Gerasimov-Drell-Hearn求和规则的Q^2依赖性质

Q^2-Dependence of the Gerasimov-Drell-Hearn Sum Rule

在组分夸克模型中重子共振态的光子激发下，通过数值计算核子上光子总吸收截面σ1／2和σ3／2，检验了Gerasimov－Drell－Heam（GDH）求和规则．这种计算包括了总计17个低激发的、非奇异重子共振态．发现纵横相干截面在随Q2变化的求和规则研究中扮演了重要角色．结果显示在94％可信度上这些共振态使GDH求和规则饱和．特别是在Q2＝0和小Q2的区域，主要是共振态P33（1232）激发使求和规则饱和．在Q2＝1．0GeV2以下，GDH积分有一个很强的Q2依赖性质，且在Q2＝0．3GeV2附近变号．由于共振态贡献的迅速下降，当Q2＞1．0GeV2时，GDH积分对Q2依赖变弱．

We test the Gerasimov-Drell-Hearn (GDH) sum rule numerically by calculating the total photon absorption cross sections σ1/2 and σ3/2 on the nucleon via photon excitation of baryon resonances in the constituent quark model. A total of seventeen, low-lying, non-strange baryon resonances are included in mis calculation.The transverse and longitudinal interference cross section, σ, is found to play an important role in the study of the Q2 variation of the sum rule. The results show that the GDH sum rule is saturated by these resonances at a confidence level of 94%. Inparticular , the P33,(1232) excitation largely saturates the stun rule at Q2 = 0, and dominates at small Q2. The GDH integers has a strong Q2-dependence below Q2 =1.0GeV2 and changes its sign around Q2 = 0.3GeV2. It becomes weakly Q2-dependence for Q2 > 1.0GeV2 because of the qinck decline of resonance contributions.