(PhysOrg.com) -- The results of a high-profile Fermilab physics experiment involving a University of Michigan professor appear to confirm strange 20-year-old findings that poke holes in the standard model, suggesting the existence of a new elementary particle: a fourth flavor of neutrino.
The new results go further to describe a violation of a fundamental symmetry of the universe asserting that particles of antimatter behave in the same way as their matter counterparts.
Neutrinos are neutral elementary particles born in the radioactive decay of other particles. The known "flavors" of neutrinos are the neutral counterparts of electrons and their heavier cousins, muons and taus. Regardless of a neutrino's original flavor, the particles constantly flip from one type to another in a phenomenon called "neutrino flavor oscillation."
An electron neutrino might become a muon neutrino, and then later an electron neutrino again. Scientists previously believed three flavors of neutrino exist. In this Mini Booster Neutrino Experiment, dubbed MiniBooNE, researchers detected more oscillations than would be possible if there were only three flavors.
"These results imply that there are either new particles or forces we had not previously imagined," said Byron Roe, professor emeritus in the Department of Physics, and an author of a paper on the results newly published online in Physical Review Letters.
"The simplest explanation involves adding new neutrino-like particles, or sterile neutrinos, which do not have the normal weak interactions."
The three known types of neutrino interact with matter primarily through the weak nuclear force, which makes them difficult to detect. It is hypothesized that this fourth flavor would not interact through the weak force, making it even harder to find.
The existence of sterile neutrinos could help explain the composition of the universe, said William Louis, a scientist at Los Alamos National Laboratory who was a doctoral student of Roe's at U-M and is involved in the MiniBooNE experiment.
"Physicists and astronomers are looking for sterile neutrinos because they could explain some or even all of the dark matter of the universe," Louis said. "Sterile neutrinos could also possibly help explain the matter asymmetry of the universe, or why the universe is primarily composed of matter, rather than antimatter."
The MiniBooNE experiment, a collaboration among some 60 researchers at several institutions, was conducted at Fermilab to check the results of the Liquid Scintillator Neutrino Detector (LSND) experiment at Los Alamos National Laboratory, which started in 1990. The LSND was the first to detect more neutrino oscillations than the standard model predicted.
MiniBooNE's initial results several years ago, based on data from a neutrino beam (as opposed to an antineutrino beam), did not support the LSND results. The LSND experiment was conducted using an antineutrino beam, though, so that was the next step for MiniBooNE.
These new results are based on the first three years of data from an antineutrino beam, and they tell a different story than the earlier results. MiniBooNE's antineutrino beam data does support the LSND findings. And the fact that the MiniBooNE experiments produced different results for antineutrinos than for neutrinos especially astounds physicists.
"The fact that we see this effect in antineutrinos and not in neutrinos makes it even more strange," Roe said. "This result means even more serious additions to our standard model would be necessary than had been thought from the first LSND result."
The result seems to violate the "charge-parity symmetry" of the universe, which asserts that the laws of physics apply in the same ways to particles and their counterpart antiparticles. Violations of this symmetry have been seen in some rare decays, but not with neutrinos, Roe said.
While these results are statistically significant and do support the LSND findings, the researchers caution that they need results over longer periods of time, or additional experiments before physicists can rule out the predictions of the standard model.
Explore further:
Long-standing neutrino question resolved
More information:
-- The paper is called "Event Excess in the MiniBooNE Search for ν̅ μ→ν̅ e Oscillations." It will be published in an upcoming edition of Physical Review Letters. prl.aps.org/abstract/PRL/v105/i18/e181801
-- MiniBooNE: www-boone.fnal.gov/index.html
deatopmg
KISS
genastropsychicallst
jsa09
Noumenon
Nik_2213
eachus
Sigh! You have to understand how science works. There is always a standard model. Experimentalists test their data against the (current) SM, and theorists propose extensions or tweaks to the standard model based on the experimental data.
Eventually fit between data and theory is strong enough, and new theory is added into the SM. It may replace or augment the existing theory. Now experimentalists test against the NEW standard model, and physics proceeds.
The thing to watch for are improvements to the SM that reduce or eliminate the large number of 'free' parameters in the model. These are numbers selected for no other reason than their fit to the data. Eliminating just one free parameter from the model is probably worth a Nobel Prize.
Tangent2
Ravenrant
Slotin
http://arxiv.org/.../9603436
http://www.scienc..._go_away
Slotin
http://www.physor...225.html
Slotin
http://link.aps.o...2.033009
http://arxiv.org/abs/1004.3464
The more then twenty constants of SM are making it sufficiently flexible for most of theorists, who are looking for continuity in jobs and professional carriers. I'd recommend you to become familiar with streetlight effect before prognosing urgent death of SM.
http://discoverma...t-effect
poktopok
Einstein didn't come up with the Standard Model... in fact, the creation of the Standard Model was a purely collaborative effort, honed over dozens of years by many scientists.
Crackpot
http://classicala...pot.com/
StandingBear
skajam66
marcin_szczurowski
http://xkcd.com/812/
IMO SM is even more hopeless than dark matter.
I wonder if we'll be ever capable of explaining the matter itself. Several years ago, professor that taught me basics of particle physics asked us to think which is more terrifying - to be able to divide matter infinitely or to reach solid, smooth surface at some point. We won't get anywhere close to answers if we stick to theories that obviously don't work. Methinks :P
Slotin
Many connections are misunderstood even by professional physicists. For example, it's generally believed, Standard Model requires the existence of Higgs boson and if we wouldn't find the Higgs boson at LHC, it would mean, SM is "wrong".
But the true is, Standard Model cannot predict/derive the rest mass of Higgs boson anyway - which means at the case of formal model (as SM undeniably is), it cannot plug it into any equation, being invariant/orthogonal to its actual value.
Why some theory should fall because we cannot find a particle, which such theory requires for anything?
Slotin
Stephen Hawking is saying in his new book, the future will use many theories, each of which will remain substantiated from its own perspective. Actually I presume, this is the multiverse, which string theorists are dreaming about.
http://www.time.c...,00.html
In my opinion, theories can be only homologies or analogies of reality. Analogies are always approximate at the quantitative level, but they're logically correct. Homologies can be exact to arbitrary degree of precision at their validity scope - but they're always wrong at logical level, as their agreement with reality is just a coincidence.
Slotin
For example, the Islamic people are fighting with western world for their oil and every part of this feud feels deeply justified in its stance. But hasn't each part of this feud its bit of truth in this fight? If we wouldn't admit it and if we wouldn't find a platform for mutual understanding and cooperation, we will all suffer the consequences.
I believe, the new generation of both physics, both humanity will not be based on authoritative selection of "good" or "wrong" theories, but on the understanding, how various theories and ideas are related mutually.
eachus
So how do you determine whether or not you have seen a particular particle? You look at all the events you see--which may be lower than one in a billion collisions. Now compute how many events you would see if the standard model were true, but without the particle you are looking for, this is H_0 (aka the null hypothesis). Also compute the expectation with your new particle, or new theory. This is H_1.
There are various methods to compare H_0 and H_1, depending on the statistical test used. If the significance is high enough, you reject H_0 and accept H_1.
Notice that you always have to have a standard model to compare to. The (current) SM has changes when a particle is added.
genastropsychicallst
MorituriMax
Wow, another cliched turd drops from the mouths of people who just can't stand it when models need to be looked at and perhaps modified to reflect new information. No, let's just pronounce it dead from their ivory towers because then we sound smart and everyone else sounds dumb.
Care to show us what you're going to replace it with? And does your replacement model fare any better upon closer examination?
TheGhostofZephir
TheWalrus
Sorry, maybe the question is too fundamental to even be answerable. I'll slink off now...
Slotin
http://www.chem.l...co24.jpg
MorituriMax
Ober
http://www.physor...ics.html
This article gives insights into wave-particle duality which makes sense. To me this seems like one of the holy grails of physics.
I suspect the SM needs to include the aether, and perhaps then the problems associated with approximations/pertubation theory will reduce or go away entirely.
Please read the link I provided on fluid dynamics and QM. It's truly an enlightening read. Try and keep this idea in the back of your head whenever you read QM articles.
Slotin
Nov 07, 2010chandram
chandram
Skeptic_Heretic
Well you're making a lot of statements that aren't provable. For example: "then all possiblities would be equally real and would exist simultaneously. Since they do not"
Prove that.
FYI: Chandram and Ober added to the list.