Version: SMASH-3.1
Output

To produce a certain output content it is necessary to explicitly configure it in the Output section of the configuration file. This means, that the Output section needs to contain one or more subsection for each desired content. Additionally, there are general output configuration parameters that can be used for further customization.

General output configuration parameters

Density_Type — string, optional, default = "none"

Determines which kind of density is printed into the headers of the collision files. Possible valuesare:

  • "hadron" → Total hadronic density
  • "baryon" → Net baryon density
  • "baryonic isospin" → Baryonic isospin density
  • "pion" → Pion density
  • "none" → Do not calculate density, print 0.0

Output_Interval — double, optional, default = End_Time

Defines the period of intermediate output of the status of the simulated system in Standard Output and other output formats which support this functionality (in fm).

Output_Times — list of doubles, optional, default = use Output_Interval

Explicitly defines the times in fm where output is generated in the form of a list. This cannot be used in combination with Output_Interval. Output times outside the simulation time are ignored and both the initial and final time are always considered. The following example will produce output at event start, event end and at the specified times as long as they are within the simulation time. 

Output:
    Output_Times: [-0.1, 0.0, 1.0, 2.0, 10.0]

Output format independently of the specific output content

A dedicated subsection in the Output section exists for every single output content and dedicated options are described further below. Refer to output contents for the list of possible contents. Independently of the content, i.e. in every subsection, it is always necessary (i.e. it is probably desired) to provide the format in which the output should be generated.

Format — list of strings, required

List of formats for writing particular content. Available formats for every content are listed and described here, while here all possible output formats are given.

Warning
If a Format list in a content section is not given or it is left empty, i.e. Format: [], SMASH will abort with a fatal error. Furthermore, SMASH also aborts if a not existing format is given in the formats list. This is meant to prevent to e.g. lose output information because of a typo in the configuration file. If no output for a given content is desired, you can suppress it by using Format: ["None"]. However, it is not allowed to use valid formats together with the "None" special "format" string.

Content-specific output options

Every possible content-specific section is documented in the following. Refer to this page for concrete output configuration examples.

♦ Particles

Extended — bool, optional, default = false

⇒ Incompatible with Oscar1999, VTK, HepMC_asciiv3 and HepMC_treeroot formats.

  • true → Print extended information for each particle
  • false → Regular output for each particle

Only_Final — string, optional, default = "Yes"

⇒ Incompatible with VTK, HepMC_asciiv3 and HepMC_treeroot

  • "Yes" → Print only final particle list.
  • "IfNotEmpty" → Print only final particle list, but only if event is not empty (i.e. any collisions happened between projectile and target). Useful to save disk space.
  • "No" → Particle list at output interval including initial time.

♦ Collisions

⇒ Format VTK not available

Extended — bool, optional, default = false

⇒ Incompatible with Oscar1999, HepMC_asciiv3 and HepMC_treeroot formats.

  • true → Print extended information for each particle
  • false → Regular output for each particle

Print_Start_End — bool, optional, default = false

⇒ Incompatible with Root, HepMC_asciiv3 and HepMC_treeroot formats.

  • true → Initial and final particle list is printed out
  • false → Initial and final particle list is not printed out

♦ Dileptons

⇒ Only Oscar1999, Oscar2013 and Binary formats.

Extended — bool, optional, default = false

⇒ Incompatible with Oscar1999 format.

  • true → Print extended information for each particle
  • false → Regular output for each particle

♦ Photons

⇒ Only Oscar1999, Oscar2013 and Binary formats.

Extended — bool, optional, default = false

⇒ Incompatible with Oscar1999 format.

  • true → Print extended information for each particle
  • false → Regular output for each particle

♦ Initial_Conditions

⇒ Only Oscar1999, Oscar2013, Binary, ROOT and ASCII (special ASCII IC, see Initial conditions) formats.

Extended — bool, optional, default = false

⇒ Incompatible with Oscar1999, ROOT and ASCII formats.

  • true → Print extended information for each particle
  • false → Regular output for each particle

Lower_Bound — double, optional, default = 0.5

Lower bound in fm for the IC proper time if Proper_Time is not provided.

Proper_Time — double, optional, default = \(f(t_{np})\)

Proper time in fm at which hypersurface is created. Its default value depends on the nuclei passing time \(t_{np}\) as follows,

\[ f(t_{np})=\begin{cases} \mathrm{\texttt{Lower_Bound}} & t_{np} \le \mathrm{\texttt{Lower_Bound}}\\ t_{np} & t_{np} > \mathrm{\texttt{Lower_Bound}} \end{cases}\;. \]

pT_Cut — double, optional, default = No cut is done

If set, employ a transverse momentum cut for particles contributing to the initial conditions for hydrodynamics. A positive value in GeV is expected. Only particles characterized by \(0<p_T<\mathrm{\texttt{pT_Cut}}\) are printed to the output file.

Rapidity_Cut — double, optional, default = No cut is done

If set, employ a rapidity cut for particles contributing to the initial conditions for hydrodynamics. A positive value is expected and the cut is employed symmetrically around 0. Only particles characterized by \(|\mathrm{\texttt{Rapidity_Cut}}|<y\) are printed to the output file.

♦ Rivet

⇒ Only YODA format (see here for more information about the format).

Note
In the following, no default means that, if the key is omitted, Rivet default behavior will be used.

Analyses — list of strings, optional, default = no default

This key specifies the analyses (including possible options) to add to the Rivet analysis.

Cross_Section — list of two doubles, optional, default = no default

Set the cross-section in pb.

Ignore_Beams — bool, optional, default = true

Ask Rivet to not validate beams before running analyses. This is needed if you use the Fermi_Motion option that disrupts the collision energy event-by-event.

Logging — map<string,string>, optional, default = no default

Specifies log levels for various parts of Rivet, including analyses. Each entry is a log name followed by a log level (one among "TRACE", "DEBUG", "INFO", "WARN", "ERROR", and "FATAL").

Paths — list of strings, optional, default = no default

This key specifies the directories that Rivet will search for analyses and data files related to the analyses.

Preloads — list of strings, optional, default = no default

Specify data files to read into Rivet (e.g., centrality calibrations) at start-up.

Weights keys

Some operations about weights can be customized in the Weights section.

Cap — double, optional, default = no default

Cap weights to this value.

Deselect — list of strings, optional, default = no default

De-select these weights for processing.

NLO_Smearing — double, optional, default = no default

Smearing histogram binning by given fraction of bin widths to avoid NLO counter events to flow into neighboring bin.

No_Multi — bool, optional, default = no default

Ask Rivet not to do multi-weight processing.

Nominal — string, optional, default = no default

The nominal weight name.

Select — list of strings, optional, default = no default

Select these weights for processing.

♦ Coulomb

⇒ Only VTK format.

No content-specific output options, apart from the Format key which accept ["VTK"] value only.

♦ Thermodynamics

The user can print thermodynamical quantities

  1. on the spatial lattice to VTK output;
  2. on the spatial lattice to ASCII output;
  3. at a given point to ASCII output;
  4. averaged over all particles to ASCII output.

About 1 and 2: Note that this output requires a lattice, which needs to be enabled in the conguration file and is regulated by the options of Lattice. See Thermodynamics VTK output for further information.

About 3 and 4: See ASCII thermodynamics output for further information.

Only_Participants — bool, optional, default = false

If set to true, only participants are included in the computation of the energy momentum tensor and of the Eckart currents. In this context, a hadron is considered as a participant if it had at least one collision. When using Potentials this option must be either left unset or set to false. The reason behind this limitation is that in this case hadrons can influence the evolution of the system even without collisions.

Position — list of 3 doubles, optional, default = [0.0, 0.0, 0.0]

Point at which thermodynamic quantities are computed (in fm).

Quantities — list of strings, optional, default = []

List of thermodynamic quantities that are printed to the output. Possible quantities are:

  • "rho_eckart" → Eckart rest frame density.
  • "tmn" → Energy-momentum tensor \(T^{\mu\nu}(t,x,y,z)\).
  • "tmn_landau" → Energy-momentum tensor in the Landau rest frame. This tensor is computed by boosting \(T^{\mu\nu}(t,x,y,z)\) to the local rest frame, where \(T^{0i}\) = 0.
  • "landau_velocity" → Velocity of the Landau rest frame. The velocity is obtained from the energy-momentum tensor \(T^{\mu\nu}(t,x,y,z)\) by solving the generalized eigenvalue equation \((T^{\mu\nu} - \lambda g^{\mu\nu})u_{\mu}=0\).
  • "j_QBS" → Electric (Q), baryonic (B) and strange (S) currents \(j^{\mu}_{QBS}(t,x,y,z) \); note that all currents are given in units of "number of charges"; multiply the electric current by the elementary charge \(\sqrt{4 \pi \alpha_{EM}} \) for charge units.

Smearing — bool, optional, default = true

Using Gaussian smearing for computing thermodynamic quantities or not. This triggers whether thermodynamic quantities are evaluated at a fixed point (true) or summed over all particles (false).

  • true → smearing applied
  • false → smearing not applied

The contribution to the energy-momentum tensor and current (be it electric, baryonic or strange) from a single particle in its rest frame is:

\[\begin{eqnarray} j^{\mu} = B \frac{p_0^{\mu}}{p_0^0} W \\ T^{\mu \nu} = \frac{p_0^{\mu}p_0^{\nu}}{p_0^0} W \end{eqnarray} \]

with B being the charge of interest and W being the weight given to this particle. Normally, if one computes thermodynamic quantities at a point, smearing should be applied, and then \(W\) takes on the following shape:

\[ W = (2 \pi \sigma^2)^{-3/2} \exp\left( - \frac{(\mathbf{r}-\mathbf{r}_0(t))^2}{2\sigma^2} \right)\]

It can however be useful to compute the thermodynamic quantities of all particles in a box with \(W=1\), which would correspond to "Smearing: false". Note that using this option changes the units of the thermodynamic quantities, as they are no longer spatially normalized. One should divide this quantity by the volume of the box to restore units to the correct ones.

Type — string, optional, default = "baryon"

Particle type taken into consideration, one among

  • "hadron"
  • "baryon" (corresponds to "net baryon")
  • "baryonic isospin"
  • "pion"
  • "none"
  • "total isospin"