タイトル：「Particle Physics with Slow Neutrons: Some Experiments Underway and on the Drawing Boards」
日時：１０月１８日１０時３０分～
講演者： Albert R. Young (North Carolina State University/Triangle Universities Nuclear Laboratory)
場所：ES館ES635
概要： Experiments performed with cold and ultracold neutrons constrain our understanding of particle physics at the TeV scale and beyond. In particular, we focus on beta-decay measurements with ultracold neutrons, including the UCNA and UCNτ experiments, where our ongoing experimental program promises a nuclear structure-independent determination of the fundamental parameters of the charged weak current of the nucleon. Ultracold neutrons provide a unique handle on some of the key systematic uncertainties in these measurements and continue to present opportunities to improve the accuracy of our understanding of the decay of the neutron. We review the status of motivation and status of these experiments, and the path forward to probe neutron beta-decay in next-generation experiments with precision at the 0.1% level and below. We also present ideas for measurements with greatly improved sensitivity for neutron-antineutron oscillations. This process would be produced by a beyond-standard-model interaction which violates baryon number by 2 units (ΔB=2). Neutron anti-neutron oscillations is expected in a number of models in which oscillations can be produced at energy scales down to the current limits and for which the classic, ΔB=1 processes such as proton decay are not observable. The detection of such a process would have enormous implications for our understanding of the baryon-antibaryon asymmetry, and touch on other important topics such as our understanding of the origin of neutrino mass. Our concept would utilize state-of-the-art neutron optics (developed in part by the group of H. Shimizu) coupled to a dedicated spallation source, to produce an intense beam of cold neutrons directed at a graphite target several hundred meters from the source. Antineutrons produced via oscillations are detected by observing annihilation events in the graphite target. This geometry can improve the sensitivity to detect oscillations by a factor of 1000 over existing experiments, probing effective energy scales in excess of 100 TeV and potentially setting the most stringent limits for years to come.
