Maximum mass of the lightest neutrino revealed using massive astronomical data

Neutrinos come in three flavors composed of a mixture of three masses of neutrinos. Although the differences between the masses are known, little information was available on the mass of the lighter species up to now.

It is important to better understand the neutrinos and the processes by which they get their mass because they could reveal secrets about astrophysics, especially about how the universe is maintained, why it is growing and about what is dark matter?

The first author, Arthur Loureiro (Physics and Astronomy of the UCL), said: "One hundred billion neutrinos cross your thumb of the Sun every second, even at night.These are very weakly interactive ghosts we know little about. What we do Know that as they move, they can move from one to the other, and this can only happen if at least two of their masses are non-zero. "

"The three flavors can be compared to ice cream where you have a ball containing strawberry, chocolate and vanilla.Three flavors are still present but in different proportions, and the changing ratio and strange behavior of the particle can only be explained as by neutrinos having a mass. "

The concept that neutrinos have a mass is relatively new. In 1998, Professors Takaaki Kajita and Arthur B. McDonald were awarded the 2015 Nobel Prize in Physics. Even in this case, the standard model used by modern physics still needs to be updated to assign a mass to neutrinos.

The study, published today in Letters of physical examination Researchers from UCL, the Federal University of Rio de Janeiro, the Institute of Astrophysics of Paris and the University of Sao Paulo, are setting for the first time the upper limit of the mass of the lightest neutrino. Technically, the particle may not have mass because a lower limit remains to be determined.

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

"We used information from various sources, including space telescopes and ground observing the first light of the Universe (cosmic background radiation), explosive stars, the largest three-dimensional map of the galaxies of the world. universe, particle accelerators, nuclear reactors and more, "said Dr. Loureiro.

"Since neutrinos are abundant but tiny and elusive, we needed all the knowledge available to calculate their mass and our method could be applied to other big questions that are of interest to both cosmologists and particle physicists. "

Researchers used this information to develop a mathematical modeling framework for neutrino mass and used the UCL supercomputer, Grace, to calculate the maximum possible mass of the lightest neutrino, 0.086 eV (95% CI). a value equivalent to 1.5 x 10-37 kg They calculated that three whole neutrino flavors had an upper limit of 0.26 eV (95% CI).

Second author, Ph.D. Andrei Cuceu, a student at UCL Physics & Astronomy, said: "We used more than half a million hours of computation to process the data; this equates to almost 60 years with a single processor This project has pushed the limits of large data analysis in cosmology "

The team says it's important to understand how the mass of neutrinos can be estimated for future cosmological studies such as DESI and Euclid, which both involve teams from all over the UCL.

The black energy spectroscopic instrument (DESI) will study with great precision the structure of the large-scale universe, as well as its content in black energy and black matter. Euclid is a new space telescope developed with the European Space Agency to map the geometry of the dark universe and the evolution of cosmic structures.

Professor Ofer Lahav (UCL Physics & Astronomy), co-author of the study and chairman of the UK consortia of the Dark Energy Survey and DESI, said: "It is impressive that large-scale galaxy clusters can speak to us the most lightweight neutrino, a result of fundamental importance for physics.This new study demonstrates that we are well on the way to actually measuring neutrino masses with the next generation of large spectroscopic galaxy surveys, such as DESI, Euclid and others. "

Arthur Loureiro et al., "On the Upper Limit of Neutrino Masses Resulting from Combined Cosmological Observations and Particle Physics Experiments" will be published in Letters of physical examination on Thursday, August 22, 2019.