质子-氘核($pd$)辐射俘获反应在大爆炸核合成(Big Bang nucleosynthesis)和恒星质子-质子链中起着至关重要的作用。低能反应的研究在实验和理论上都具有挑战性。利用势模型框架,我们分析了1 MeV以下的$pd$辐射俘获,包括电偶极($E1$)和磁偶极($M1$)跃迁。得到的天体物理$S$因子与近期结果吻合良好,尤其是在与敏感的氘丰度相关的能量处。计算得到的反应率与近期工作相比显示出良好的一致性,差异小于5%。包括两种跃迁的外推值$S(0)$确定为$0.211 \pm 0.016$ eV b。使用$χ^2$检验与实验数据的比较揭示了低能下$M1$截面对散射势深度的敏感性。
英文摘要:
The $pd$ radiative capture reaction plays a vital role in Big Bang nucleosynthesis and stellar proton-proton chain. The study of the low-energy reaction is challenging in both experiments and theories. Using the framework of potential model, we analyze $pd$ radiative capture below 1 MeV for both electric dipole ($E1$) and magnetic dipole ($M1$) transitions. The obtained astrophysical $S$ factors agree well with recent results, especially at energies relevant to sensitive deuterium abundance. The calculated reaction rate shows good agreement, with less than a 5\% difference compared to recent works. The extrapolated value for $S(0)$ including both transitions is determined to be $0.211 \pm 0.016$ eV b. A comparison with experimental data using the $χ^2$ test reveals the sensitivity of the $M1$ cross section at low energies to the scattering potential depth.
Probing CP Violation with the Deuteron Electric Dipole Moment
本文分析了4维、5维和6维CP破坏算符(包括θ QCD、夸克的电偶极矩和色电偶极矩、四夸克相互作用和Weinberg算符)诱导的氘核电偶极矩。我们证明,EDM协作的建议,以寻找氘EDM,(1-3)\times 10^{-27} e cm的精度目标,将提供一个改进的灵敏度,这些源的一个-两个数量级相对于现有的界限。我们认为详细的水平,CP-奇相位可以探测内的MSSM。
背景资料:直接测量中子的电偶极矩(EDM)是未来的事;核EDM的测量很可能是第一位的。氘核是一种可以用精确模型计算的原子核。目的:探讨氘EDM计算的模型依赖性。研究方法:使用可分离的潜在制定的哈密顿量,我们研究的灵敏度的氘核EDM变化的核子-核子相互作用。我们将EDM写为两项的和,第一项取决于具有平面波中间状态的目标波函数,第二项取决于3 P1通道中的中间多次散射,后者对3 P1振幅的离壳行为敏感。结果如下:我们比较完整的计算与平面波近似的结果,检查张量力的模型结果的贡献,并探讨短程排斥的影响,发现在现实的,当代的潜在模型的氘核。结论:由于一π介子交换占主导地位的EDM计算,可分离的潜力模型计算将提供一个足够的描述,直到这样的时间作为一个更好的2 H EDM的10%的测量获得。
We calculate the electric dipole moment (EDM) of the deuteron in the standard model with $|ΔS| =1$ interactions by taking into account the $NN - ΛN - ΣN$ channel coupling, which is an important nuclear level systematics. The two-body problem is solved with the Gaussian Expansion Method using the realistic Argonne $v18$ nuclear force and the $YN$ potential which can reproduce the binding energies of $^3_Λ$H, $^3_Λ$He, and $^4_Λ$He. The $|ΔS| =1$ interbaryon potential is modeled by the one-meson exchange process. It is found that the deuteron EDM is modified by less than 10\%, and the main contr…
Explicit Delta(1232) Degrees of Freedom in Compton Scattering off the Deuteron
在次主导阶的手征有效场论框架下,研究了光子能量在50 MeV ~ 100 MeV之间的氘核弹性康普顿散射.我们比较了一个理论方案,只有π介子和核子作为显式自由度,另一个在德尔塔(1232)共振被视为一个显式的自由度。虽然π自由度足以描述在约70 MeV测量的实验数据,明确的德尔塔(1232)给出了重要的贡献,有助于再现在更高的能量的角度依赖性。将静态等密度偶极子极化率α_E^s和β_M^s与现有数据进行拟合,得到中子极化率α_E^n=(14.2+-2.0(stat)+-1.9(syst))*10^(-4 fm ^3),β_M^n=(1.8+-2.2(stat)+-0.3(syst))*10^(-4 fm ^3)。这些值与以前的实验分析吻合得很好。将它们与众所周知的质子值进行比较,我们得出结论,目前没有证据表明质子和中子电磁偶极极化率之间存在显着差异。
We calculate for the first time the electric dipole moment (EDM) of the deuteron, $^3$H, and $^3$He nuclei generated by the one-meson exchange CP-odd nuclear force in the standard model. The effective $|ΔS| = 1$ four-quark operators are matched to the $|ΔS| = 1$ standard model processes involving the CP phase of the Cabibbo-Kobayashi-Maskawa matrix at the electroweak scale and run down to the hadronic scale $μ= 1$ GeV according to the renormalization group evolution in the next-to-leading logarithmic order. At the hadronic scale, the hadron matrix elements are modeled in the factorization appr…
The generalized Gerasimov-Drell-Hearn sum rule for deuteron electrodisintegration
本文用显式积分法计算了氘核电致衰变$d(e,e')np$的广义Gerasimov-Drell-Hearn求和规则$I^{GDH}_{γ^*d}(Q^2)$作为平方四动量转移$Q^2$的函数。计算是基于一个传统的非相对论框架,使用一个现实的$NN$势,并包括介子交换流,等压位形和领先的相对论性条款的贡献。实现了良好的收敛。显著的特点是一个深负的最小值,$I_{γ^* d}^{GDH}=-9.5$ mb,在低$Q^2\approx 0.2$ fm $^{-2}$,这是几乎完全由核子等矢量异常磁矩贡献的磁偶极子过渡到$^1S_0$状态。高于$Q^2=20$ fm $^{-2}$,积分$I^{GDH}_{γ^*}(Q^2)$迅速接近零。
Potential for measurement of the tensor electric and magnetic polarizabilities of the deuteron in storage-ring experiments with polarized beams
测量氘核的张量极化率和张量极化率是非常有意义的,特别是与COSY和GSI的可能性有关。这些极化率可以通过提供g-2旋进消失的冻结自旋方法在储存环中测量。该方法将用于计划中的储存环氘电偶极矩实验。在上述实验中,氘核的张量极化率显著影响垂直极化的建立。自旋相互作用依赖于电偶极矩,张量极化率,和场失调引起的主要系统误差具有非常不同的对称性。对于所考虑的实验条件,$1\times10^{-29} e\cdot$ cm对氘EDM的灵敏度对应于以$δα_T\approxδβ_T\approx5\times10^{-42}$ cm $^3$的精度测量两个张量极化率。这种保守估计可以通过排除由场不稳定性引起的系统误差来改善,因为场不稳定性对于张量极化率的测量是可以忽略的。为了得到张量磁极化率,需要测量极化矢量的水平分量。
A nonzero electric dipole moment (EDM) of the neutron, proton, deuteron or helion, in fact, of any finite system necessarily involves the breaking of a symmetry, either by the presence of external fields (i.e. electric fields leading to the case of induced EDMs) or explicitly by the breaking of the discrete parity and time-reflection symmetries in the case of permanent EDMs. We discuss two theorems describing these phenomena and report about the cosmological motivation for an existence of CP breaking beyond what is generated by the Kobayashi-Maskawa mechanism in the Standard Model and what thi…
Percent-Level Prediction of the Deuteron Magnetic Polarizability
University of Maryland, College Park(马里兰大学帕克分校);National Taiwan University(台湾大学);National Center for Theoretical Sciences(国家理论科学中心);Shanghai Jiao Tong Unviersity(上海交通大学)
The magnetic form factors of $^2$H, $^3$H, and $^3$He, deuteron photodisintegration cross sections at low energies, and deuteron threshold electrodisintegration cross sections at backward angles in a wide range of momentum transfers, are calculated with the chiral two-nucleon (and three-nucleon) interactions including $Δ$ intermediate states that have recently been constructed in configuration space. The $A\,$=$\,$3 wave functions are obtained from hyperspherical-harmonics solutions of the Schrödinger equation. The electromagnetic current includes one- and two-body terms, the latter induced by…
Nucleon spin structure functions have been investigated mainly by longitudinally-polarized ones for finding the origin of the nucleon spin. Other types of spin structure functions are transversely-polarized ones. In particular, quark transversity distributions in the nucleons have very different properties from the longitudinally-polarized quark distribution functions, especially in scaling violation, because they are decoupled from the gluon transversity, due to the fact that they are helicity-flip (chiral-odd) distributions. Such studies are valuable for finding not only the origin of the nu…
Nuclei in the $sd$-shell demonstrate a remarkable interplay of cluster and mean-field phenomena. The $N=Z$ nuclei, such as $^{24}$Mg and $^{28}$Si, have been the focus of the theoretical study of both these phenomena in the past. The cluster and vortical mean-field phenomena can be probed by excitation of isoscalar monopole and dipole states in scattering of isoscalar particles such as deuterons or $α$ particles. Inelastically scattered $α$ particles were momentum-analysed in the K600 magnetic spectrometer at iThemba LABS, Cape Town, South Africa. The scattered particles were detected in two m…