`flag `

** Vincia:CheckAntennae **
(`default = `

)**on**

Switch to control whether to perform
antenna self-consistency checks or not.

`mode `

** Vincia:nPointsCheck **
(`default = `

; **1000**`minimum = 0`

; `maximum = 1e6`

)

Number of random points to check each antenna functions for positivity.

`parm `

** Vincia:PacceptFuss **
(`default = `

; **1.05**`minimum = 1.0`

; `maximum = 2.0`

)

Warning messages about P>1 violations will be suppressed if lower
than this level.

`parm `

** Vincia:PacceptPT0 **
(`default = `

; **1.5**`minimum = 0.5`

; `maximum = 10.0`

)

Warning messages about P>1 violations will be suppressed if the pT
scale of the offending branching is lower than this scale.

`flag `

** Vincia:PrintPacceptVariations **
(`default = `

)**off**

Switch to control whether to print a warning when violations of the accept
probability in the shower variations occur.

`flag `

** Vincia:PrintReWeightVariations **
(`default = `

)**off**

Switch to control whether to print a warning when the reweight factor
in the shower variations is reset (reject weight).

`parm `

** Vincia:deadZoneAvoidance **
(`default = `

; **0.0001**`minimum = 0.0`

; `maximum = 1.0`

)

During initialisation, warnings are issued if any
antenna functions (in dimensionless form, with the Eikonal
proportional to 2/y1/y2) become smaller than this number, anywhere in the resolved part of phase space (away from phase-space boundaries).
This is to warn against spurious radiation zeroes or large
negative finite terms creating "dead zones", or near-dead zones,
in the shower. For LL showering and matching up to
NLO, there is in principle no problem in taking this parameter to zero if
so desired. However, for the NLL and higher-order matching
corrections, very small values of this parameter may result in weights
greater than unity being generated, since the corrections are
multiplicative and large reweighting factors may be needed
to "make up" for any near-dead zones at the previous branching step.

Note that the sector shower can not be used in this version of Vincia. In order to use the sector shower shower for the final state in electron-positron annihilation we refer to Vincia version 1.X.

Sector showers are implemented as a non-default option and can be switched on using the flag`flag `

** Vincia:sectorShower **
(`default = `

)**off**

`option `

** off** : No sector ordering is imposed. All antennae are
allowed to contribute freely, independently of overlapping
radiation.
`option `

** on** : Only one antenna is allowed to contribute to each
phase space point. Note: when this option is on, a set of additional
terms will automatically be added to VINCIA's
antenna functions, such that the entire collinear singularity of
each gluon is present in each antenna.

When the sector option is on, the following switch determines whether the additional gluon-collinear terms are added to the global antenna functions in order to create proper sector antennae from them,

`flag `

** Vincia:useSectorTerms **
(`default = `

)**on**

Switch for the additional gluon-collinear terms that should be added
in the sector approach. Should be
`on`

for normal runs. Setting it to `off`

will
set the additional gluon-collinear sector antenna term coefficients to
zero.

For the time being, only one option for how to distinguish between
sectors has been implemented, as follows. A given trial emission will
only be accepted if, after the branching, it has the lowest pT (as
defined for Type 1 evolution above) of all possible colour-ordered
*3→2* clusterings after the branching.

Note that the one-loop matching can not be used in this version of Vincia. In order to use it for Z decay electron-positron annihilation we refer to Vincia version 1.X.

`mode `

** Vincia:matchingNLO **
(`default = `

; **0**`minimum = 0`

; `maximum = 2`

)

Selects the order of one-loop matrix-element corrections, also
called Next-to-Leading-Order matching.
The value should
interpreted as counting the
total number of powers of alphaS beyond the Born that are matched to
matrix elements.
I.e., for the basic process X, setting this switch
to `2`

would invoke one-loop matching
up to and including `X+1`

partons (one emission plus one
loop gives two powers of alphaS), to the extent the
relevant matrix elements are available in the code, see
the list below. In other words, to include
one-loop matching for `X+n`

partons, this switch must be
set to `n+1`

.
The value `0`

is equivalent to switching matching off.
Note: values larger than the leading-order value above will be
ignored. Thus, to switch off all matrix-element corrections,
it is sufficient to switch off the LO ones.

The choice of functional form of the renormalisation scale used for the alphaS power associated with the one-loop correction amounts to an NNLO effect and is hence formally beyond the explicit control of the NLO matching. It is controlled by the following parameter:

`mode `

** Vincia:alphaSmodeNLO **
(`default = `

; **0**`minimum = 0`

; `maximum = 1`

)

`option `

** 0** : The invariant mass of the parton system, m(ijk).
`option `

** 1** : Transverse momentum, defined as in ARIADNE, pT = m(ij)*m(jk)/m(ijk).

**Note 1:** for a generic multileg topology, the effective renormalisation
scale is computed as the geometric mean of such scales, taken
over all ordered three-parton clusterings in the event.

**Note 2:** the default value, `0`

, has been chosen to limit the absolute size of the NLO corrections, especially for soft branchings. For hard corrections, there should not be much difference between the two choices (though one can of course always argue about factors of 2). For soft corrections, differences appear starting from order aS^{2}*Log(s/pT2). Thus, changing to `1`

increases the absolute size of the NLO corrections for soft branchings. Ideally, the shower and hadronisation parameters should then be retuned.

**Note 3:** In the current formulation of the VINCIA NLO matching formalism,
option `1`

is intended mostly for theoretical reference. The matching expression used in the code is of the form (1 + V), which implicitly assumes that the correction, V, is small. For option `1`

, however, V becomes large for soft branchings. In this case, a resummed form of the matching expression would have to be used instead, but such an expression has so far not been derived.

`mode `

** Vincia:matchingNLOnPointsMin **
(`default = `

; **25**`minimum = 10`

; `maximum = 10000`

)

Minimal number of MC points used for the numerical evaluation of the real-emission correction integrals (deltaA) terms when computing NLO matching coefficients. Note that all possible forward branchings are cycled through, so e.g. for Z to 3 jets, four 4-parton matrix elements (2 qggq and 2 qqqq ones)
are tested for each MC point.

`mode `

** Vincia:matchingNLOnPointsMax **
(`default = `

; **100000**`minimum = 10`

; `maximum = 1000000`

)

Max number of MC points used for the numerical evaluation of the real-emission correction integrals (deltaA) terms.

`flag `

** Vincia:hyperjet **
(`default = `

)**off**

(Experimental flag. Not fully implemented yet. Leave in off position
for physics studies.)
When this flag is switched `on`

, VINCIA will automatically
use modified gluon emission antenna functions, in which the Eikonal (soft)
terms have been subtracted out, for the showers off the hardest
interaction. The gluon splitting antennae and the gluon emission
antennae for radiation inside resonance decays (and for showers off
MPI) are left
unmodified. Since the modified gluon emission antennae no longer contain
a soft singularity, this will NOT generate the correct DGLAP evolution
if used together with normal matrix elements for the hard
process. This option is therefore **only** intended for use together with
matrix element events in which the soft Eikonal has already been
resummed, such as when VINCIA is used together with J. Andersen's
high-energy-limit matrix elements. Since these matrix element
expressions are correct in the high-y-per-jet limit,
we have dubbed this running mode `HyperJet`

.

`flag `

** Vincia:postponeMarkov **
(`default = `

)**off**

This flag controls whether generated trial branchings are considered
by the accept/reject veto algorithm at their nominal branching scale
or whether they are "postponed" until the evolution scale reaches
the Markov scale of the would-be post-branching event.