Version: SMASH-2.1
OSCAR Collisions Format

The OSCAR particles format follows the general block structure of the OSCAR format: OSCAR Block Structure. We distinguish between two versions - OSCAR2013 and OSCAR1999. Information about OSCAR standard can be found at https://karman.physics.purdue.edu/OSCAR and http://phy.duke.edu/~jeb65/oscar2013.
Enabling the OSCAR output for collisions in the config.yaml file (see Output Configuration), a so-called full_event_history.oscar file is produced when executing SMASH. It allows for a certain degree of flexibility, see Content-specific output options for further details.
Collision output always gives a list of collisions/decays/box wall crossings plus optionally initial and final configuration.

See also Collision Output in Box Modus.

Oscar1999

Oscar1999 is an ASCII (text) human-readable output following the OSCAR 1999 standard. The format specifics are the following:

Header

# OSC1999A
# full_event_history
# smash <version>
# Block format:
# nin nout event_number
# id pdg 0 px py pz p0 mass x y z t
# End of event: 0 0 event_number
#

The header consists of 8 lines starting with '#', of which the last one is basically empty. They contain the following information:

  1. The specific OSCAR1999 version the formatting follows - OSC1999A
  2. The filename
  3. The SMASH version with which the oputput was generated
  4. - 7. Info on the block structure


Output block header
Each output block starts with a line of the following format:

nin nout density tot_weight part_weight proc_type

With

  • nin: Number of ingoing particles (initial state particles)
  • nout: Number of outgoing particles (final state particles)
  • density: Density at the interaction point
  • tot_weight: Total weight of the interaction. This is the total cross section in case of a scattering and the total decay width in case of a decay. If there is no weight for the specific process, e.g. a wall crossing, it's value is 0.0.
  • part_weight: The partial weight of the interaction. This is the specific weight for the chosen final state.
  • proc_type: The type of the underlying process. See Process Types for possible types.

If the Print_Start_End option is set (see content-specific output options for details), (nin, nout) = (0, Nparticles) in the initial timestep and (nin, nout) = (Nparticles, 0) in the final timestep.


Particle line
The particle lines are formatted as follows:

id pdg 0 px py pz p0 mass x y z t

Where

  • id: Particle identifier in terms of an integer. It is unique for every particle in the event.
  • pdg: PDG code of the particle (see http://pdg.lbl.gov/). It contains all quantum numbers and uniquely identifies its type.
  • px, py, pz, p0: 3-momentum and energy
  • mass: Particle's rest-mass
  • x, y, z, t: Space-time coordinates


Event end line
The end of an event is indicated by the following line:

0 0 event_number impact_parameter

With

  • event_number: Number of the event
  • impact_parameter: Impact parameter of the collisions. In case of a box or sphere setup, this value is 0.0.


Oscar2013

Oscar2013 is an ASCII (text) human-readable output following the OSCAR 2013 standard. The format specifics are the following:

Header

#!OSCAR2013 full_event_history t x y z mass p0 px py pz pdg ID charge
# Units: fm fm fm fm GeV GeV GeV GeV GeV none none
# SMASH_version

The header consists of 3 lines starting with '#'. They contain the following information:

  1. Output version (OSCAR2013) and the type of output (particle_lists), followed by the substructure of the particle lines.
  2. Units of the quantities in the particle lines
  3. SMASH version


Extended Output: Header
If desired, the OSCAR2013 output can be extended by additional particle properties. This requires enabling the extended output in the configuration file, see the Extended switch in content-specific output options for further details. The header of the extended OSCAR output is structured identically to the non-extended version, but simply contains more columns because of the additional entries:

#!OSCAR2013 particle_lists t x y z mass p0 px py pz pdg ID charge ncoll form_time xsecfac proc_id_origin proc_type_origin t_last_coll pdg_mother1 pdg_mother2
# Units: fm fm fm fm GeV GeV GeV GeV GeV none none e none fm none none none fm none none
# SMASH_version


Output block header
Just as the OSCAR1999 format, the OSCAR2013 format is based on a block structure, where each block corresponds to one interaction. Each block starts with a line formatted as follows:

# interaction in nin out nout rho density weight tot_weight partial part_weight type proc_type

where

  • nin: Number of ingoing particles (initial state particles)
  • nout: Number of outgoing particles (final state particles)
  • density: Density at the interaction point
  • tot_weight: Total weight of the interaction. This is the total cross section in case of a scattering and the total decay width in case of a decay. If there is no weight for the specific process, e.g. a wall crossing, it's value is 0.0.
  • part_weight: The partial weight of the interaction. This is the specific weight for the chosen final state.
  • proc_type: The type of the underlying process. See Process Types for possible types.

Note, that "interaction", "in", "out", "rho", "weight", "partial" and "type" are no variables, but words that are printed.

Particle line
The particle lines are formatted as follows:

t x y z mass p0 px py pz pdg ID charge

Apart from the order, the entries are identical to those of the OSCAR1999 output, the only additional one is:

  • charge: the electric charge of the particle in units of the elementary charge e.


For the extended version the particle line contains

t x y z mass p0 px py pz pdg ID charge Ncoll formation_time xsecfac process_ID_origin process_type_origin t_last_coll PDG_mother1 PDG_mother2

The additional particle properties available in the extended output format are:

  • ncoll: Number of collisions the particle has undergone
  • form_time: Formation time of the particle
  • xsecfac: Cross section scaling factor (if the particles are not yet fully formed at the time of interaction, the cross section for the underlying process is scaled down by the cross section scaling factor)
  • proc_id_origin: ID of the process of the particle's last interaction
  • proc_type_origin: Type of the last process the particle has undergone. The possible process types are listed in Process Types.
  • t_last_coll: time of the particle's last interaction (except wall crossings)
  • pdg_mother1: PDG code of the 1st mother particle
  • pdg_mother2: PDG code of the 2nd mother particle (0 in case the particle results from the decay of a resonance, then pdg_mother1 is the PDG code of this resonance)

The mother particles are also set in case of an elastic scattering process.

Event end line
The end of an event is indicated by the following line:

# event ev_num end 0 impact impact_parameter

where

  • ev_num: The event's number
  • impact_parameter: impact parameter of the collision in case of a collider setup, otherwise 0.0.

Note, that "event", "end" and "impact" are no variables, but words that are printed.