Extra large galactic survey puts limits on ultralight particles

July 12, 2010

Physicists have long known that neutrinos are among the lightest and most evasive fundamental particles. Now a survey of the galaxies is helping to narrow down the neutrino mass even further. It seems that neutrinos are at best half as massive as previously estimated, according to an analysis appearing today in the journal Physical Review Letters.

The lower neutrino mass estimate is the result of a 3-dimensional survey of more than 700,000 galaxies called MegaZ DR7. Although neutrinos are very light and interact with matter very rarely, they are so numerous that they can have a significant effect on the evolution of the material distribution in the universe. The galactic distributions revealed in the MegaZ map appear consistent with a reduced upper limit of neutrino mass estimates.

There are restrictions on the information the map can provide, in part because there are three varieties of neutrinos (electron, muon, and tau neutrinos), each of which likely have different masses. As a result, MegaZ can only estimate the sum of the three neutrino masses. The galactic distribution suggests that the combined mass the three neutrino varieties is less than 0.28 electron volts. Although the survey doesn't offer a lower limit of neutrino masses, it's clear from the detection of neutrinos coming from our sun, as well as from laboratory experiments, that neutrinos have at least some mass.
-end-
A Viewpoint article by Julien Lesgourgues of CERN provides an overview of the neutrino mass estimates in the current edition of APS Physics (physics.aps.org)

About APS Physics:

APS Physics (http://physics.aps.org) publishes expert written commentaries and highlights of papers appearing in the journals of the American Physical Society.

American Physical Society

Related Neutrinos Articles from Brightsurf:

Big answers from tiny particles
A team of physicists led by Kanazawa University demonstrate a theoretical mechanism that would explain the tiny value for the mass of neutrinos and point out that key operators of the mechanism can be probed by current and future experiments.

Physicists cast doubt on neutrino theory
University of Cincinnati physicists, as part of an international research team, are raising doubts about the existence of an exotic subatomic particle that failed to show up in twin experiments.

Exotic neutrinos will be difficult to ferret out
An international team tracking the 'new physics' neutrinos has checked the data of all the relevant experiments associated with neutrino detections against Standard Model extensions proposed by theorists.

Excess neutrinos and missing gamma rays?
A new model points to the coronoe of supermassive black holes at the cores of active galaxies to help explain the excess neutrinos observed by the IceCube Neutrino Observatory.

Where neutrinos come from
Russian astrophysicists have come close to solving the mystery of where high-energy neutrinos come from in space.

Where did the antimatter go? Neutrinos shed promising new light
We live in a world of matter -- because matter overtook antimatter, though they were both created in equal amounts when our universe began.

Strongest evidence yet that neutrinos explain how the universe exists
New data throws more support behind the theory that neutrinos are the reason the universe is dominated by matter.

Why didn't the universe annihilate itself? Neutrinos may hold the answer
New results from an experiment called T2K suggest that physicists are closer than ever before to answering a major mystery: Why didn't the universe annihilate itself in a humungous burst of energy not long after the Big Bang?

T2K insight into the origin of the universe
Lancaster physicists working on the T2K major international experiment in Japan are closing in on the mystery of why there is so much matter in the universe, and so little antimatter.

Radar and ice could help detect an elusive subatomic particle
A new study published today in the journal Physical Review Letters shows, for the first time, an experiment that could detect a class of ultra-high-energy neutrinos using radar echoes.

Read More: Neutrinos News and Neutrinos Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.