Baryon-Spectrocopy at BESIII

BESIII 的重子光谱

• 批准号: 456136384
• 负责人: Professorin Dr. Miriam Fritsch
• 金额: --
• 依托单位: Institut für Experimentalphysik I (Experimentelle Hadronenphysik)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/456136384?language=en
• 关键词: Baryon; Spectrocopy; BESIII

One of the main topics of interest in physics is the composition and structure of matter. Especially for hadrons, which are bound states of quarks and gluons such as the proton and neutron, the description is incomplete. Quantum chromo dynamics (QCD), the theory of the strong interaction, is able to describe most experimental. However, neither QCD nor derived effective theories or lattice-QCD calculations are able to fully explain the rich hadron spectrum. The excitation spectra of hadrons reflect the underlying strong dynamics complementary to polarizabilities, elastic form factors, and parton distributions. Most data concerning N* and hyperon resonances were taken in photo and electroproduction. Using J/ψ decays to investigate these states provides complementary information which is necessary to shed light on the nature of these states and gives input for theoretical calculations.The goal of this project is the analysis of various meson-nucleon final states in charmonium decays at BESIII. The BESIII experiment has recently multiplied its J/ψ data set by a factor of 8 and reached the number of 10 billion J/ψ events. This unique J/ψ data set gives the opportunity to study excited baryons with high statistics in a completely different environment with respect to photoproduction. Within the SFB1044 project S3 we started to perform the analysis of the two decay channels: J/ψ → p anti-p η and J/ψ → anti-p Σ^+ K_S. The determination of the branching fractions is finished and entered the internal review process at BESIII for the publication of the results. Now, we want to perform a partial wave analysis for these two decay channels. For the interpretation of the experimental data this method is used to determine the baryon resonance properties with minimal model dependence. In addition, we want to investigate the decay channel J/ψ → p anti-p η’. As next step we plan to extend the investigation to the decay channels ψ’ → p anti-p η, ψ’ → anti-p Σ^+ K_S and ψ’ → p anti-p η’ in order to learn more about the differences of the excited ψ’ state in comparison to J/ψ. In parallel, by performing the analysis described above we want to further complete the PWA tool TensorWaves which is based on the machine learning software package TensorFlow.

在物理学中感兴趣的主要课题之一是物质的组成和结构。特别是对于强子，它是夸克和胶子（如质子和中子）的束缚态，描述是不完整的。量子染色体动力学（QCD）是强相互作用理论，能够描述大多数实验现象。然而，无论是量子色动力学，还是导出的有效理论或格点量子色动力学计算都不能完全解释丰富的强子谱。强子的激发谱反映了与极化率、弹性形状因子和部分子分布互补的潜在强动力学。大多数关于N* 和超子共振的数据是在光和电产生中获得的。利用J/π衰变来研究这些态提供了必要的补充信息来阐明这些态的性质，并为理论计算提供了输入。本项目的目标是在BESIII上分析粲偶素衰变中的各种介子-核子末态。最近，BESIII实验将其J/m2数据集增加了8倍，达到了100亿J/m2事件的数量。这一独特的J/π数据集提供了在完全不同的光生环境中研究具有高统计数据的激发重子的机会。在SFB 1044项目S3中，我们开始对两个衰变通道进行分析：J/π → p anti-p η和J/π → anti-p π ^+ K_S。支化分数的测定已经完成，并进入BESIII的内部审查程序，以公布结果。现在，我们要对这两个衰减通道执行分波分析。对于实验数据的解释，这种方法被用来确定重子共振性质与最小的模型依赖。此外，我们还想研究J/π → p anti-p π '衰变通道。下一步，我们计划将研究扩展到衰变通道：γ ' → p anti-p η，γ' → anti-p γ ^+ K_S和γ ' → p anti-p η'，以便更多地了解激发态γ '与J/γ相比的差异。同时，通过执行上述分析，我们希望进一步完善基于机器学习软件包TensorFlow的PWA工具TensorWaves。