Version: SMASH-3.1
Process types

The available process types are summarized in the following table.

Process numberDescription
0No previous process yet, particle was created at initialization
1Elastic scattering
2Resonance formation (2 → 1)
3Inelastic binary scattering (2 → 2)
4Inelastic multi-particle scattering (2 → 3)
5Resonance decay
6Box wall crossing (due to periodic boundary conditions)
7Forced thermalization, many particles are replaced by a thermalized ensemble
8Hypersurface crossing, Particles are removed from the evolution and printed to a separate output to serve as initial conditions for hybrid models.
9Bremsstrahlung process: a + b → a + b + photon
10Inelastic multi-particle meson scattering (3 → 1)
11Inelastic multi-particle scattering (3 → 2)
12Inelastic multi-particle scattering (5 → 2)
13Inelastic multi-particle scattering (2 → 5)
14Inelastic multi-particle scattering (4 → 2)
15Inelastic multi-particle scattering (2 → 4)
41Soft string excitation, single diffractive AB → AX. Both quark and anti-/di-quark taken from B.
42Soft string excitation, single diffractive AB → XB. Both quark and anti-/di-quark taken from A. It makes sense to distinguish it from AB → AX, because A and B can be particles of different types, for example, a pion and a proton. It matters then, whether the pion creates a string or the proton.
43Soft string excitation, double diffractive. Two strings are formed, one from A and one from B.
44Soft string N-Nbar annihilation, a special case of baryon-antibaryon annihilation. One pair qqbar annihilates immediately and then two strings are formed.
45Soft string excitation, non-diffractive. Two strings are formed both have ends in A and B.
46Hard string excitation, hard string process involving 2 → 2 QCD process by PYTHIA. Here quarks do not simply form a string. They actually scatter on parton level first.
47Failed string process, Soft String NNbar annihilation process can fail by lack of energy. This is a tag we add to avoid mislabeling the events.
90Add or remove particle(s) process, which ignores conservation laws. It can be thought of as a 0 → 1 or a 1 → 0 process.