First results from RENO: Observation of the weakest neutrino transformation

Apr 09, 2012

The Reactor Experiment for Neutrino Oscillations (RENO) research team announced the first result of the search for the remaining, most elusive puzzle of the neutrino transformation. They have found disappearance of neutrinos emitted from six reactors at the Yonggwang nuclear power plant in Korea, on the way to their 1.4 km distant detector. The exciting result of solving the longstanding secret provides a complete picture of neutrino transformation among three kinds of neutrinos, and opens a bright window of understanding why there is much more matter than antimatter in the Universe today.

Neutrinos are almost invisible and massless particles with no electric charge, traveling at close to the and interacting with matter so weakly. In 1998, the Super-Kamiokande detector found transformation among the and therefore existence of their masses for the first time. Two out of three different neutrino-transformation strengths are observed to be rather large, close to 100% or 80%, but the last one is known to be less than 15%.

The RENO is the first experiment to search for the last smallest neutrino transformation, so-called "mixing angle θ13", with two identical detectors at different distances, 290 m and 1400m, from the center. The construction of both detectors was completed in February 2011 and after commissioning, the data taking began from August 2011. More than 7 months of unprecedentedly copious neutrino data revealed a quite clear signal of the neutrino transformation, with a significance of 6.3 standard deviations, as an effect of the unknown mixing angle that physicists have been anxiously searching for. The RENO determined the new type of neutrino transformation strength to a good precision, to be 10.3%.

"This was the hardest neutrino transformation to measure, but it turns out to be rather large", says Soo-Bong Kim of Seoul National University, spokesperson of the RENO experiment. "This surprisingly large value of θ13 will strongly promote the next round of neutrino experiments to find the reason for asymmetry of matter-antimatter in this universe. An exciting time ahead..."

During the power production, a nuclear reactor emits a trillion-times-billion neutrinos every second. The measurement in the detector close to the reactor predicts how many reactor neutrinos should be counted in the other detector far from the reactor if there were no neutrino transformation. Comparison with the actual measurement in the far detector can determine how much the reactor neutrinos were transformed to other neutrinos, namely the smallest mixing angle.

The RENO takes full advantage of 6 nuclear reactors with 16.5 Giga-watt of full thermal power, located at a town of Yonggwang on the west coast of Korean peninsula. The total of 16.5 ton of organic transparent and scintillating liquid mixed with 0.1% of Gadolinium can capture some of these neutrinos and emits light, which are subsequently recorded by about 350 photo sensors ("photomultipliers") of radius 25cm. The main part of the detector is then shielded by several layers of other materials in order to enhance its performance and also to protect it from natural radiation produced outside. To reduce cosmic rays resulting in substantial backgrounds, the two detectors are located at underground.

The result was submitted to the Physical Review Letters on April 2, 2012.

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User comments : 9

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Blakut
5 / 5 (1) Apr 09, 2012
This article has the quality of 300 billion gallons of power. That's enough energy to melt the sun into a star!
HannesAlfven
1 / 5 (4) Apr 09, 2012
Neutrinos are the smallest validated particle, no? These observations seem to put us right at the edge of what is observable, right?

Also, there is very strong motivation for producing positive results here. Without an indication that neutrinos change flavor, then there remains an undercount on the Sun's observed neutrino emissions. And this would cast doubt upon the existing solar theory.

These are absolutely vital details to this story, which no serious-minded journalist should ever intentionally leave out. When these stories are presented without the underlying history and motivation for the research, the quest for the neutrino flavor changes are made to appear like a pure act of curiosity. But, the more accurate truth is that if this experiment had failed to generate the intended results, others would likely follow. One is left wondering: Were there negative results which were NOT published, simply because they did not confirm the neutrino flavor change?
Tennex
1 / 5 (5) Apr 09, 2012
In dense aether model the neutrinos correspond the Falaco solitons, i.e. the vortex rings floating along water surface. If you'll watch it carefully, the size of vortex is changing during this (it's commented loudly at the middle of video). What the vortex does during this is so called Widnall's instability (animated picture) It means, the angular momentum inside of particle travels across nested dimensions. At the case of neutrino vortex three nested levels of dimensions exist, which corresponds the three generations of neutrino, which can oscillate independently with different frequency between each other.
HannesAlfven
1 / 5 (3) Apr 09, 2012
An implication of this research -- for better or worse -- is that theorists now have license to ignore any neutrino anomalies which they might observe, which might have otherwise cast doubt upon existing theory.

During his time, David Bohm commented that there are 16 orders of magnitude between the "smallest detectable physical distance", (10^-17 cm) and the "smallest distance beyond which space no longer has any meaning" (10^-33 cm). A lot could be happening in those 16 orders of magnitude to explain many of the quantum effects we observe.

It doesn't make a whole lot of sense to consider this latest measurement to be the final word on anything.
Tennex
1 / 5 (4) Apr 09, 2012
An implication of this research -- for better or worse -- is that theorists now have license to ignore any neutrino anomalies which they might observe, which might have otherwise cast doubt upon existing theory.

Neutrino oscillations are anomaly by itself, Standard Model predict zero rest mass for neutrinos and therefore no oscillations. Actually, just the oscillations could explain superluminal neutrinos without violation of relativity: the neutrinos are doing literally jumps through space, but we cannot observe them during it, so that from relativistic perspective is everything OK. Actually, what we are seeing between neutrino jumps are two different particles, which could differ with their spin or rest mass.
Jitterbewegung
1 / 5 (2) Apr 09, 2012
"The main part of the detector is then shielded by several layers of other materials in order to enhance its performance and also to protect it from natural radiation produced outside."

What substance is this shielding made of and why isn't it used to detect neutrinos if it interacts so well?
Terriva
5 / 5 (1) Apr 09, 2012
What substance is this shielding made of and why isn't it used to detect neutrinos if it interacts so well?
It's mineral oil and it purpose is to trap the radioactivity in the photomultiplier tubes, not the neutrinos.

http://arxiv.org/...91v1.pdf
Graeme
5 / 5 (1) Apr 10, 2012
The shielding is supposed to stop the non-neutrinos not detect the neutrinos. I will guess that it is not transparent. In one installation it is lead with polythene, with detectros for muons embedded. If muons are detected the results from the inside of the detector are ignored.
Kinedryl
5 / 5 (1) Apr 10, 2012
I will guess that it is not transparent.
It's transparent, as the photomultipliers are outside of buffer layer, it just doesn't contain Gd scintillator. http://www.symmet...RENO.png

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