Define a triple Gaussian PDF in RooFit

triple_gaussian.py

# Name of the delta mass variable in the workspace
dmass_var = 'Dst_delta_M'
# Species of the PDF we're about to build
species = 'sig'
workspace.factory('mu_dm_{0}[141, 146]'.format(species))
workspace.factory('sigma_one_dm_{0}[1, 0, 5]'.format(species))
workspace.factory('nsigma_two_dm_{0}[1.5, 1, 3]'.format(species))
workspace.factory('nsigma_three_dm_{0}[1.5, 1, 3]'.format(species))
workspace.factory((
    'expr::sigma_two_dm_{0}('
    "'@0*@1',"
    '{{sigma_one_dm_{0}, nsigma_two_dm_{0}}}'
    ')'
).format(species))
workspace.factory((
    'expr::sigma_three_dm_{0}('
    "'@0*@1',"
    '{{sigma_two_dm_{0}, nsigma_three_dm_{0}}}'
    ')'
).format(species))
workspace.factory('num_gauss_one_dm_{0}[0.5, 0, 1]'.format(species))
workspace.factory('num_gauss_two_dm_{0}[0.5, 0, 1]'.format(species))
workspace.factory((
    'RooGaussian::pdf_dm_gauss_one_{0}('
    '{1}, mu_dm_{0}, sigma_one_dm_{0}'
    ')'
).format(species, dmass_var))
workspace.factory((
    'RooGaussian::pdf_dm_gauss_two_{0}('
    '{1}, mu_dm_{0}, sigma_two_dm_{0}'
    ')'
).format(species, dmass_var))
workspace.factory((
    'RooGaussian::pdf_dm_gauss_three_{0}('
    '{1}, mu_dm_{0}, sigma_three_dm_{0}'
    ')'
).format(species, dmass_var))
workspace.factory((
    'RSUM::pdf_dm_{0}('
    'num_gauss_one_dm_{0}*pdf_dm_gauss_three_{0},'
    'num_gauss_two_dm_{0}*pdf_dm_gauss_two_{0},'
    'pdf_dm_gauss_one_{0}'
    ')'
).format(species))