Precision Study of the Radiative Decay Widths of Light Pseudoscalar Mesons via the Primakoff Effect

点击翻译按钮获取中文摘要

The nuclear physics group at North Carolina A&T State University (NCAT) has the lead role in the PrimEx experimental project at the Thomas Jefferson National Accelerator Facility (JLab). The aim of this project is to test the fundamental effects of symmetry breaking phenomena in the theory of the nuclear interaction of matter in contemporary physics. This will be achieved through measuring with unprecedented precisions the decay probabilities of two of the lightest elementary particles the neutral pion and the eta-meson. These subatomic particles are the lightest particles known in nature that consist of the more fundamental constituents of matter, the quarks. Therefore, the predictions of the theory are more accurate and much less model dependent for the decay processes of these particles. The first experiment in this project, the decay probability of the neutral pions, was developed in the past several years and successfully executed in the fall of 2004. A rich and high statistics experimental data set has been collected. The PrimEx collaboration is currently analyzing the data to extract the neutral pion lifetime with a high precision. We expect that these results, with an anticipated 1.5% accuracy, will serve as an ultimate test of the level of the left-right symmetry breaking phenomena in our understanding of the interaction of matter with the radiation. The second stage of this project includes the high precision measurement of the eta-meson decay process in to two particles of radiation (the photons). We expect that, with the doubling of the JLab energies (the 12-GeV upgrade project), we will be able to perform an experiment with significantly improved uncertainties over previous experiments. The results of this experiment will possibly remove the current discrepancy between two types of different experimental data sets. With that, it will make a significant impact in the determination of more precise decay probabilities in the eta-meson sector of the current Particle Data Book. This will lead to the extraction of the relative masses of the light quarks in a direct and model independent way. North Carolina A&T State University is a historically and predominately African-American institution. The research activities of the nuclear physics group have had a significant impact on the NCAT community. This project has given both our graduate and undergraduate students the opportunity to engage in world class experimental research. We have had 5 graduate and 8 undergraduate students engaged in this research. Of the graduate students, 4 (including two African American males and one female) have now successfully defended their Masters Degree theses. We expect to continue to have both graduate and undergraduate students participate in the PrimEx project. In the near future, this participation will be in the realm of data analysis to help achieve the ultimate goal of the experiment. The research they engage in greatly enhances the ability of both the undergraduate and graduate students to be accepted into competitive graduate programs. This is especially important in light of the extremely low number of M.S. and Ph.D. degrees in physics held by Americans from traditionally underrepresented groups.