How To: Compute NLL cross sections for a given SLHA file¶

# Set up the path to SModelS installation folder
import sys; sys.path.append("."); import smodels_paths

# Import those parts of smodels that are needed for this exercise
from smodels.tools import xsecComputer
from smodels.tools.physicsUnits import TeV, fb
from smodels.installation import installDirectory
from smodels.tools.xsecComputer import LO, NLL

/usr/lib/python3.6/importlib/_bootstrap.py:219: RuntimeWarning: numpy.dtype size changed, may indicate binary incompatibility. Expected 96, got 88
  return f(*args, **kwds)
/usr/lib/python3.6/importlib/_bootstrap.py:219: RuntimeWarning: numpy.dtype size changed, may indicate binary incompatibility. Expected 96, got 88
  return f(*args, **kwds)

# Define the SLHA file name
filename="%s/inputFiles/slha/gluino_squarks.slha" % installDirectory()

# Lets compute the NLL cross-sections for 8 TeV. The xsecComputer will first use Pythia to compute
# the LO cross-sections and then NLLfast to compute the k-factors.
# The output will contain only the processes contained in NLLfast (gluino and squark production)
# For the Pythia step we have to define the number of MC events (1k)
# (To see how to also include LO cross-sections for all processes check the LO HowTo)
computer = xsecComputer.XSecComputer ( maxOrder=NLL, nevents = 100, pythiaVersion=6 )
xsecsNLL=computer.compute(sqrts = 8*TeV, slhafile=filename )

# the output is a XSectionList ...
type(xsecsNLL)

smodels.theory.crossSection.XSectionList

# Each entry in the list contains the cross-section value:
print(xsecsNLL[0].value)
# The PDGs of the particles produced:
print(xsecsNLL[0].pid)
# And some additional info
print("label =",xsecsNLL[0].info.label,"Sqrts =",xsecsNLL[0].info.sqrts, "QCD order =",xsecsNLL[0].info.order)

1.03E-01 [pb]
(1000021, 2000002)
label = 8 TeV (NLO+NLL) Sqrts = 8.00E+00 [TeV] QCD order = 2

# Finally, lets write the cross-sections back to the file 
# (will write only the cross-sections not overlapping the existing ones):
computer.addXSecToFile(xsecsNLL,filename)

True