Source code for pdg

#!/usr/bin/env python3

##########################################################################
# basf2 (Belle II Analysis Software Framework)                           #
# Author: The Belle II Collaboration                                     #
#                                                                        #
# See git log for contributors and copyright holders.                    #
# This file is licensed under LGPL-3.0, see LICENSE.md.                  #
##########################################################################

"""
pdg - access particle definitions
---------------------------------

This module helps to access particle definitions. When the software is loaded a
list of known particles is read from the EvtGen particle definition file
:file:`framework/particledb/data/evt.pdl`. This file contains all well-known
standard-model particles and their properties: mass, width or lifetime, charge,
spin.
...

This module allows to easily access this information (see `get`) or if necessary
add new particles using `add_particle` and even replace the whole particle
definition list using `load`.

It also provides simple getters to convert `PDG codes`_ into particle names and
vice versa for use with modules which require a list of PDG codes for the
particles to generate. See `from_name`, `from_names`, `to_name` and `to_names`

.. _PDG codes: http://pdg.lbl.gov/2020/reviews/rpp2020-rev-monte-carlo-numbering.pdf
"""

import re
import basf2
from fractions import Fraction


def _get_instance():
    """
    Function to return an instance of the EvtGenDatabasePDG class.
    """
    # Always avoid the top-level 'import ROOT'.
    from ROOT import Belle2  # noqa
    instance = Belle2.EvtGenDatabasePDG.Instance()
    return instance




[docs]
def get(name):
    """
    Function to return particle information (TParticlePDG) from ROOT Database.

    'name' can be either the name of the particle, or a pdg code.
    Will throw an LookupError of no such particle exists.
    """

    p = _get_instance().GetParticle(name)
    if not p:
        raise LookupError(f"No particle with name '{name}'")

    return p






[docs]
def from_name(name):
    """
    Function to return pdg code for the given particle name.

    >>> pdg.from_name("pi+")
    211
    """

    return get(name).PdgCode()






[docs]
def from_names(names):
    """
    for a list/tuple of particle names, return list of pdg codes.

    >>> pdg.from_names(["e+","e-","gamma"])
    [-11, 11, 22]
    """

    assert not isinstance(names, str), 'Argument is not a list!'

    return [from_name(n) for n in names]






[docs]
def to_name(pdg):
    """
    Return particle name for given pdg code.

    >>> pdg.to_name(321)
    K+
    """

    return get(pdg).GetName()






[docs]
def to_names(pdg_codes):
    """
    for a list/tuple of pdg codes, return list of paricle names.

    >>> pdg.to_names([11, -11, -211, 3212])
    ['e-', 'e+', 'pi-', 'Sigma0']
    """

    assert not isinstance(pdg_codes, int), 'Argument is not a list!'

    return [to_name(pdg) for pdg in pdg_codes]






[docs]
def conjugate(name):
    """
    Function to return name of conjugated particle
    """

    try:
        return to_name(-from_name(name))
    except LookupError:
        return name






[docs]
def load(filename):
    """
    Read particle database from given evtgen pdl file
    """
    _get_instance().ReadEvtGenTable(filename)






[docs]
def load_default():
    """Read default evt.pdl file"""
    _get_instance().ReadEvtGenTable()






[docs]
def add_particle(name, pdgCode, mass, width, charge, spin, max_width=None, lifetime=0, pythiaID=0,
                 define_anti_particle=False):
    """
    Add a new particle to the list of known particles.

    The name cannot contain any whitespace character.

    Args:
        name (str): name of the particle
        pdgCode (int): pdg code identifiert for the particle
        mass (float): mass of the particle in GeV
        width (float): width of the particle in GeV
        charge (float): charge of the particle in e
        spin (float): spin of the particle
        max_width (float): max width, if omitted 3*width will be used
        lifetime (float): lifetime in ns, should be 0 as geant4 cannot handle it correctly otherwise
        pythiaID (int): pythiaID of the particle (if any), if omitted 0 will be used
        define_anti_particle (bool): if True, an anti-particle with the default name anti-{name} is defined and added.
    """
    if lifetime > 0:
        basf2.B2WARNING("Userdefined particle with non-zero lifetime will not be simulated correctly")

    if max_width is None:
        # FIXME: is 3 a good default?
        max_width = width * 3

    particle = _get_instance().AddParticle(name, name, mass, False, width, charge * 3, "userdefined",
                                           pdgCode, 0, 0, lifetime, spin, max_width, pythiaID)
    if particle:
        basf2.B2INFO(
            f"Adding new particle '{name}' (pdg={int(pdgCode)}, mass={mass:.3g} GeV, width={width:.3g} GeV, " +
            f"charge={int(charge)}, spin={Fraction(spin)})")

        if define_anti_particle:
            anti_particle = _get_instance().AddParticle(
                f'anti-{name}', f'anti-{name}', mass, False, width, -charge * 3, "userdefined", -pdgCode, 0, 0,
                lifetime, spin, max_width, pythiaID
            )
            particle.SetAntiParticle(anti_particle)
            basf2.B2INFO(f"Adding new particle 'anti-{name}' as anti-particle of '{name}'")

        return True

    return False