Neutrino Astrophysics

The Smoot group is active in the field of high-energy neutrino detection.


Why high-energy neutrino astronomy?

The reason for high-energy neutrino astronomy is to open up all wavelengths for astronomy and to peer into sources that would be opaque to photons and protons. Above GeV (roughly the rest-mass energy of a proton) energy wavelengths are less than 10^{-14} cm.

At high energies photons (gamma-rays) and protons are not viable probes.

With a high-energy neutrino detector we can open up a new window on the Universe. New windows have usually meant new discoveries.

Scientific Motivation

The fundamental scientific motivation for high-energy neutrino astronomy is that
Thus neutrinos will allow us to observe what we cannot with other detectors. In particular we will be able to observe sources at cosmological distances. This includes both diffuse and nearly point-like sources. E.g., Based upon the GRO (Compton Gamma-Ray Observatory) full sky survey one would anticipate that there are of the order of one hundred ultra-high-energy particle sources, probably Active Galaxies (AGNs) that should be detectable with a sufficiently large detector. It is also quite likely that Gamma-Ray Bursters (GRBs) are sources of high-energy neutrinos. There is roughly one GRB per day detectable by GRO type instruments. (Over 1000 observed todate.)

A measurement of the flux, energy spectrum, angular distribution, and timing of high-energy neutrinos is a fundamental observation of the Universe.

Neutrino Astronomy/Astrophysics

Measuring the flux is the goal but it is useful to make a rough estimate of what the diffuse and point source flux might be. The figure below show such an estimate.
For more recent and detail calculations by group members see Neutrino Event Rate Estimate page

A high-energy neutrino detector will also be able to conduct a number of Particle/High Energy Physics measurements.

Particle/High Energy Physics measurements

Additional Outstanding Science

Scientific Goals and Requirements on the Detector

The scientific goals/requirements for the detector to achieve outstanding scientific return are:

Detector Scientific Goals

Detector Scientific Requirements

Km-scale Detector Concept

We do not detect the neutrino directly but detect its interaction and interaction products. When a neutrino interacts with a proton or neutron (or an electron) it will produce a cascade of particles. This cascade of particles will generally build up to a substantial number of particles and then die out on the scale of 10 meters. If it is a charged-current reaction, The

These particles and particle cascade when in water (or ice) will produce a lot of light primarily through the Cerenkov effect. This Cherenkov light comes out as a cone-shaped shock wave at about 40-degrees from the particles' trajectory.

The detector concept is an array of optical modules (OMs) which detects the time of arrival (to roughly one nanosecond) and intensity of the Cherenkov light. By comparing the arrival timing and intensity of this light one can attempt to reconstruct the event geometry and energy deposition.

KM3 Project

KM3 a telescope designed to detect and identify point sources of high-energy (greater than 1 TeV) neutrinos

At present a group at the University of California, specifically at LBNL (Lawrence Berkeley National Laboratory) and at the Space Sciences laboratory, and their collaborators at JPL, ... are engaged in a Research and Development Effort for a detector on the scale of a cubic kilometer (hence KM3).

Stage I: Major R & D Thrusts

  • RAND (Radio Array Neutrino Detection)
    a receiver array to detect radio emission from ultra-high energy neutrino interactions in the South Polar Ice Cap.

    More Information

    IcCube an extension of the AMANDA project to the kilometer scale.

    Return to the Smoot Group page for a complete description of Dr. Smoot's group's research activities.