The antiprotons were created by the "Antiproton Source". ATHENA was an antimatter research project that took place at the Antiproton Decelerator. It consists of an antiproton with a positron. The antiproton, , (pronounced "p-bar") is the antiparticle of the proton. For example, a proton has positive charge while an antiproton has negative charge. All free hadrons except (possibly) the proton and antiproton are unstable. By carefully analyzing the tracks ALPHA distinguishes between cosmic rays and antiproton annihilations. Its antiparticle, the antihypertriton, is formed of an antiproton, an antineutron and any antihyperon. For example, the charges of a proton and antiproton must sum to exactly zero. An antiproton consists of two up antiquarks and one down antiquark (). For example, the proton and antiproton are denoted as and , respectively. This is the signature of an antiproton annihilation. When an antiproton interacts with a normal particle, both are annihilated. The Facility for Antiproton and Ion Research (FAIR) is an international accelerator facility under construction. This also provides a lower limit on the antiproton lifetime of about 1-10 million years.