numpythia 1.0.1

The interface between PYTHIA and NumPy

numpythia provides an interface between PYTHIA and NumPy allowing you to generate events as NumPy arrays of particle four-momenta. By default numpythia only depends on NumPy and builds internal copies of the PYTHIA and HepMC source code.

Standalone Installation

To simply use the built-in PYTHIA and HepMC:

pip install -v numpythia

And you’re good to go!

Support for building against an external PYTHIA is on the wishlist.

Strict dependencies

• Python (2.7+, 3.4+)

• Numpy

• six

Getting started

from numpythia import Pythia, hepmc_write, hepmc_read
from numpythia import STATUS, HAS_END_VERTEX, ABS_PDG_ID
from numpythia.testcmnd import get_cmnd
from numpy.testing import assert_array_equal

pythia = Pythia(get_cmnd('w'), random_state=1)

selection = ((STATUS == 1) & ~HAS_END_VERTEX &
            (ABS_PDG_ID != 12) & (ABS_PDG_ID != 14) & (ABS_PDG_ID != 16))

# generate events while writing to ascii hepmc
for event in hepmc_write('events.hepmc', pythia(events=1)):
   array1 = event.all(selection)

# read the same event back from ascii hepmc
for event in hepmc_read('events.hepmc'):
   array2 = event.all(selection)

assert_array_equal(array1, array2)

The dtype of any array of particle information is:

np.dtype([('E', 'f8'), ('px', 'f8'), ('py', 'f8'), ('pz', 'f8'), ('mass', 'f8'),
          ('prodx', 'f8'), ('prody', 'f8'), ('prodz', 'f8'), ('prodt', 'f8'),
          ('pdgid', 'i4'), ('status', 'i4')])

Also see pyjet for jet clustering.

Tutorial

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.