down quark

down-quark的词性：
n.Abbr. d（名词）缩写 d

1. A quark with a charge of ^-!/3, a mass about 607 times that of the electron, and a downward spin. It is a component of protons and neutrons.See table at subatomic particle
下夸克：电荷为^-!/3的夸克，质量是电子的607倍，有向下的旋转动量。下夸克是质子和中子的组成部分参见 subatomic particle