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Using data from the large-scale structure of galaxies, the Cosmic Microwave Background (CMB), the Type Ia supernovae, and the Big Bang nucleosynthesis, a team of physicists calculated the maximum possible mass of neutrino species. the lightest.
First observation of neutrinos in the world in a hydrogen bubble chamber. It was found on November 13, 1970 in this photo of the 12-foot bubble chamber of the zero gradient synchrotron. The invisible neutrino strikes a proton from which three traces of particles (bottom right) originate. The neutrino is transformed into mu-meson, the long central track (which extends to the top and the left). The short track is the proton. The third track (which extends down and to the left) is a pi-meson created by the collision. Image credit: Argonne National Laboratory.
Physicists know that there are three types of neutrinos: electronic neutrinos, muons and tau. But there are also three different mass neutrinos.
Each neutrino of a specific flavor is actually a combination of neutrinos of different masses.
"One hundred billion neutrinos traverse your thumb of the sun every second, even at night," said Dr. Arthur Loureiro, a researcher at the Department of Physics and Astronomy at University College London.
"They are very weakly interactive ghosts that we know little about. What we do know is 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. They are always present but in different ratios, and the changing ratio – as well as the strange behavior of the particle – can only be explained by the fact that neutrinos have a mass. "
Dr. Loureiro and his colleagues used an innovative approach to calculate the mass of neutrinos using data collected by both 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 have used information from various sources, including space and ground telescopes observing the first light of the Universe (CMB radiation), explosive stars, the largest 3D map of the Universe galaxies, accelerators particles, 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 confuse cosmologists and particle physicists."
Physicists used this information to develop a framework for mathematical modeling of neutrino mass and used a supercomputer to calculate the maximum possible mass of the lightest neutrino, 0.086 eV, equivalent to 1.5 * 10.-37 kg.
They calculated that three whole neutrino flavors had an upper limit of 0.26 eV.
"We used more than half a million hours of computing to process the data. This equates to almost 60 years on a single processor. This project has pushed the boundaries of massive data analysis in cosmology, "said Andrei Cuceu, PhD student at University College London.
The results were published in the journal Letters of physical examination.
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Arthur Loureiro et al. 2019. Upper limit of neutrino masses extracted from combined experiments of cosmological observations and particle physics. Phys. Rev. Lett 123 (8): 081301; doi: 10.1103 / PhysRevLett.123.081301
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