Neutrinos: Heralds of the stars

Collaborators on the MiniBooNE experiment searched for supernovae using data from neutrinos, which are often emitted when stars explode.

The field of astronomy is one of the oldest sciences, originating in Babylon as early as 1,800 BCE. While the field has advanced greatly since that time, many details about supernovae, or exploding stars, remain a mystery.

It is very difficult to spot a supernova in the sky - if your telescope isn't pointed in the right direction, you'll miss the light it emits. Looking for neutrinos emitted by a supernova is one alternative detection method. A recent search by collaborators from the MiniBooNE experiment at Fermilab was able to set a limit on the Milky Way's supernova rate.

We expect there to be only a few supernovae per century in our galaxy -- the last observed supernova in the Milky Way occurred in 1604. Although scientists using neutrino detectors in 1987 saw data from a visually observed supernova in the Large Magellenic Cloud, it wasn't until 1992 that they began publishing analyses of supernova searches using data from neutrino detectors.

It turns out that certain types of supernovae release a powerful burst of particles in addition to photons, the basic units of light. These particles, the neutrinos interact very weakly with matter - they breeze through the outer layers of supernovae and galactic dust to arrive at Earth hours before the visible photons. Correspondingly, neutrino detectors are a first point for supernova observation.

So, when scientists observe a supernova using a neutrino detector, they can immediately share the phenomenon's coordinates with observatories across the world, allowing them to align their telescopes in time to observe the supernova's photons.

MiniBooNE's supernova search, led by Matt Fisher and Heather Ray of the University of Florida, covers a recent period of time during which no other experiments have published supernova search data. By looking for anomalously large bursts of consecutive low-energy neutrino interactions occurring in 10 second intervals, MiniBooNE was able to search approximately 73 percent of the Milky Way, even though the comparably small neutrino detector is located on the Earth's surface. After weeding through the background cosmic-ray data, MiniBooNE collaborators set a limit on the rate of core-collapse supernovae in the Milky Way at less than 0.69 supernovae per year at the 90 percent confidence level, within a distance of 13.4 kiloparsecs from the Earth. (Kiloparsecs are common units used in supernova searches. One kpc is equal to roughly 67 million times the distance between the Earth and sun.)

For more information, please see this article.

-- Heather Ray

Learn about enhancements to your retirement plans

Fermilab has partnered with TIAA-CREF to enhance your retirement plans. We are excited about adding these new changes, but at the same time realize that the enhancements have made the retirement plans more varied, complex and larger in scope than the plans currently in place. Here are the enhancements:

• Mutual funds and Lifecycle funds are new investment choices. These choices will allow for you to further diversify your portfolio.
• A Roth 403(b) has been added. You can now make an after-tax contribution, which allows tax-free distributions under certain conditions.
• Effective April 1 Fermilab will have a dedicated TIAA-CREF Web site. It will allow easy access to your Fermilab retirement plan information and accounts. TIAA-CREF will now offer online enrollment.
• Investment "advice" services will enable TIAA-CREF's individual consultants to assist you in developing your investment portfolio. They will carefully analyze your goals and needs and provide in detail their investment recommendations.

Since the meetings are scheduled during working hours and will last for an hour, you will need your supervisor's approval to attend.

Please contact Wilma Cardona, x6800, with any questions.

CMS event display - decoded!

The LHC is once again moving into world-record-setting territory as it gears up to smash protons at the unprecedented energy of seven trillion electron volts. As the accelerator gets ready to speed up and smash particles, the LHC experiments-which record and analyze the debris from high-energy collisions-are running through their final checks and preparing to take center stage.

Whenever the first 7 TeV collisions happen, particle physicists from the experiments will proudly show off snapshots of the very first collisions in their detectors. These snapshots, known as event displays, show the information recorded by the massively complex detectors. However, much like a baby's first ultrasound image, it can be hard to make heads or tails of the physicists' pictured pride and joy.

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