Clustering/reweighting page

OBJECT MEANING

* WARNING * THIS IS ONLY MY CURRENT UNDERSTANDING OF JOHAN's CODE. IT MIGHT BE ... WRONG

idacl(NEXTERNAL,2)

Returns an id identifying uniquely a particles: For an external particles the id is $2^{(N-1)$. For a propagator this is the sum of the id of all particles in which this particles decays.}

The first index indicates the various merging steps and the second index which particles is merging with wich ones.

icluster(4,nexternal)

Not clear, the code comment says: c variable for LH output of clustering info (R,E,S,I) but no idea what those four letter means...

imocl(NEXTERNAL)

Returns an id identifying uniquely a particles associated to the merging of that level. we therefore have idacl(I,1) + idacl(I,2) -> imocl(I)

iproc

I guess that's refer to the which matrix.f we have to consider for the graph.

igraphs(0:n_max_cg)

The first component is special (syze for the specific process?) I guess that this is the link to the various diagrams (in the various matrix.f) for the specific config.

ipart(2,n_max_cl)

ipart gives the external particle number corresponding to the present quark or gluon line. For t-channel lines, ipart(1) contains the connected beam. For s-channel lines, it depends if it is quark or gluon line: For quark lines, ipart(2) is 0 and ipart(1) connects to the corresponding final-state quark. For gluons, if it splits into two gluons, it connects to the hardest gluon. If it splits into qqbar, it ipart(1) is the hardest and ipart(2) is the softest.

other comment/variable

1. jfirst(2) is first parton splitting on this side
2. jlast(2) is last parton on this side
3. jcentral(2) is the central scale vertex on this side
4. qcdline(2) gives whether this IS line is QCD
5. partonline(2) gives whether this IS line is parton (start out true for any QCD)
6. goodjet(n_max_cl) gives whether this cluster line is considered a jet
7. jcode helps keep track of how many QCD/non-QCD flips we have gone through
8. increasecode gives whether we should increase jcode at next vertex

clustering technique

1. The last step of the clustering is (always?) the one with ipart(1, X) and ipart(2,X) are [1,2]!