Usage¶

Warning

The PWA Expert System has been split up into QRules and AmpForm. Please use these packages instead!

Main interface¶

The expertsystem consists of two main components: reaction and amplitude. Here’s a small example of how to use them!

Investigate intermediate resonances¶

import expertsystem as es

result = es.reaction.generate(
    initial_state="J/psi(1S)",
    final_state=["K0", "Sigma+", "p~"],
    allowed_interaction_types="strong",
    formalism_type="canonical-helicity",
)

import graphviz

dot = es.io.asdot(result, collapse_graphs=True)
graphviz.Source(dot)

Next, you use the amplitude module to convert these transitions into a mathematical description that you can use to fit your data and perform Partial Wave Analysis!

Quantum number search¶

The load_pdg() function creates a ParticleCollection containing the latest PDG info. Its find() and filter() methods allows you to quickly look up the quantum numbers of a particle and, vice versa, look up particle candidates based on a set of quantum numbers.

import expertsystem as es

pdg = es.reaction.load_pdg()
pdg.find(22)
delta = pdg.find("Delta(1920)++")
es.io.asdict(delta)

{'name': 'Delta(1920)++',
 'pid': 22224,
 'latex': '\\Delta(1920)^{++}',
 'spin': 1.5,
 'mass': 1.92,
 'width': 0.3,
 'charge': 2,
 'isospin': {'magnitude': 1.5, 'projection': 1.5},
 'baryon_number': 1,
 'parity': {'value': 1}}

subset = pdg.filter(
    lambda p: p.spin in [2.5, 3.5, 4.5] and p.name.startswith("N")
)
subset.names

{'N(1675)+',
 'N(1675)0',
 'N(1675)~-',
 'N(1675)~0',
 'N(1680)+',
 'N(1680)0',
 'N(1680)~-',
 'N(1680)~0',
 'N(2190)+',
 'N(2190)0',
 'N(2190)~-',
 'N(2190)~0'}

Tip

See Particle database

Check allowed reactions¶

The expertsystem can be used to check whether a transition between an initial and final state is violated by any conservation rules:

es.check_reaction_violations(
    initial_state="pi0",
    final_state=["gamma", "gamma", "gamma"],
)

{frozenset({'c_parity_conservation'})}

Advanced¶

Each of the expertsystem’s sub-modules offer functionality to handle more advanced reaction types. The following notebooks illustrate how use them.