numpythia 1.3.1

Setting PYTHIA

PYTHIA settings can be passed in one of three ways: through the **kwargs arguments of the constructor Pythia(…, **kwargs):

>>> pythia = Pythia(..., Beams_eCM=13000.)

Or as a dictionary:

>>> pythia = Pythia(..., params={'Beams:eCM':  13000.})

Or via a Python command file:

>>> pythia = Pythia(config='path/to/config.cmd')

The full list of settings can be found on the PYTHIA homepage.

Note that the “:” in settings names is replaced by a “_” if using kwargs. kwargs take precedence over params and they both take precedence over config. Example config files can be found under the numpythia.testcmnd directory.

Generate events

To generate events do

>>> events = pythia(events=100)
>>> events
<generator at 0x10cf06f78>

where events is a generator of GenEvent containing all the generated particles.

Generated particles can be accessed through the all, first and last methods which have two optional arguments selection and return_hepmc. Selection is a filter or a combination of filters with bitwise operations (as shown in the getting started example) applied on the particles in the event. The available filters are

STATUS, PDG_ID, ABS_PDG_ID, HAS_END_VERTEX, HAS_PRODUCTION_VERTEX,
HAS_SAME_PDG_ID_DAUGHTER, IS_STABLE, IS_BEAM

return_hepmc is by default set to False when using all:

>>> for e in events:
>>>     array = e.all(selection)

returns an array of particles, with the dtype described above. return_hepmc is by default set to True for first and last:

>>> for e in events:
>>>     gen_part_f = e.first(selection)
>>>     gen_part_l = e.last(selection)

returns a GenParticle.

Generated particle

GenParticle is the numpythia interface of HepMC::GenParticle, and has the following attributes

pid, status, e, px, py, pz, pt, eta, phi, mass, theta, rap

GenParticle also has the following methods parents, children, ancestors, descendants and siblings both with the two optional arguments selection and return_hepmc described before. For instance:

>>> for e in events:
>>>     w = e.last((ABS_PDG_ID == 24) & HAS_END_VERTEX))
>>>     w.children()
array([(240.60708981, 115.76101664, 126.16766767, -169.03439984, 171.22760682, 0.5, -0.87228439, -0.87228739, 2.34974894, 0.82838703, 0., 0., 0., 0.,  3, 23),
   ( 52.59241372,   9.21296404,  50.77873929,  -10.01763001,  51.60774235, 1.5, -0.19283178, -0.19291222, 1.76252302, 1.39131523, 0., 0., 0., 0., -4, 23)],
  dtype=[('E', '<f8'), ('px', '<f8'), ('py', '<f8'), ('pz', '<f8'), ('pT', '<f8'), ('mass', '<f8'), ('rap', '<f8'), ('eta', '<f8'), ('theta', '<f8'), ('phi', '<f8'), ('prodx', '<f8'), ('prody', '<f8'), ('prodz', '<f8'), ('prodt', '<f8'), ('pdgid', '<i4'), ('status', '<i4')])