Search For Trapped Antihydrogen: First Candidate Events

ALPHA (Antihydrogen Laser PHysics Apparatus) is an international project located at CERN whose prime goal is to perform tests of CPT symmetry on antihydrogen. While substantial numbers of antihydrogen atoms have been produced in several experiments, their trapping has not yet been achieved. In the ALPHA apparatus, cold plasmas of typically 3 x 10(4) antiprotons and of 4 x 10(6) positrons are mixed in a Penning trap to form cold antihydrogen. A multipolar magnetic trap of depth 0.5 Kelvin is superimposed on the Penning trap to confine the anti-atoms. In 2009, we have reached, for the first time, the detection sensitivity and trap conditions for which observation of antihydrogen trapping may be expected. In this talk, we will present results from that run, where we have observed first candidate events [1].