Standard model upheld in comparison of protons, antiprotons
No matter how precise the measurement, matter and antimatter look stubbornly similar.
An ultrasensitive experiment comparing protons with their antimatter counterparts found no difference in the ratios of their charge to mass, researchers report in the Aug. 13 Nature. The result is consistent with the standard model of particle physics, which predicts that antiprotons are essentially protons with negative charge — the particles’ mass, spin and nearly every other property should be identical. Many physicists would love to discover even minute discrepancies, which could signal the existence of new particles and forces and help reveal why the universe is made of matter rather than antimatter.
Stefan Ulmer, a particle physicist from RIKEN in Wako, Japan, and colleagues analyzed antiprotons and negative hydrogen ions (a proton plus two electrons) one by one inside an instrument called a Penning trap. The