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arXiv 1612.05511nucl-thhep-ph
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核子外的电弱单π介子产生：从阈值到高不变质量

Electroweak single-pion production off the nucleon: from threshold to high invariant masses

R. González-Jiménez, N. Jachowicz, K. Niewczas, J. Nys, V. Pandey, T. Van Cuyck, N. Van Dessel

备注：
30 pages, 21 figures. Includes comparison with NuWro predictions. New references added
发表信息：
Phys. Rev. D 95, 113007 (2017)
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摘要：

[研究背景]中微子诱导的单π介子产生（SPP）对中高能中微子-核相互作用有重要贡献。在文献中有许多低能模型描述了π介子在Delta共振附近区域的中微子产生。这些模型只考虑了最低阶的相互作用项，因此在高能区（π-核子不变质量，$W$ >2 GeV）失效。[目的]建立一个适用于当前和未来中微子振荡实验的全能量范围的核子外电弱SPP模型。[方法]从[Phys.Rev.D76，033005（2007）]的低能模型出发，考虑了由手征微扰理论的π-核子拉格朗日量导出的共振贡献和背景项。然后，从背景的贡献，我们建立了一个高能量模型，使用Regge方法。低能量和高能量模型相结合，在一个唯象的方式，成为一个混合模型。[结果]在低W区，Hybrid模型与低能模型完全相同，但当W>2 GeV时，Hybrid模型实现了Regge理论所要求的高能行为。通过与电子和中微子反应的单π介子产生数据的比较，我们对高能模型进行了检验。混合模型进行了比较与电子-质子散射数据，中微子SPP数据和预测的NuWro蒙特卡罗事件发生器。[结论]该模型能够较好地预测从π介子阈值到高$W$的电弱单π介子产生截面。需要进一步的研究和更多的数据，以更好地了解在高W区的电弱SPP过程中发挥作用的机制，特别是那些涉及轴向电流的贡献。

英文摘要：

[Background] Neutrino-induced single-pion production (SPP) provides an important contribution to neutrino-nucleus interactions, ranging from intermediate to high energies. There exists a good number of low-energy models in the literature to describe the neutrinoproduction of pions in the region around the Delta resonance. Those models consider only lowest-order interaction terms and, therefore, fail in the high-energy region (pion-nucleon invariant masses, $W$>2 GeV). [Purpose] Our goal is to develop a model for electroweak SPP off the nucleon, which is applicable to the entire energy range of interest for present and future neutrino-oscillation experiments. [Method] We start with the low-energy model of [Phys.Rev.D76,033005(2007)], which includes resonant contributions and background terms derived from the pion-nucleon Lagrangian of chiral-perturbation theory. Then, from the background contributions, we build a high-energy model using a Regge approach. The low- and high-energy models are combined, in a phenomenological way, into a hybrid model. [Results] The Hybrid model is identical to the low-energy model in the low-W region, but, for W>2 GeV, it implements the desired high-energy behavior dictated by Regge theory. We have tested the high-energy model by comparing with one-pion production data from electron and neutrino reactions. The Hybrid model is compared with electron-proton scattering data, with neutrino SPP data and with the predictions of the NuWro Monte Carlo event generator. [Conclusions] Our model is able to provide satisfactory predictions of the electroweak one-pion production cross section from pion threshold to high $W$. Further investigation and more data are needed to better understand the mechanisms playing a role in the electroweak SPP process in the high-W region, in particular, those involving the axial current contributions.

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