Tel Aviv University, Tel Aviv 69978, Israel.
Florida International University, Miami, FL 33199, USA.
Science. 2014 Oct 31;346(6209):614-7. doi: 10.1126/science.1256785. Epub 2014 Oct 16.
The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.
质子和中子。如果质子和中子没有相互作用，泡利不相容原理将迫使大多数费米子（通常是中子）具有更高的平均动量。我们使用（12）C、（27）Al、（56）Fe 和（208）Pb 靶的高能电子散射测量表明，即使在重的、富含中子的原子核中，费米子之间的短程相互作用也会形成相关的高动量中子-质子对。因此，在富含中子的原子核中，质子比中子更有可能具有大于费米动量的动量。这一发现的意义范围从核少体系统到中子星，并且在双自旋态、超冷原子气体系统中也可能在实验上观察到。
