An atennna-based jet clustering algorithm is under development. So far, only a set of elementary 3→2 clustering maps are provided.
The VinClu clustering map is a 3->2 clustering
map rather similar to that of the ARCLUS jet clustering algorithm.
Its principal advantage is that it
contains the exact inverses of the Vincia kinematics mappings, and
hence it can be used to "undo" branchings and/or reconstruct the exact
intermediate shower states from a given momentum configuration. The
clustering is invoked by creating an instance of the class
VinClu and using either of the two methods:
iMapis the index number of the kinematics map to be used (the numbering follows
pInis a vector of arbitrary size containing the input momentum configuration (in PYTHIA 8's
Vec4format), and the indices
brepresent the 3 particles to be clustered in the backwards reconstruction of AB->arb. For the variant with massive momenta,
mBshould be used to specify the on-shell masses of A and B.
Technically, the clustering is done as follows.
pClu is initially
set equal to
The reconstructed momenta of the
and B, are then stored in
pClu[b], respectively, and
pClu[r] is erased. (Note that this last step
may cause the indices of A and/or B
pClu to be different from
those of a and b in
pIn. For the most
common case, a
colour-ordered clustering with r=a+1 and b=a+2,
the indices of A and B after the clustering will
be A=a and B=A+1.)