用KDAR中微子探测中子皮：从相干到衍射弹性中微子-核散射
Probing Neutron Skins with KDAR Neutrinos: From Coherent to Diffractive Elastic Neutrino--Nucleus Scattering
AI总结：
利用KDAR中微子进行相干弹性中微子-核散射研究，以探测中子皮和核弱密度，提供与电子散射测量互补的高灵敏度方法。
摘要：
我们研究由介子衰变静止（πDAR）和K介子衰变静止（KDAR）中微子诱导的相干弹性中微子-核散射（CEνNS），重点在于从严格相干到衍射区域的过渡。通过将CEνNS可观测变量按无量纲变量qR组织，我们表明πDAR测量对于所有核均局限于近相干区域，而KDAR中微子（E_ν=236 MeV）将动力学扩展到qR≈1，其中 recoil谱发展出真正的形状敏感性到核弱形式因子。使用代表性的轻、中等质量及重核（¹²C，⁴⁰Ca，⁴⁸Ca和²⁰⁸Pb），我们检查了相关的截面并量化了在JSNS²类设施中可实现的中子皮厚度统计灵敏度。对于总曝光量为10吨·年和现实的KDAR通量，预计1σ灵敏度达到⁴⁸Ca的ΔR_{np}^{(1σ)}≈0.09-0.02 fm和²⁰⁸Pb的≈0.07-0.02 fm。这些灵敏度与CREX和PREX等违反宇称的电子散射测量具有竞争力和互补性，同时依赖于一个电弱清洁的中性流探测器，具有不同的系统误差。我们的结果确立了基于KDAR的CEνNS作为探测中子皮和核弱密度在相干极限之外的定量稳健且互补的途径。
英文摘要：
We investigate coherent elastic neutrino--nucleus scattering (CE$ν$NS) induced by pion--decay--at--rest ($π$DAR) and kaon--decay--at--rest (KDAR) neutrinos, with emphasis on the transition from strict coherence to the diffractive regime. Organizing CE$ν$NS observables in terms of the dimensionless variable $qR$, we show that $π$DAR measurements remain confined to the near--coherent region for all nuclei, whereas KDAR neutrinos ($E_ν=236$~MeV) extend the kinematics into $qR\gtrsim1$, where recoil spectra develop genuine shape sensitivity to the nuclear weak form factor. Using representative light, medium--mass, and heavy nuclei ($^{12}$C, $^{40}$Ca, $^{48}$Ca, and $^{208}$Pb), we examine relevant cross sections and quantify the statistical sensitivity to the neutron skin thickness achievable at a JSNS$^2$--like facility. For a total exposure of 10~ton$\cdot$year and realistic KDAR fluences, projected $1σ$ sensitivities reach $ΔR_{np}^{\,(1 σ)}$ $\simeq0.09$--$0.02$~fm for $^{48}$Ca and $\simeq0.07$--$0.02$~fm for $^{208}$Pb as the fluence increases. These sensitivities are competitive with, and complementary to, parity--violating electron--scattering measurements such as CREX and PREX, while relying on an electroweakly clean neutral--current probe with distinct systematic uncertainties. Our results establish KDAR--based CE$ν$NS as a quantitatively robust and complementary avenue for probing neutron skins and nuclear weak densities beyond the coherent limit.
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