用于测量重子共振态Δ(1232)空间尺寸的玻色-爱因斯坦关联方法研究

测量超短寿命核子共振态的空间尺度受限于难以制备相应的靶，无法采用传统的电子散射法。本项目基于玻色-爱因斯坦关联（BEC）方法，探索一种适合低能区三体系统BEC观测的有效事件混合方法，创建一种新的用于测量Δ（1232）共振态空间尺寸的BEC测量技术。具体研究包括：（1）建立1 GeV能区光生反应γp→π^0Δ→π^0π^0p末态π^0π^0关联用于测量Δ共振态空间尺寸的物理模型；（2）研究能量动量守恒关系、Δ共振态及相关限制条件对三体系统事件混合的影响机制和规律，并探索适用于低能区Δ共振态存在时三体系统两玻色子BEC分析的有效事件混合方法；（3）测量实验数据π^0π^0 的BEC效应，最终获得Δ共振态空间尺寸，并研究空间尺寸与入射光子能量的依赖关系。研究成果对于理解核子共振态内部结构性质具有重要意义和科学价值，并拓展了BEC在低能区的应用，提供了一种测量超短寿命核子共振态空间尺寸的新途径。

Limited to target preparing, traditional electron scattering cannot be applied to measuring the spatial extension of ultra-short lifetime excited nucleon. In this project, we propose a new event mixing method for Bose-Einstein correlations (BEC) observation at low energies with low multiplicity, in order to measure the spatial size of Delta resonance (Δ (1232)) of ultra-short lifetime. This project includes the following three main works: 1) to establish a theoretical frame to describe the relation between π^0π^0 BEC effects and the spatial size of Δ produced in γp→π^0Δ→π^0π^0p; 2) to investigate how energy-momentum conservation, Δ resonance and given kinematic constraints affect the event mixing process which plays a crucial role in BEC analysis, and to develop an effective event mixing method for two-boson BEC analysis in three-body system in the presence of Δ resonance; 3) to extract BEC parameters of experimental π^0π^0 data using the developed event mixing method, and to deduce the space size of Δ resonance and its dependence on the incident photon energy. This study will provide a novel approach to measure the space-time characteristics of excited nucleons. Any breakthroughs in this study will drastically improve our understanding of excited nucleons properties.