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arXiv 2001.03677hep-phastro-ph.HEnucl-exnucl-th
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高能中微子相互作用中的核效应

Nuclear effects in high-energy neutrino interactions

Spencer R. Klein, Sally A. Robertson, Ramona Vogt

发表信息：
Phys. Rev. C 102, 015808 (2020)
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摘要：

像IceCube，KM 3 NeT和Baikal-GVD这样的中微子望远镜为物理学家提供了研究中微子的机会，这些中微子的能量远远超出了地球加速器的范围。这些中微子被用来研究高能中微子相互作用，并通过吸收层析成像探测地球。目前TeV中微子的研究使用的截面是计算自由核子与目标，其中假设包含相同数量的质子和中子。在这里，我们考虑由于两种核效应的高能中微子相互作用的修改：修改的部分子密度在核中，这里称为阴影，和非等密度的目标，与不相等的中子和质子数的影响。这两种效应都依赖于相互作用介质。因为对于较重的原子核，例如在地核中发现的铁，遮蔽更大，所以它在吸收截面中引入了依赖于天顶角的变化。这些修改在能量低于100 TeV时使截面增加1- 2%（反遮蔽），在能量较高时使截面减小3- 4%（遮蔽）。核效应还通过增加低非弹性相互作用的数量来改变水/冰中中微子相互作用的非弹性分布，对$ν$的影响大于$\barν$。这些效应在低于几TeV的能量范围内特别大。这些影响可能会改变从活动探测器体积内产生的轨迹的事件推断的横截面以及从非弹性测量推断的比率$ν/\barν$。这些核效应的不确定性大于自由质子截面的不确定性，因此将限制中微子望远镜未来高精度测量的系统精度。

英文摘要：

Neutrino telescopes like IceCube, KM3NeT and Baikal-GVD offer physicists the opportunity to study neutrinos with energies far beyond the reach of terrestrial accelerators. These neutrinos are used to study high-energy neutrino interactions and to probe the Earth through absorption tomography. Current studies of TeV neutrinos use cross sections which are calculated for free nucleons with targets which are assumed to contain equal numbers of protons and neutrons. Here we consider modifications of high-energy neutrino interactions due to two nuclear effects: modifications of the parton densities in the nucleus, referred to here as shadowing, and the effect of non-isoscalar targets, with unequal numbers of neutrons and protons. Both these effects depend on the interaction medium. Because shadowing is larger for heavier nuclei, such as iron, found in the Earth's core, it introduces a zenith-angle dependent change in the absorption cross section. These modifications increase the cross sections by 1-2\% at energies below 100 TeV (antishadowing), and reduce it by 3-4\% at higher energies (shadowing). Nuclear effects also alter the inelasticity distribution of neutrino interactions in water/ice by increasing the number of low inelasticity interactions, with a larger effect for $ν$ than $\barν$. These effects are particularly large in the energy range below a few TeV. These effects could alter the cross sections inferred from events with tracks originating within the active detector volume as well as the ratio $ν/\barν$ inferred from inelasticity measurements. The uncertainties in these nuclear effects are larger than the uncertainties on the free-proton cross sections and will thus limit the systematic precision of future high-precision measurements at neutrino telescopes.

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