| The High Altitude Water Cherenkov (HAWC) Observatory is a gamma-ray experiment currently under construction at Sierra Negra in Mexico. When complete it will consist of a 22,000 square meter array of 300 water Cherenkov detectors. Although HAWC is designed to study gamma rays from galactic and extra-galactic sources, the large volume of instrumented water (each tank holds ∼188,000 liters) gives the opportunity to search for rare objects. One such target is the Q-ball, a very massive, subrelativistic particle that can have a large baryon number and can be stable since their creation in the early universe. If stable, Q-balls would make up some of the dark matter of the universe, but their large mass means their flux is very low. HAWC has a flexible data acquisition system which, with a dedicated trigger algorithm for non-relativistic species, allows a search for Q-balls traversing the detector. Using a 174.5 days of live time and a portion of the planned array, a search was performed with negative results. The obtained upper limits are competitive with previously published limits on Q-balls, and HAWC will be able to set a better limit than any other when it is complete. |
