VINCIA's shower evolution can be biased to populate the multi-jet phase space more efficiently and/or enhance the rate of rare processes such as g→bb and g→cc splittings. It is also possible to inhibit radiation (e.g., to focus on Sudakov regions), by choosing biasing factors smaller than unity. When these options are used, it is important to note that the event weights will be modified, reflecting that some types of events (e.g., multijet events, or events with gluon splittings to heavy quarks) will be "overrepresented" statistically, and others (events with few jets, or events with no gluon splittings to heavy quarks) underrepresented. Averages and histograms will therefore only be correct if computed using the correct weight for each generated event. A description and proof of the algorithm can be found in [MS16]. Note that care has been taken to ensure that the weights remain positive definite; under normal circumstances, VINCIA's biasing algorithm should not result in any negative weights.
flag
Vincia:biasInHardProcess
(default = on
)flag
Vincia:biasInResonanceDecays
(default = on
)flag
Vincia:biasInMPIshowers
(default = off
)parm
Vincia:biasAll
(default = 1.0
; minimum = 0.01
; maximum = 100.0
)parm
Vincia:biasBottom
(default = 1.0
; minimum = 0.01
; maximum = 100.0
)Vincia:biasAll
.
parm
Vincia:biasCharm
(default = 1.0
; minimum = 0.01
; maximum = 100.0
)Vincia:biasFacBottom
but for charm quarks. Note: this factor is applied on top of Vincia:biasAll
.
parm
Vincia:biasCutoff
(default = 10.0
; minimum = 0.0
; maximum = 1000.0
)