1
2
3
4
5
6
Lagrangian of QED:
8
9
fine-structure constant =
11 Feynman diagram
Quantum Field Theory: Finestructure constant function of energy or scale due to quantum fluctuations of electron-positron pairs => partial screening of bare charge of the electron at distances less than the compton wavelength of the electron 12
+
+
LEP
Abelean gauge theory: gauge bosons interact only with the fermions
Non-Abelean gauge theories 18
19
20
21
non-Abelean gauge theory gauge bosons interact with the fermions and with the gauge bosons
LEP experiments: at 91 GeV
as as experiment =>
3 Quarks: u,d,s
violation of „scaling“
p: proton momentum x p: quark momentum 0 < x < 1
+ …
scaling violations in QCD quarks emit gluons! Q1Q1 Q 2 > Q 1 The structure function data exhibit systematic violations of Bjorken scaling
scaling violations
quark – antiquark potential
Large distance: linear term
54
55
56 Feynman
57
58
59
60
61
62 gluon quark antiquark
63
64
65
„dimesons“ „pentaquarks“ „dibaryons“
67
68
69
70
71
glue mesons strong mixing with neutral quark-antiquark mesons (thus far not observed)