R & D activities toward a High Pressure Xenon TPC ( NEXT )

Double beta decay is a very rare nuclear decay process in nature characterized by changing the ordering number Z by two units and leaving the massnumber A constant. It can occur in two modes, with the emission of two electrons and two anti-neutrinos or the emission of two electrons only. While the first mode is in agreement within the Standard Model, the neutrino-less double beta decay is not. It can only occur if the neutrino is its own antiparticle and massive (MajoranaMechanism). As 136Xenon is one of the few elements, which decays by a double beta decay a high-pressure, gaseous 136Xenon TPC has good prospects to proof the existence of the Majorana nature of the neutrino. Our Collaboration follows the gaseous concept, as pioneered by the Gotthard experiment [1]. The name of our project is NEXT which stands for Neutrino Experiment with a Xenon TPC. Different to the Gotthard approach the NEXT TPC will use either pure Xenon or Xenon with a small contribution of a quencher. This will provide a significant amount of primary scintillation light which triggers the data acquisition and allows a full three dimensional particle reconstruction. It overcomes one significant drawback of the Gotthard approach. Such an object could explore the degenerated hierarchy and provide a deep understanding of the experimental techniques to suppress backgrounds required for larger detectors. A general introduction and the physics motivation of this topic can be found in [2]. The current R&D status will be presented in this paper.