ICECUBE &Limits on neutrino emission from gamma-ray

bursts

IceCube collaboration

Journal Club talk 4.15.2011 Alex Fry

Outline

• Neutrinos: The little neutral particles which are just right for exploring the universe.

• IceCube: A detector for neutrinos.• Gamma-Ray Burst model constraints from

IceCube• Conclusions

Neutrinos

• Neutrinos are leptons like electrons, but neutrinos interact only via the weak force

• Neutrinos come in three flavors: electron, muon, and tau

• Neutrinos have a small, but nonzero mass• Neutrinos are created prodigiously by the Sun

(70 billion per second per square cm on Earth) and other nuclear reactions in the Universe.

Neutrinos are specialParts of the universe are inaccessible for study using other types of cosmic rays: • protons do not carry directional information

because they are deflected by magnetic fields• neutrons decay before reaching the earth and

high-energy photons are absorbed• high-energy photons are absorbed

Neutrino mixing

• Neutrinos change ‘flavors’ and so can be any of the three types

• For example, the T2K experiment being worked on by some people here at UW will measure the mixing from νμ to νe by leveraging the mixing as a function of distance

Neutrino sources

• Supernovae• AGN• Cosmic Ray collisions in Earth’s atmosphere• Cosmic Neutrino Background from Big Bang• Dark Matter annihilations• Gamma-Ray Bursts

IceCube

IceCube is at the Amundson-Scott South Pole Station.

Each photomultiplier is enclosed in a transparent pressure sphere, a Digital Optical Module (DOM). The DOM also contains a digitally controlled high voltage supply to power the photomultiplier, an analog transient waveform digitizer and LED flashers.

DOMs measure the arrival time of every photon to an accuracy of better than 5 nanoseconds.

They cost about $350 each for a total cost of 1.7 million for the DOMs alone.

Detecting Neutrinos in Ice

electron neutrino creates an electron, the muon neutrino a muon, and the tau neutrino a tau lepton.

Detecting Neutrinos in Ice

Cherenkov light

electromagnetic radiation is emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in the medium

Muon events are most easily detected because the muon travels for a long time (much further than the Cherenkov light in the ice)

IceCubeIcecube also uses surface detector modules to help reject cosmic ray showers from above.In this paper 160 million events detected and 99.9% were rejected.

IceCube Neutrino Science

• Ice properties• Gamma-Ray Bursts• Diffuse neutrino backgrounds• Extremely high energy astrophysics• Dark matter, WIMPS• Supernova monitor• Relativistic magnetic monopoles

Gamma-Ray Burst Constraints

• Gamma-ray bursts are one of the few plausible candidates for ultra-high energy cosmic rays.

• Long duration GRBs (>2 s) are thought be collapse of massive stars into BH and short duration GRB (<2 s) are thought be merger compact objects

• Both events are consistent with the fireball model and producing lots of high energy cosmic rays and neutrinos.

Gamma-Ray Burst Constraints

The fireball model:• Mass rapidly accretes onto the newly formed

black hole. • A highly relativistic outflow/fireball dissipates

energy via synchrotron or IC (electrons)• Radiation emitted in Kev-Mev range is seen as

the gamma-ray signal (energy 1051 to 1054 erg)

Gamma-Ray Burst Constraints

The fireball model continued:• Protons are also accelerated via the Fermi

mechanism with an energy spectrum E-2 and energy=1020 eV (Waxman 1995).

• The protons interact with the Mev photons and create other particles (Δ+ to pions) and ultimately neutrinos in the ratio (1:2:0 for νe:νμ:ντ).

• Thus high energy cosmic rays and neutrinos (which arrive at earth in the ratio 1:1:1) are plausibly explained by GRBs.

Gamma-Ray Burst Constraints

So IceCube should be able to detect GRB’s

Sensitivity of the IceCube detector to astrophysical sources of high energy muon neutrinos. Ahrens et al. 2004

Gamma-Ray Burst Constraints

Thin lines - 41 selected neutrino spectra for 41 bursts.Thick dotted line - standard Waxman spectra for single burst.Thick solid line – sum of allThick dashed lined – sum of 41 Waxman like spectra.

Gamma-Ray Burst Constraints

IceCube has found no evidence for neutrino emission excluding prevailing models at 90% confidence.

Conclusions

• In the coming years data will improve and better constraints will be had. Stay tuned.

• But where are the missing neutrinos?

Emperor Penguins

• Emperor Penguins are endemic to Antartic costal regions.

• An Emperor Penguin can hold its breath for 20 minutes, and dive to depths of over 550 m (1/5 the depth of IceCube).

• Emperor Penguins are awesome.

ref

• Search for muon neutrinos from Gamma-Ray Bursts with the IceCube neutrino telescope IceCube Collaboration: R. U. Abbasi, et al

• Sensitivity of the IceCube detector to astrophysical sources of high energy muon neutrinos. Ahrens et al. 2004