First results from Daya Bay find new kind of neutrino transformation

Mar 08, 2012
Each antineutrino detector at the Daya Bay Reactor Neutrino Experiment is lined with photomultiplier tubes to catch the faint trace of antineutrino reactions in the scintillator fluids that fill the detectors. Credit: Roy Kaltschmidt, Lawrence Berkeley National Laboratory

The Daya Bay Reactor Neutrino Experiment, a multinational collaboration operating in the south of China, today reported the first results of its search for the last, most elusive piece of a long-standing puzzle: how is it that neutrinos can appear to vanish as they travel? The surprising answer opens a gateway to a new understanding of fundamental physics and may eventually solve the riddle of why there is far more ordinary matter than antimatter in the universe today.

Traveling at close to the , the three basic neutrino "" – electron, muon, and tau neutrinos, as well as their corresponding antineutrinos – mix together and oscillate (transform), but this activity is extremely difficult to detect. From Dec. 24, 2011, until Feb. 17, 2012, scientists in the Daya Bay observed tens of thousands of interactions of electron antineutrinos, caught by six massive detectors buried in the mountains adjacent to the powerful nuclear reactors of the Guangdong Nuclear Power Group. These reactors, at Daya Bay and nearby Ling Ao, produce millions of quadrillions of elusive electron antineutrinos every second.

The copious data revealed for the first time the strong signal of the effect that the scientists were searching for, a so called "mixing angle" named theta one-three (written θ13), which the researchers measured with unmatched precision. Theta one-three, the last mixing angle to be precisely measured, expresses how electron neutrinos and their antineutrino counterparts mix and change into the other flavors. The Daya Bay collaboration's first results indicate that sin2 2 θ13 is equal to 0.092 plus or minus 0.017.

"This is a new type of neutrino oscillation, and it is surprisingly large," says Yifang Wang of China's Institute of High Energy Physics (IHEP), co-spokesperson and Chinese project manager of the Daya Bay experiment. "Our precise measurement will complete the understanding of the neutrino oscillation and pave the way for the future understanding of matter-antimatter asymmetry in the universe."

Neutrinos, the wispy particles that flooded the universe in the earliest moments after the big bang, are continually produced in the hearts of stars and other nuclear reactions. Untouched by electromagnetism, they respond only to the weak nuclear force and even weaker gravity, passing mostly unhindered through everything from planets to people. The challenge of capturing these elusive particles inspired the Daya Bay collaboration in the design and precise placement of its detectors.

"Although we're still two detectors shy of the complete experimental design, we've had extraordinary success in detecting the number of electron antineutrinos that disappear as they travel from the reactors to the detectors two kilometers away," says Kam-Biu Luk of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley. Luk is co-spokesperson of the Daya Bay Experiment and heads U.S. participation. "What we didn't expect was the sizable disappearance, equal to about six percent. Although disappearance has been observed in another reactor experiment over large distances, this is a new kind of disappearance for the reactor electron antineutrino."

The Daya Bay experiment counts the number of electron antineutrinos detected in the halls nearest the Daya Bay and Ling Ao reactors and calculates how many would reach the detectors in the Far Hall if there were no oscillation. The number that apparently vanish on the way (oscillating into other flavors, in fact) gives the value of theta one-three. Because of the near-hall/far-hall arrangement, it's not even necessary to have a precise estimate of the antineutrino flux from the reactors.

"Even with only the six detectors already operating, we have more target mass than any similar experiment, plus as much or more reactor power," says William Edwards of Berkeley Lab and UC Berkeley, the U.S. project and operations manager for the Daya Bay Experiment. Since Daya Bay will continue to have an interaction rate higher than any other experiment, Edwards explains, "it is the leading theta one-three experiment in the world."

The first Daya Bay results show that theta one-three, once feared to be near zero, instead is "comparatively huge," Kam-Biu Luk remarks, adding that "Nature was good to us." In coming months and years the initial results will be honed by collecting far more data and reducing statistical and systematic errors.

"The Daya Bay experiment plans to stop the current data-taking this summer to install a second detector in the Ling Ao Near Hall, and a fourth detector in the Far Hall, completing the experimental design," says Yifang Wang.

Refined results will open the door to further investigations and influence the design of future neutrino experiments – including how to determine which neutrino flavors are the most massive, whether there is a difference between neutrino and antineutrino oscillations, and, eventually, why there is more matter than in the universe – because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.

"It has been very gratifying to be able to work with such an outstanding international collaboration at the world's most sensitive reactor neutrino experiment," says Steve Kettell of Brookhaven National Laboratory, the chief scientist for the U.S. effort. "This moment is exciting because we have finally observed all three mixing angles, and now the way is cleared to explore the remaining parameters of neutrino oscillation."

"This is really remarkable," says Wenlong Zhan, vice president of the Chinese Academy of Sciences and president of the Chinese Physical Society. "We hoped for a positive result when we decided to fund the project, but we never imagined it could come so quickly!"

"Exemplary teamwork among the partners has led to this outstanding performance," says James Siegrist, DOE Associate Director of Science for High Energy Physics. "These notable first results are just the beginning for the world's foremost neutrino experiment."

Explore further: Uncovering the forbidden side of molecules

More information: For more information, visit dayawane.ihep.ac.cn/twiki/bin/view/Public/WebHome

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Mike_Massen
1.9 / 5 (10) Mar 08, 2012
Interesting article & makes me wonder about the whole matter/anti-matter issue afresh, helped by a glass of natural source of suitably tinted resveratrol...

I wonder if the "Great Attractor" (observed only by its massive gravitational effect on galaxy clusters) is actually just (ha!) the whole mass of very old and very distant anti-matter in some stupendous black hole on or near the edge of the universe's (light) event horizon so we dont actually have an imbalance after all !

How did it get there, easy, the butterfly effect, from one schism of quantum foam virtual particle effect on earliest stage at a critical time very very shortly after/during the so called 'big bang' rippling through so any remaining matter/anti-matter after initial annihilation left us with the fractions of a percent which we now see & do so humbly partake in and agonise over so willingly :-)

Mike
PS: How would one go about gathering the appropriate evidence/observations for such an idea, ney, a nascent theory
rah
5 / 5 (8) Mar 08, 2012
This is really significant science research and discovery and sadly, it is not taking place in the United States. While the science community tries to be as apolitical as possible, the rest of the world can't help but notice how the US is paying for the last 60 years of arrogance and missed opportunities. We could have used the greatest teaching tool ever invented, television (now, the Internet) to teach every American student 4 times more than they know now. But instead of studying 6 hours per day, Americans averaged 6 hours of watching TV per day. Which is why Americans can tell you everything about the Kardashians but have never heard of neutrino's. That is why this story is coming to us from China.
Blakut
5 / 5 (3) Mar 08, 2012
Hey rah, many Chinese people don't even own television sets. It's all about managing your elites, not about educating the masses.
Lurker2358
1.1 / 5 (9) Mar 08, 2012
because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.


Ah yes, the conjecture without any evidence whatsoever.

couldn't possibly recognize that something must be wrong with the theory, not the evidence.
bnrtn
2 / 5 (4) Mar 08, 2012
The more we know ... (sigh) The experimentalists (as per here) are going great guns, but the theoreticians not so much! Too many particles/waves, too much hand-waving and not enough understanding. The "standard model" thinking doesn't do much for me. I am quite aware that this view is dismissed and ignored by the "mainstream" physics community nowadays. That's ok, I'll keep my money on old Einstein!
bnrtn
4.5 / 5 (2) Mar 08, 2012
Hey rah, many Chinese people don't even own television sets. It's all about managing your elites, not about educating the masses.

Dead on!
El_Nexus
3.7 / 5 (3) Mar 08, 2012
The Daya Bay collaboration's first results indicate that sin2 2 13 is equal to 0.092 plus or minus 0.017.


Can we not get proper formatting of equations on this site?
Callippo
1.4 / 5 (5) Mar 08, 2012
how is it that neutrinos can appear to vanish as they travel
It can explain the superluminal neutrino results observed at MINOS and OPERA experiments (between others). The antineutrino transforms into neutrino and back again and during this brief moment it behaves like so-called sterile or Majorana particle (sometimes called the Goldstone boson, too), i.e. like the gravitational wave without charge. Gravitational waves are superluminal in water surface analogy of spacetime in dense aether model, because they do play an analogy of underwater sound waves for surface ripples - so that the sterile neutrino makes a brief jump through space in this moment. Therefore such a result would be a very good confirmation of dense aether model as well.
Chinese people don't even own television sets
It may be an evolutionary advantage under certain circumstances. For example, I don't own a TV set too: it just steals the time and it makes the people imbecile.
Seeker2
1 / 5 (1) Mar 08, 2012
because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.


Ah yes, the conjecture without any evidence whatsoever.

couldn't possibly recognize that something must be wrong with the theory, not the evidence.
I think the evidence is missing for a good reason - antimatter travelling backwards in time would be repelled by gravitational fields just like unlike charges are attractive instead of repulsive.

jsdarkdestruction
not rated yet Mar 09, 2012
This is really significant science research and discovery and sadly, it is not taking place in the United States. While the science community tries to be as apolitical as possible, the rest of the world can't help but notice how the US is paying for the last 60 years of arrogance and missed opportunities. We could have used the greatest teaching tool ever invented, television (now, the Internet) to teach every American student 4 times more than they know now. But instead of studying 6 hours per day, Americans averaged 6 hours of watching TV per day. Which is why Americans can tell you everything about the Kardashians but have never heard of neutrino's. That is why this story is coming to us from China.

oddly enough, what are "the kardashians?" I've never heard of that before. at first i was thinking you meant like their is a country called that but then i realized odds are americans WOULD not of heard of them. U.W. Madison did contribute to this project,america played a part.
antialias_physorg
not rated yet Mar 11, 2012
This is really significant science research and discovery and sadly, it is not taking place in the United States.

Who cares where it takes place? Certainly the scientific community doesn't give a ratticus' behind where significant findings are made.
Callippo
1 / 5 (2) Mar 11, 2012
Certainly the scientific community doesn't give a ratticus' behind where significant findings are made.
Well, not quite: we could expect, after few such an events many physicists will move to China, because they will get a better job opportunity. In particularly today, where everything in science is about grants and money. It's not good or bad in general, but its symptomatic for the gradual shift of center of research from USA to the Eastern world. Anyway, the physics of USA has still a very good starting position, it just should become less conservative and more pragmatic.
Certainly the scientific community doesn't give a ratticus'
You would be surprised, how many times the name of Marconi was mentioned in the recent study about spiral way of radiowave spreading. http://www.physor...ice.html
kaasinees
1 / 5 (2) Mar 11, 2012
Hey rah, many Chinese people don't even own television sets. It's all about managing your elites, not about educating the masses.

Dead on!

What do you learn from TV nowadays anyways? in the old days there were great documentaries on natgeo and discovery, but if you want those you have to pay extra $ nowadays. MTV used to broadcast music... same story. TV is crap and outdated.
Shinichi D_
not rated yet Mar 12, 2012
because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.


Could it simply be quantummechanical uncertainty? In the early universe, as particle-antiparticle pairs appeared, for very short periods there could a "normal" particle dominance occure, and then an antiparticle dominance. That could shift back and forth very quickly. And as the universe expanded and cooled, at one point it "froze" into a matter dominance. Simply by chance. The particles that had a antiparticle pair, annihilated each other and the univers was left with a slight matter dominance.
All the matter we see today, is the remnant of a cosmic margin of error.
Kinedryl
1 / 5 (4) Mar 12, 2012
In aether theory the antimatter didn't disappear, it was simply dispersed. I've one nice analogy for it: when you visit the Indian camp in forest, you will find only women in it. Where all their husbands are? Well, the men aren't so social, so they do prefer to hunt in diaspora. The antimatter tends to behave like tiny bubbles of space-time, so its dispersed in vacuum into finest possible particles: the positrons, neutrinos, axions and photons inside of streaks of dark matter. Note that despite men are competitive and asocial mutually, they're still attracted to women (you know, the love...) - so you can mostly find them at the proximity of camp in the same way, like we are observing the dark matter around galaxies.
Kinedryl
1 / 5 (4) Mar 12, 2012
In the collective of pupils we can observe often, that the boys are attracted to girls, but they're bashful in their presence, so they avoid their proximity. But when boys appear together in gang, they muster their courage and they do communicate with girls a way easier. After all, the girls aren't different in this extent. So do the elementary particles: the heavier the antimatter particles are, the less bashful behaviour they do exhibit. As the result, the antigravitational behaviour of heavier antiparticles it's not so easy to distinguish from gravity of particles of normal matter. Only the most lightweight particles like the neutrinos differ sufficiently from their antimaterial counterparts.