Theoretical and experimental physics team up in the search for particle flavor change

An essential current discovery in physics got here from measuring neutrinos—impartial, weakly interacting particles—produced by the solar. Nuclear reactions within the solar produce solely electron neutrinos. In accordance with the usual mannequin, neutrinos are available three distinct “flavors” (electron, mu, and tau). Scientists initially thought neutrinos to be massless, however they lately found that neutrinos have mass.

An attention-grabbing consequence of this discovery is that neutrinos can change taste. This implies two-thirds of the neutrinos reaching Earth from the solar are usually not electron neutrinos. Now, advances in principle and experiment are serving to scientists to find out whether or not the neutrinos’ charged counterparts—electrons, muons, and tauons—can even change taste.

In two new experiments, scientists will seek for a negatively charged muon, the electron’s extra large cousin, decaying into an electron. This may violate the usual mannequin. These experiments, Mu2e at Fermilab and COMET at J-PARC in Japan, will be capable to detect electrons from this course of even when the conversion chance is just one in 100 quadrillion.

This makes these experiments 10,000 occasions extra delicate than earlier searches. Latest theoretical work has recognized new physics info out there in these experiments and the right way to measure it. The outcomes could inform scientists about interactions which may exist past the usual mannequin.

Muons are captured in a nuclear goal, the place they bind—like electrons—in an atom. When muon-to-electron conversion happens, scientists can solely observe these electrons that depart the nucleus in its lowest-energy state. These electrons have a exact vitality, simplifying their detection and eliminating backgrounds if solely they're chosen for measurement. As a result of the nucleus stays in its floor state, it restricts what could be measured.

Researchers on the College of California, Berkeley, Lawrence Berkeley Nationwide Laboratory, Shanghai Jiao Tong College, and the College of Massachusetts, Amherst discovered that with this filter in place, experimentalists can measure six unbiased observables if researchers use a set of nuclear targets fastidiously chosen for his or her properties.

Nuclear principle may help information this choice, as it could predict which goal properties will improve a given observable. The six observables signify the “fingerprint” of the brand new physics and outline a program of measurements that groups like Mu2e and COMET can full. As soon as this program is carried out, particle theorists can have six new clues about potential physics lacking from the usual mannequin.