Status of MadGraph5

53 Pages·2014·5.06 MB·English

Stefano Frixione
Status of MadGraph5 aMC@NLO
ATLAS NLO MC meeting
CERN, 17/12/2014
Developers of the core code
Johan Alwall
Rikkert Frederix
Stefano Frixione
Valentin Hirschi
Fabio Maltoni
Olivier Mattelaer
Roberto Pittau
Hua-Sheng Shao
Tim Stelzer
Paolo Torrielli
Marco Zaro
I am speaking on their behalf
Other very important contributors
MadSpin Pierre Artoisenet, Robbert Rietkerk
(spin corr)
HW++, PY8, and NLO merging Andreas Papaefstathiou,
Stefan Prestel
aMCfast Valerio Bertone, Juan Rojo
(fast NLO for PDFs)
w/SusHi → Marius Wiesemann
(gg H 2HDM/MSSM)
EW corrections Davide Pagani, Stefano Carrazza
Others Benjamin Fuks, Eleni Vryonidou,
(EFT, BSM, loop-induced, ...)
Andrew Papanastasiou, Kentarou Mawatari, Cen Zhang
A significant help from the CMS MC conveners, and from
Josh Bendavid in particular
Please bear in mind that both MadGraph5 and aMC@NLO have been
superseded by:
MadGraph5 aMC@NLO
Regardless of whether one is interested in LO or NLO simulations,
one must use the latter code, not the former ones
It is a single code: switch from LO to NLO through input parameters.
1405.0301
Main reference (and many physics applications):
The basic philosophy, common to LO and NLO:
Given a Lagrangian, transform it in a set of rules (eg with FeynRules):
this is what is called a (UFO) model. MadGraph5 aMC@NLO imports
the model, and carries out computations according to its rules
The basic philosophy, common to LO and NLO:
Given a Lagrangian, transform it in a set of rules (eg with FeynRules):
this is what is called a (UFO) model. MadGraph5 aMC@NLO imports
the model, and carries out computations according to its rules
(cid:7) Models that underpin NLO computations have more information than
those restricted to LO (chiefly, the type of corrections: QCD, QED, ...).
This is what is meant by “NLO models” or “LO models”; one can
obviously perform a LO calculation using an NLO model
The basic philosophy, common to LO and NLO:
Given a Lagrangian, transform it in a set of rules (eg with FeynRules):
this is what is called a (UFO) model. MadGraph5 aMC@NLO imports
the model, and carries out computations according to its rules
(cid:7) Models that underpin NLO computations have more information than
those restricted to LO (chiefly, the type of corrections: QCD, QED, ...).
This is what is meant by “NLO models” or “LO models”; one can
obviously perform a LO calculation using an NLO model
(cid:7) Such NLO-specific information used to be computed by hand.
This is fine with the SM, but untenable beyond that.
New in 2014
: now automated (NLOCT: Degrande, 1406.3030)
(more on this later)
In practice:
> ./bin/mg5 aMC
MG5 aMC> generate p p > t t~ h [QCD]
MG5 aMC> output MY TTH DIR
MG5 aMC> launch
An NLO model is imported automatically, which corresponds to QCD
¯
corrections to SM processes, as in this example relevant to ttH production
−→
Alternatively
For EW corrections:
> ./bin/mg5 aMC
MG5 aMC> import model loop qcd qed SM
MG5 aMC> generate p p > t t~ h [QED]
MG5 aMC> output MY TTH DIR QED
MG5 aMC> launch
One may push the code rather far. For example:
102 109
VVVV production at pp colliders at NLO in QCD Multiple Z production at pp colliders at NLO in QCD
108
101
107
[fb]O 100 [fb]O
L L
N N
!
(cid:0) O 106 O
L L
N N
pp WWW (4FS) @ @
(cid:2) (cid:3) C C
10-1 pppp (cid:2) WWWWWWZW 4 (F4SFS)) _aM pppp ## ZZZ (x103) _aM
pppp (cid:2)(cid:2) WWWZZZZZ (4FS) raph5 105 pppp ## ZZZZZZ Z( x(1x0150)7) raph5
pp (cid:2) ZZZZ dG pp # ZZZZZ (x109) dG
10-2 (cid:2) Ma Ma
104
8 13 14 25 33 50 75 100 8 13 14 25 33 50 75 100
s[TeV] "s[TeV]
(cid:1)
SM at NLO: thickness of lines is scale+PDF uncertainties
arXiv:1407.1623 [hep-ph]
(Paolo Torrielli)