New results confirm standard neutrino theory

Feb 16, 2010
New results confirm standard neutrino theory
The MINOS detector a half mile underground in Soudan, Minn.

(PhysOrg.com) -- In its search for a better understanding of the mysterious neutrinos, a group of experimenters at DOE’s Fermi National Accelerator Laboratory has announced results that confirm the theory of neutrino oscillations and help rule out two alternative scenarios: neutrino decay and the existence of sterile neutrinos.

The Main Injector Neutrino Oscillation Search experiment, or MINOS, explores the properties of muon produced at Fermilab. When sending a beam of neutrinos 735 kilometers through the earth to a neutrino detector in the Soudan Underground Laboratory in Soudan, Minn., scientists find that a significant fraction of the muon neutrinos disappears along the journey. The standard explanation is that the missing muon neutrinos morph into two other known types of neutrinos: electron neutrinos and tau neutrinos. This process is known as neutrino oscillations or neutrino mixing.

But could there be another explanation? Scientists are exploring alternatives such as the decay of muon neutrinos into yet-to-be discovered particles or the transformation of muon neutrinos into a fourth type of neutrino, which is often called a sterile neutrino since it would not interact with ordinary matter like the other three known types of neutrinos.

MINOS scientists found that neutrino decay is an unlikely option. They looked at two scenarios: First, the possibility that no neutrino oscillations take place and hence all muon neutrinos decay. Second, they considered the possibility that some muon neutrinos transform into other neutrinos and some decay during their trip from Fermilab to Soudan, which takes about four hundredths of a second. In both analyses, the MINOS results provide strong evidence against the existence of neutrino decay.

The MINOS results also disfavor the existence of a fourth, sterile neutrino. Past analyses have shown that if muon neutrinos are oscillating into sterile neutrinos, only 68 percent of the disappearing neutrinos can do so. The new MINOS analysis shrinks that percentage to 50 percent, and future MINOS data are expected to reduce it further.

The MINOS collaboration submitted its results to Physical Review D.

Explore further: X-ray powder diffraction beamline at NSLS-II takes first beam and first data

More information: www-numi.fnal.gov/PublicInfo/index.html

Provided by Fermi National Accelerator Laboratory

4.3 /5 (9 votes)

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seneca
2.3 / 5 (3) Feb 16, 2010
The absence of Majorana neutrinos could falsify the concept neutrino-antineutrino oscillations, which are predicted by some theories and which would violate conservation of lepton and fermion number. Existence of sterile neutrinos is assumed to be an intermediate step of this transition.

http://arxiv.org/abs/0906.5072
mrlewish
1 / 5 (3) Feb 16, 2010
Correct me if I am wrong but doesn't one of those types of neutrinos have mass and the other does not? And if so how does this not violate that old equal but opposite reaction thing? (lets say I can build a gun or somesuch that emits neutrinos that have mass, thereby pushing the gun .. and have a collector facing opposite that collects the energy of neutrinos that have decayed to no mass neutrinos.. and then transfer that energy to the gun which would fire more mass baring neutrinos) have I just invented a reactionless drive?
mtsher
3 / 5 (3) Feb 16, 2010
mrlewish--you aren't right. It makes no sense to say that the muon neutrino has a mass of X grams. The objects that have mass are called (for example) nu_1 and nu_2. They have a certain mass in grams. But nu_1 (for example) behaves like a muon neutrino 2/3 of the time and an electron neutrino 1/3 of the time, and nu_2 is the opposite. Conversely, when a muon emits a muon neutrino, it actually emits a nu_1 2/3 of the time and a nu_2 1/3 of the time. So nu_1 and nu_2 are the states that propagate from one place to another. When a muon neutrino is created, 2/3 of the time it is a nu_1 and when it gets to the other point it will interact mostly as a muon neutrino and sometimes as an electron neutrino. So no mass changes are involved. This is a very crude explanation, of course (the 2/3 and 1/3 are completely made up)---I think there's a good Scientific American that is more precise and better, and doable in more than 1000 characters.
Bloodoflamb
not rated yet Feb 17, 2010
The statement is that energy eigenstates of a neutrino cannot be made to be simultaneous with the mass eigenstates. It follows that since the emission of a neutrino corresponds to a certain energy loss, the emitted neutrino is in an energy eigenstate that is a linear combination of mass eigenstates that oscillate as the neutrino moves through spacetime.

If the masses of the separate types of neutrinos were identical, neutrino oscillation would not occur. Current theory can nail down fairly closely what the mass differences are between the three and experiment will tell us (eventually) what the mass of the smallest one is.
daywalk3r
3.7 / 5 (13) Feb 18, 2010
Maybe there is no separate types of neutrinos, but only 1, which oscilates between those 3 (or more) different states as it propagates through space/time. And what we detect at the detectors only depends on the state of each neutrino at the moment of its detection.

When something has energy, then it should have mass.. or at least a "mass-potential". And it should only depend on the state/form (structure/construct?) of that energy in regard to wether it exhibits a "mass-effect" or not. (E=mc^2)

And maybe that's exactly what's happening here with the neutrinos - continuous oscilations between energy and mass states(?)

Just a thought.. I'm no expert, so please don't eat me :D
seneca
1 / 5 (1) Feb 18, 2010
The oscillation between "energy and mass states" can be observed at the case of so called Falaco solitons (vortex rings) at water surface (note the end of video). It's called a Widnall's instability at the case of vortex rings.

http://www.youtub...wZ39EDmw

Muon neutrino was found in 1962 in Brookhaven lab, but so far there is no conclusive evidence that even the muon neutrino is stable. There are some indicia, muon neutrino is just faster, more energetic version of normal neutrino, so your idea could be valid.
daywalk3r
3.5 / 5 (11) Feb 18, 2010
The oscillation between "energy and mass states" can be observed at the case of so called Falaco solitons (vortex rings) at water surface (note the end of video). It's called a Widnall's instability at the case of vortex rings.

http://www.youtub...wZ39EDmw
The oscilations of the upper vortex look like phase transitions. And the bottom one maybe just has a longer period(?). Thanks for the link.
seneca
1 / 5 (1) Feb 23, 2010
..And the bottom one maybe just has a longer period..
The former vortex pair (in fact it's just an one half of common vortex ring) moved more slowly. The frequency of neutrino oscillations would depend on the neutrino speed as well.

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