talk @ MadGraph meeting at FermiLab 2011.05.06

1. Recursive relations in
MadGraph
Yoshitaro Takaesu (Sokendai, KEK)
November 2, 2016 1Y. Takaesu - Recursiverelations in MG

2. What is the Recursive Relation
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Off-shell R.R. for gluons in fixed color-order

3. Why do we use R.R. ?
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4. MG5 is Fantastic!
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from Johan’s talk
More Efficient than MG4

5. BUT still not satisfied!
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Because
For some processes, GeneratedHELAS codes
cannotbe
compiledand calculated...
Multi-partonQCD processes
Especially for

6. Why codes for
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cannot be evaluated?
# of diagrams (Function Calls)
because of

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AMPs cannot be compiled
7,000
QCD processes with

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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?
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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
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GLUON4_0.f, GLUON4_1.f, …
GLUON5_0.f, GLUON5_1.f, …
.
.
.

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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

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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. .
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15. Future works
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• Apply to processes with quarks,
qg > q ng, qq > qq ng
• Phase space integration and event generation

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