arXiv 1909.026962019-09-06hep-phnucl-th

核子外耦合的$K^+Λ$和$K^0Λ$光生：最近CLAS和MAMI数据和$N(1680)P_{11}$窄态的结果

Coupled $K^+Λ$ and $K^0Λ$ photoproduction off the nucleon: Consequences from the recent CLAS and MAMI data and the $N(1680)P_{11}$ narrow state

T. Mart

备注：: 22 pages, 11 figures, submitted to Phys. Rev. D
发表信息：: Phys. Rev. D 100, 056008 (2019)
DOI：: 10.1103/PhysRevD.100.056008

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摘要：

新的$γn\to K^0Λ$数据从CLAS和MAMI合作获得的分析采用有效的拉格朗日方法。该模型可以同时描述$γp \to K^+Λ$和$γn\to K^0Λ$通道中所有可用的实验数据。该模型的背景部分是建立从适当的中间状态，涉及核子，K介子和超子交换，而共振部分是从一致的相互作用拉格朗日和传播。为了检验模型的性能，在两个同位旋通道的计算观测值和实验数据之间的详细比较，从中可以观察到一个很好的协议。利用三种不同的模型分析了$γn\to K^0Λ$通道中CLAS和MAMI数据之间的差异; M1，M2和M3分别拟合CLAS，MAMI以及CLAS和MAMI数据集。这种差异的影响进行了研究，通过调查的意义，个别核子共振和预测的束靶螺旋不对称$E$，最近已被测量的CLAS合作。发现$N(1720)P_{13}$、$N(1900)P_{13}$和$N(2060)D_{15}$共振对于提高模型计算与数据之间的一致性具有重要意义。这一结果对模型的选择是相对稳定的。螺旋度不对称性$E$可以用模型M1和M3更好地解释。最后，探讨了$N(1680)P_{11}$窄共振对两个同位旋通道横截面的影响。发现该效应在$γn\to K^0Λ$通道中更敏感。在这种情况下，拟合CLAS和MAMI数据的模型M3产生了更真实的效果。

英文摘要：

The new $γn\to K^0Λ$ data obtained from the CLAS and MAMI collaborations are analyzed by employing an effective Lagrangian method. The constructed model can describe all available experimental data in both $γp \to K^+Λ$ and $γn\to K^0Λ$ channels, simultaneously. The background part of the model is built from the appropriate intermediate states involving the nucleon, kaon, and hyperon exchanges, whereas the resonance part is constructed from the consistent interaction Lagrangians and propagators. To check the performance of the model a detailed comparison between the calculated observables and experimental data in both isospin channels is presented, from which a nice agreement can be observed. The discrepancy between the CLAS and MAMI data in the $γn\to K^0Λ$ channel is analyzed by utilizing three different models; M1, M2, and M3 that fit the CLAS, MAMI, and both CLAS and MAMI data sets, respectively. The effect of this discrepancy is studied by investigating the significance of individual nucleon resonances and the predicted beam-target helicity asymmetry $E$ that has been measured by the CLAS collaboration recently. It is found that the $N(1720)P_{13}$, $N(1900)P_{13}$, and $N(2060)D_{15}$ resonances are significant for improving the agreement between model calculation and data. This result is relatively stable to the choice of the model. The helicity asymmetry $E$ can be better explained by the models M1 and M3. Finally, the effect of the $N(1680)P_{11}$ narrow resonance on the cross section of both isospin channels is explored. It is found that the effect is more sensitive in the $γn\to K^0Λ$ channel. In this case the model M3, that fits both CLAS and MAMI data, yields a more realistic effect.

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