Recursive relations in MadGraph
0 likes133 views
This document discusses the use of recursive relations in MadGraph to more efficiently calculate multi-parton QCD processes. Recursive relations reduce the number of amplitude terms that must be calculated by relating higher-point terms to sums of lower-point terms. The author implemented off-shell recursive relation subroutines in the HELAS library to allow MadGraph to calculate processes with 5 or more gluons in the final state. Future work includes applying these techniques to processes with quarks and performing phase space integration and event generation.
Recursive relations in MadGraph
- 1. Recursive relations in MadGraph Yoshitaro Takaesu (Sokendai, KEK) November 2, 2016 1Y. Takaesu - Recursiverelations in MG
- 2. What is the Recursive Relation November 2, 2016 Y. Takaesu - Recursiverelations in MG 2 Off-shell R.R. for gluons in fixed color-order
- 3. Why do we use R.R. ? November 2, 2016 Y. Takaesu - Recursiverelations in MG 3
- 4. MG5 is Fantastic! November 2, 2016 Y. Takaesu - Recursiverelations in MG 4 from Johan’s talk More Efficient than MG4
- 5. BUT still not satisfied! November 2, 2016 Y. Takaesu - Recursiverelations in MG 5 Because For some processes, GeneratedHELAS codes cannotbe compiledand calculated... Multi-partonQCD processes Especially for
- 6. Why codes for November 2, 2016 Y. Takaesu - Recursiverelations in MG 6 cannot be evaluated? # of diagrams (Function Calls) because of
- 7. November 2, 2016 Y. Takaesu - Recursiverelations in MG 7 AMPs cannot be compiled 7,000 QCD processes with
- 8. November 2, 2016 Y. Takaesu - Recursiverelations in MG 8 matrix.f gg > ng Rearrangementof diagrams (AMPs) into JAMPs takes large amount of compilationtime for many AMPs. JAMPHELAS (AMP)
- 9. How can we go further? November 2, 2016 Y. Takaesu - Recursiverelations in MG 9 from Johan’s talk
- 10. November 2, 2016 Y. Takaesu - Recursiverelations in MG 10 Recursive relation for gluonic subamp. Reduce the # of diagrams (AMPs)
- 11. We added n-point off-shell R.R. subroutines to HELAS Library November 2, 2016 Y. Takaesu - Recursiverelations in MG 11 GLUON4_0.f, GLUON4_1.f, … GLUON5_0.f, GLUON5_1.f, … . . .
- 12. November 2, 2016 Y. Takaesu - Recursiverelations in MG 12 We also forbid gluon propagator between multi- gluon vertices to avoid double counting. is also made by For example, 4-point R.R. current contains 2×(3-point R.R. currents). Double counting
- 13. November 2, 2016 Y. Takaesu - Recursiverelations in MG 13 Using those off-shell R.R. subroutines, We calculateJAMPs. ( OK but slow..)
- 14. Conclusion • Generated Codes by MG5 for multi-parton QCD process cannot be compiled for more than 5 final states processes. • Off-shell recursive relations helps us to reduce the # of AMPs and the size of the codes. • We proposed a way to calculate gg > 5g, 6g, 7g processes by making use of the R.R. . November 2, 2016 Y. Takaesu - Recursiverelations in MG 14
- 15. Future works November 2, 2016 Y. Takaesu - Recursiverelations in MG 15 • Apply to processes with quarks, qg > q ng, qq > qq ng • Phase space integration and event generation
- 16. November 2, 2016 Y. Takaesu - Recursiverelations in MG 16