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Sun Nov 24, 2019, 08:12 PM

The mystery of neutrino mass could soon be solved

Neutrinos are a billion times more abundant in the universe than atoms.

NOVEMBER 23, 2019

The neutrino is incredibly tiny. For many years, scientists thought they were massless. Experiments showing that neutrinos change type proved that wasn’t the case, but we still don’t know the absolute mass of the neutrino.

Physicists are just one step closer to reveal the mystery of mass of the neutrino, a subatomic particle that is very similar to an electron but has no electrical charge. Once thought to be massless, the particle probably has a mass no more than 500,000 times that of an electron.

In a new study that aims to examine the upper limit of the neutrino’s mass, scientists analyzed the decay of a radioactive form of hydrogen called tritium. By estimating the vitality of the released electrons, they were able to appraise the mass of the neutrino with more accuracy than was previously conceivable.

Christian Weinheimer, at the University of Münster, Germany, said, “Neutrinos are a billion times more abundant in the universe than atoms, so even tiny neutrino masses would make a big contribution to the mass in the universe.”


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Reply The mystery of neutrino mass could soon be solved (Original post)
Judi Lynn Nov 24 OP
Kurt V. Nov 24 #1
eppur_se_muova Nov 24 #2
eppur_se_muova Nov 24 #3

Response to Judi Lynn (Original post)

Sun Nov 24, 2019, 08:53 PM

1. hard to catch such a tiny critter.

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Response to Judi Lynn (Original post)

Sun Nov 24, 2019, 11:16 PM

2. 500,000 *TIMES* that of an electron ??? Try 1/500,000 th, maybe ?

The rest mass of an electron is about 511 keV; the sum of the masses of the three flavors of neutrinos is probably ≤ 1 eV.

This much was known already from calculations: https://www.natureworldnews.com/articles/5968/20140210/mass-neutrinos-accurately-calculated-first-time-physicists-report.htm

The recent results appear to confirm it experimentally, though the upper bound given here is still larger than that calculated: https://arxiv.org/pdf/1909.06048.pdf

We report on the neutrino mass measurement result from the first four-week science run of theKarlsruhe Tritium Neutrino experiment KATRIN in spring 2019. Beta-decay electrons from a high-purity gaseous molecular tritium source are energy analyzed by a high-resolution MAC-E filter. Afit of the integrated electron spectrum over a narrow interval around the kinematic endpoint at 18.57keV gives an effective neutrino mass square value of (−1.0+ 0.9−1.1) eV2. From this we derive an upperlimit of 1.1 eV (90% confidence level) on the absolute mass scale of neutrinos. This value coincideswith the KATRIN sensitivity. It improves upon previous mass limits from kinematic measurementsby almost a factor of two and provides model-independent input to cosmological studies of structureformation.

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Response to Judi Lynn (Original post)

Sun Nov 24, 2019, 11:33 PM

3. Sounds like they're doing (Fermi-) Kurie plots, using more accurate data from a new detector ...

... but I could be wrong.

Kurie plot

A Kurie plot (also known as a Fermi–Kurie plot) is a graph used in studying beta decay developed by Franz N. D. Kurie, in which the square root of the number of beta particles whose momenta (or energy) lie within a certain narrow range, divided by the Fermi function, is plotted against beta-particle energy.[34][35] It is a straight line for allowed transitions and some forbidden transitions, in accord with the Fermi beta-decay theory. The energy-axis (x-axis) intercept of a Kurie plot corresponds to the maximum energy imparted to the electron/positron (the decay's Q value). With a Kurie plot one can find the limit on the effective mass of a neutrino.[36]


"Ordinary" double beta decay results in the emission of two electrons and two antineutrinos. If neutrinos are Majorana particles (i.e., they are their own antiparticles), then a decay known as neutrinoless double beta decay will occur. Most neutrino physicists believe that neutrinoless double beta decay has never been observed.[43]


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