Here, parameters specific to VINCIA's QED and EW antenna showers are collected, including VINCIA's interleaved treatment of resonance decays. See the main VINCIA antenna shower page for more general parameters that are common to both the QCD and QED/EW showers.
VINCIA contains two alternative implementations of QED/EW shower effects. One is restricted to pure QED but allows for a fully coherent (multipole) treatment of that sector. The other is limited to dipole-style coherence in the photon sector but includes a full set of electroweak (EW) branching kernels with the appropriate (quasi-)collinear limits.
mode   Vincia:EWmode   
 (default = 2; minimum = 0; maximum = 3)Vincia:QEDmodeMPI below for the 
handling of QED corrections in MPI systems.) 
option  0 : No QED or weak showers at all. 
   
option  1 : Dipole QED showers. Partially coherent, based on 
maximally screening dipole pairs. Spin-dependent antenna terms can be 
switched on/off using Vincia:QEDfullKernels, see below. 
   
option  2 : Multipole QED showers. Fully coherent but 
computationally slower than the dipole approximation. Spin-dependent 
antenna terms can be switched on/off using 
Vincia:QEDfullKernels, see below. 
   
option  3 : Dipole QED + Weak showers. All electroweak 
branchings are enabled, comprising emissions, splittings, and 
self-interactions of W, Z, and H bosons, in addition to QED. Note 
that the weak shower operates on helicity eigenstates; this is 
particularly relevant for W and Z bosons for which the longitudinal 
polarisations have different splitting amplitudes than the transverse 
ones. Typically, the hard process does not provide helicity 
information for the in- and outgoing legs in Pythia. In this case, 
VINCIA will attempt to use its MG5 matrix-element interface and its 
internal EW splitting amplitudes to assign such helicities. Note that 
this requires Pythia to be configured using the 
--with-mg5mes option (see also the 
example program 
main404.cc). If the given hard process is not available 
in the linked MG5 library, or if the helicity assignment fails for any 
other reason, then the QED dipole shower is used as a fallback. 
   
   
 
mode   Vincia:QEDmodeMPI   
 (default = 1; minimum = 0; maximum = 2)QEDmodeMPI is forced to be less than or equal to the main 
EWmode switch above so that the treatment of QED 
corrections for MPI cannot be more sophisticated than that of the hard 
interaction. Also note that there is currently no option to include 
weak showers for MPI. 
option  0 : No QED showers in MPI systems. 
   
option  1 : Dipole QED showers in MPI systems. 
   
option  2 : Multipole QED showers in MPI systems. This is the 
most advanced option, with full coherence, but is somewhat 
computationally slower and would normally be overkill for MPI. 
   
   
 
mode   Vincia:QEDmodeHadDec   
 (default = 2; minimum = 1; maximum = 2)HadronLevel:QED = on, this switch determines whether 
QED multipole interference effects (similar to YFS) are taken into 
account or not, for QED showers in hadron and tau decays (with spin 
dependence according to Vincia:useSpinsQEDHadDec). 
option  1 : Dipole QED showers in hadron and tau decays. 
   
option  2 : Multipole QED showers in hadron and tau decays. 
   
   
 
 
mode   Vincia:nGammaToQuark   
 (default = 5; minimum = 0; maximum = 6)mode   Vincia:nGammaToLepton   
 (default = 3; minimum = 0; maximum = 3)flag   Vincia:convertGammaToQuark   
 (default = on)flag   Vincia:convertQuarkToGamma   
 (default = on)mode   Vincia:alphaEMorder   
 (default = 1; minimum = 0; maximum = 1)option  0 : zeroth order, i.e. αem is kept 
fixed. 
   
option  1 : first order, i.e., one-loop running. 
   
   
 
parm   Vincia:alphaEM0   
 (default = 0.00729735; minimum = 0.0072973; maximum = 0.0072974)parm   Vincia:alphaEMmZ   
 (default = 0.00781751; minimum = 0.00780; maximum = 0.00783)parm   Vincia:QminChgQ   
 (default = 0.5; minimum = 0.1; maximum = 2.0)parm   Vincia:QminChgL   
 (default = 1e-6; minimum = 1e-10; maximum = 2.0)fvec   Vincia:useSpinsQED   
 (default = {on, on, on})on) 
or just their (spin-independent, YFS-style) scalar eikonal terms 
(off), for QED in hard processes, resonance decays, and 
MPI. The first entry switches the spin-dependent collinear terms 
on/off for spin-1/2 radiators, the second for spin-1 radiators, and 
the third for spin-3/2 ones. Note that the spin-3/2 case is not fully 
implemented and currently defaults to use the same terms as the 
spin-1/2 case. 
   
 
fvec   Vincia:useSpinsQEDHadDec   
 (default = {on, on, on})Vincia:useSpinsQED for QED in hadron and tau decays. 
   
 
parm   Vincia:mMaxGamma   
 (default = 10.; minimum = 0.001; maximum = 5000.0)mode   Vincia:kineMapEWFinal   
 (default = 3; minimum = 1; maximum = 3)option  1 : The Ariadne angle.   
option  2 : Longitudinal (dipole) map.   
option  3 : The Kosower map.   
   
 
flag   Vincia:doBosonicInterference   
 (default = on)mode   Vincia:bwMatchingMode   
 (default = 2; minimum = 1; maximum = 3)option  1 : Resonance-type branchings in the shower are 
disabled. Resonances are instead decayed according to a Breit-Wigner 
distribution exclusively. 
   
option  2 : A suppression factor $\frac{Q^4}{(Q^2 + 
Q^2_{\mathrm{EW}})^2} is applied to the resonance decay-type 
branchings in the shower. Any resonance that does not disappear due to 
a shower branching before its Breit-Wigner-sampled off-shellness is 
instead decayed according to the Breit-Wigner distribution. 
   
option  3 : No off-shellness is sampled from a 
Breit-Wigner. Only the shower is ran without suppression factor. Does 
not guarantee that all resonances decay. 
   
   
 
parm   Vincia:EWScale   
 (default = 100.; minimum = 80.; maximum = 175.)Vincia:bwMatchingMode = 2. 
   
 
flag   Vincia:EWoverlapVeto   
 (default = off)on in conjunction with Vincia:interleaveResDec = 
off. 
   
 
parm   Vincia:EWoverlapVetoDeltaR   
 (default = 0.6; minimum = 0.1)flag   Vincia:BWstrongOrdering   
 (default = off)parm   Vincia:EWheadroomF   
 (default = 1.1; minimum = 1.; maximum = 2.)parm   Vincia:EWheadroomI   
 (default = 3; minimum = 1.; maximum = 5.)As there are such a very large number of electroweak branchings, the technical problem of determining the overestimate function (used for generating trial branchings) has been automated. The overestimate function is first parameterised in terms of four functions; the coefficients of these are then extracted by numerically minimising the difference between the corresponding functional and the branching kernels themselves. The coefficients determined by this procedure are collected in the XML file and are read in during initialisation.