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arXiv 2301.02137nucl-thhep-ph
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氘核电致解离及其他过程的约化核螺旋度振幅

Reduced nuclear helicity amplitudes for deuteron electrodisintegration and other processes

J. Flores, S. S. Chabysheva, J. R. Hiller

AI总结:

本研究拓展约化核振幅理论以描述单个螺旋度振幅,应用于氘核相关遍举过程,结合点状核子树图与经验形状因子计算,所得光致解离不对称性更贴合实验,还给出了标度起始的动量转移参考。

摘要:

我们将约化核振幅的原始思路拓展至可描述单个螺旋度振幅,并探讨其在涉及氘核的遍举过程中的多种应用,具体涵盖氘核形状因子、结构函数、张量极化可观测量、光致解离与电致解离过程。该方法的基本前提是:高动量转移下的核过程可通过点状核子的树图近似,再为每个核子补充经验形状因子;后者表征核子的内部结构,纳入了非微扰物理效应,可让标度行为更早出现。核子形状因子在给定核子所受的净动量转移下计算,无翻转贡献使用$G_E$,螺旋度翻转贡献使用$G_M$。我们将计算结果与现有可用数据进行了对比:得到的氘核光致解离不对称性$Σ$在$90^\text{o}$时取值约为$-0.06$,远优于最初预期的$-1$,与实验结果更为接近。该方法还可估算标度起始所需的动量转移值,我们发现氘核结构函数$B$是合适的研究对象,对应动量转移需高于10 GeV$^2$。

英文摘要:

We extend the original idea of reduced nuclear amplitudes to capture individual helicity amplitudes and discuss various applications to exclusive processes involving the deuteron. Specifically, we consider deuteron form factors, structure functions, tensor polarization observables, photodisintegration, and electrodisintegration. The basic premise is that nuclear processes at high momentum transfer can be approximated by tree graphs for point-like nucleons supplemented by empirical form factors for each nucleon. The latter represent the internal structure of the nucleon, and incorporate nonperturbative physics, which can allow for early onset of scaling behavior. The nucleon form factors are evaluated at the net momentum transfer experienced by the given nucleon, with use of $G_E$ for a no-flip contribution and $G_M$ for a helicity-flip contribution. Results are compared with data where available. The deuteron photodisintegration asymmetry $Σ$ is obtained with a value of $Σ(90^\circ)\simeq -0.06$, which is much closer to experiment than the value of -1 originally expected. The method also provides an estimate of the momentum transfer values required for scaling onset. We find that the deuteron structure function $B$ is a good place to look, above momentum transfers of 10 GeV$^2$.

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