Scientists from the BASE collaboration, led by scientists from RIKEN, have developed a new cooling method that will make it easier to measure a property of protons and antiprotons called the magnetic moment. This is one of the properties that is being studied to solve the mystery of why our universe contains matter but almost no antimatter.
Our universe should, according to the Standard Model, have equal amounts of matter and antimatter, but in reality it doesn’t. To find out why, scientists around the world are trying to uncover tiny differences between the two that could solve the mystery. One promising avenue is to explore whether there are differences in the magnetic moment of the proton and the antiproton, and the BASE experiment, based at CERN, is trying to determine this. Using a sophisticated device – a Penning trap capable of capturing and detecting a single particle – the BASE team has in the past succeeded in improving the accuracy of measurements of the magnetic moments of protons and antiprotons of a factor thirty and over three orders of magnitude, respectively, leading to a test for matter / antimatter symmetry at the 1.5 parts in a billion level, essentially finding that the magnets in the proton and antiproton are nine-digit similar significant!
One difficulty among many in performing such experiments is that to measure magnetic moments accurately, the particles must be maintained at temperatures near absolute zero, -273.15 ° C. In previous experiments, cold temperatures were prepared using a technique known as “selective resistive cooling”, which is time consuming and, according to researchers, “similar to rolling a die with 100 faces, trying to roll. a 1”.
For the current experiment, published in Nature, the BASE collaboration reported the very first demonstration of ‘sympathetic cooling’ of a single proton by coupling the particle to a cloud of laser-cooled 9Be + ions. Sympathetic cooling involves using lasers or other devices to cool one type of particle, and then using those particles to transfer heat from the particle they want to cool. With this technique, the group simultaneously cooled a resonant mode of a tuned macroscopic superconducting circuit with laser-cooled ions, and also achieved sympathetic cooling of a single trapped proton, reaching temperatures near absolute zero.
The technique described in the recent article is an important first step towards drastically reducing the faces on the dice collector, with the vision of ideally reducing the surface to one. “We report an important first step, and further development of this method will ultimately lead to an ideal spin-tilt experiment, in which a single low-temperature proton will be prepared in just a few seconds. This will allow us to determine the spin state of the particle in a single measurement which takes about a minute, ”explains Christian Smorra, one of the scientists leading the study. “This is considerably faster than our previous magnetic moment measurements and will improve both the sampling statistics and the resolution of our systematic studies,” adds Matthew Bohman, doctoral student at the Max Planck Institute for Nuclear Physics in Heidelberg and premier author to study it.
“In addition, the reported achievement has applications not only in proton / antiproton magnetic moment measurements. It adds general new technology to the toolbox of precision Penning trap physics, and also has potential applications in other nuclear magnetic moment measurements, ultra-precise comparisons of charge-to-mass ratios in traps. of Penning, or even in improving production. antihydrogen ”, adds Stefan Ulmer, spokesperson for the BASE collaboration and chief scientist of the RIKEN Fundamental Symmetries Laboratory.
The BASE collaboration runs three experiments, one at the CERN Antimatter Plant, one at the University of Hanover and one at the University of Mainz, the laboratory where the new method was actually implemented. The reported study is the result of collaboration between RIKEN, the German company Max Planck, the universities of Mainz, Hanover and Tokyo, the German metrology institute PTB, CERN and GSI Darmstadt. The work was supported by the Max Planck Center, RIKEN, PTB for time, constants and fundamental symmetries.