基本粒子3.pptVIP

* Think of the two charm quarks as being connected by a tight spring.As the spring stretches, the energy stored in it increases. If you keepon pulling, eventually, the spring “snaps”.In the case of quarks, as they separate, the energy stored in the “gluon spring”increases until it eventually “snaps”. When it does, the energy stored in thisspring is converted into mass in the form of a quark-antiquark (down-antidown quarks) pair.So, the initial charm-anticharm state has now become two particles,a charm-antidown + a down-anticharm. An example of conversion of energy into mass! Also note that the strong interaction can only produce quark-antiquark pairs ofthe same type. That is (down-antidown, up-antiup, strange-antistrange, etc) As quarks move apart from one another, the energy stored I the 包含重夸克的介子的衰变 M=5280 [MeV/c2] M=1870 [MeV/c2] M=0.51 [MeV/c2] M~0 [MeV/c2] B0 介子 D+ 介子 bR dR cR dR W - e- ne b c d B0 ? D+ m - nm 也可以 B0 ? D+ t - nt -1/3+1/3 +2/3+1/3 弱力可以发生于夸克和胶子之间 !!!! 包含重夸克 (c, s, b, t)的强子通过发射W变为下一个次重的夸克  t b c s u d Generation/Family 1 2 3 Charge +2/3 -1/3 电荷总是改变一个单位 中子衰变 中子寿命 14 分 M = 0.51 [MeV/c2] M~0 [MeV/c2] M=940 [MeV/c2] M=938 [MeV/c2] n ? p + e - + ne d u d n u u d p e - ne W - n ? p + m - + nm Mm = 106 [MeV/c2] ? 粒子及其相互作用 夸克 带电轻子(e,m,t) 中性轻子(n) 色荷? 电荷? ‘弱’荷 ? Y Y Y Y Y Y N N N 夸克：强，电磁和弱相互作用 ! 夸克和轻子带弱核. 中微子只带弱核 ! Higgs 粒子 为什么夸克和轻子具有其质量? 获得质量的机制： Higgs 机制. 需要一个Higgs粒子 Higgs 粒子的质量 100 [GeV/c2] Hadrons Matter Leptons Baryons Mesons Charged Neutrinos Forces Weak EM Strong Gravity Quarks Anti-Quarks 原子 99.999% 是空的 Nucleus Electron g . 质子和中子 99.999% 空 Proton g u d u 物质的强度 ? 力 !!!! * In all cases, you will see that I have given the quarks inside baryons the colors red, green, and blue.This is because quarks also have an intrinsic “color charge”, or simply “color” for short. We willget into this in more detail later when we discuss the strong interaction.For now, assume that all baryons must have 1 RED, 1 GREEN and