Collider

Possible Incident Energies, only one can be given:

• Sqrtsnn (double, optional, no default):
  Defines the energy of the collision as center-of-mass energy in the collision of one participant each from both nuclei (using the average participant mass in the given nucleus).

• E_Kin (double, optional, no default):
  Defines the energy of the collision by the kinetic energy per nucleon of the projectile nucleus (in AGeV). This assumes the target nucleus is at rest.

• P_Lab (double, optional, no default):
  Defines the energy of the collision by the initial momentum per nucleon of the projectile nucleus (in AGeV). This assumes the target nucleus is at rest.

Note that using E_kin or P_Lab to quantify the collision energy is not sufficient to configure a collision in a fixed target frame. You need to additionally change the Calculation_Frame. Any format of incident energy can however be combined with any calculation frame, the provided incident energy is then intrinsically translated to the quantity needed for the computation.

Calculation_Frame (string, optional, default = "center of velocity"):
The frame in which the collision is calculated.

• "center of velocity"
• "center of mass"
• "fixed target"

Fermi_Motion (string, optional, default = "off"):

• "on" - Switch Fermi motion on, it is recommended to also activate potentials
• "off" - Switch Fermi motion off
• "frozen" - Use "frozen" if you want to use Fermi motion without potentials

Collisions_Within_Nucleus (string, optional, default = false)
Determine whether to allow the first collisions within the same nucleus.

• true - First collisions within the same nucleus allowed
• false - First collisions within the same nucleus forbidden

To further configure the projectile, target and the impact parameter, see

• Projectile and Target
• Impact Parameter

Examples: Configuring Heavy-ion Collisions
The following example configures a Cu63-Cu63 collision at \(\sqrt{s_{NN}}=3.0\) GeV with zero impact parameter and Fermi motion taken into consideration. The calculation frame is the default, center of velocity, and the nuclei are not deformed.

Modi:
    Collider:
        Projectile:
            Particles:    {2212: 29, 2112 :34}
        Target:
            Particles:    {2212: 29, 2112 :34}
        Sqrtsnn: 3.0

To further use Fermi motion and allow the first collisions within the projectile or target nucleus, the corresponding options need to be activated by means of:

        Fermi_Motion: "on"
        Collisions_Within_Nucleus: True

Additionally, the impact parameter may be specified manually. See Impact Parameter for an example.

Note

By default, executing SMASH without further specifying the configuration, particles or decaymodes, a collider simulation is set up according to the default 'config.yaml', 'particles.txt' and 'decaymodes.txt' files located in /input. Note though that these files were previously copied to the build directory, so changng the ones in the /input directory will not affect the default SMASH run. To run SMASH in the (default) collider setup, execute

   ./smash