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Particle: PDG particle data and identification codes

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Particle provides a pythonic interface to the Particle Data Group <http://pdg.lbl.gov/>_ (PDG) particle data tables and particle identification codes, with extended particle information and extra goodies.

The PDG defines the standard particle identification (ID) numbering scheme. The package provides the PDGID class implementing queries on those PDG IDs. The queries are also accessible through free standing functions mimicking, and expanding from, the HepPID/HepPDT C++ interface.

The Particle class wraps the information in the PDG particle data tables and provides an object-oriented interface and powerful search and look-up utilities.

Installation

Install particle like any other Python package:

.. code-block:: bash

python -m pip install particle

or similar (use --user, virtualenv, etc. if you wish).

Strict dependencies

• Python <http://docs.python-guide.org/en/latest/starting/installation/>_ (3.7+)
• importlib_resources backport <http://importlib-resources.readthedocs.io/en/latest/>_ if using Python < 3.9
• attrs <http://www.attrs.org/en/stable/>_ provides classes without boilerplate (similar to DataClasses in Python 3.7)
• hepunits <https://github.com/scikit-hep/hepunits>_ provides units for the Scikit-HEP packages

Changelog

See the changelog <https://github.com/scikit-hep/particle/blob/master/docs/CHANGELOG.md>__ for a history of notable changes.

Getting started: PDG IDs

.. code-block:: python

>>> from particle import PDGID
>>>
>>> pid = PDGID(211)
>>> pid
<PDGID: 211>
>>> pid.is_meson
True
>>> pid = PDGID(99999999)
>>> pid
<PDGID: 99999999 (is_valid==False)>

For convenience, all properties of the PDGID class are available as standalone functions that work on any SupportsInt (including Particle):

.. code-block:: python

>>> from particle.pdgid import is_meson
>>>
>>> is_meson(211)
True

These composable functions qualifying PDG IDs make it easy to classify particles. For the sake of example, quarkonia can be specified with the following user-defined functions:

.. code-block:: python

>>> is_heavy_flavor = lambda x: has_charm(x) or has_bottom(x) or has_top(x)
>>> is_quarkonium = lambda x: is_meson(x) and is_heavy_flavor(x) and Particle.from_pdgid(x).is_self_conjugate

PDG ID literals provide (PDGID class) aliases for all particles loaded, with easily recognisable names. For example:

.. code-block:: python

>>> from particle.pdgid import literals as lid
>>>
>>> lid.pi_plus
<PDGID: 211>
>>>
>>> from particle.pdgid.literals import Lambda_b_0
>>> Lambda_b_0
<PDGID: 5122>
>>> Lambda_b_0.has_bottom
True

You can quickly display PDGID info from the command line with:

.. code-block:: bash

$ python -m particle pdgid 323
<PDGID: 323>
A              None
J              1.0
L              0
S              1
Z              None
abspid         323
charge         1.0
has_bottom     False
...

Similarly, classes exist to express identification codes used by MC programs, see information on converters below.

Getting started: Particles

You can use a variety of methods to get particles. If you know the PDG ID number or, say, the name used in EvtGen, you can get a particle directly.

.. code-block:: python

>>> from particle import Particle
>>> Particle.from_pdgid(211)
<Particle: name="pi+", pdgid=211, mass=139.57039 ± 0.00018 MeV>
>>>
>>> Particle.from_evtgen_name("J/psi")
<Particle: name="J/psi(1S)", pdgid=443, mass=3096.900 ± 0.006 MeV>
>>>
>>> Particle.from_nucleus_info(a=12, z=6)
<Particle: name="C12", pdgid=1000060120, mass=11177.9291399 MeV>

A similar method exists to get a list of particles from a PDG style name:

.. code-block:: python

>>> Particle.findall(pdg_name="pi")

returns the list of matching particles whose PDG name is "pi", which in this case comprises the three charged states of the pseudoscalar pion.

Else, and more generally, you can use a search. A basic example is the following:

.. code-block:: python

>>> next(Particle.finditer('pi'))  # first item in iterator of particles
<Particle: name="pi0", pdgid=111, mass=134.9768 ± 0.0005 MeV>
>>>
>>> Particle.findall('pi')[0]  # Same as above but returning a list of particles
<Particle: name="pi0", pdgid=111, mass=134.9768 ± 0.0005 MeV>

You can search for the properties using keyword arguments, which include pdg_name, name, mass, width, charge, three_charge, anti_flag, rank, I, J, G, P, quarks, status, mass_upper, mass_lower, width_upper, and width_lower. You can pass a callable or an exact match for any property. The argument particle can be set to True/False, as well, to limit the search to particles or antiparticles.

You can also build the search yourself with the first positional argument, which accepts a callable that is given the particle object itself. If the first positional argument is a string, that will match against the particle's name.

Here are possible sophisticated searches, all of which work with either Particle.findall or Particle.finditer, where the former method provides a list whereas the latter returns an iterator.

.. code-block:: python

>>> # Print out all particles with asymmetric decay width uncertainties
>>> ps = Particle.finditer(lambda p: p.width_lower != p.width_upper)
>>> for p in ps:
...     print(p.name, p.pdgid, p.width_lower, p.width_upper)
>>>
>>> # Find all antiparticles with 'Omega' in the name
>>> Particle.finditer('Omega', particle=False)   # several found
>>>
>>> # Find all antiparticles of name=='Omega'
>>> Particle.finditer(name='Omega', particle=False)  # none found
>>>
>>> # Find all antiparticles of pdg_name=='Omega'
>>> Particle.findall(pdg_name='Omega', particle=False)  # only 1, of course
[<Particle: name="Omega~+", pdgid=-3334, mass=1672.5 ± 0.3 MeV>]
>>>
>>> # Find all neutral beauty hadrons
>>> Particle.findall(lambda p: p.pdgid.has_bottom and p.charge==0)
>>>
>>> # Find all strange mesons with c*tau > 1 meter
>>> from hepunits import meter
>>> Particle.findall(lambda p: p.pdgid.is_meson and p.pdgid.has_strange and p.ctau > 1 * meter, particle=True)
[<Particle: name="K(L)0", pdgid=130, mass=497.611 ± 0.013 MeV>,
 <Particle: name="K+", pdgid=321, mass=493.677 ± 0.016 MeV>]

Once you have a particle, any of the properties can be accessed, along with several methods. Though they are not real properties, you can access is_name_barred, and spin_type. You can also .invert() a particle.

There are lots of printing choices for particles: describe(), programmatic_name, latex_name, html_name, HTML printing outs in notebooks, and of course repr and str support.

You can get the .pdgid from a particle, as well. Sorting particles will put lowest abs(PDGID) first.

Particle literals provide (Particle class) aliases for the particles loaded, with easily recognisable names. For example:

.. code-block:: python

>>> from particle import literals as lp
>>> lp.pi_plus
<Particle: name="pi+", pdgid=211, mass=139.57061 ± 0.00024 MeV>
>>>
>>> from particle.literals import Lambda_b_0
>>> Lambda_b_0
<Particle: name="Lambda(b)0", pdgid=5122, mass=5619.60 ± 0.17 MeV>
>>> Lambda_b_0.J
0.5

You can quickly search for particles from the command line with (note: quotes may be used/needed but only double quotes work as expected on Windows):

.. code-block:: bash

$ python -m particle search "K*0"
<Particle: name="K*(892)0", pdgid=313, mass=895.55 ± 0.20 MeV>
<Particle: name="K*(1680)0", pdgid=30313, mass=1718 ± 18 MeV>
<Particle: name="K*(1410)0", pdgid=100313, mass=1421 ± 9 MeV>

If you only select one particle, either by a search or by giving the PDG ID number, you can see more information about the particle:

.. code-block:: bash

$ python -m particle search 311
Name: K0             ID: 311          Latex: $K^{0}$
Mass  = 497.611 ± 0.013 MeV
Width = -1.0 MeV
Q (charge)        = 0       J (total angular) = 0.0      P (space parity) = -
C (charge parity) = ?       I (isospin)       = 1/2      G (G-parity)     = ?
    SpinType: SpinType.PseudoScalar
    Quarks: dS
    Antiparticle name: K~0 (antiparticle status: Barred)

Advanced: Loading custom tables ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You can control the particle data tables if you so desire. You can append a new data table using the following syntax:

.. code-block:: python

>>> from particle import Particle
>>> Particle.load_table('new_particles.csv', append=True)

You can also replace the particle table entirely with append=False (the default).

If you want a non-default data file distributed with the package just proceed as follows:

.. code-block:: python

>>> from particle import data
>>> Particle.load_table(data.basepath / "particle2022.csv"))
>>> Particle.load_table(data.basepath / "nuclei2022.csv"), append=True)  # I still want nuclei info
>>> Particle.table_names()  # list the loaded tables

Advanced: how to create user-defined particles ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

There are situations where it may be handy to create user-defined particles. But do so with care and having in mind the limitations, many of which are discussed or exemplified below!

The simplest "particle" one may create is effectively a placeholder with no real information stored:

.. code-block:: python

>>> # A Particle instance the simplest possible. Contains basically no info
>>> p = Particle.empty()
>>> p
<Particle: name="Unknown", pdgid=0, mass=None>
>>>
>>> print(p.describe())
Name: Unknown

A more useful particle definition will likely involve at least a name and a PDG ID. It is important to keep in mind that a meaningful PDG ID encodes by construction internal quantum numbers and other information. As such, the definition of a particle with a "random" PDG ID will result in a particle with undefined and/or wrong properties such as quantum numbers or the quality of being a meson.

.. code-block:: python

>>> p2 = Particle(9912345, 'MyPentaquark')
>>> p2
<Particle: name="MyPentaquark", pdgid=9912345, mass=None>
>>>
>>> p2.pdgid.is_pentaquark
False
>>> print(p2.describe())  # J=2 is an example of something effectively encoded in the PDG ID.
Name: MyPentaquark   ID: 9912345      Latex: $Unknown$
Mass  = None
Width = None
Q (charge)        = None    J (total angular) = 2.0      P (space parity) = None
C (charge parity) = None    I (isospin)       = None     G (G-parity)     = None
    Antiparticle name: MyPentaquark (antiparticle status: Same)

A yet more sophisticated definition:

.. code-block:: python

>>> p3 = Particle(pdgid=9221132,pdg_name='Theta',three_charge=3,latex_name='\Theta^{+}')
>>> p3
<Particle: name="Theta", pdgid=9221132, mass=None>
>>>
>>> print(p3.describe())
Name: Theta          ID: 9221132      Latex: $\Theta^{+}$
Mass  = None
Width = None
Q (charge)        = +       J (total angular) = 0.5      P (space parity) = None
C (charge parity) = None    I (isospin)       = None     G (G-parity)     = None
    SpinType: SpinType.NonDefined
    Antiparticle name: Theta (antiparticle status: Same)

Advanced: Conversion ^^^^^^^^^^^^^^^^^^^^

You can convert and update the particle tables with the utilities in particle.particle.convert. This requires the pandas package, and is only tested with Python 3. Run the following command for more help:

.. code-block:: bash

$ python3 -m particle.particle.convert --help

Getting started: Converters

You can use mapping classes to convert between particle MC identification codes and particle names. See the particle.converters modules for the available mapping classes. For example:

.. code-block:: python

>>> from particle.converters import Pythia2PDGIDBiMap
>>> from particle import PDGID, PythiaID
>>>
>>> pyid = Pythia2PDGIDBiMap[PDGID(9010221)]
>>> pyid
<PythiaID: 10221>

>>> pdgid = Pythia2PDGIDBiMap[PythiaID(10221)]
>>> pdgid
<PDGID: 9010221>

This code makes use of classes similar to PDGID, which hold particle identification codes used by MC programs. Possible use cases are the following:

.. code-block:: python

>>> from particle import Particle
>>> from particle import Corsika7ID, Geant3ID, PythiaID
>>>
>>> g3id = Geant3ID(8)
>>> p = Particle.from_pdgid(g3id.to_pdgid())
>>>
>>> (p,) = Particle.finditer(pdgid=g3id.to_pdgid())  # syntax (p,) throws an error if < 1 or > 1 particle is found
>>> p.name
'pi+'

>>> pythiaid = PythiaID(211)
>>> p = Particle.from_pdgid(pythiaid.to_pdgid())

>>> (p,) = Particle.finditer(pdgid=pythiaid.to_pdgid())
>>> p.name
'pi+'

>>> cid = Corsika7ID(5)
>>> p = Particle.from_pdgid(cid.to_pdgid())
>>> p.name
'mu+'

Corsika7 ^^^^^^^^

The Corsika7ID class implements features to make it easier to work with Corsika7 output. For a full feature set, please refer to the particle.corsika submodule.

Corsika7ID.from_particle_description(from_particle_description: int) returns (Corsika7ID, bool) to automatically parse the particle_description from the Corsika7 particle data sub-block.

Corsika7ID.is_particle() checks if the ID refers to an actual particle or something else (like additional information).

Corsika7ID.to_pdgid() converts the Corsika7ID to a PDGID if possible.

Getting started: experiment-specific modules

Experiment-specific submodules are welcome if they tie in nicely with the functionality of the package while providing add-ons of particular relevance to experiments.

LHCb-specific module ^^^^^^^^^^^^^^^^^^^^

Available via

.. code-block:: python

>>> from particle import lhcb

it contains the following converter and functions:

.. code-block:: python

>>> dir(lhcb)
['LHCbName2PDGIDBiMap', 'from_lhcb_name', 'to_lhcb_name']

.. code-block:: python

>>> n, e, l = Particle.from_pdgid(-531).name, Particle.from_pdgid(531).evtgen_name, lhcb.to_lhcb_name(Particle.from_pdgid(-531))
>>> print(f"Name: {n}\nEvtGen name: {e}\nLHCb name: {l}")
Name: B(s)~0
EvtGen name: B_s0
LHCb name: B_s~0

>>> p = Particle.from_pdgid(-531)
>>> p
<Particle: name="B(s)~0", pdgid=-531, mass=5366.88 ± 0.14 MeV>
>>>to_lhcb_name(p)
'B_s~0'

Conversions PDG ID <-> LHCb name are available via a predefined bidirectional map similarly to what is available in the standard (i.e. non-experiment-specific) converters:

.. code-block:: python

>>> name = LHCbName2PDGIDBiMap[PDGID(-531)]
>>> name
'B_s~0'

>>> pdgid = LHCbName2PDGIDBiMap['B_s~0']
>>> pdgid
<PDGID: -531>

Acknowledgements

The UK Science and Technology Facilities Council (STFC) and the University of Liverpool provide funding for Eduardo Rodrigues (2020-) to work on this project part-time.

Support for this work was provided by the National Science Foundation cooperative agreement OAC-1450377 (DIANA/HEP) in 2016-2019 and has been provided by OAC-1836650 (IRIS-HEP) since 2019. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

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