Bartolini Lorenzo, Bigazzi Francesco, Bolognesi Stefano, Cotrone Aldo L, Manenti Andrea
Dipartimento di Fisica "E. Fermi," Universitá di Pisa and INFN, Sezione di Pisa; Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy.
INFN, Sezione di Firenze; Via G. Sansone 1, I-50019 Sesto Fiorentino (Firenze), Italy.
Phys Rev Lett. 2017 Mar 3;118(9):091601. doi: 10.1103/PhysRevLett.118.091601. Epub 2017 Feb 27.
We compute the electric dipole moment of nucleons in the large N_{c} QCD model by Witten, Sakai, and Sugimoto with N_{f}=2 degenerate massive flavors. Baryons in the model are instantonic solitons of an effective five-dimensional action describing the whole tower of mesonic fields. We find that the dipole electromagnetic form factor of the nucleons, induced by a finite topological θ angle, exhibits complete vector meson dominance. We are able to evaluate the contribution of each vector meson to the final result-a small number of modes are relevant to obtain an accurate estimate. Extrapolating the model parameters to real QCD data, the neutron electric dipole moment is evaluated to be d_{n}=1.8×10^{-16}θ e cm. The electric dipole moment of the proton is exactly the opposite.
我们在由维滕、酒井和杉本提出的具有(N_f = 2)个简并质量味的大(N_c) QCD模型中计算核子的电偶极矩。该模型中的重子是描述整个介子场塔的有效五维作用量的瞬子孤子。我们发现，由有限拓扑(\theta)角诱导的核子偶极电磁形状因子表现出完全的矢量介子主导。我们能够评估每个矢量介子对最终结果的贡献——少量模式对于获得准确估计是相关的。将模型参数外推到真实的QCD数据，中子电偶极矩被评估为(d_n = 1.8×10^{-16}\theta,e,cm)。质子的电偶极矩正好相反。
