talk @ kiasph 2013.11.11
TRANSCRIPT
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Yoshitaro TakaesuKIAS/KNRC
Generating multi-gluon events with the color-flow decomposition and optimized phase space integration
In collaboration with J. Alwal, K. Hagiwara (KEK), F. Maltoni (UCL)and T. Stelzer (UIU)
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Introduction
2
• Accurate simulation of multi-jet events based on Matrix-Elementcalculations would become more important at the upgraded LHC.
Flexible multi-jet event generator is desired which can deal with SM and many possibilities of New Physics in the same footing.
MadGraph5 + multi-jet (> 4 jets)
• Production & Decay of more massive particles• Harder & more ISRs• Spin-correlations of pair-produced particles• Sub structure of broad jets
New Physics signal multi-jet SM BG&AlpgenHelacSherpa
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Problems in multi-jet generation
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2. Heavy Color Summation
3. Huge # of integration channels
1. Huge # of diagrams
Channel Optimization
Color-Flow decomposition (1/Nc expansion)
Off-shell recursive relationsF.A.Berens, W.T.Giele, NPB306 (1988)Y.T, K.Hagiwara, EPJC71:1668 (2011), J.Alwal
for MG
F. Maltoni et.al., PRD67 (2003)
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2. Heavy Color Summation
4February 11, 2016
Color flow
Color Factorcolor-ordered amp.
i: Color flow
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February 11, 20165
1/Nc expansion
Polynomial of Nc:
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February 11, 20166
@ 100 phase space points
@ 100 phase space points
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February 11, 20167
@ 106 phase space points
@ 61 phase space points
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Problems in multi-jet generation
8
2. Heavy Color Summation
3. Huge # of integration channels
1. Huge # of diagrams
Channel Optimization
Color-Flow decomposition (1/Nc expansion)
Off-shell recursive relationsF.A.Berens, W.T.Giele, NPB306 (1988)Y.T, K.Hagiwara, EPJC71:1668 (2011), J.Alwal
for MG
F. Maltoni et.al., PRD67 (2003)
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3. Huge # of integration channels
i_th Channel
Channel Optimization
Convergence
# of Channels (~10,000 channels for gg > 6g)
~ 100 channels for gg > 6g
represent singularitiesF.Maltoni, T.Stelzer JHEP0302:027(2003)
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ResultsLeading Colorgluon scattering process
as the first step
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Cross section
11
Agrees with MG LC
Error of LC Approx. is just what is expected
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Distributions: gg -> 4g
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Good agreement with MG LC results
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Distributions: gg -> 5g
13
Failed
Bad example
Passes self-consistency checks
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Distributions: gg -> 6g
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LC ch WgtedLC ch Unwgted
LC ch WgtedLC ch Unwgted
LC ch WgtedLC ch Unwgted
LC ch WgtedLC ch Unwgted
LC ch WgtedLC ch Unwgted
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Time measurement (preliminary)
15
Our reduced channeling seems not to sacrifice the computationaltime significantly. (need more study on gg>6g ?)
100,000 events with 1 core CPU or ~ 100 core cluster (KEKCC)
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Summary & Outlook
16
• It is shown that gg > 6g events can be generated at Leading Color Order, using recursive amps and peripheral channeling.
• Inclusion of NLC and quark subprocesses are next step.
aMC@NLO with many jets
Tree, LC
NLCquark subprocesses
multi-jetMG5
New Physics with many jets