ATRAP measures most accurate antiproton magnetic moment ever
The ATRAP experiment at CERN’s Antiproton Decelerator [AD] has measured the magnetic moment of the antiproton with highest accuracy to date. ATRAP’s new result may help to eventually unveil one of the great mysteries of modern physics: the matter-antimatter imbalance of the Universe. Results are described in a paper published in Physical Review Letters last month.
In order to make the most accurate measurements of the antiprotons’ properties, the ATRAP’s team was able to confine individual antiprotons using the so-called Penning trap, a sort of electromagnetic cage. This device, which is cooled down to very low temperatures (4.2K) to avoid the annihilation of the antiprotons, allows the scientists to perform a direct measurement of the antiproton magnetic moment – an intrinsic property that characterizes its behavior under a magnetic field – with high precision.
The physicists were able to estimate the antiproton magnetic moment with an unprecedented uncertainty of just 4.4 parts per million, about 680 times more precise than any previous result.
Extensive comparisons of the properties of antiproton and proton are of utmost importance since the fundamental cause of the dramatic imbalance of matter and antimatter in the Universe has yet to be addressed. For instance, by comparing the antiproton’s magnetic moment to that of the proton, scientists are able to probe one of the most fundamental symmetries, known as CPT1, at high precision.
As expected by the predictions of the Standard Model and the CPT theorem, the team found that the magnetic moments of the antiproton and proton are equal in strength but opposite in direction with an unprecedented high precision of 5 parts per million. Even though this result had been already confirmed with previous experiments, it is crucial to test the Standard Model predictions much more stringently since this fundamental model, as reliable as it has been proven over the years, does not account for all forces present in the Universe, such as the gravity.
When CERN resumes antiproton operations in 2014, the ATRAP team plans to incorporate state-of-the-art quantum methods that will allow increasing the accuracy of the measurements. This should make possible to eventually test the Standard Model and the CPT symmetry by comparing the proton and antiproton to a 1 part per billion precision or better.
More information can be found in CERN website.
- CPT symmetry is a fundamental symmetry of physical laws under transformations that involve the simultaneous inversion of charge parity and time. [↩]
