Writing a basf2 analysis steering file

Hint

This example shows a basic basf2 analysis steering file within b2luigi.

import basf2 as b2
import modularAnalysis as ma
import variables.utils as vu
import vertex as vx


import b2luigi
from b2luigi.contrib.basf2 import Basf2PathTask
from Ex06_basf2_reconstruction import ReconstructionTask


@b2luigi.requires(ReconstructionTask)
class AnalysisTask(Basf2PathTask):
    treeFit = b2luigi.BoolParameter(default=True)
    result_dir = "results/Analysis"

    def output(self):
        yield self.add_to_output(f"ntuple_{self.identifier}.root")

    def create_path(self):
        main = b2.Path()

        particle = "mu" if str(self.event_type) == "mumu" else "e"

        ma.inputMdstList(
            environmentType="default", filelist=self.get_input_file_names("reconstruction.root"), path=main
        )

        # Fill final state particles
        ma.fillParticleList(decayString=f"{particle}+:fsp", cut="[abs(dr) < 2.0] and [abs(dz) < 4.0]", path=main)

        ma.fillParticleList(
            decayString="K+:fsp", cut="[abs(dr) < 2.0] and [abs(dz) < 4.0] and [kaonID > 0.2]", path=main
        )

        # reconstruct J/psi -> l+ --
        ma.reconstructDecay(
            decayString=f"J/psi:ll -> {particle}+:fsp {particle}-:fsp", cut="[2.92 < M < 3.22]", path=main
        )

        # reconstruct B+ -> J/psi K+
        ma.reconstructDecay(
            decayString="B+:jpsik -> J/psi:ll K+:fsp", cut="[Mbc > 5.24] and [abs(deltaE) < 0.2]", path=main
        )

        # Run truth matching
        ma.matchMCTruth(list_name="B+:jpsik", path=main)

        # Perform tree fit if requested
        if self.treeFit:
            vx.treeFit(list_name="B+:jpsik", conf_level=0.00, massConstraint=["J/psi"], path=main)

        # Define variables to save
        variables = ["Mbc", "deltaE", "chiProb", "isSignal"]
        variables += vu.create_aliases_for_selected(
            list_of_variables=["InvM", "M"], decay_string="B+:jpsik -> ^J/psi:ll K+:fsp", prefix="jpsi"
        )

        # Write variables into ntuple
        ma.variablesToNtuple(
            decayString="B+:jpsik",
            variables=variables,
            filename=self.get_output_file_name(f"ntuple_{self.identifier}.root"),
            treename="Bp",
            path=main,
            storeEventType=False,
        )

        return main


if __name__ == "__main__":
    b2luigi.process(AnalysisTask(n_events=10))