Recommended by us:"First evidence for extraterrestrial sources of high-energy neutrinos"

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IceCube Neutrino Observatory reports first evidence for extraterrestrial sources of high-energy neutrinos

A massive telescope in the Antarctic ice reports the detection of 28 extremely high-energy neutrinos that might have their origin in cosmic sources. Two of these reached energies greater than 1 petaelectronvolt (PeV), an energy level thousands of times higher than the highest energy neutrino yet produced in a manmade accelerator.

Francis Halzen

The IceCube Neutrino Observatory, run by an international collaboration and headquartered at the Wisconsin IceCube Particle Astrophysics Center (WIPAC) at the University of Wisconsin–Madison, identified the neutrinos, which were described today (May 15) in a talk at the IceCube Particle Astrophysics Symposium at UW–Madison.

“We’re looking for the first time at high energy neutrinos that are not coming from the atmosphere,” says Francis Halzen, principal investigator of IceCube and the Hilldale and Gregory Breit Distinguished Professor of Physics at UW–Madison. “This is what we were looking for,” he adds. “I would never have imagined that the science would be more exciting than building this instrument.”

(Continue to read on www.news.wisc.edu)

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Recommended by us: Organizing the masses at MINOS

Organizing the masses at MINOS

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By combining its neutrino and antineutrino data sets, 

MINOS  has  provided first constraints on the spectrum 

of neutrino masses (represented by the sign of Δm2), the 

CP-violating phase δ,and whether muon or tau neutrinos 

are more strongly mixed  with the so-called ν3 mass state 

(indicated by θ23). The relative goodness of each scenario

 is given along the vertical axis in terms of a difference of 

log-likelihoods. The parameter Δm2 and the angles θ13 

and θ23 relate to the relative masses of the neutrinos and

to how quantum mechanically "mixed" the three types are.

Over a decade ago the evidence became clear that neutrinos, which come in three varieties, can morph from one type to another as they travel, a phenomenon known as neutrino oscillation. By tallying how often this transformation happens under various conditions—different neutrino energies, different distances of travel—one can tease out a number of fundamental properties of neutrinos, for example, their relative masses. The MINOS collaboration has been doing exactly this by sending an intense beam of muon-type neutrinos from Fermilab to northern Minnesota, where a 5-kiloton detector lies in wait deep underground.

In this new result, MINOS has observed the rare case of muon-type neutrinos changing into electron-type neutrinos. This transformation is governed by a parameter known as θ13, and the MINOS data provide new constraints on θ13 using different experimental techniques than previous measurements. MINOS also collected data with an antineutrino beam, and the real excitement comes in when combining the antineutrino and neutrino data sets. Differences between the rates of this particular oscillation mode between neutrinos and antineutrinos would point to a violation of something called CP symmetry. While physicists know that CP symmetry is violated by quarks, it remains unknown whether the same is true for neutrinos. A new source of CP violation is required to explain why the universe began with more particles than antiparticles, and neutrinos could hold the key. (If the universe began with equal numbers of particles and antiparticles, they would have subsequently annihilated away, leaving nothing left over to make the stars and galaxies we have today.)

(Continue to read on Fermilab Today)

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How to Make a Neutrino Beam

“ How to make a neutrino beam

Neutrinos are elusive particles that are difficult to study, yet they may help explain some of the biggest mysteries of our universe. Using accelerators to make neutrino beams, scientists are unveiling the neutrinos’ secrets.

By Jessica Orwig

Neutrinos are among the most abundant particles in the universe, but they rarely interact with matter. Some of today’s outstanding scientific mysteries, such as why there is more matter than antimatter in the universe, could be solved by studying neutrinos and detecting their interactions with matter.

Billions of neutrinos from natural sources, including the Sun, zip through every square centimeter of the Earth each second. Yet scientists cannot easily determine their initial type or exactly how far they traveled before reaching a detector.

To study neutrinos more effectively, scientists produce high-intensity neutrino beams using proton accelerators. Only a few laboratories in the world can manufacture such neutrino beams: the J-PARC laboratory in Japan, the research center CERN in Europe and Fermi National Accelerator Laboratory in the United States.  Every two seconds, Fermilab fires a trillion neutrinos toward particle detectors located in northern Minnesota, more than 450 miles away. This intense beam produces about a thousand neutrino interactions per year in the detectors. 

Continue to read on: http://www.symmetrymagazine.org

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Consensus and/or reality

Physics is certainly an experimental science where everybody can prove or disprove hypotheses...... but!

But as experiments become more and more expensive and difficult the possibility to test a theory is restricted to a small number of collaborations.
This is certainly true in particle physics where some hypothesis can be tested only by some very specific experiments.

Therefore is true that part of the "truth" behind a theory is built upon consensus among the physics community. This is certainly good, and means, for example, that one cannot come up with a stupid idea and pretend to be founded for inconclusive experiments. This also means that theories cannot be disproved by one single crucial experiment (yes naive Popper fans I'm talking to you).

But consensus leads also to some interesting features.
Here is a plot (obtained with this nice website) about the percentage of arXiv.org papers talking about neutrinos (blue), Majorana neutrinos (green) and superluminal neutrinos (red) in the category "phenomenology of high energy physics".

Do you notice any interesting bump?