external_vbf_nlo.py

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# Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
 
from ... import Logging
from .external_base import ExternalBase
 

logger = Logging.logging.getLogger("PowhegControl")
 
 
class ExternalVBFNLO(ExternalBase):
    """! Class for running external VBFNLO process.
 
    @author James Robinson  <james.robinson@cern.ch>
    """
 
    def __init__(self, vector_boson, allowed_decay_modes):
        """! Constructor.
 
        @param process  VBFNLO process
        """
        super(ExternalVBFNLO, self).__init__("VBFNLO")
 
        
        self.allowed_decay_modes = allowed_decay_modes
 
        # Add parameters used by VBFNLO
        self.add_keyword("alphaem_inv")
        self.add_keyword("vdecaymode", list(self.allowed_decay_modes)[0], name="decay_mode", description="{} boson decay mode. [{}]".format(vector_boson, allowed_decay_modes))
        self.add_keyword("G_F")
        self.add_keyword("mass_b")
        self.add_keyword("mass_c")
        self.add_keyword("mass_H")
        self.add_keyword("mass_t")
        self.add_keyword("mass_tau")
        self.add_keyword("mass_W")
        self.add_keyword("mass_Z")
        self.add_keyword("sthw2")
        self.add_keyword("width_H")
 
    def needs_scheduling(self, process):
        """! Report whether the VBFNLO process should be scheduled.
 
        @param process PowhegBox process.
        """
        self.expose()  # convenience call to simplify syntax
        if self.decay_mode not in self.allowed_decay_modes:
            logger.fatal("Decay mode {} not recognised!".format(self.decay_mode))
            raise ValueError("VBF NLO cannot be correctly configured.")
        # Convert allowed decay mode into PROC_ID/DECAYMODE
        __vector_boson_type = self.decay_mode.split(">")[0].strip()
        __vector_boson_decay = self.decay_mode.split(" ")[2].replace("+", "").replace("-", "")
        if __vector_boson_type in ["w+", "w-", "z"] and __vector_boson_decay == "tau":
            logger.warning("Powheg/VBFNLO does support directly tau decays for VBF W, Z production")
            logger.warning("Ask to generate muon decays and hack the LHE files - make sure to validate!")
            __vector_boson_decay = "mu"
            process.add_algorithm("mu2tau")
        # Add runcard entries
        VBF_runcard_entries = [("PROC_ID", {"z": 120, "w+": 130, "w-": 140}[__vector_boson_type], "{} boson".format(__vector_boson_type)),
                               ("DECAYMODE", {"e": 11, "mu": 13}[__vector_boson_decay], self.decay_mode),
                               ("HMASS", self.mass_H, list(self.parameters_by_name("mass_H"))[0].description),
                               ("HWIDTH", self.width_H, list(self.parameters_by_name("width_H"))[0].description),
                               ("EWSCHEME", 4, "Explicitly specify all EW parameters"),
                               ("ANOM_CPL", 0, "Disable anomalous couplings as these are not supported by the authors"),
                               ("TOPMASS", self.mass_t, list(self.parameters_by_name("mass_t"))[0].description),
                               ("TAU_MASS", self.mass_tau, list(self.parameters_by_name("mass_tau"))[0].description),
                               ("BOTTOMMASS", self.mass_b, list(self.parameters_by_name("mass_b"))[0].description),
                               ("CHARMMASS", self.mass_c, list(self.parameters_by_name("mass_c"))[0].description),
                               ("FERMI_CONST", self.G_F, list(self.parameters_by_name("G_F"))[0].description),
                               ("INVALFA", self.alphaem_inv, list(self.parameters_by_name("alphaem_inv"))[0].description),
                               ("SIN2W", self.sthw2, list(self.parameters_by_name("sthw2"))[0].description),
                               ("WMASS", self.mass_W, list(self.parameters_by_name("mass_W"))[0].description),
                               ("ZMASS", self.mass_Z, list(self.parameters_by_name("mass_Z"))[0].description)]
        # Write special VBF runcard
        with open("vbfnlo.input", "w") as f:
            for runcard_entry in VBF_runcard_entries:
                f.write("{:<15} {:<15} ! {}\n".format(*runcard_entry))
        return True