Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session C3: Invited Session: Nuclear Physics at the Gamma-ray Intensity Frontier |
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Sponsoring Units: DNP Chair: Calvin Howell, Duke University Room: Chatham Ballroom B |
Saturday, April 5, 2014 1:30PM - 2:06PM |
C3.00001: The ``light-est'' of all Projectiles: Nuclear Structure Studies Using Photonuclear Reactions Invited Speaker: Norbert Pietralla Nuclear reactions induced by photons have had and continue to have a large impact on the course of nuclear physics. Photons interact purely electromagnetically with the atomic nucleus and induce minimal momentum transfer at given excitation energy. Photonuclear reaction processes can be expanded in terms of QED and photonuclear excitations are by far dominated by one-step processes. They allow for a model independent measurement of nuclear observables and, hence, for a clean characterization of effective nuclear forces. Apart from the pioneering photonuclear reactions by Bothe and Gentner in the 1930s [1], bremsstrahlung has been used most widely as an intense source of gamma-rays for photonuclear reactions from the 1940s until today. The nuclear dipole strength distribution has largely been mapped out at bremsstrahlung facilities [2,3]. While the continuous-energy distribution of bremsstrahlung photons offers a complete view of the spectrum of photonuclear excitations, it suffers from a poor sensitivity to specific energy intervals. Intense, energy-tunable, quasi-monochromatic gamma-ray beams from laser-Compton backscattering processes have revolutionized the field of photonuclear reactions for the last ten years [4]. A set of new techniques is under development and new information on fundamental nuclear modes, such as the IVGDR, IVGQR, Pygmy Dipole Resonance, and the Scissors Mode, has recently been obtained. We will attempt to give a brief overview of the state of the art and dare an outlook at the research opportunities at the next generation of gamma-ray facilities under construction in the U.S. and Europe. \\[4pt] [1] W. Bothe and W. Gentner, Z. Phys. 106, 236 (1937).\\[0pt] [2] F.R. Metzger, Proc. in Nucl. Phys. 7, 54 (1959).\\[0pt] [3] U. Kneissl, N. Pietralla, and A. Zilges. J. Phys. G: Nucl. Part. Phys. 32, R217 (2006).\\[0pt] [4] H.R. Weller et al., Prog. Part. Nucl. Phys. 62, 257 (2009). [Preview Abstract] |
Saturday, April 5, 2014 2:06PM - 2:42PM |
C3.00002: Nuclear Astrophysics with Gamma-ray Beams Invited Speaker: Ernst Rehm Experiments with $\gamma$-ray beams have opened many new opportunities in nuclear astrophysics. They include studies of photonuclear ($\gamma$,p), ($\gamma$,n) and ($\gamma,\alpha$) reactions which play an important role in the large $\gamma$-ray flux during stellar explosions. Furthermore ($\alpha,\gamma$) captures can be investigated through their time-inverse ($\gamma,\alpha$) reactions with much thicker targets and, thus, increased luminosities. I will discuss the experimental program in nuclear astrophysics at HI$\gamma$S, with particular emphasis on the present status and future plans of the $^{12}$C($\alpha,\gamma$)$^{16}$O reaction studies. This work was supported by the US Department of Energy, Office of Nuclear Physics, under contract DE-AC02-06CH11357. [Preview Abstract] |
Saturday, April 5, 2014 2:42PM - 3:18PM |
C3.00003: Studies of Few-Nucleon Systems and Nucleon Structure with Gamma-ray Beams Invited Speaker: Haiyan Gao The High Intensity Gamma Source (HI$\gamma $S) at the Duke Free Electron Laser Laboratory (DFELL), an important experimental facility of the Triangle Universities Nuclear Laboratory (TUNL), is located on the campus of the Duke University. The HI$\gamma $S facility, capable of delivering the most intense mono-energetic photon beam with either circularly polarized or linearly polarized photons in the world, opens up new opportunities for studies of the few-nucleon system through photodisintegration processes, and nucleon structure through Compton scattering. These measurements either with polarized or unpolarized few nucleon target systems provide high precision tests of the state-of-the-arts few-body calculations. Single polarized and double polarized Compton scattering experiments allow for significantly improved determinations of electric and magnetic polarizabilities of the nucleon, as well as spin polarizabilities of the nucleon, which so far have never been determined separately. In this talk, I will present latest results from HI$\gamma $S on the studies of few-nucleon systems and upcoming experiments. I will also discuss new experiments on polarized and unpolarized Compton scattering at HI$\gamma $S. This work is supported in part by the U.S. Department of Energy under Contracts No. DE-FG02- 03ER41231, No. DE-FG02-97ER41033, and No. DE- FG02-97ER41041. [Preview Abstract] |
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