Scientists at U.S. Department of Energy (DOE) national laboratories are collaborating to test a magnetic property of the muon. Their experiment could point to the existence of physics beyond our current understanding, including undiscovered particles.
The experiment follows one that began in 1999 at the DOE's Brookhaven National Laboratory in which scientists measured the spin precession of the muon—i.e., the speed at which its spin changes direction—to be different from the theoretical predictions. Scientists from Argonne National Laboratory and Fermi National Accelerator Laboratory, along with collaborators from more than 25 other institutions, are recreating the experiment with much higher precision to confirm or disprove the former earlier results.
The muon is like the (very) big brother of the electron; they have the same charge, but the muon is over 200 times more massive. The two also share the same spin, a quantum mechanical property that determines a particle's behavior in the presence of a magnetic field.
Particles with spin act like tiny magnets, and when placed in a magnetic field, their spins change direction in a circular motion, much like a spinning gyroscope. The speed of a particle's spin precession is determined by a quantity known as its g-factor, which depends on the particle's spin and the strength of the magnetic field in which it moves.
In modern quantum mechanical theories, the vacuum is not empty. It is full of bubbles of so-called virtual particles, appearing and disappearing very quickly. Interactions between these virtual particles and a real particle, like the muon, can change how the real particle interacts with the magnetic field, affecting its g-factor. Theoretical physicists have calculated, based on our current understanding of the fundamental structure of nature, all the ways that each known particle affects the muon's g-factor, but the measurements that Brookhaven scientists took differed from what they expected by a few parts per million. This difference, if it persists in the new experiment, would point to completely new physics—an exciting discovery for particle physicists.
"If there is actually a discrepancy between the predicted and measured values, it is further proof that the Standard Model, our current understanding of the contents of the universe, is incomplete," said Argonne physicist Peter Winter. "The unexpected effect could be due to an undiscovered particle."
Read more at: https://phys.org/news/2018-04-muons-tales-undiscovered-particles.html#jCp
Scientists at U.S. Department of Energy (DOE) national laboratories are collaborating to test a magnetic property of themuon. Their experiment could point to the existence of physics beyond our current understanding, including undiscovered particles.
The experiment follows one that began in 1999 at the DOE's Brookhaven National Laboratory in which scientists measured the spin precession of the muon—i.e., the speed at which its spin changes direction—to be different from the theoretical predictions. Scientists from Argonne National Laboratory and Fermi National Accelerator Laboratory, along with collaborators from more than 25 other institutions, are recreating the experiment with much higher precision to confirm or disprove the former earlier results.
Themuon is like the (very) big brother of the electron; they have the same charge, but the muon is over 200 times more massive. The two also share the same spin, a quantum mechanical property that determines a particle's behavior in the presence of a magnetic field.
Particles with spin act like tiny magnets, and when placed in a magnetic field, their spins change direction in a circular motion, much like a spinning gyroscope. The speed of a particle's spin precession is determined by a quantity known as its g-factor, which depends on the particle's spin and the strength of the magnetic field in which it moves.
In modern quantum mechanical theories, the vacuum is not empty. It is full of bubbles of so-called virtual particles, appearing and disappearing very quickly. Interactions between these virtual particles and a real particle, like the muon, can change how the real particle interacts with the magnetic field, affecting its g-factor. Theoretical physicists have calculated, based on our current understanding of the fundamental structure of nature, all the ways that each known particle affects the muon's g-factor, but the measurements that Brookhaven scientists took differed from what they expected by a few parts per million. This difference, if it persists in the new experiment, would point to completely new physics—an exciting discovery for particle physicists.
"If there is actually a discrepancy between the predicted and measured values, it is further proof that the Standard Model, our current understanding of the contents of the universe, is incomplete," said Argonne physicist Peter Winter. "The unexpected effect could be due to an undiscovered particle."