Opened 14 years ago
Last modified 5 years ago
#142 closed enhancement
Generalized color structures — at Version 8
| Reported by: | Juergen Reuter | Owned by: | ohl |
|---|---|---|---|
| Priority: | P2 | Milestone: | v4.0 |
| Component: | omega | Version: | 2.0.0rc2 |
| Severity: | major | Keywords: | color correlations |
| Cc: |
Description (last modified by )
Generalized color structures (sextets, eps_ijk couplings, etc.) should be supported by the colorizer inside O'Mega.
Change History (8)
comment:1 Changed 14 years ago by
| Milestone: | v2.1 → v2.0final |
|---|---|
| Owner: | changed from jr_reuter, cnspeckn to ohl |
| Priority: | P3 → P1 |
| Severity: | normal → critical |
| Type: | task → defect |
| Version: | → 2.0rc2 |
comment:2 Changed 14 years ago by
| Status: | new → assigned |
|---|
comment:3 Changed 14 years ago by
| Milestone: | v2.0.0final → v2.0-rc4 |
|---|
comment:4 Changed 14 years ago by
| Owner: | changed from ohl to kilian |
|---|---|
| Status: | assigned → new |
OK, I have new implemented CS's algorithm in the O'Mega color factors. WHIZARD should use the result or reimplement it in Fortran (see src/omega/src/color.ml).
An algorithm using the "(i,-i)-Gluons" runs into two problems:
- it works for gl gl -> H, but requires more and more patchwork in higher orders
- it becomes homelessly inefficient, because too many new color structures must be tried out.
comment:5 Changed 14 years ago by
| Priority: | P1 → P3 |
|---|---|
| Severity: | critical → normal |
This now basically depends on ticket #20. Ranking it down.
comment:6 Changed 14 years ago by
| Owner: | changed from kilian to ohl |
|---|---|
| Status: | new → assigned |
comment:7 Changed 14 years ago by
| Severity: | normal → critical |
|---|
I take the liberty to bump this and raise the severity again as other vertices like graviton-gluon-gluon also depend on this.
comment:8 Changed 14 years ago by
| Description: | modified (diff) |
|---|---|
| Milestone: | v2.0-rc4 → v2.1 |
| Priority: | P3 → P2 |
| Summary: | H -> gg coupling and generalized color structures → Generalized color structures |
| Type: | defect → enhancement |
Since #20 is closed, the Hgg part is done and the generalized color structures can be moved to milestone:v2.1
Note: See
TracTickets for help on using
tickets.
I just discussed this with Christian and we've found the solution: introduce a set of "ghost" particles that couple only to color singlets and are counted just like the normal ghosts. Each closed loop of these ghosts receives a (-1) so that we get 9 - 1 = 8. This can be derived formally by treating the Higgs as an external field and using the gluon propagator in this external field (i.e. with Higgs insertions resummed).
This can be implemented directly in O'Mega, once the color summation is moved to O'Mega.