The following switches control which quarks and leptons are treated as massive during the perturbative evolution. Note: the values of the masses are in all cases taken from PYTHIA's particle database, minimizing the risk of conflict. The parameters here only control whether the corresponding particles are treated as massive or massless by VINCIA.
flag
Vincia:isMassiveS
(default = false
)flag
Vincia:isMassiveC
(default = true
)flag
Vincia:isMassiveB
(default = true
)flag
Vincia:isMassiveTau
(default = true
)Note: New-physics particles will generally be treated as massive if their masses are larger than the lightest quark for which mass corrections are switched on.
Note 2: For particles that are treated as massive, the mass corrections to the antenna functions are discussed separately, in the section on Antenna Functions.
parm
Vincia:alphaSvalue
(default = 0.139
)mode
Vincia:alphaSorder
(default = 1
; minimum = 0
; maximum = 1
)option
0 : zeroth order, i.e. αs is kept
fixed.
option
1 : first order. This option is recommended for LO
matrix elements and LL showers.
Vincia:alphaSorder
is non-zero,
the actual value is then regulated by running to the scale
k*μR, at which the shower evaluates
αs. The functional form of μR is given by
Vincia:alphaSmode
and the scale factor
kμ is given by Vincia:alphaSscaleFactor
.
mode
Vincia:alphaSmode
(default = 3
; minimum = 1
; maximum = 3
)option
1 : The evolution variable (specified by
evolutionType
) evaluated at the
current branching.
option
2 : The invariant mass of the mother antenna.
option
3 : Transverse momentum, specifically
the Type 1 Evolution variable, regardless of what
ordering variable is being used
in evolutionType
. Note that, since the VINCIA normalization
of the transverse-momentum variable corresponds to 2pT, this should
normally be used with Vincia:alphaSscaleFactor = 0.5
,
see below.
parm
Vincia:alphaSscaleFactor
(default = 0.5
; minimum = 0.0
)Vincia:alphaSmode
times this
scale factor, i.e., it gives the value of kμ in
the argument to
alphaS(kμ*μR). Thus, e.g., for transverse momentum, this scale
factor should be 0.5, since VINCIA uses 2pT as evolution variable.
parm
Vincia:alphaSmuMin
(default = 0.5
; minimum = 0.0
)parm
Vincia:alphaSMax
(default = 1.0
; minimum = 0.0
)