The APS Division of Nuclear Physics (DNP) held its 2008 annual meeting 19‑23 October in Oakland, California. The technical program featured talks on the latest in neutrino physics, the status of a new project to probe the nature of dark matter/dark energy, and the role nuclear physics is now playing in planned space missions and hadron radiotherapy, among other research topics. In addition, three half‑day topical workshops were held the day before the meeting on quantifying the character of the quark gluon plasma; large‑scale computation in nuclear physics; and underground nuclear physics experiments. Cracking the Neutrino Code.
For a particle with no charge and very little mass, neutrinos are appear to be very complicated in terms of their properties, according to R.G. Hamish Robertson of the University of Washington. For instance, it took 70 years after their discovery before scientists realized they had a tiny amount of mass, although the exact value of that mass remains unknown.
Melissa Jenkins (University of Texas at Austin) believes that recent advances in atomic slowing and cooling are opening up new avenues for exploring neutrino properties, such as mass. Neutrino physicists have long used tritium beta decay to probe the “ghost particle,” but thus far have failed to detect the mass. Jenkins proposes to improve matters by using a slow, cold beam of tritium atoms as a neutrino source.
Although the central focus of current neutrino experiments not involving accelerators is the study of their properties, other researchers are harking back to the past and using neutrinos as probes to investigate the processes by which they are produced by the sun. According to University of California, Berkeley’s Michal Patrick Decowski, some of these new experiments will also measure anti‑neutrinos from the decay of uranium and thorium in Earth’s crust and mantle, thereby possibly providing information on the radiogenic contribution to the planet's heat balance. Other experiments will utilize neutrinos produced in reactors for nuclear non‑proliferation purposes. Probing the Dark Side of the Cosmos
. Tony Tyson of University of California, Davis, gave an overview of the status of the Large Synoptic Survey Telescope (LSST), which is slated to begin analyzing a wide range of cosmological phenomena in 2014. For instance, according to Tyson, the nature of dark matter can be constrained by measuring the scales on which it clumps, while the nature of dark energy can be constrained by measuring the time evolution of cosmic dark matter structures, as well as measuring the distribution of galaxies and the cosmic “shear” of their apparent shapes. The LSST will also make it possible to compile maps of dark matter and carry out several independent cross‑checking probes into the nature of dark energy. Nuclear Physics and Human Biology
. Ram Tripathi of NASA’s Langley Research Center reviewed the vital role nuclear physics is now playing in such diverse areas as planned space missions, hadron radiotherapy, and low‑dose radiobiology. For instance, NASA’s future vision for space exploration includes missions to the moon, Mars, and beyond, with a corresponding focus on long‑duration space missions, and thus, protecting astronauts from long‑term exposure to space radiation. Furthermore, advances in human genome sequencing and new radiobiological techniques have made it possible to determine at the cellular level how living systems respond to low doses of radiation. And proton radiotherapy is becoming more common as a cancer treatment. Computational Modeling of Supernovae
. Adam Burrows of Princeton University discussed recent progress on simulating a supernova explosion in six‑dimensional phase space (plus a seventh dimension of time), which he expects to improve even more over the next five years. In particular, he probed the theoretical mechanism of supernova core collapse via a series of massive computations, which he believes will shed light on the enigma of star death in the cosmos.
Burrows’ efforts will likely benefit from plans to expand development of petascale computational systems for nuclear physics research. James Sexton (IBM T.J. Watson Research Center) reported that the first sustained petaflop system has now been delivered to Los Alamos National Laboratory, and described the current status of systems architectures for petascale computing and the present challenges in terms of power, memory capacity, data management, and reliability.