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Physicists sent a Neutrino particle under the Earth's crust
:: 25 October, 2007
Physicists have taken a snapshot of an elusive neutrino, in research that could one day explain why some of the universe's mass seems to be missing.
European physicists sent a neutrino particle on a 730 kilometre trip under the earth's crust and taken a snapshot of the instant it slammed into lab detectors.
The particle zoomed from the European Organisation for Nuclear Research (CERN) in Switzerland to an underground laboratory at the Italian Institute for Nuclear Research at San Grasso.
The journey took about 2.4 milliseconds, with the particle travelling close to the speed of light, says France's National Centre for Scientific Research (CNRS).
Neutrinos are elementary particles that lack an electrical charge and do not appear to interact with mass, as they can travel through ordinary matter almost effortlessly.
Trillions of them pass through each of our bodies every day.
Neutrinos come in three types, or flavours, as physicists call them: electron neutrinos, muon neutrinos and tau neutrinos.
In 2006, CERN started beaming neutrinos from its accelerator complex near Geneva, and has so far detected several hundred impacts in San Grasso.
The scientists have taken the venture a step forward by starting to fill the San Grasso detector with small film plates that accurately measure the cascade of particles produced when a neutrino hits.
These plates, called bricks, are each made of a sandwich of lead tiles and photographic films.
In the event earlier this month, a neutrino hit one of the 60,000 bricks that had been installed in San Grasso, leaving a telltale track of a muon on the film.
What happened to all that mass?
The experiment is important, say the investigators, as it could help explain one of the biggest mysteries about the universe - its missing mass.
When scientists tot up the mass of all the visible matter in the universe, they arrive at a total of just 10% of what they know to exist.
For years, neutrinos were not thought to have any mass, although that theory has been challenged by experiments at Japan's Super-Kamiokande lab, which suggests that they may have a mass, albeit a very tiny one.
The new experiment seeks to amplify and confirm this finding.
CERN sends muon neutrinos to San Grasso, with the hope that a few tau neutrinos will show up at the other end among all the muons.
If so, this would prove that neutrinos can oscillate between flavours, and if so, the ability to switch can only be explained by mass.
And if neutrinos do have mass, that could partly explain what happened to the universe's missing mass.
About 10 more 'neutrino events' occurred in the following days, the CNRS says.
Eventually, 150,000 bricks are to be installed in San Grasso.
Note for Neutrinos
Neutrinos are elementary particles that travel close to the speed of light, lack an electric charge, are able to pass through ordinary matter almost undisturbed, and are thus extremely difficult to detect. Neutrinos have a minuscule, but non-zero, mass too small to be measured as of 2007. They are usually denoted by the Greek letter ν (nu).
Neutrinos are created as a result of certain types of radioactive decay or nuclear reactions such as those in the sun, in nuclear reactors, or when cosmic rays hit atoms. There are three types, or "flavors", of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos; each type also has an antimatter partner, called an antineutrino. Electron neutrinos are generated whenever protons change into neutrons, while electron antineutrinos are generated whenever neutrons change into protons. These are the two forms of beta decay. Interactions involving neutrinos are generally mediated by the weak nuclear force.
Most neutrinos passing through the Earth emanate from the sun, and more than 50 trillion solar electron neutrinos pass through the human body every second.
About European Organization for Nuclear Research
The European Organization for Nuclear Research (French: Organisation européenne pour la recherche nucléaire), commonly known as CERN (see Naming), pronounced [sɝn] (or [sɛʀn] in French), is the world's largest particle physics laboratory, situated just northwest of Geneva on the border between France and Switzerland. The convention establishing CERN was signed on 29 September 1954. From the original 12 signatories of the CERN convention, membership has grown to the present 20 member states. Its main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research. Numerous experiments have been constructed at CERN by international collaborations to make use of them.
The main site at Meyrin also has a large computer centre containing very powerful data processing facilities primarily for experimental data analysis, and because of the need to make them available to researchers elsewhere, has historically been (and continues to be) a major wide area networking hub.
CERN currently has approximately 2600 full-time employees. Some 7931 scientists and engineers (representing 500 universities and 80 nationalities), about half of the world's particle physics community, work on experiments conducted at CERN.
As an international facility, the CERN sites are not officially under Swiss or French jurisdiction, and some company vehicles have diplomatic number plates.
Release link: http://www2.cnrs.fr/en/8.htm
Tags: snapshot , neutrino , universe's mass , earth's crust , European Organisation for Nuclear Research (CERN) , Nuclear Research , France's National Centre for Scientific Research (CNRS) , electron neutrinos , muon neutrinos , tau neutrinos , Geneva. ,
