Deep in the mountains of China’s Sichuan province, the PandaX experiment has joined the international hunt to detect the so far elusive Dark Matter in the Universe. Installed in the deepest, most radio-pure facility of its kind in the world, covered by 2,400 meters of marble rock in JinPing Mountain, PandaX is starting to monitor 125 kg of liquid xenon. The team, led by a physicist from U-M sister university Shanghai Jiao Tong University (SJTU), along with the U-M Dark Matter Group, has set out to initially probe the low-mass WIMP regime before exploring the higher-mass regime with a ton-scale detector. This research is featured in the latest issue of
U-M Dark Matter Group:
The U-M Dark Matter group consists of Physics Professors Wolfgang Lorenzon (Principal Investigator), Tom Schwarz and Gregory Tarlè; Research Scientist Michael Schubnell, Postdoctoral Fellow Kirill Pushkin, Senior Engineer Curtis Weaverdyck and Ph.D. candidate Scott Stephenson. Although small in number, the U-M group plays a central role in the planning and execution of the experiment, which includes responsibilities in the slow-control system, time projection chamber development, background assays as well as background and detector response modeling. Most recently, the group has started to develop low energy recoil calibration capabilities on the U-M central campus that are crucial for the understanding and interpretation of the phase 1 data being collected right now.
“The start of data collection marks a major milestone in our quest to detect Dark Matter,” says U-M Physics Professor Wolfgang Lorenzon, whose team joined the PandaX effort in 2011.
Dark Matter Issue:
Astrophysical observations, accumulated over the last eight decades, have led to the inescapable conclusion that the bulk of the matter of our Universe (80 %) is non-baryonic and consists of a previously unobserved type of particle not encompassed by the Standard Model of particle physics. Determining the exact nature of this Dark Matter has emerged as one of the deepest scientific inquiries of our time spanning the fields of cosmology, astrophysics and fundamental particle physics. Despite overwhelming indirect evidence for its existence, Dark Matter has eluded direct detection. There is good reason to believe that we are now poised at the threshold of discovery, that the next generation of direct detection experiments will not only observe the Dark Matter directly but will constrain its properties. A particularly well-motivated hypothesis is that the Dark Matter consists of Weakly Interacting Massive Particles (WIMPs) produced in the hot environment of the early Universe and stabilized against further decay by some discrete symmetry. Such particles would interact weakly with ordinary matter and could be detected with a suitably sensitive detector operating in an extremely low background environment.
The PandaX experiment utilizes the well-established dual phase liquid xenon detection technique in the unique environment afforded by the newly constructed JinPing underground laboratory in southern China. With an overburden of 7,200 meter water equivalent of solid marble, it is the deepest underground laboratory in the world. Using a phased approach, PandaX will explore the Dark Matter frontier on two fronts; the low mass, low nuclear recoil threshold regime and the high mass, high sensitivity regime. PandaX has been planned from the beginning as a ton-scale detector, and most of the infrastructure for the ton-scale detector is already in place. This infrastructure will enable PandaX to emerge in mid-2016 as one of the first ton-scale liquid xenon detectors in operation. By the end of 2018, sensitivity is expected to reach 4 x 10-47 cm-2 at a WIMP mass of 50 GeV.
The U-M Dark Matter group is the first U.S. group that has gained access to the JinPing facility in southern China, the deepest underground laboratory in the world to perform low-background science programs. Now that PandaX has started to collect science data, the U-M Dark Matter group is very excited by the prospect for the next few years. With first results expected from PandaX later this year, the team hopes to scale up the detector to over 1 ton by 2016, and play a major role in the hunt for Dark Matter.