The 2→3 (LL) VINCIA antennae have names such as
Vincia:qQ:emit
(for gluon emission off a qqbar
antenna), Vincia:qg:split
(for gluon splitting to a
quark-antiquark pair inside a qg antenna).Vincia:AB:x
, where A
and B
are
the "mothers" and x
is either emit
or
split
, depending on whether the process is gluon emission
or gluon splitting.
The radiating (parent) antenna is interpreted as
spanned between the Les Houches colour tag of
A
and the anti-colour tag of B
, see
illustration to the right.
The functional form of the antennae are specified by giving the
coefficients of a double Laurent series in the two branching
invariants (the third invariant, specifying a
rotation around the dipole axis, is chosen uniformly).
The Laurent expansion starts at power (-1,-1)
corresponding to the double singularity.
For so-called "global" antennae (the default in VINCIA),
each antenna is fully specified by giving the
coefficients LaurentC(i,j)
of the following expansion:
A(y_ar,y_rb;s_AB) = 1/s_AB 4 pi
alpha_s chargeFactor LaurentC(i,j) pow(y_ar,i) pow(y_rb,j);
where i
and
j
are implicitly summed over,
s_AB
is the mass of the mother antenna,
chargeFactor
should be normalized to tend to NC
raised to the number of new color lines created in
the splitting in
the large-NC limit (i.e., the limiting value should be 3 for gluon
emission and 1 for gluon splitting), and y_ar,y_rb
are the
branching invariants scaled by the mass of the mother antenna,
y_ij = s_ij/s_AB
.
The coefficients with negative i
or j
indices are universal and should not be
changed by the user. Finite terms, i.e., with both indices greater than or equal
to zero, are arbitrary and in general the best choice to make will
depend on the specific process considered. They are therefore not to
be regarded as "tunable" parameters, but rather as an independent way
of estimating the uncertainty due do uncalculated higher orders, an
uncertainty which can be explicitly reduced by matrix-element matching.
The default is therefore to allow these terms to be nonzero,
but for special applications it may be convenient to have one global
switch that switches them on and off:
flag
VinciaShower:useFiniteTerms
(default = on
)on
for normal runs. Setting it to off
will
set all finite term coefficients to zero.
In the case of sector-ordered antennae (as opposed to the "global"
ones described above), explicit singularities at y_ij→1
may also be present. In addition to the C_ij
coefficients
defined above, we therefore also allow for the following
additional terms in the antenna function parametrization when sector
ordering is switched on:
... + LaurentD(i) pow(y_ar,i)
/ (1-y_rb) +
LaurentE(i) pow(y_rb,i) / (1-y_ar) + K / (1-y_ar) / (1-y_rb);
parm
Vincia:CollinearGluonSplitting
(default = 0.0
; minimum = 0.0
; maximum = 1
)flag
Vincia:qQ:emit
(default = on
)parm
Vincia:qQ:emit:chargeFactor
(default = 2.66666667
)parm
Vincia:qQ:emit:LaurentC(-1,-1)
(default = 2.0
)parm
Vincia:qQ:emit:LaurentC(-1,0)
(default = -2.0
)parm
Vincia:qQ:emit:LaurentC(0,-1)
(default = -2.0
)parm
Vincia:qQ:emit:LaurentC(-1,1)
(default = 1.0
)parm
Vincia:qQ:emit:LaurentC(1,-1)
(default = 1.0
)parm
Vincia:qQ:emit:LaurentC(0,0)
(default = 0.0
)parm
Vincia:qQ:emit:LaurentC(1,0)
(default = 0.0
)parm
Vincia:qQ:emit:LaurentC(0,1)
(default = 0.0
)flag
Vincia:qg:emit
(default = on
)parm
Vincia:qg:emit:chargeFactor
(default = 3.0
)parm
Vincia:qg:emit:LaurentC(-1,-1)
(default = 2.0
)parm
Vincia:qg:emit:LaurentC(-1,0)
(default = -2.0
)parm
Vincia:qg:emit:LaurentC(0,-1)
(default = -2.0
)parm
Vincia:qg:emit:LaurentC(1,-1)
(default = 1.0
)parm
Vincia:qg:emit:LaurentC(-1,1)
(default = 1.0
)parm
Vincia:qg:emit:LaurentC(2,-1)
(default = -1.0
)parm
Vincia:qg:emit:LaurentC(0,0)
(default = 2.5
)parm
Vincia:qg:emit:LaurentC(1,0)
(default = -1.0
)parm
Vincia:qg:emit:LaurentC(0,1)
(default = -0.5
)flag
Vincia:gg:emit
(default = on
)parm
Vincia:gg:emit:chargeFactor
(default = 3.0
)parm
Vincia:gg:emit:LaurentC(-1,-1)
(default = 2.0
)parm
Vincia:gg:emit:LaurentC(-1,0)
(default = -2.0
)parm
Vincia:gg:emit:LaurentC(0,-1)
(default = -2.0
)parm
Vincia:gg:emit:LaurentC(-1,1)
(default = 1.0
)parm
Vincia:gg:emit:LaurentC(1,-1)
(default = 1.0
)parm
Vincia:gg:emit:LaurentC(2,-1)
(default = -1.0
)parm
Vincia:gg:emit:LaurentC(-1,2)
(default = -1.0
)parm
Vincia:gg:emit:LaurentC(0,0)
(default = 2.66666667
)parm
Vincia:gg:emit:LaurentC(1,0)
(default = -1.0
)parm
Vincia:gg:emit:LaurentC(0,1)
(default = -1.0
)flag
Vincia:qg:split
(default = on
)parm
Vincia:qg:split:chargeFactor
(default = 1.0
)parm
Vincia:qg:split:LaurentC(-1,-1)
(default = 0.0
)parm
Vincia:qg:split:LaurentC(-1,0)
(default = 0.0
)parm
Vincia:qg:split:LaurentC(-1,1)
(default = 0.0
)parm
Vincia:qg:split:LaurentC(0,-1)
(default = 0.5
)parm
Vincia:qg:split:LaurentC(1,-1)
(default = -1.0
)parm
Vincia:qg:split:LaurentC(2,-1)
(default = 1.0
)parm
Vincia:qg:split:LaurentC(0,0)
(default = -0.4
)parm
Vincia:qg:split:LaurentC(1,0)
(default = 0.8
)parm
Vincia:qg:split:LaurentC(0,1)
(default = 0.0
)flag
Vincia:gg:split
(default = on
)parm
Vincia:gg:split:chargeFactor
(default = 1.0
)parm
Vincia:gg:split:LaurentC(-1,-1)
(default = 0.0
)parm
Vincia:gg:split:LaurentC(-1,0)
(default = 0.0
)parm
Vincia:gg:split:LaurentC(-1,1)
(default = 0.0
)parm
Vincia:gg:split:LaurentC(0,-1)
(default = 0.5
)parm
Vincia:gg:split:LaurentC(1,-1)
(default = -1.0
)parm
Vincia:gg:split:LaurentC(2,-1)
(default = 1.0
)parm
Vincia:gg:split:LaurentC(0,0)
(default = -0.8
)parm
Vincia:gg:split:LaurentC(1,0)
(default = 0.8
)parm
Vincia:gg:split:LaurentC(0,1)
(default = 0.4
)flag
Vincia:qQ:emit:useMassTerms
(default = on
)parm
Vincia:qQ:emit:LaurentMNum(-1,0,0,2,0,0)
(default = 0
)parm
Vincia:qQ:emit:LaurentMNum(0,0,-1,0,0,2)
(default = 0
)flag
Vincia:qg:emit:useMassTerms
(default = on
)parm
Vincia:qg:emit:LaurentMNum(-1,-1,1,3,0,0)
(default = -1.00
)parm
Vincia:qg:emit:LaurentMNum(-1,-1,1,4,0,0)
(default = 1.00
)parm
Vincia:qg:emit:LaurentMNum(-1,-1,2,2,0,0)
(default = -1.00
)parm
Vincia:qg:emit:LaurentMNum(-1,0,1,2,0,0)
(default = -2.00
)parm
Vincia:qg:emit:LaurentMNum(0,0,0,1,0,0)
(default = 1.00
)parm
Vincia:qg:emit:LaurentMNum(0,0,0,2,0,0)
(default = -3.00
)flag
Vincia:gg:emit:useMassTerms
(default = on
)flag
Vincia:qg:split:useMassTerms
(default = on
)parm
Vincia:qg:split:LaurentMNum(0,0,0,0,4,0)
(default = -3.2
)parm
Vincia:qg:split:LaurentMNum(0,0,0,1,4,0)
(default = -6.4
)parm
Vincia:qg:split:LaurentMNum(0,0,1,0,2,0)
(default = -2.4
)parm
Vincia:qg:split:LaurentMNum(0,0,1,1,2,0)
(default = -4.8
)parm
Vincia:qg:split:LaurentMNum(0,0,1,2,2,0)
(default = 0.8
)parm
Vincia:qg:split:LaurentMNum(0,0,2,1,0,0)
(default = -0.8
)parm
Vincia:qg:split:LaurentMNum(0,0,2,2,0,0)
(default = 0.4
)parm
Vincia:qg:split:LaurentMNum(1,0,0,0,4,0)
(default = 3.2
)parm
Vincia:qg:split:LaurentMNum(1,0,1,0,2,0)
(default = 3.2
)flag
Vincia:gg:split:useMassTerms
(default = on
)parm
Vincia:gg:split:LaurentMNum(0,0,0,0,4,0)
(default = -6.4
)parm
Vincia:gg:split:LaurentMNum(0,0,0,0,6,0)
(default = 6.4
)parm
Vincia:gg:split:LaurentMNum(0,0,1,0,2,0)
(default = -4.8
)parm
Vincia:gg:split:LaurentMNum(0,0,1,0,4,0)
(default = 8
)parm
Vincia:gg:split:LaurentMNum(0,0,2,0,2,0)
(default = 3.2
)parm
Vincia:gg:split:LaurentMNum(1,0,0,0,4,0)
(default = 3.2
)parm
Vincia:gg:split:LaurentMNum(1,0,1,0,2,0)
(default = 3.2
)