Neutrino Astronomy

Ph 135Scott Wilbur

Why do Astronomywith Neutrinos?

Stars, active galactic nuclei, etc. are opaque tophotons

High energy photons are absorbed by the CMBbeyond ~100 Mpc

1020 eV protons, which should be created withneutrinos, have been seen

Can be used to observe possible dark matterreactions

In short: we can probe new phenomena andlook farther back

Why do Astronomywith Neutrinos?

Three main areas of research: Astronomy

More information about high-energy protons and γ rays

Particle Physics Extremely long baseline for neutrino oscillation studies

Dark Matter Searches Many dark matter candidates would leave neutrino

signatures

The Detector

A neutrino interacts with matter in thetelescope, creating a muon or a hadronic orelectromagnetic shower

The muon (or shower) emits Cherenkovradiation as it travels through the ice

Photomultipliers pick up the Cherenkovradiation and can infer the direction of travel

To select only neutrino events, only trackscoming through the Earth are kept

The Detector

Picture from AMANDA II Web Site: http://www.amanda.uci.edu

Advantages ofNeutrino Astronomy

Can see through nearly anything Wide viewing angle

Disadvantages ofNeutrino Astronomy

Need gigantic telescopes Still see very few events

AMANDA

Many arrays (A, B10,and II) at the SouthPole

Operational sinceJanuary 1997

ANTARES

Astronomy with a Neutrino Telescope andAbyss environmental RESearch

Currently under construction, 5/12 stringscompleted

1000 photomultipliers, 0.1 km2 planned Data will combine with AMANDA to provide

better sky coverage

IceCube

Next generation ofneutrino telescopes

4200 photomultipliers, 1km2 telescope area

1O angular resolution formuons, 10O for showers

30% resolution in log ofenergy for muons, 20% inenergy for showers

Astronomy

Extremely high energy protons (over 1020 eV)have been observed

Expected to come from supernova remnantsand neutron stars accreting matter fromcompanions

These processes are expected to generateneutrinos as well, which would point back totheir source

Astronomy

Active Galactic Nuclei are the most luminousknown objects in the Universe (1035 – 1041 W)‏

Some emit relativistic jets with γ rays exceeding1012 eV

Theoretical models of AGNs have largeuncertainties

Any observations of these sources (such asneutrino emissions) are helpful

Astronomy

γ ray bursts are extremely violent releases ofenergy (1045 J in ~1 sec in γ rays alone) ‏

We don't have a good theory about themechanism of γ ray bursts

By observing the afterglow, we can determinewhat happens, but not how it starts

Neutrino Physics

A neutrino telescope can see atmosphericneutrinos produced on the other side of theEarth

This gives a very long baseline for neutrinooscillation observations

Much more accurate neutrino oscillationmeasurements, possibly including a sterileneutrino

Dark Matter Searches

WIMPs can get trapped in gravity wells andannihilate at great rates

γ rays would be absorbed, but neutrinos couldbe detected

Neutrinos have energies 1/3 - 1/2 of WIMPmass

Kaluza-Klein dark matter annihilates intoneutrinos at a higher rate than WIMPs

Dark Matter Searches

Both dark matter candidates would lead to anincreased neutrino rate from the Sun:

rqR

1= 0.1

rqR

1= 0.2

rqR

1= 0.3

Possible Exotic Results

Neutrino telescopes are essentially detectorsfor extremely high energy accelerators (10PeV) ‏

We might see new physics at energy scales thishigh

Quantum Gravity

Earth becomesopaque above ~100TeV

Angular distributioncan give crosssection

Don't need knownluminosity of source

Magnetic Monopoles

Magnetic monopoles wouldhave a large equivalentcharge

Cherenkov radiation goesas charge squared

AMANDA has improved thebound on monopole fluxdensity

References

Francis Halzen, Astroparticle Physics with HighEnergy Neutrinos: from AMANDA to IceCube

Dan Hooper, High Energy Neutrino Astronomy:Opportunities for Particle Physics

Gianfranco Bertone, Dan Hooper and JosephSilk, Particle Dark Matter: Evidence,Candidates and Constraints

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