README.md

lhereader

A Python module to read LHE files. Originally by diptaparna, significantly rewritten by me. No dependency on ROOT, requires python version >= 3.6.

Usage example:

import numpy as np
from lhereader import LHEReader


reader = LHEReader('path/to/file.lhe')

# Mediator mass in each event
mmed = []
counter = 0
for iev, event in enumerate(reader):
    # Find DM particles
    dm = filter(lambda x: abs(x.pdgid)== 52, event.particles)

    # Sum over all DM four-momenta in the event
    combined_p4 = None
    for p4 in map(lambda x: x.p4(), dm):
        if combined_p4:
            combined_p4 += p4
        else:
            combined_p4 = p4
    mmed.append(combined_p4.mass)

print(f'Mean mediator mass: {np.mean(mmed)}')
print(f'Median mediator mass: {np.median(mmed)}')

Treatment of weights

The parser assumes that each weight XML element has an attribute called id that uniquely identifies the weight per event. In practical terms, each entry should look roughly like this:

<wgt id='some string'> 123456.7 </wgt>

Weights are read in one of two modes: list or dict, which can be set via the weight_mode argument to the LHEReader constructor. In the first case, weights are returned as an unlabelled list in the order of appearance. In the second case, weights are returned as a dictionary per event, which the id attribute serving as the key, and the weight as the value.

The weights can easily be filtered using the weight_regex argument. Only weights with an id matching this regular expression will be returned.

In case no id attribute can be found, the dict mode, as well as filtering are not supported