<chapter name="Dire Splitting Enhancements"> 
 
<h2>Dire Splitting Enhancements</h2> 
 
The Dire parton shower allows to weight individual splittings to allow 
efficient isolation and study of their impact. This can e.g. be used 
to increase the rate of a single splitting, and/or decrease the rate 
of others, thus e.g. allowing to study rare splittings. It should be 
noted that this can make some splittings much more frequent, at the 
expense of a new event weight, whose fluctuations might require larger 
event samples. 
 
 
<p/> 
Nevertheless, sometimes enhancements can be useful. Dire offers the 
option to enhance each available splitting kernel separately. For 
brevity, we here only describe auxiliary parameters, then one 
enhancement factor, and then just list all other corresponding 
keywords. 
 
<parm name="Enhance:pTmin" default="-1.0"> 
The minimal pT value <i>t</i> (in GeV) of 
emissions below which no enhancement of emission probabilities is 
applied. Negative values mean that enhancements may be applied to 
emissions at any pT. Default value is -1.0 GeV. 
</parm> 
 
<parm name="Enhance:Dire_fsr_qcd_1->1&21" default="1.0"> 
The (double) value with 
which the final-state <i>q->qg</i> splitting is enhanced. Note that 
the enhancement is compensated by an additional weight factor included 
in the parton shower weight, to guarantee the correct real-emission and 
no-emission probabilities are generated. 
</parm> 
 
<h3>QCD splittings</h3> 
 
<parm name="Enhance:Dire_fsr_qcd_1->21&1" default="1.0"> 
(FSR, q -> g q) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&21a" default="1.0"> 
(FSR, g -> g g, 1st color structure) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&21b" default="1.0"> 
(FSR, g -> g g, 2nd color structure) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->1&1a" default="1.0"> 
(FSR, g -> q qbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->1&1b" default="1.0"> 
(FSR, g -> q qbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->2&1&2" default="1.0"> 
(FSR, q -> q' q qbar') 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&1&1" default="1.0"> 
(FSR, q -> qbar q qbar) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&21_notPartial" default="1.0"> 
(FSR q -> q g, with full soft logarithms, as e.g. needed in radiation off 
top decay products) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&21_notPartial" default="1.0"> 
(FSR g -> g g, with full soft logarithms, as e.g. needed in radiation off 
top decay products) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->1&1_notPartial" default="1.0"> 
(FSR g -> q qbar, with full soft logarithms, as e.g. needed in radiation 
off top decay products) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&21&21" default="1.0"> 
(FSR q -> q g g) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&d&dbar" default="1.0"> 
(FSR q -> q d dbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&dbar&d" default="1.0"> 
(FSR q -> q d dbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&u&ubar" default="1.0"> 
(FSR q -> q u ubar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&ubar&u" default="1.0"> 
(FSR q -> q u ubar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&s&sbar" default="1.0"> 
(FSR q -> q s sbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&sbar&s" default="1.0"> 
(FSR q -> q s sbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&c&cbar" default="1.0"> 
(FSR q -> q c cbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&cbar&c" default="1.0"> 
(FSR q -> q c cbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&b&bbar" default="1.0"> 
(FSR q -> q b bbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_1->1&bbar&b" default="1.0"> 
(FSR q -> q b bbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&21&21" default="1.0"> 
(FSR g -> g g g) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&d&dbar" default="1.0"> 
(FSR g -> q d dbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&dbar&d" default="1.0"> 
(FSR g -> g d dbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&u&ubar" default="1.0"> 
(FSR g -> g u ubar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&ubar&u" default="1.0"> 
(FSR g -> g u ubar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&s&sbar" default="1.0"> 
(FSR g -> g s sbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&sbar&s" default="1.0"> 
(FSR g -> g s sbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&c&cbar" default="1.0"> 
(FSR g -> g c cbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&cbar&c" default="1.0"> 
(FSR g -> g c cbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&b&bbar" default="1.0"> 
(FSR g -> g b bbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qcd_21->21&bbar&b" default="1.0"> 
(FSR g -> g b bbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_1->1&21" default="1.0"> 
(ISR q -> q g) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_21->1&1" default="1.0"> 
(ISR g -> q qbar) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_21->21&21a" default="1.0"> 
(ISR g -> g g, soft quark) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_21->21&21b" default="1.0"> 
(ISR g -> g g, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_1->21&1" default="1.0"> 
(ISR q -> g q) 
</parm> 
<parm name="Enhance:Dire_isr_qcd_1->2&1&2" default="1.0"> 
(ISR q -> q' q qbar') 
</parm> 
<parm name="Enhance:Dire_isr_qcd_1->1&1&1" default="1.0"> 
(ISR q -> qbar q qbar) 
</parm> 
 
<h3>QED splittings</h3> 
 
<parm name="Enhance:Dire_fsr_qed_1->1&22" default="1.0"> 
(FSR q -> q a) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_1->22&1" default="1.0"> 
(FSR q -> a q) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_11->11&22" default="1.0"> 
(FSR l -> l a) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_11->22&11" default="1.0"> 
(FSR l -> a l) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->1&1a" default="1.0"> 
(FSR a -> d dbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->1&1b" default="1.0"> 
(FSR a -> d dbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->2&2a" default="1.0"> 
(FSR a -> u ubar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->2&2b" default="1.0"> 
(FSR a -> u ubar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->3&3a" default="1.0"> 
(FSR a -> s sbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->3&3b" default="1.0"> 
(FSR a -> s sbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->4&4a" default="1.0"> 
(FSR a -> c cbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->4&4b" default="1.0"> 
(FSR a -> c cbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->5&5a" default="1.0"> 
(FSR a -> b bbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->5&5b" default="1.0"> 
(FSR a -> b bbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->11&11a" default="1.0"> 
(FSR a -> e+ e-, soft e-) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->11&11b" default="1.0"> 
(FSR a -> e+ e-, soft e+) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->13&13a" default="1.0"> 
(FSR a -> mu+ mu-, soft mu-) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->13&13b" default="1.0"> 
(FSR a -> mu+ mu-, soft mu+) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->15&15a" default="1.0"> 
(FSR a -> tau+ tau-, soft tau-) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_22->15&15b" default="1.0"> 
(FSR a -> tau+ tau-, soft tau+) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_1->1&22_notPartial" default="1.0"> 
(FSR q -> q a, with full soft logarithms, as e.g. needed in radiation off 
top decay products) 
</parm> 
<parm name="Enhance:Dire_fsr_qed_11->11&22_notPartial" default="1.0"> 
(FSR l -> l a, with full soft logarithms, as e.g. needed in radiation off 
top decay products) 
</parm> 
<parm name="Enhance:Dire_isr_qed_1->1&22" default="1.0"> 
(ISR q -> q a) 
</parm> 
<parm name="Enhance:Dire_isr_qed_1->22&1" default="1.0"> 
(ISR q -> a q) 
</parm> 
<parm name="Enhance:Dire_isr_qed_22->1&1" default="1.0"> 
(ISR a -> q qbar) 
</parm> 
<parm name="Enhance:Dire_isr_qed_11->11&22" default="1.0"> 
(ISR l -> l a) 
</parm> 
<parm name="Enhance:Dire_isr_qed_11->22&11" default="1.0"> 
(FSR l -> a l) 
</parm> 
<parm name="Enhance:Dire_isr_qed_22->11&11" default="1.0"> 
(FSR a -> l+ l-). 
</parm> 
 
 
<h3>Electroweak splittings</h3> 
 
At present, electroweak evolution is under development, so that these 
settings should not be touched for production for now. 
 
<parm name="Enhance:Dire_fsr_ew_1->1&23" default="1.0"> 
(FSR q -> q z) 
</parm> 
<parm name="Enhance:Dire_fsr_ew_1->23&1" default="1.0"> 
(FSR q -> z q) 
</parm> 
<parm name="Enhance:Dire_fsr_ew_23->1&1a" default="1.0"> 
(FSR z -> q qbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_ew_23->1&1b" default="1.0"> 
(FSR z -> q qbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_ew_24->1&1a" default="1.0"> 
FSR w -> q qbar', soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_ew_24->1&1b" default="1.0"> 
(FSR w -> q qbar', soft antiquark). 
</parm> 
<parm name="Enhance:Dire_fsr_ew_24->24&22" default="1.0"> 
(FSR w -> w a). 
</parm> 
<parm name="Enhance:Dire_fsr_ew_25->21&21" default="1.0"> 
(FSR h -> g g, as e.g. needed for Higgs hypothesis testing). 
</parm> 
<parm name="Enhance:Dire_fsr_ew_25->22&22" default="1.0"> 
(FSR h -> a a, as e.g. needed for Higgs hypothesis testing). 
</parm> 
 
<h3>Dark U(1) splittings</h3> 
 
At present, dark photon evolution is under development, so that these 
settings should not be touched for production for now. 
 
<parm name="Enhance:Dire_fsr_u1new_1->1&22" default="1.0"> 
(FSR q -> q aDark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_1->22&1" default="1.0"> 
(FSR q -> aDark q) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_11->11&22" default="1.0"> 
(FSR l -> l aDark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_11->22&11" default="1.0"> 
(FSR l -> aDark l) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->1&1a" default="1.0"> 
(FSR aDark -> d dbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->1&1b" default="1.0"> 
(FSR aDark -> d dbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->2&2a" default="1.0"> 
(FSR aDark -> u ubar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->2&2b" default="1.0"> 
(FSR aDark -> u ubar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->3&3a" default="1.0"> 
(FSR aDark -> s sbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->3&3b" default="1.0"> 
(FSR aDark -> s sbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->4&4a" default="1.0"> 
(FSR aDark -> c cbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->4&4b" default="1.0"> 
(FSR aDark -> c cbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->5&5a" default="1.0"> 
(FSR aDark -> b bbar, soft quark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->5&5b" default="1.0"> 
(FSR aDark -> b bbar, soft antiquark) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->11&11a" default="1.0"> 
(FSR aDark -> e+ e-, soft e-) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->11&11b" default="1.0"> 
(FSR aDark -> e+ e-, soft e+) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->13&13a" default="1.0"> 
(FSR aDark -> mu+ mu-, soft mu-) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->13&13b" default="1.0"> 
(FSR aDark -> mu+ mu-, soft mu+) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->15&15a" default="1.0"> 
(FSR aDark -> tau+ tau-, soft tau-) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->15&15b" default="1.0"> 
(FSR aDark -> tau+ tau-, soft tau+) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->211&211a" default="1.0"> 
(FSR aDark -> pi+ pi-, soft pi-) 
</parm> 
<parm name="Enhance:Dire_fsr_u1new_22->211&211b" default="1.0"> 
(FSR aDark -> pi+ pi-, soft pi+) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_1->1&22" default="1.0"> 
(ISR q -> q aDark) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_1->22&1" default="1.0"> 
(ISR q -> aDark a) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_22->1&1" default="1.0"> 
(ISR aDark -> q qbar) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_11->11&22" default="1.0"> 
(ISR l -> l aDark) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_11->22&11" default="1.0"> 
(ISR l -> aDark l) 
</parm> 
<parm name="Enhance:Dire_isr_u1new_22->11&11" default="1.0"> 
(ISR aDark -> l+ l-). 
</parm> 
 
</chapter> 
 
<!-- Copyright (C) 2025 Stefan Prestel --> 
