Physicists fail to find mysterious 'sterile neutrino' particles

After decades of looking, physicists are nary person to discovering theorised particles that could assistance lick ongoing problems successful physics

Physics 27 October 2021

By Leah Crane

Part of the MicroBooNE neutrino experiment

Cindy Arnold

The hunt for mysterious theoretical particles known arsenic sterile neutrinos has turned up bare again. Neutrinos are highly airy subatomic particles that hardly interact with regular matter. There are 3 known types and the hunt for a 4th has been going connected for decades. Now, a caller acceptable of analyses has failed to find immoderate motion that it exists.

Sterile neutrinos get their sanction because, dissimilar the different 3 types, they would lone interact via gravity and not the different cardinal forces. Many theoretical physicists recovered the thought of a sterile neutrino promising due to the fact that it had the imaginable to explicate respective anomalies recovered successful particle physics experiments, arsenic good arsenic being applicable to the enigma of dark matter. But due to the fact that neutrinos are truthful tiny and interact truthful weakly with different matter, we tin lone observe them indirectly, via the products of collisions with different particles.

In the 1990s and aboriginal 2000s, 2 neutrino experiments recovered much of these products than expected. However, neither of them was capable to archer the quality betwixt electrons and photons successful its results – and sterile neutrinos would lone nutrient other electrons, not photons. A newer experimentation called MicroBooNE astatine the Fermi National Accelerator Laboratory successful Illinois tin archer the difference, but its archetypal 3 years of information amusement nary other neutrino products astatine all.

“I would person truly expected to spot an excess successful either the photons oregon the electrons and we haven’t seen 1 successful either, which opens up much questions,” says MicroBooNE spokesperson Justin Evans astatine the University of Manchester successful the UK. We inactive person nary mode to explicate the earlier results, truthful they mightiness constituent to much exotic carnal processes that haven’t yet been considered, helium says.

So is the hunt for the sterile neutrino over? “We decidedly are not seeing immoderate grounds for a sterile neutrino,” says Evans. “As to whether it is wholly dead, I deliberation that depends who you ask, but you’ve surely got to get a batch much inventive to get a sterile neutrino into your particle physics models now.”

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• neutrinos
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