Version: SMASH-3.1
OSCAR particles format
Process types

The OSCAR particles format follows the general block structure of the OSCAR format: OSCAR format. We distinguish between two versions, OSCAR2013 and OSCAR1999. Information about OSCAR standard can be found at http://phy.duke.edu/~jeb65/oscar2013.
Enabling the OSCAR output for particles in the config.yaml file (see Output), a so-called particle_lists.oscar file is produced when executing SMASH. It allows for a certain degree of flexibility, see Content-specific output options for further details.
Unless IC output is enabled, the Particle output always provides the current particle list at a specific time. See Initial conditions for details about the particles IC output.

Oscar1999

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


Header

# OSC1999A
# final_id_p_x
# 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 impact_parameter
#

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 - OSCAR1999A
  2. The substructure of each particle line: (id - momentum - coordinates)
  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 indicating the numbers of ingoing and outgoing particles as well the number of the event.

nin nout event_number

With

  • nin: Number of ingoing particles
  • nout: Number of outgoing particles
  • event_number: Number of the event

For initial timesteps, (nin, nout) = (0, Nparticles), while (nin, nout) = (Nparticles, 0) for intermediate and final timesteps. Nparticles is the total number of particles at the specific timestep. It may differ from one timestep to another if the test case allows more interactions than only elastic scatterings. The output block header is followed by Nparticles particle lines.


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 particle_lists t x y z mass p0 px py pz pdg ID charge
# Units: fm fm fm fm GeV GeV GeV GeV GeV none none e
# 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 baryon_number strangeness
# 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. The beginning of a new block is marked by either the start of a new event or a new intermediate output (at the next timestep).

Output block header for a new event:

# event ev_num in Nparticles

Where

  • ev_num: Event number
  • Nparticles: Number of particles initialized at the beginning of the event

Note that 'event' and 'in' are no variables, but words that are printed in the header.

Output block header for an intermediate output:

# event ev_num out Nparticles

Where

  • ev_num: Event number
  • Nparticles: Number of particles at the end of the timestep

Note that 'event' and 'out' are no variables, but words that are printed in the header.

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 form_time xsecfac proc_id_origin proc_type_origin time_last_coll pdg_mother1 pdg_mother2 baryon_number strangeness

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 (0 in case the particle is sampled in a thermal bubble. It is not updated by elastic scatterings.)
  • pdg_mother2: PDG code of the 2nd mother particle (0 in case the particle results from the decay of a resonance or the appearance of a thermal bubble. In the former case, pdg_mother1 is the PDG code of this resonance. It is not updated by elastic scatterings.)
  • baryon_number: Baryon number of the particle. 1 for baryons, -1 for anti-baryons and 0 for mesons.

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 empty yes_or_no

Where

  • ev_num: Event number
  • Nparticles: Number of particles at the end of the timestep
  • impact_parameter: Impact parameter of the collision in case of a collider setup, 0.0 otherwise.
  • yes_or_no: "no" if there was an interaction between the projectile and the target, "yes" otherwise. For non-collider setups, this is always "no".

Note that 'event', 'end', 'impact' and 'empty' are no variables, but words that are printed in the header.