夸克有内部结构吗?

Does quark have internal structures?

"夸克"是目前人类所知的构成物质世界的基本粒子之一,也是在粒子物理"标准模型"中参与所有已知的基本相互作用的唯一的基本粒子.实验寻找比夸克更小的基本粒子,或者验证是否夸克具有更加细微的内部结构,这是现代高能物理研究寻找超出标准模型新粒子的重要手段,也是高能量前沿的重要研究课题.

Quark is one of the fundamental particles so far known by human being as a building block of our matter world. It is the only one which participates all known fundamental interactions in the framework of the Standard Model（SM）. As part of the SM, the gauge theory that describes the strong interactions between quarks and gluons is called Quantum Chromo-Dynamics（QCD）. Since quarks and gluons always carry ＂color charges＂, any single quark or gluon cannot be isolated from hadrons to act as a free particle. This phenomenon, known as ＂color confinement＂, implies that hadrons instead of quarks or gluons are actually the so-far smallest inseparable particles. The other feature with QCD is that when the larger energy or momentum transfers occur between quarks, the weaker their interactions become. This paves a way for probing the structure of quarks by high energy hadron-hadron scatterings or electron-hadron scatterings which can better resolve the structure of such tiny colored objects. Evidence for smaller fundamental particles than the quarks or possible proof for internal refined structures of the quarks would request new physics beyond the SM and they may dramatically change our view of the matter world. These studies are actually the high energy frontier of modern high energy physics in both experiment and theory.