Parameter

Symbolica documentation for getting started, symbolic expressions, numerical evaluation, pattern matching, and APIs in Python and Rust.

`Parameter`

class Parameter

A numerical or symbolic parameter in a particle-physics model.

External parameters carry parameter-card coordinates and values; internal parameters carry expressions derived from the external inputs.

Examples

from symbolica import S, E
from symbolica.community import hepkit as hep
model = hep.Model.standard_model()
mass = model.parameter("MM")
assert mass.nature == hep.ParameterNature.EXTERNAL

Attributes

Name	Description
`expression`	Return the defining expression for an internal parameter.
`lhablock`	Return the Les Houches block name, when defined.
`lhacode`	Return the Les Houches entry indices, when defined.
`name`	Return the parameter name.
`nature`	Return whether the parameter is external or internal.
`parameter_type`	Return whether the parameter is real or complex.
`symbol`	Return the symbolic reference used by this model’s expressions
`texname`	The model’s LaTeX display label, or None when no label was supplied.
`typstname`	Native Typst math label, without dollar delimiters.
`value`	Return the evaluated value as a native Python complex number

`expression`

Parameter.expression: typing.Optional[Expression]

Return the defining expression for an internal parameter.

Examples

Using the setup in the Parameter class example:

internal = next(p for p in model.parameters if p.expression is not None)
formula = internal.expression

`lhablock`

Parameter.lhablock: typing.Optional[builtins.str]

Return the Les Houches block name, when defined.

Examples

Using the setup in the Parameter class example:

mass = model.parameter(model.particle_by_pdg(13).mass_parameter)
mass.lhablock
'MASS'

`lhacode`

Parameter.lhacode: typing.Optional[builtins.list[builtins.int]]

Return the Les Houches entry indices, when defined.

Examples

Using the setup in the Parameter class example:

mass = model.parameter(model.particle_by_pdg(13).mass_parameter)
mass.lhacode
[13]

`name`

Parameter.name: builtins.str

Return the parameter name.

Examples

Using the setup in the Parameter class example:

assert mass.name == "MM"

`nature`

Parameter.nature: ParameterNature

Return whether the parameter is external or internal.

Examples

Using the setup in the Parameter class example:

mass = model.parameter(model.particle_by_pdg(13).mass_parameter)
mass.nature == hep.ParameterNature.EXTERNAL
True

`parameter_type`

Parameter.parameter_type: ParameterType

Return whether the parameter is real or complex.

Examples

Using the setup in the Parameter class example:

mass = model.parameter(model.particle_by_pdg(13).mass_parameter)
mass.parameter_type == hep.ParameterType.REAL
True

`symbol`

Parameter.symbol: Expression

Return the symbolic reference used by this model’s expressions. TeX and Typst output use texname and typstname, respectively. Plain output keeps its symbolic name; no defining expression or numerical value is substituted.

Examples

from symbolica.community import hepkit as hep
model = hep.Model.standard_model()
reference = model.parameter("ee").symbol
mass = model.parameter("Me").symbol
assert "m_e" in (mass**2).to_latex()

`texname`

Parameter.texname: typing.Optional[builtins.str]

The model’s LaTeX display label, or None when no label was supplied. Native Typst output uses typstname independently.

hep.Model.standard_model().parameter(“ee”).texname ‘e’

Examples

Using the setup in the Parameter class example:

label = model.parameter("ee").texname
assert label == "e"

`typstname`

Parameter.typstname: typing.Optional[builtins.str]

Native Typst math label, without dollar delimiters.

Examples

from symbolica.community import hepkit as hep
hep.Model.standard_model().parameter("aS").typstname
'alpha_s'

`value`

Parameter.value: complex

Return the evaluated value as a native Python complex number.

Raises :class:ModelError when this parameter has not been evaluated.

Examples

Using the setup in the Parameter class example:

mass_value = model.parameter("MM").value
print("mass:", mass_value.real, "width component:", mass_value.imag)

Methods

Name	Description
`__repr__`	Summarize the defining data as well as the parameter name.
`_repr_html_`	Display the model member’s physical data and defining expressions.
`_repr_pretty_`	Write the complete text summary to an IPython pretty printer.

`repr`

Parameter.__repr__() -> builtins.str

Summarize the defining data as well as the parameter name.

Examples

Using the setup in the Parameter class example:

print(model.parameter(model.particle_by_pdg(13).mass_parameter))

`_repr_html_`

Parameter._repr_html_() -> builtins.str

Display the model member’s physical data and defining expressions.

Examples

Using the setup in the Parameter class example:

from IPython.display import display
display(mass)

`_repr_pretty_`

Parameter._repr_pretty_(pretty: typing.Any, cycle: builtins.bool) -> None

Write the complete text summary to an IPython pretty printer.

Examples

Using the setup in the Parameter class example:

from IPython.lib.pretty import pretty
text = pretty(mass)

Parameters

pretty (object) IPython pretty printer receiving the text.
cycle (bool) Whether the object occurs recursively in the current display.