标题： 电子激发下Roper共振在1.7 < Q2 < 4.5 GeV2范围内的ep -> enpi+过程 显示英文标题

标题： Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 GeV2 in ep -> enpi+

摘要： 从最近高精度的JLab-CLAS质子上π+电产生过程的W=1.15-1.69 GeV以及1.7 < Q2 < 4.5 GeV2范围内的微分散射截面和纵向极化束流不对称数据中提取了Roper共振的电激发的螺旋度振幅。 使用两种方法进行了分析，即色散关系和一个单位等效模型，这两种方法给出了一致的结果。 发现对于γ* p -> N(1440)P11跃迁的横向螺旋度振幅A_{1/2}，其在Q2=0时大且为负，在Q2约为2 GeV2时变得大且为正，然后随着Q2缓慢下降。 之前从CLAS ep -> eppi0, enpi+数据分析得出，在Q2=0.4和0.65 GeV2时S_{1/2}的纵向螺旋度振幅大且为正，但随着Q2下降。 现有的gamma* p -> N(1440)P11模型预测使我们能够得出结论，这些结果有力地支持N(1440)P11作为3q基态的第一个径向激发。 本文的结果也确认了我们之前对于Q2 < 1 GeV2的分析结论，即把N(1440)P11描述为3qG混合态是不合理的。 显示英文摘要

摘要： The helicity amplitudes of the electroexcitation of the Roper resonance are extracted for 1.7 < Q2 < 4.5 GeV2 from recent high precision JLab-CLAS cross section and longitudinally polarized beam asymmetry data for pi+ electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two approaches, dispersion relations and a unitary isobar model, which give consistent results. It is found that the transverse helicity amplitude A_{1/2} for the gamma* p -> N(1440)P11 transition, which is large and negative at Q2=0, becomes large and positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. The longitudinal helicity amplitude S_{1/2}, which was previously found from CLAS ep -> eppi0,enpi+ data to be large and positive at Q2=0.4,0.65 GeV2, drops with Q2. Available model predictions for gamma* p -> N(1440)P11 allow us to conclude that these results provide strong evidence in favor of N(1440)P11 as a first radial excitation of the 3q ground state. The results of the present paper also confirm the conclusion of our previous analysis for Q2 < 1 GeV2 that the presentation of N(1440)P11 as a 3qG hybrid state is ruled out.