Synopsis: Where are the neutrinos?

The IceCube neutrino detector buried in the Antarctic ice reports that high-energy neutrinos, expected from gamma-ray bursts, have yet to be observed.
Synopsis figure
Credit: NSF/IceCube

Gamma-ray bursts are the most luminous objects in the universe for the few brief seconds that they shine. Theory predicts that a fraction of their enormous energy should be coming out in neutrinos. However, as reported in Physical Review Letters, a search at the world’s largest neutrino detector at the South Pole has come up empty, which rules out certain gamma-ray burst (GRB) models.

GRBs result from a giant star explosion or the collision of star remnants. These cosmic cataclysms produce—in addition to gamma rays—high-speed protons that are thought to account for the highest energy cosmic rays observed on Earth. Near the source, these protons may run into photons and end up generating neutrinos with energies far above 1 TeV. In the past, neutrino detectors on Earth have not been large enough to capture one of these high-energy neutrinos with any likelihood.

IceCube, which was completed in December 2010, is a kilometer-cubed array of photodetectors that have been drilled down into the Antarctic ice cap. Neutrinos typically fly through the array without leaving a trace, but occasionally one will collide with a nucleus and create a charged particle that emits light as it moves through the ice. The IceCube team compared 13 months of their data (collected when the array was half finished) to observations of 117 GRBs measured independently over the same time period. Contrary to expectations, no high-energy neutrinos were detected within a half-hour of each GRB. Theorists may need to rethink their models of GRBs, as well as look for other possible sources for the highest energy cosmic rays. – Michael Schirber


Announcements

More Announcements »

Subject Areas

Particles and FieldsCosmology

Previous Synopsis

Graphene

Imaging puddles

Read More »

Next Synopsis

Soft Matter

Bubble bath

Read More »

Related Articles

Viewpoint: Connecting the Bright and Dark Sides of Galaxies
Cosmology

Viewpoint: Connecting the Bright and Dark Sides of Galaxies

A universal law shows that the rotation of a disk galaxy is determined entirely by the visible matter it contains, even if the disk is mostly filled with dark matter. Read More »

Synopsis: Seeing Dark Matter Through the Clouds
Astrophysics

Synopsis: Seeing Dark Matter Through the Clouds

A correlation between the cosmic microwave background and hydrogen absorption lines may reveal a connection between dark matter and intergalactic gas clouds. Read More »

Viewpoint: Cosmic-Ray Showers Reveal Muon Mystery
Particles and Fields

Viewpoint: Cosmic-Ray Showers Reveal Muon Mystery

The Pierre Auger Observatory has detected more muons from cosmic-ray showers than predicted by the most up-to-date particle-physics models. Read More »

More Articles