ICECUBE & Limits on neutrino emission from gamma-ray bursts IceCube collaboration Journal Club talk 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 special Parts 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 ν μ to ν e 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)

IceCube Icecube 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 to 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=10 20 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 ν e :ν μ :ν τ ). 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 all Thick 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 IceCube CollaborationR. U. Abbasi Sensitivity of the IceCube detector to astrophysical sources of high energy muon neutrinos. Ahrens et al. 2004