R2D2 spherical TPC: first energy resolution results

Spherical time projection chambers (TPC), also known as spherical proportional counters, are employed in the search for rare phenomena, such light Dark Matter candidates. The TPC exhibits a number of essential features, making it promising candidate neutrinoless double beta decay (??0?). A tonne-scale experiment could cover region parameter space relevant inverted mass hierarchy with few years data taking. In this direction, major R&D goal R2D2 effort is demonstration required energy resolution. First results from an argon-filled prototype detector reported, demonstrating resolution 1.1% FWHM 5.3 MeV ? tracks 0.2 to 1.1 bar pressure range. This milestone terms resolution, paving way further studies xenon gas, and possible use technology ??0? searches.