## Hadronization Variations

The hadronization variation framework allows a user to calculate
reweighting factors taking a given event from one set of hadronization
parameters to another, by changing the probability with which this
specific event would occur given the altered parameter set. This
feature is still experimental and is under active development, so use
at your own risk. The method for reweighting the Lund string
fragmentation function is documented in [Bie23], and the
flavor reweighting method is currently being written up.
Users familiar with
Parton Shower Variations will recognize
much of the logic from there. It is currently possible to vary a
number of parameters relating to kinematics and flavour selection,
listed in the following. Currently this is a proof-of-concept feature,
and it is expected that the selection of parameters will be extended
going forward.
Be particularly aware that the code will not warn you, in case you have
no statistical coverage for the values you are attempting to reweight to.
Use with caution.
`wvec `

** VariationFrag:List **
(`default = `**{}**

)

Vector of uncertainty-variation strings defining groups of parameter
variations for string fragmentation. The groups are separated by commas,
and the elements of the group are separated by spaces, where the first
element is the group name, and the following elements are the varied
parameters of the form `parameter=value`

.

For completeness, we note that an example command-file specification
could look as follows:

VariationFrag:List = {
kinVars frag:ptsigma=0.3 frag:alund=0.6,
flavVars frag:rho=0.2 frag:x=0.9 frag:y=0.04
}

### List of Recognised Keywords for Hadronization Variations

The following keywords adjust the Lund string fragmentation function:
`frag:aLund`

: value for `StringZ:aLund`

,
the *a* parameter of the Lund symmetric fragmentation
function.
`frag:bLund`

: value for `StringZ:bLund`

,
the *b* parameter of the Lund symmetric fragmentation
function.
`frag:rFactC`

: value for `StringZ:rFactC`

,
*r_c*, i.e. the Bowler parameter for *c* quarks.
`frag:rFactB`

: value for `StringZ:rFactB`

,
*r_c*, i.e. the Bowler parameter for *b* quarks.
`frag:ptSigma`

: value for `StringPT:sigma`

,
the width sigma in the fragmentation process.

Flavour parameters can be adjusted with the following keywords:

`frag:xi`

: value for
`StringFlav:ProbQQtoQ`

, the suppression of diquark
production relative to quark production, i.e. of baryon relative to
meson production.
`frag:rho`

: value for
`StringFlav:ProbStoUD`

, the suppression of *s* quark
production relative to ordinary *u* or *d* one.
`frag:x`

: value for
`StringFlav:StringFlav:ProbSQtoQQ`

, the suppression of
strange diquark production relative to light
diquark production, over and above the one already given by
`StringFlav:ProbStoU`

.
`frag:y`

: value for
`StringFlav:StringFlav:ProbQQ1toQQ0`

, the suppression of
spin 1 diquark production relative to spin 0 one, apart from the
factor of 3 enhancement of spin 1 from counting the number of
states.