sig.py

#!/usr/bin/python

'''
 Romain Madar's significance formula
 see s7 here for more details:
 https://indico.cern.ch/event/696609/contributions/2943410/attachments/1625903/2589232/Btagging.pdf
'''

import math
from optparse import OptionParser

parser = OptionParser()
parser.add_option("--s", help="How many signal events?", type=float, default=1)
parser.add_option("--b", help="How many background events?", type=float, default=10)
parser.add_option("--db", help="Percent uncertainty on background?", type=float, default=0.3)
parser.add_option("--verbose", action='store_true', help="Verbose output? Default is False", default=False)
(options, args) = parser.parse_args()


s=options.s
b=options.b
db=options.db

t1 = (s+b)*math.log((s+b)*(b+db*db)/(b*b+(s+b)*db*db))
t2 = b*b/(db*db)*math.log(1.+s*db*db/(b*(b+db*db)))

Sum = math.sqrt(2.*(t1-t2));

if( Sum != Sum or math.isinf(Sum)): Sum = 0;

print Sum