003 1 of 12 floors deployed 4000 m deep completion: 2006

• 12 lines • 25 storeys / line • 3 PMT / storey ANTARES Layout 14. 5 m 350 m 100 m Junction box 40 km to shore ~60 -75 m Readout cables

GZK Cosmic Rays & Neutrinos • Cosmogenic Neutrinos are Guaranteed if primaries Nucleons. • May be much larger fluxes, for some models, such as topological defects p + g. CMB p + ….

Radio Emission from neutrinoinduced electromagnetic cascades • Electromagnetic cascades: electron-positron pairs and (mostly) gammas electrically neutral, no radio emission. • Compton scattering of photons on atomic electrons creates negative charge excess of ~ 20% • Negative charge radiates coherently at MHz ~ GHz Power = Energy 2 • Askarian effect demonstrated at SLAC: consistent with calculations

RICE Radio Detection in South Pole Ice Neutrino enters ice Neutrino interacts Antenna & Cable • Installed ~15 antennas few hundred m depth with AMANDA strings. • Tests and data since 1996. • Most events due to local radio noise, few candidates. • Continuing to take data, and first limits prepared. • Proposal to Piggyback with ICECUBE Cube is. 6 km on side Two cones show 3 d. B signal strength

ANITA Radio from Ee. V ν’s in Polar Ice • NASA proposal now • Data in 2005 if successful

Tau. Watch Using Mountains to Convert ντ 3/02 Workshop in Taiwan, see http: //hep 1. phys. ntu. edu. tw/vhetnw

Ocean Acoustic Detection New Stanford Effort using US Navy Array US Navy acoustic tracking range in Tongue of the Ocean, Atlantic Hydrophones 1550 -1600 m deep pancake beam pattern G. Gratta, atro-ph/0104033

Compare Potential GZK Neutrino Detectors

notes to previous table

Event Rates volume • OWL 1013 ton • Ice. Cube 109 ton eff. area 106 km 2 1 km 2 Events per year • OWL ne • Ice Cube nm TD 16 11 zburst 9 30 threshold 3 x 1019 e. V 1015 e. V* p 2. 7 5 1. 5 Cline, Stecker astroph 0003459 Alvarez-Muniz astroph 0007329 Warning: models identical? *actual threshold ~100 Ge. V, > 1 Pe. V no atmospheric n background

l n Psurvival = exp -(l/ ln) ln = n sn (En) The Earth as a cosmic ray muon filter n = NA

Neutrino Detection Probability neutrino detected neutrino survives - e L L _ ln ne m t nm nt for nm : L Rm [Em = (1 - y) En] for nt : L E __t mt c t t - 1 -e L _ ln L ~ _ _ ln Pdet= n. L sn

Range of the Muon d. E ___m = - ( a m + b m E m ) (R m ) d. Rm 2 Me. V cm 2/g low Em large Em 6 x 10 -6 cm 2/g (0. 8 x 10 -6 for t) E m ___ ~ _ Rm am Em = 5 m Ge. V 1 E n ___ ~ _ Rm ln ( ) bm Em

Energy reconstruction • Energy reconstruction will be a powerful tool in order to discriminate between astrophysical neutrinos and those coming from atmospheric interactions. • The muon energy reconstruction is based on the fact that the higher its energy, the higher the energy loss along its track. • The method is only valid above the critical energy ( 600 Ge. V), where energy losses caused by radiative processes dominate over ionisation processes. : ionisation : radiative processes

Neutrino Astronomy Explores Higher Dimensions 100 x σSM GZK range

Detection of n(En) Nevents = Psurvival Pdetected Area n Area = L 2 for detailed geometry and kinematics: Physics Reports 258 (3), 173 (1995) hep-ph/0105067

sn secondary lepton l (k') (1 - y) E = E' n(k) _ M 2 Q 2 = - (k - k')2 ~ W y. E p hadronic shower q(x) 2 s 2 d G _____ ___F dxd. Q 2 = p 2 M _____ W [ Q 2 + M 2 ]2 q( x, Q 2 ) W

sn 2 s 2 d G _____ ___F = 2 dxd. Q p 2 M W [ _____ Q 2 + M 2 W ]2 q ( x, Q 2 ) d 2 s _____ dxd. Q 2 M 2 W x q(x) x-l Q 2 QCD evolution Increasing Q 2 x M 2 W