View into the principle spectrometer of the KATRIN experiment to find out the mass of the neutrino on Campus North of KIT. Credit score: Markus Breig, KIT
New world document: Neutrinos are lighter than 0.8 electron volts.
Neutrinos are arguably essentially the most fascinating elementary particles in our universe. In cosmology they play an necessary function within the formation of large-scale constructions, whereas in particle physics their very small mass units them aside, pointing to new physics phenomena past our present theories. And not using a measurement of the mass of neutrinos, our understanding of the universe will stay incomplete.
That is the problem taken by the worldwide KArlsruhe TRItium Neutrino (KATRIN) experiment at KIT because the world’s most delicate scale for neutrinos. Companions from six international locations are concerned. KATRIN makes use of the beta decay of tritium, an unstable hydrogen isotope, to find out the mass of the neutrino through the vitality distribution of electrons launched within the decay course of. This requires a significant technological effort: The 70 m lengthy experiment homes the world´s most intense tritium supply in addition to an enormous spectrometer to measure the energies of decay electrons with unprecedented precision. After beginning scientific measurements in 2019, the prime quality of the information has been repeatedly improved during the last two years. “KATRIN as an experiment with the very best technological necessities is now working like an ideal clockwork,” says Professor Guido Drexlin from KIT, the challenge chief and one of many two co-spokespersons of the experiment. Professor Christian Weinheimer, College of Münster, the opposite co-spokesperson, provides: “Discount of the background charge and enhance within the sign charge had been decisive for the brand new outcome.”
Schematic illustration of the setup of the KATRIN experiment. Credit score: Leonard Köllenberger for the KATRIN collaboration
Detailed Knowledge Evaluation: First Push into the Vary under 1 eV
In-depth evaluation of those knowledge represented a giant problem for the worldwide staff led by the 2 coordinators Dr. Magnus Schlösser, KIT, and Professor Susanne Mertens, Max Planck Institute for Physics and Technical College of Munich: Every impact on the neutrino mass, irrespective of how small, needed to be investigated intimately. “This laborious and complicated work was the one strategy to exclude a scientific bias of our outcome because of distorting processes. We're significantly happy with our evaluation staff that accepted this big problem with nice dedication and was profitable, “ Schlösser and Mertens say. The experimental knowledge from the primary yr of measurements and modeling based mostly on a vanishingly small neutrino mass matched completely: It allowed them to find out a brand new higher restrict of 0.8 eV for the neutrino mass, the scientists level out. That is the primary time that a direct neutrino mass experiment has entered the sub-eV mass vary that's of excessive relevance to cosmology and particle physics, as it's right here the place the elemental mass scale of neutrinos is assumed to lie. “The particle physics group is worked up that the 1-eV barrier has been damaged by KATRIN,” feedback neutrino professional John Wilkerson, College of North Carolina, who chairs the KATRIN Govt Board.
“The success was based mostly decisively on the truth that the ramp-up of the supply to nominal supply intensities on the Karlsruhe Tritium Laboratory and the operation of the spectrometer, detector, and cryoinfrastructure went easily. This was as a result of skilled dedication of our extremely motivated employees which supported this large-scale experiment,” Schlösser emphasizes.
Additional Measurements to Enhance Sensitivity
The researchers concerned within the KATRIN challenge describe their subsequent targets: “Additional measurements of the neutrino mass will proceed till the tip of 2024. To exhaust the total potential of this distinctive experiment, we'll steadily enhance the statistics of sign occasions and repeatedly develop and set up upgrades to additional scale back the background charge.” The event of the brand new TRISTAN detector system can be of specific significance. From 2025, it's going to enable KATRIN to embark on a seek for “sterile“ neutrinos with plenty within the keV vary. Such sterile neutrinos could be candidates for the mysterious darkish matter that has already turn into manifest in lots of astrophysics and cosmological observations, however the bodily nature of which remains to be unknown.
For extra on this analysis, see New World Document: “Ghost Particle” Experiment Limits Neutrino Mass With Unprecedented Precision.
Reference: “Direct neutrino-mass measurement with sub-eV sensitivity” by The KATRIN Collaboration, 14 February 2022, Nature Physics.
DOI: 10.1038/s41567-021-01463-1
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