Cosmic Neutrinos and High Energy Neutrino Telescopes Spåtind 2006 lecture 1

2006-01-07 Spåtind Norway P.O.Hulth

Cosmic Neutrinos and

High Energy Neutrino Telescopes

Spåtind 2006 lecture 1Per Olof Hulth

Stockholm [email protected]


Neutrino sky 5-40 MeV


Neutrino sky > 1 GeV

Nothing seen so far…….


Outline• Lecture 1

– Why do we expect to see cosmic neutrinos?• Cosmic rays• Dark matter

– Neutrino detection principles• Lecture 2

– Running High Energy Neutrino telescopes • Some physics results

– Near future telescopes


+CMB -> e+ + e-

p+CMB -> +->n+

+ GZK - neutrinos

(Greisen, Zatsepin, Kusmin)

P. Gorham

Universe is not transparent for HE photons or nuclei!

Protons deflected by magnetic field in space for

E < 1019 eV!

Not pointing back to the source!


photonselectrons/positrons

muons neutrons


photonselectrons/positrons

muons neutronsIn the same time also atmospheric neutrinos from meson and muon decays!!


LHC

~E-2.7

~E-2.7

~E-3

Ankle 1 part km-2 yr-1

knee 1 part m-2 yr-1

T. Gaisser 2005

- The accelerators?

Nature accelerates particles 10 7 times the energy of LHC!

What are the sources?

Cosmic rays


The size of the Universe “LHC” accelerator?

R

To use LHC magnets to deliver 1020 eV we need a radius of the

accelerator to be about 1.5 times the distance Earth -Sun


Galactic sources• Supernova are assumed to

be able to accelerate particles up 1016 eV

• But the observed gammas could have electromagnetic orgin and not hadronic.

• If gammas are from 0 decays you expect about the same flux of neutrinos!

• MicroquasarHESS gamma flux


Very High Energy Gamma sources


Ultra High Energy Cosmic Rays

• UHECR are assumed to be extra galactic

• There are still uncertainties about flux.

• No obvious sources for the particles > 1019.5 eV within 20 Mpc…?

• GZK effect observed?Shigeru Yoshida, ICRC 2005, Pune


Possible sources of UHE Cosmic Rays


Active galaxiesGalaxy 3C296


Gamma Ray Bursts

Cosmological sources!!

But what is it??

Source 9000 Million light years away!


Gamma Ray Burst ?


• We expect to have neutrinos produced when the accelerated UHECR collides with matter or light in the vicinity of the source!

• Detect the neutrinos!


Observing neutrinos

Fermi acceleration of protons gives particle spectrum

dNp/dE~ E-2

Neutrino production at source: p+ or p+p collisions gives pionse- + e

Neutrino flavors:e : : 1:2:~0 at source1:1:1 at detector (?)


NGC 2300


Dark matter searchThere exists about 5 times more dark matter in the universe than our baryonic matter

“Best” dark matter candidate: neutralino

Neutralinos are trapped in large objects like the Sun and Earth and self-annihilate.

Search for neutrinos from the centers of Earth and SunSee talks by Thomas Burgess and Gustav Wikström today


Neutrino Astronomy

• + Neutrinos penetrate the whole Universe • + Neutrinos direction points back to the source• + Neutrinos are produced at the sources of the cosmic rays• + Neutrinos are not reprocessed at the sources• + Neutrinos expected from dark matter particle

annihilation

• - Low expected flux of extragalactic neutrinos • - Small cross section• - Needs gigantic detector volumes


Backgrounds

• Atmospheric muons– Produced in cosmic ray interactions above the

telescope. In AMANDA there are 106 downward going atmospheric muons for every upward going atmospheric neutrino induced muon -> select only upward going muons as neutrino candidates. The Earth acts as a filter.

• Atmospheric neutrinos


log

[E2

· flu

x(E

) / G

eV c

m-2 s

-1 s

r-1]

-9

-7

-8

-6

-5

atmospheric

2 43 5 8 109 log (E /GeV)6 7

AGN

core

(SS)

AGN Jet (M

PR)

GRB (WB)

WB bound GZK

Required sensitivity

many specific models fornon-resolved sources ...

Waxman, Bahcall (1999)

derive generic limits from limits on extragalactic p‘s -ray flux

... for discovering extraterrestrial neutrinos

TeV PeV EeV

E-2 flux

50 events/year/km2


MeV GeV Tev PeV EeV

Different energy range for detectors

Underground

Optical Cherenkov

deep in water and ice

Radio, acoustic,

air showers


Neutrino interactions in ice and water

The muon can travel several km in e.g. ice

< 1 degree

eV

e

e

Hadronic shower length

logE (10th of metres)

CCCharge Current

NCNeutral Current


275 GeV muon neutrino interaction in BEBC

1 m


Muon range in ice

Muon propagator: MMC , Chirkin, D. 27th ICRC, HE 220, Hamburg 2001

The muon starts to loose energy above 500 GeV to pair production, bremstrahlung

The muon will be dressed up by many e+ and e-.

More Cherenkov light!


e

low energy)“Cascades”

Length of cascades 10th of meters (L prop. logE)


CCCharge Current


e

high energy)“Cascades”

Length of cascades 10th of meters (L prop. logE)


CCCharge Current


Neutrino cross-section

€

σ tot (νN) = 7.84 ×10−36cm2 Eν

1GeV ⎛ ⎝ ⎜

⎞ ⎠ ⎟0.363

For E< 104 GeV the x-section rises linearly with the energy

For E> 104 GeV (due to the W-boson propagator:

Cross-section measured up to 300 GeV. Up to about 10 TeV based on structure functions from HERA. Above different extrapolations.


Cross-section larger in e.g. -BH models

Standard Model

Strings

σ (m

b)

Micro black holes


Shadowing effect of the Earth


PeV acceptance around horizon

EeV acceptance above horizon

Shadowing effect of the Earth


AMANDA-B10 efficiency for UHE neutrinos

upup

E-2 neutrino flux 2.5 1015eV -> 5.6 1018eV


But for neutrinos the earth is transparent…

The tau neutrino will degrade in energy due to interactions in the Earth but will continue through.


The y-distributions

0 y 1.0 0 y 1.0

N N

(1-y)2

υq,υ q υ q,υq

Muon energy is harder in antineutrino interactions!

hadrons

muon

y = (Ehad - MN)/E


y = Ehadrons /E

lepton = (1-y)E


Z-bursts

• From Big Bang there should be about 330 neutrinos/cm3 with an average energy of 0.0004 eV

• The ultimate neutrino experiment to detect these….

CNB-> Z0-> decays

This process has been proposed to explain the UHECR events.

But you need a neutrino with 1024 eV energy..


up/down energy direction timeAtmospheric X

Diffuse neutrinos X X

Point sources; AGN, X X X

WIMPS

GRB X X X X

Reconstruction handles

X

XX

X

X X

X X X X


Optical Cherenkov detection


Detection principleO(km) long muon tracks

direction determination by Cherenkov light timing

15 m

O(10m) Cascades, e Neutral Current

Spåtind Norway P.O.Hulth

2006-01-07neutrino

muon Cherenkov

light cone

Detector interaction

•The muon radiates blue light in its wake•Optical sensors capture (and map) the light


Neutrino interaction in AMANDA QuickTime™ and a

GIF decompressorare needed to see this picture.


Acoustic Detection


d

R

Particle cascade ionization heat pressure wave

P

t

50s

Attenuation length of sea water at 15-30 kHz: a few km(light: a few tens of meters)

→ given a large initial signal, huge detection volumes can be achieved.

Threshold > 10 PeV

Maximum of emission at ~ 20 kHz

C. Spiering


Radio Detection


e + n p + e-

e- ... cascade

relativist. pancake ~ 1cm thick, ~10cm

each particle emits Cherenkov radiation

C signal is resultant of overlapping Cherenkov cones

for >> 10 cm (radio) coherence

C-signal ~ E2

nsec

negative charge is sweeped into developing shower, which acquiresa negative net chargeQnet ~ 0.25 Ecascade (GeV).

Threshold > 10 PeVC. Spiering


The Future• We should be optimistic !

• New York Times, December 29, 1932

Robert A. Millikan

From S. Westerhoff, Lepton Photon 2005


• Since we are in Norway.• And that the point of gravity for High

Energy Neutrino telescopes is at the South Pole which I will talk about tomorrow morning…

• A short historical comment.


Sydpolsfarare då och nu

Övervintra vid kusten


Sydpolsfarare då och nuTre timmars flyg från kusten


Sydpolen december 1911


Sydpolen januari 1912


Sydpolen november 2003

2006-01-07 Spåtind Norway P.O.Hulth Joakim Edsjö SU

Cosmic Neutrinos and High Energy Neutrino Telescopes Spåtind 2006 lecture 1

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