Maximum mass of lightest neutrino revealed using astronomical big data

Credit: CC0 Public Domain

Neutrinos come in three flavours made up of a mix of three neutrino masses. While the differences between the masses are known, little information was available about the mass of the lightest species until now.

It's important to better understand and the processes through which they obtain their as they could reveal secrets about astrophysics, including how the universe is held together, why it is expanding and what dark matter is made of.

First author, Dr. Arthur Loureiro (UCL Physics & Astronomy), said: "A hundred billion neutrinos fly through your thumb from the Sun every second, even at night. These are very weakly interactive ghosts that we know little about. What we do know is that as they move, they can change between their three flavours, and this can only happen if at least two of their masses are non-zero."

"The three flavours can be compared to ice cream where you have one scoop containing strawberry, chocolate and vanilla. Three flavours are always present but in different ratios, and the changing ratio-and the weird behaviour of the particle-can only be explained by neutrinos having a mass."

The concept that neutrinos have mass is a relatively new one with the discovery in 1998 earning Professor Takaaki Kajita and Professor Arthur B. McDonald the 2015 Nobel Prize in Physics. Even so, the Standard Model used by modern physics has yet to be updated to assign neutrinos a mass.

The study, published today in Physical Review Letters by researchers from UCL, Universidade Federal do Rio de Janeiro, Institut d'Astrophysique de Paris and Universidade de Sao Paulo, sets an for the mass of the lightest neutrino for the first time. The particle could technically have no mass as a lower limit is yet to be determined.

The team used an innovative approach to calculate the mass of neutrinos by using data collected by both cosmologists and particle physicists. This included using data from 1.1 million galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) to measure the rate of expansion of the universe, and constraints from particle accelerator experiments.

"We used information from a variety of sources including space- and ground-based telescopes observing the first light of the Universe (the ), exploding stars, the largest 3-D map of galaxies in the Universe, particle accelerators, nuclear reactors, and more," said Dr. Loureiro.

"As neutrinos are abundant but tiny and elusive, we needed every piece of knowledge available to calculate their mass and our method could be applied to other big questions puzzling cosmologists and particle physicists alike."

The researchers used the information to prepare a framework in which to mathematically model the mass of neutrinos and used UCL's supercomputer, Grace, to calculate the maximum possible mass of the lightest neutrino to be 0.086 eV (95% CI), which is equivalent to 1.5 x 10-37 Kg. They calculated that three neutrino flavours together have an upper bound of 0.26 eV (95% CI).

Second author, Ph.D. student Andrei Cuceu (UCL Physics & Astronomy), said: "We used more than half a million computing hours to process the data; this is equivalent to almost 60 years on a single processor. This project pushed the limits for big data analysis in cosmology."

The team say that understanding how neutrino mass can be estimated is important for future cosmological studies such as DESI and Euclid, which both involve teams from across UCL.

The Dark Energy Spectroscopic Instrument (DESI) will study the large scale structure of the universe and its dark energy and contents to a high precision. Euclid is a new space telescope being developed with the European Space Agency to map the geometry of the dark Universe and evolution of cosmic structures.

Professor Ofer Lahav (UCL Physics & Astronomy), co-author of the study and chair of the UK Consortiums of the Dark Energy Survey and DESI said: "It is impressive that the clustering of galaxies on huge scales can tell us about the mass of the lightest neutrino, a result of fundamental importance to physics. This new study demonstrates that we are on the path to actually measuring the neutrino masses with the next generation of large spectroscopic galaxy surveys, such as DESI, Euclid and others."

Arthur Loureiro et al., 'On The Upper Bound of Neutrino Masses from Combined Cosmological Observations and Particle Physics Experiments' will be published in Physical Review Letters on Thursday 22 August 2019.

Explore further

Scientists in Germany seek to find mass of neutrino

More information: On The Upper Bound of Neutrino Masses from Combined Cosmological Observations and Particle Physics Experiments, arXiv:1811.02578 [astro-ph.CO] , … ysRevLett.123.081301
Journal information: Physical Review Letters

Citation: Maximum mass of lightest neutrino revealed using astronomical big data (2019, August 22) retrieved 17 September 2019 from
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User comments

Aug 22, 2019
I think there must be a misprint on the upper bound of the three neutrinos together.

Aug 22, 2019
Still no breaking of the mass ordering (between electron m1, muon m2 or tau m3 neutrinos): "m1 < m2 << m3, known as the normal hierarchy (NH), or m3 << m1 < m2, the inverted hierarchy (IH)."

But cosmology becomes simpler, they show it suffice to go simple. We can use normal hierarchy models with a total mass sum and have no need to study mass degeneracy (the small correction due to neutrino interactions, seen right after the hit big bang).

Aug 22, 2019
The field change due to diametrical field centers parting! There are no particles; only field centers and there infinite field. The Universe, and infinite set of bi-polar pairs in an infinite space and time; which, is only our concept. But, if one sets c=1; q=+/-1; T=Lambda, it becomes clear! Note: Mass is only a mathematical constant; Field Centers Exist!

Aug 22, 2019
Still interested in the possible contribution of these neutrino masses to observed dynamics lumped together as "dark matter." As you know, @torbjorn, my guess is a combination of multiple effects, not a single particle or a single field. This accounts for it not being detected in particle experiments, because no single experiment can detect all the different factors that add up to it.

Aug 23, 2019
If neutrinos do indeed oscillate from flavor to flavor, I don't see how any of the 3 flavors could have zero mass, because a zero mass neutrino would move at the speed of light, and relativity tells us that, to an outside observer, any observed internal process in a particle moving at the speed of light would come to an absolute halt. Therefore the massless neutrinos could never oscillate to a different flavor, and massless neutrinos would soon become almost all the neutrinos which exist.

Aug 23, 2019
You'll need to learn enough GRT to understand the energy-momentum tensor. Suffice it to say that energy and momentum are mixed, with a different mix for different observers.

Aug 23, 2019
I dont get why we dont use the idea of electrons and neutrinos being equivilent to protons and neutrons. We know there has to be the same number of electrons to protons, so why not a symetry between neuteons and neuteinos.

The only difference between what is quark and what is lepton is the spacetime they exist in. Because neutrinos are in spacetime expanding away from the nucleus they cant be confined to an atom to share charge with the electrons, as neutrons do with protons. Because of that we have fission of large particles as a way to balance spin between inside and outside the nucleus (because they cant hold neuteinos in outter shells, like thennucleus does for neutrons).

To me symetry could explain a lot about these elusive little particles.

Aug 23, 2019
To understand how spacetime in the nucleus is different to that in the electron cloud, you have to accept time (just like space), has both up and down spin (complex and its conjugate). So quarks exist in the up version of time, electrons in the down conjugate version.

That difference, gives one the ability to clump in the nucleus and it takes energy to seperate them (quark binding), and the other requires energy to keep them (electric charge). So the more neutrons in the nucleus, the more lop sided the spin is and unstable it becomes. Effectively fission is just the nucleus shaking itself apart as there are no neutrinos to balance it out and stabilize it.

Ergo electrons and neutrinos are compound particles, acting in a negative curvature spacetime.

Aug 24, 2019
The Absolute Velocity - Light Speed - Albert Einstien

- Neutrinos in time and space by the University College of London -
Neutrinos come in three flavours
Made up of a mix of three neutrino masses
While the differences between the masses are known
Little information was available about the mass of the lightest species
Until now

Only Massless Objects Travels at Lightspeed - Albert Einstein

Aug 24, 2019
Neutrinos Change Flavour in Fight

This is only possible
Because a flavour is an energy level
For when the sun ejects a neutrino
This means
What we are about to receive
Is not necessarily that we receive
Neutrinos change energy levels in flight
Because, just like neutrinos, energy levels are massless

Flavours are energy levels; as energy is massless, only massless objects travel at lightspeed

Aug 24, 2019
The Moral of this Neutrino Tail

For this neutrino seems to have a very long tail
Is, a neutrino is massless
And its flavours are massless
If you divide these three neutrino flavours by the square of lightspeed equals this neutrinos mass
E = MC² is not inertial mass
E = MC² is Kinetic Energy
Which is why, E = MC² is massless energy!

Aug 24, 2019
The photon and the Neutrino

Both the photon and the neutrino
Mathematically can be said to have velocity, momentum and mass
Except, Albert Einstein forbade mass to travel at lightspeed
Therefore; dear old Albert, postulated that only electromagnetic energy, travels at lightspeed
This meaneths

1, energy is massless
2, kinetic energy is massless
3, flavours are massless
4, neutrinos are massless
5, photons are massless
6, electromagnetic energy is massless

In Traditional Haiku

In short
Any entity travelling lightspeed
Is massless

Aug 24, 2019
One must realize, we only see a changing E Field within a limited spectrum and can only acknowledge after about 15ms unless using instrumentation. Then we define what is seen spatially with our concepts of time and space. Our concepts have nothing to do with what is seen; only what you believe and think. Without logic, we are blind! All we see, all we measure is the E field. Coulomb expressed it as a Spherical Graded Infinite E Field. We use it for all measurements. Particles; then, would be invisible and illogical since the Field centers, Charge, are never created or destroyed! And "Solid Particles with or without infinite density would simply be nonsense!

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