PandaX-III: Searching for Neutrinoless Double Beta Decay with High Pressure $^{136}$Xe Gas Time Projection Chambers

Abstract

Searching for the Neutrinoless Double Beta Decay (NLDBD) is now regarded as the topmost promising technique to explore the nature of neutrinos after the discovery of neutrino masses in oscillation experiments. PandaX-III (Particle And Astrophysical Xenon Experiment III) will search for the NLDBD of 136 Xe at the China Jin Ping underground Laboratory (CJPL). In the first phase of the experiment, a high pressure gas Time Projection Chamber (TPC) will contain 200 kg, 90% 136 Xe enriched gas operated at 10 bar. Fine pitch micro-pattern gas detector (Microbulk Micromegas) will be used at both ends of the TPC for the charge readout with a cathode in the middle. Charge signals can be used to reconstruct tracks of NLDBD events and provide good energy and spatial resolution. The detector will be immersed in a large water tank to ensure ∼5 m of water shielding in all directions. The second phase, a ton-scale experiment, will consist of five TPCs in the same water tank, with improved energy resolution and better control over backgrounds. * BambooMC is a modularized Geant4 based simulation program, developed by the SJTU group. It has been used extensively in the PandaX-II dark matter project for the prediction of backgrounds.† Drift velocity values and gas properties have been calculated using Magboltz

Discovery probability of next-generation neutrinoless double- β decay experiments

“…Various larger-scale experiments with the sensitivity to probe the full IO parameter space are being mounted or proposed for the near or far future. This work focuses on those projects considered recently by the U.S. DOE/NSF Nuclear Science Advisory Committee's Subcommittee on Neutrinoless Double Beta Decay [58]: CU-PID [59,60], KamLAND-Zen [61], LEGEND [62,63], nEXO [64], NEXT [65], PandaX-III [66], SNO+ [67,68], and SuperNEMO [69,70]. Most of these projects follow a staged-approach in which the target mass will be progressively increased.…”

“…Another experiment using the same technique of NEXT is PandaX. After two phases dedicated to dark matter searches, a 0νββ decay search program -denoted PandaX-III -is planned [66]. The TPC of PandaX-III will be about twice as big as that of NEXT, but will have an energy resolution of about 3% FWHM [66].…”

“…After two phases dedicated to dark matter searches, a 0νββ decay search program -denoted PandaX-III -is planned [66]. The TPC of PandaX-III will be about twice as big as that of NEXT, but will have an energy resolution of about 3% FWHM [66]. As for NEXT, one of the major expected backgrounds is 214 Bi.…”

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in 136Xe

“…The concept of a high-pressure Xe (HPXe) TPC for 0𝜈𝛽𝛽 searches in 136 Xe, developed by the NEXT collaboration [56] and recently adopted by PandaX-III [57], has two unique features: excellent energy resolution (0.5-0.7% FWHM at 𝑄 𝛽𝛽 = 2.46 MeV), and track reconstruction capability. High energy resolution is critical for rejecting 2𝜈𝛽𝛽 events with energy close to 𝑄 𝛽𝛽 , while accurate imaging can provide effective discrimination against gamma-induced background events, based on the track topology.…”

Dark matter search results from first data from the PandaX-II experiment

“…PandaX-II, with a half-ton scale xenon target, has started to take data since the end of 2015. The third experiment PandaX-III [3], which is being prepared, will search for neutrinoless double beta decay of 136 Xe. Both PandaX-I and PandaX-II experiments use the dual-phase xenon time projection chamber (TPC) technique to search for WIMPs.…”