"""
Classes supporting decays and branching fractions/ratios.
"""
from sqlalchemy import bindparam, select
from pdg.data import PdgProperty
from pdg.errors import PdgAmbiguousValueError, PdgInvalidPdgIdError, PdgNoDataError
from pdg.particle import PdgItem, PdgParticle
[docs]class PdgDecayProduct(object):
"""Class for all information about one product of a decay, including its
PdgItem (which may resolve to one or more PdgParticles), its multiplier, and
its subdecay (if any).
"""
def __init__(self, item, multiplier, subdecay):
"""Instantiate a PdgDecayProduct."""
assert isinstance(item, PdgItem)
assert isinstance(multiplier, int)
assert subdecay is None or isinstance(subdecay, PdgBranchingFraction)
self.item = item
self.multiplier = multiplier
self.subdecay = subdecay
def __repr__(self):
fmt = "PdgDecayProduct(item='%s', multiplier=%d, subdecay=%r)"
return fmt % (self.item.name, self.multiplier, self.subdecay)
[docs]class PdgBranchingFraction(PdgProperty):
"""Class for all information about a decay, including its branching
fraction, decay products, and subdecays.
"""
def _get_decay(self):
"""Load decay information from the database."""
if 'pdgdecay' not in self.cache:
pdgdecay_table = self.api.db.tables['pdgdecay']
query = select(pdgdecay_table).where(pdgdecay_table.c.pdgid == bindparam('pdgid'))
with self.api.engine.connect() as conn:
try:
result = conn.execute(query, {'pdgid': self.baseid}).fetchall()
self.cache['pdgdecay'] = [row._mapping for row in result]
except AttributeError:
raise PdgInvalidPdgIdError('No PDGDECAY entry for ' % self.pdgid)
return self.cache['pdgdecay']
def _repr_extra(self):
return '"%s"' % self.description
@property
def decay_products(self):
"""A list of all PdgDecayProducts for the decay."""
products = []
for row in self._get_decay():
if not row['is_outgoing']:
continue
product = PdgDecayProduct(
item=PdgItem(self.api, row['pdgitem_id']),
multiplier=row['multiplier'],
subdecay=(PdgBranchingFraction(self.api, row['subdecay'])
if row['subdecay_id'] else None))
products.append(product)
return products
@property
def mode_number(self):
"""Mode number of this decay.
Note that the decay mode number may change from one edition of the Review of Particle Physics
to the next one."""
return self._get_pdgid()['mode_number']
@property
def is_subdecay(self):
"""True if this is a subdecay ("indented") decay mode."""
data_type_code = self.data_type
if len(data_type_code) < 4:
return False
else:
return data_type_code[0:3] == 'BFX' or data_type_code[0:3] == 'BFI'
@property
def subdecay_level(self):
"""Return indentation level of a decay mode."""
if self.is_subdecay:
return int(self.data_type[3])
else:
return 0