Complex sentence: In 1995, the CERN laboratory in Geneva first produced antihydrogen in the LEAR by shooting antiprotons, which were produced in a particle accelerator, at xenon clusters.
Split into simpler sentences: In 1995, the first antihydrogen was produced at the CERN laboratory in Geneva. The experiment took place in the LEAR, where antiprotons, which were produced in a particle accelerator, were shot at xenon clusters.