qcd multi-jet calculation on madgraph
TRANSCRIPT
QCD mul(-‐jet calcula(on on MadGraph
Yoshitaro Takaesu (Sokendai) In collabora7on with K. Hagiwara (KEK)
May 10, 2011 1 Y.Takaesu -‐ PHENO 2011
What is MadGraph?
テキスト
2
Automa7c Amplitude Generator
Input
Output
Model + process
Diagram HELAS Code
MG
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MG is very useful and popular
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BUT …
Current Limits of MG Generated Codes > 8MB cannot be compiled.
8 MB
100
101
102
103
104
105
2 3 4 5 6
log 10
File
Siz
e (K
B)
# of Final State Particles
gg > ngug > ug nguu > uu ng
gg → 5gqg → q5gqq → qq4g
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The file size of codes for QCD processes
What makes the codes to be
LARGE ?
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The structure of the code
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Color Matrix
Dual Amp. M =
�
i
CiAi
Color Factor dual amp. ex) Tr[T aT bT cT d]
The size of Color Matrix and Dual Amps get Large as # of final par7cles grows.
�
color
|M|2 =�
ij
Ai(�
color
CiC∗j )A∗
j
Overcome the limit
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Dual Amp.
Color Matrix
Overcome the limit
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Dual Amp.
Remove Color Matrix Calculate it on the fly
Overcome the limit
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Divide the subrou7ne part into small pieces (1 Source file for 1 Dual Amp)
Remove Color Matrix Calculate it on the fly
Overcome the limit
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Divide the subrou7ne part into small pieces (1 Source file for 1 Dual Amp)
Remove Color Matrix Calculate it on the fly
Compile those files
Making the new Code • Modified MG to generate small codes for each Dual Amp.
• Implemented the subrou7ne which calculate the color matrix from the informa7on of Dual Amps
• Evaluated by using those codes and the subrou7ne
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�
color
|M|2
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Example: gg -‐> ng
Codes can be compiled and evaluated.
Run7me of the Code
Preliminary
0.01
0.1
1
10
100
1000
10000
100000
2 3 4 5 6 7
log 10
Run
Tim
e (s
)
# of Final State Particles
gg > ng
gg → 5ggg → 6ggg → 7g ( OK but slow..)
Conclusion • Generated Codes by MG for mul7-‐parton QCD process cannot be compiled for > 5 final states processes.
• Proposed a way to overcome the limita7on by dividing and reducing a code into small files.
• Calculated mul7-‐gluon processes (> 5g)
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Future works
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• Apply our method to processes with quarks: qg > q ng, qq > qq ng
• Phase space integra7on and event genera7on
• Speed up by using GPU
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