Final Report Summary - SPECAP (Precision laser spectroscopy of antiprotonic and pionic atoms)
Samples of 2 billion atoms containing antiprotons were cooled to very low temperature between 1.5 and 1.7 K. By shining high-power laser beams at the samples, the ratio between the antiproton and electron masses was determined to a precision of 0.8 parts per billion. The result was the same as the proton-to-electron mass ratio, thus verifying the so-called CPT symmetry between matter and antimatter. Experimental attempts were carried out to achieve laser spectroscopy of an atom containing a meson for the first time. The promising results are now being analyzed. A positive signal would in principle prove the existence of a heretofore hypothetical atom containing a negatively-charged pion, a helium nucleus, and electron.