Phillips Daniel R, Samart Daris, Schat Carlos
Institute of Nuclear and Particle Physics and Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA.
Department of Applied Physics, Faculty of Sciences and Liberal Arts, Rajamangala University of Technology Isan, Nakhon Ratchasima, 30000, Thailand and Thailand Center of Excellence in Physics (ThEP), Commission on Higher Education, Bangkok 10400, Thailand.
Phys Rev Lett. 2015 Feb 13;114(6):062301. doi: 10.1103/PhysRevLett.114.062301. Epub 2015 Feb 10.
Several experimental investigations have observed parity violation (PV) in nuclear systems-a consequence of the weak force between quarks. We apply the 1/N(c) expansion of QCD to the P-violating T-conserving component of the nucleon-nucleon (NN) potential. We show there are two leading-order operators, both of which affect p[over →]p scattering at order N(c). We find an additional four operators at order N(c)(0)sin(2)θ(W) and six at O(1/N(c)). Pion exchange in the PV NN force is suppressed by 1/N(c) and sin(2)θ(W), providing a quantitative explanation for its nonobservation up to this time. The large-N(c) hierarchy of other PV NN force mechanisms is consistent with estimates of the couplings in phenomenological models. The PV observed in p[over →]p scattering data is compatible with natural values for the strong and weak coupling constants: there is no evidence of fine-tuning.
多项实验研究在核系统中观测到了宇称破坏（PV）——这是夸克之间弱力的一个结果。我们将量子色动力学（QCD）的1/N(c)展开应用于核子 - 核子（NN）势中违反宇称但守恒时间反演（T）的分量。我们表明存在两个领头阶算符，它们在N(c)阶都对p[上箭头]p散射有影响。我们在N(c)(0)sin(2)θ(W)阶发现了另外四个算符，在O(1/N(c))阶发现了六个算符。PV NN力中的π介子交换被1/N(c)和sin(2)θ(W)抑制，这为迄今未观测到它提供了一个定量解释。其他PV NN力机制的大N(c)层次结构与唯象模型中耦合的估计一致。在p[上箭头]p散射数据中观测到的PV与强耦合常数和弱耦合常数的自然值兼容：没有微调的证据。
