Linear confinement V(r) = σr, string tension σ ≈ 0.18 GeV², Regge trajectory
Color confinement in QCD: the chromoelectric flux between quark-antiquark pairs collimates into a flux tube (string) of constant energy density σ ≈ 0.18 GeV² ≈ (440 MeV)² ≈ 1 GeV/fm. The Cornell potential V(r) = −4α_s/3r + σr combines short-range Coulomb (one-gluon exchange) with linear confinement. At large r ≈ 1–1.5 fm, the string stores enough energy (≈2m_q) to create a new q-q̄ pair, breaking the string — observable as meson pair creation. Regge trajectories: J = α₀ + α'·m² with α' = 1/(2πσ) ≈ 0.9 GeV⁻².