α
s
(Q²)
Running of the Strong Coupling Constant
COUPLING MONITOR
α
s
(Q) =
0.1179
Q
91.2
GeV
n
f
5
Λ
QCD
217
MeV
β₀
23
1-loop
2-loop
3-loop
α
s
(Q²) =
4π
β₀ · ln(Q²/Λ²)
β₀ = 11 − ⅔ n
f
Energy Scale Q (GeV)
0.5
Λ
QCD
m
c
m
b
M
Z
m
t
1 TeV
Active Flavors n
f
Λ
QCD
(MeV)
CONFINEMENT
α
s
→ ∞ · Quarks bound
ASYMPTOTIC FREEDOM
α
s
→ 0 · Quarks free
FPS
60
Regime
pQCD