Cosmic Ray Air Showers (2D)

Primary Cosmic Ray

Primary energy (log₁₀ eV) 10^17.5

Primary particle

Zenith angle 15°

Highlight muon component

Live Readout

Shower max (X_max)

— km

Particles at max

—

Ground footprint

— m

Generations

—

How it works

A toy Heitler cascade: each generation of particles roughly doubles in count while each carries half its parent's energy, until the per-particle energy falls to the critical energy in air (~86 MeV) and the cascade dies out. The atmospheric depth where particle count peaks is the shower maximum, X_max — higher primary energy needs more generations to reach the critical energy, so X_max sits deeper (closer to the ground).

Nucleus type — a proton starts one cascade; a heavier nucleus like iron behaves like A independent nucleons each carrying E₀/A ("superposition"), developing higher up with a shallower X_max.
Muon component — charged pions from hadronic collisions decay into muons, which barely interact and punch through to the ground, unlike the electromagnetic (electron/photon) part that gets absorbed.
Zenith angle — an inclined shower travels a longer slant path through the same vertical atmosphere, shifting where it reaches the critical energy.

Electromagnetic cascade Muon component Ground hits