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!
MadGraph Tutorial
!
BSM Tutorial
Valentin Hirschi
SLAC
Olivier Mattelaer
IPPP/Durham
Exercise I: Install MadGraph 5!
•
https://launchpad.net/madgraph5
•
•
•
•
untar it (tar -xzpvf MG5_XXX.tgz)
launch it ( $ ./bin/mg5_amc)
learn it!
➡
•
use version 2.3_beta
Type tutorial and follow instructions
install external package
➡
MadGraph Tutorial.
install MadAnalysis
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MC4BSM 2015
Install
MadGraph Tutorial.
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MC4BSM 2015
Where to find help?
•
•
Ask us!
Use the command “help” / “help XXX”
➡
•
“help” tell you the next command that you need to do.
Launchpad:
https://answers.launchpad.net/madgraph5
➡ FAQ: https://answers.launchpad.net/madgraph5/+faqs
➡
MadGraph Tutorial.
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MC4BSM 2015
Download the BSM Model
•
BSM Physics from UFO Model
https://cp3.irmp.ucl.ac.be/projects/madgraph/rawattachment/wiki/MC4BSM2015/
Tutorial_MC4BSM2015.tar.gz
➡ This model is generated via FR+NLOCT and is able to
do NLO computation.
➡ Tutorial on how create this UFO model in FR can be
found online: https://cp3.irmp.ucl.ac.be/projects/
madgraph/wiki/Lund2014
➡
MadGraph Tutorial.
5
MC4BSM 2015
m1 2 m2 2 2 2
2
= 1/2@
m12 1 2 .
(1)
ar
µ 1@
1 + 1/2@µ 2 @
2
The
model
1
2
ll call mass
eigenstates 1 and 2 , and 2their
masses
M
and
M
,
respectively,
and
we will assume
2
1
2
M2 .
ates
and scalar
their masses
M.1 They
and M
and
we
will
assume
1 real
2 , and
2 , respectively,
dd
two
fields,
and
are
singlets
under
all
SM
gauge
Their
2 Their SM quantum numbers are those of thegroups.
e add two Dirac fermion fields,1 U and E.
SM uR and
eR ,mass
µ
µ
Model Description
tively. These fields have mass terms
ion fields, U and E. Their SM quantum
numbers areµ those m
of21the
SM
mu22 R 2and e2R ,
µ
2
Lkin,scalar = 1/2@µ 1 @ 1 + 1/2@µ 2 @ 2
m12 1 2 .
2
have mass terms
Ldirac,mass = MU U U + ME EE 2 1
(2)
2
ill call mass
eigenstates
, Eand
and we will a
U U + 2M
EE their masses M1 and M2 , respectively,
(2)
interact
withLscalars
via = M1U and
dirac,mass
M2 .
0
0
evia
add two Dirac
E.
Their
SM
quantum
are those of the SM
LF F S fermion
= 1 1 Ufields,
PR t + U2 and
U
P
t
+
EP
e
+
EPR e + H.c.,
(3) uR a
2
R
R
1 1
2 2 numbers
ctively. These fields have mass terms
0 electron fields.
0 Note that there is a Z2 symmetry under which all
e are the SM top-quark and
=t and
(3)
1 1 U PR t + 2 2 U PR t + 1 1 EPR e + 2 2 EPR e + H.c.,
we added ( 1,2 , U, E) flip sign, whileLall SM fields=doMnot,
so the new particles must be pair-produced
dirac,mass
U U U + ME EE
e lightest new
particle
(LNP)
is stable.
U u under
and E which
e mixing
particle
content
2 also
top-quark
and
electron
fields.
Note This
that same
thereZis
a Z2forbids
symmetry
all via Yukawas
SMsign,
Higgs.
)he
flip
while
all SM
interact
with
scalars
viafields do not, so the new particles must be pair-produced
elewill
assume
the following
ordering
of
masses:
(LNP)
is Lagrangian
stable.
This same
Z2Model
also
forbids
U u and E e mixing via Yukawas
name
0
0
LF F S = 1 1 U PRM
t + >2M2 U
P
t
+
EP
e
+
R
1
R
2 2 EPR e + H.c.,
(4)
U
2 > ME > M11 ,
lowing ordering of U
masses:
uv / uv~
1/2
2/3
e are
theThe
SMgoal
top-quark
and electron
fields.with
Note
that there
is process
a Z2 symmetry under wh
t t and
LNP.
of the tutorial
is to simulate
MadGraph
5 the
1 is the
>M
ME while
> M1 all
, SM fields do not, so the new particles
(4) must be pair-pro
we added ( 1,2 M
, U,U E)
flip
sign,
2 >
ev
/
ev~
1/2
-1
E
p pThis
! U same
U,
he lightest new particle (LNP) is stable.
Z2 also forbids U u and E e mixing(5)via Yu
ehegoal
ofHiggs.
the tutorial is to simulate with MadGraph 5 the process
SM
0
0
TeV LHC, and the subsequent
U decays p1
1
e will assume the following ordering of masses:
pp ! U U ,
(5)
subsequent U decays2
U !t
1
,
p2
Spin
charge
0
0
2 ,> M
1,
U ! t 2 , MU2 >
!M
eE
E E!>e M
1.
etmodel
forLNP.
this tutorial
is based
thetutorial
model presented
in the tutorial
of arXiv:1209.0297.
the
The
goal
of on
the
is to simulate
with
MadGraph 5
1 isused
U
!
t
,
1
6
Lagrangian
parameters,
here and below, are assumed to be real
MadGraph
Tutorial.
(6)
the process
MC4BSM 2015
(6)
Exercise I: Check the model validity
•
Check the model validity:
check p p > uv uv~
➡ check p p > ev ev~
➡ check p p > t t~ p1 p2
➡ ...
➡
•
Check with MG the width computed with FR:
generate uv > all all; output; launch
➡ generate ev > all all; output; launch
➡ generate p1 > all all; output; launch
➡ generate p2 > all all; output; launch
➡
•
•
MadGraph Tutorial.
FR Number
0.0706 GeV
0.00497 GeV
0 GeV
0.0224 GeV
Muv = 400 GeV Mev = 50 GeV λ=0.1 m1 = 1GeV m2 = 100GeV m12 = 0.5 GeV
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Beijing 2015
Exercise II:
•
Compute cross-section and distribution ➡
uv pair production with decay in top and
decay for the top)
1/
2 (semi
leptonic
The width of the new physics particles has to be set
• Hint:
correctly in the param_card. ➡
You can either use “Auto” ➡
or use the value computed in exercise 1
arXiv:1402.1178
• Hint: For sub-decay, you have to put parenthesis:
➡
example:
p p > t t~ w+, ( t > w+ b, w+ >e+ ve), (t~ > b~ w-, w- > j j), w+ > l+ vl
MadGraph Tutorial.
8
Beijing 2015
Exercise III
•
Generate the loop-induced contribution for p1 p2
pair production
➡
MadGraph Tutorial.
generate p p > p2 p2 [QCD]
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MC4BSM 2015
Exercise IV
•
Do the same for Simulating the background.
➡
•
for p1 p1 decay, the main background to consider
is •
•
Compare the distributions
p p > t t~ (with decay)
for p1 p2 decay, the main background is
•
MadGraph Tutorial.
p p > t t~ w+ w- (with decay)
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Beijing 2015
HINT: Too Slow?
•
Use MadSpin!
➡
•
arXiv:1212.3460
Use Narrow Width Approximation to factorize
production and decay
instead of ➡
p p > t t~ w+, ( t > w+ b, w+ >e+ ve), (t~ > b~ w-, w- > j j),
w+ > l+ vl
• Do
➡
p p > t t~ w+
• At the question:
• Put MadSpin on ON and at the next question edit the
madspin_card and define the decay
MadGraph Tutorial.
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Beijing 2015