Isolation of a particle would be calculated by requiring the
sum of cells lying within an isolation cone centered on the
particle to exceed a
threshold (this requirement already exists in AT and AA).
Self-vetos are avoided by subtracting the particle
from the sum.
Note that a nearby electron or gamma could cause the particle being
considered to be non-isolated, but this reflects the inability of the
detector to resolve overlapping particles.
Armed with the list of isolated electrons and gammas, and the list of clusters, one can make an order independent match. The match requirement would be coded in a manner to make it easily modifiable.
As a further step, the match requirement -
which is currently the requirement that the match is between the cluster
and particle that are closest - could be modified to ensure good
energy matching.
For example, the requirement could become the match
that minimises
.