This year, APS’s Division of Nuclear Physics held its third joint meeting with the Physical Society of Japan, on Hawaii’s Big Island from October 13th to the 17th. Over 900 scientists attended ninety-three sessions (plus one luau) presenting the latest research in all areas of nuclear physics including nuclear astrophysics, hadronic physics, and quantum chromodynamics.
Wednesday morning’s plenary sessions gave participants an inside look at where nuclear physics has been and where it is headed in the future. Stuart Freedman from UC Berkeley gave a brief history of neutrinos and suggested a roadmap for future developments. Duke University’s Berndt Mueller showed how Brookhaven’s Relativistic Heavy Ion Collider (RHIC) has revolutionized the field of Quantum Chromodynamics, and speculated about possible discoveries still in store. Similarly, Tomofumi Nagae from Kyoto University briefed attendees as to how Japan’s recently completed Proton Accelerator Research Complex (J-PARC) is poised to take its place as a leader in the field for investigating nuclear strangeness.
International collaborations are becoming more and more prominent throughout nuclear physics as particle accelerators grow in size and expense. Individual governments can scarcely afford to fund big science projects without support from other nations. Nowhere is this more evident than with CERN’s Large Hadron Collider, which straddles the border between Switzerland and France. At a cost of over $6 billion to build and with a diameter of over five miles, twenty member nations and six observer nations have joined together to bring the world’s largest science experiment to fruition.
Ken Oyama from the University of Heidelberg highlighted how over 1000 physicists from 105 separate institutions have come together to study the nuclear collisions at the LHC’s ALICE experiment. He said that the experiment has huge potential to shed new light on the persisting mysteries of quantum chromodynamics once proton collisions start up in mid-December and ion collisions commence sometime next year. When the collider is running, Hisayuki Torii from Hiroshima University said that the advanced photon detectors within ALICE will be able to measure the thermal photons of a heavy ion collision with unprecedented accuracy, continuing work started at RHIC.
Since the meeting was joint with the Physical Society of Japan, speakers emphasized the collaboration between the two nations. A brief history of these partnerships was described by Akito Arima, chairman of the Japan Science Foundation. He showed how the early collaborations between UC Berkeley and the Institute for Nuclear Study at the University of Japan led to the first rare isotope beam experiments, ultimately laying the groundwork for RHIC. David Dean of Oak Ridge described how today, the Japan-United States Institute for Theoretical Physics with Exotic Nuclei (JUSTIPEN) at RIKEN works to bring together theoretical physicists from both sides of the Pacific.
A neutrino’s minuscule mass allows these peculiar particles to travel through vast amounts of solid matter without interacting with it. Physicists have theorized since the 1930s that a neutrino might be its own antiparticle, but no one has yet observed evidence for this. Boris Kayser of Fermilab underscored what he described as “the profound implications” of this seemingly outlandish concept. He said that the observation of neutrinoless beta decay would imply physics outside the currently accepted standard model, and provide evidence for the leptogenesis theory explaining the universe’s matter-antimatter asymmetry.
Teams around the world are working to first observe neutrinoless double-beta decay. Sei Yoshida of Tohoku University reported that the KamLAND detector located deep in the Kamioka mine outside of Toyama Japan is being upgraded to pick up low energy solar neutrinos from beta decays in the sun. Likewise, Yury Kolomensky from Lawrence Berkeley National Lab gave an update on the construction of the Cryogenic Underground Observatory for Rare Events (CUORE) at the Gran Sasso National Laboratory in Italy which measures the slight temperature variations caused by a neutrino reacting with the detector’s tellurium oxide crystals. The recently opened Enriched Xenon Observatory, located near Carlsbad, New Mexico, uses over 200 kilograms of liquid xenon-136 to detect the tiny amounts of light emitted when an energetic electron reacts with it. Giorgio Gratta at Stanford described how the project is partnering with scientists from nations including Canada, Russia, and Switzerland to complete testing with the 200 kg prototype and move to build the full-fledged experiment using at least a ton of liquid xenon.