SUPERSYMMETRY

SUPERSYMMETRY
Searches&at&hadron&colliders
Lecture'20
Shahram&Rahatlou
Fisica&delle&Par,celle&Elementari,&Anno&Accademico&201382014
http://www.roma1.infn.it/people/rahatlou/particelle/
UNDISCOVERED&MSSM&ZOOLOGY
The undiscovered particles in the MSSM:
Names
Spin
PR
Mass Eigenstates
Gauge Eigenstates
Higgs bosons
0
+1
Hu0 Hd0 Hu+ Hd−
−1
h0 H 0 A0 H ±
u
!L u
!R d!L d!R
“”
−1
e!L e!R ν!e
squarks
sleptons
0
0
neutralinos
1/2
−1
charginos
1/2
−1
gluino
1/2
−1
s!L s!R !
cL !
cR
!
t1 !
t2 !b1 !b2
µ
!L µ
!R ν!µ
τ!1 τ!2 ν!τ
!1 N
!2 N
!3 N
!4
N
!± C
!±
C
1
2
g!
“”
“”
!
tL !
tR !bL !bR
“”
τ!L τ!R ν!τ
!0 W
"0 H
! u0 H
!0
B
d
"± H
! u+ H
!−
W
d
“”
32
Shahram Rahatlou, Roma Sapienza & INFN
39
ℓ!i
γ, Z
γ, Z
q
q
Z
u
ν!
ℓ!i
W
W+
SUSY&PRODUCTION&VIA&QCD
Z
q
ℓ!−
ν!ℓ
d
ν!∗
j !−
∗
q
q
ℓj
ν!ℓ
d
ν!
∗
q
q
!
ℓ!−
ν
d
!
ν
ℓ
j
Figure 9.1: Feynman diagrams
for electroweak production of sparticles at hadron colliders from quarkFigure 9.1:
Feynman diagrams
for electroweak
production
of t-channel
sparticles diagrams
at hadrononly
colliders
from
quarkantiquark
annihilation.
The charginos
and neutralinos
in the
couple
because
Figure
9.1:
Feynman
diagrams
for
electroweak
production
of
sparticles
at
hadron
colliders
from
quarkannihilation.
The
charginos
and neutralinos
only superimposed
couple because
ofantiquark
their gaugino
content, for
massless
initial-state
quarks, in
andthe
so t-channel
are drawndiagrams
as wavy lines
antiquark
annihilation.
The
charginos
and
neutralinos
in
the
t-channel
diagrams
only
couple
because
their gaugino content, for massless initial-state quarks, and so are drawn as wavy lines superimposed
onofsolid.
ofon
their
gaugino content, for massless initial-state
quarks, and so are
g! drawn as
g!
q
q wavy lines superimposed
solid.
g
on solid.
q!
SUSY particles are produced in pairs (because of R-parity).
q
Production via QCD generally dominates, even though squarks
and gluinos are typically heavy:
q
g
g
g
Gluino pairs
g
g
Squark pairs
g
g
g
g
g
g
g
g
g!
g
g
g
g
g!
g
q!
q!
g!
g!
q!
g
g!
g!
g
g
g
g
g
q!∗
q!∗
∗
q!
g
g
q!
q!
g
q!
g!
g!
q
g!
q!
q!
q
q!
q!∗
q!∗
∗
q!
g
qg
g
g
g
gq
g!
g!
g!
g!
g
g!
g
g
g
q
g
etc. g
g!
q!g!
g!
g
q!
q!
g!q!
q!
q!
q!∗
q! q!
g!
g
g
g
q
g!
q
g!
q
g!
g!
etc.
g
q!∗
∗
g
q! q!
∗
g
q!
q
g!
g!
g!
q!
q!
g!
q!
g!
q!∗
q!∗
∗
q!
q!
q! at ha
Figure
9.3: Feynman diagrams
for gluino
and squark production
g
g
q!
q!quark-quark
q!
q
g
g
g scattering.
antiquark
annihilation
and
!
!
!
!
!
q
g
q
q
q
g
g
q
g
q!
g!
q
q
q
!
!
q
g
q
g!
g!
! +C
! − and g!C
!1 N
!2 channels,
q
q
belong
to
the
C
because
they
have
significant
q
!
g
g!
1 1
g!
q
q
q
!
!
g
g!
respectively,
andproduction
becausegof kinematics.
At the LHC,
situation
is ty
Figure 9.2: Feynman diagrams for gluino
and squark
at hadron colliders
from the
gluon-gluon
of gluinos
squarks
by gluon-gluon
and
gluon-quark
fusion usually d
Figure
9.2: Feynman
and and
squark
production
at hadron
colliders
from gluon-gluon
and
gluon-quark
fusion.diagrams for gluino
Figure
9.2: Feynman
diagrams for gluino
and are
squark
production
at hadron
gluon-gluon
squarks
heavier
than 1 TeV
or so. colliders
At both from
colliders,
one can also
and gluon-quark
fusion.
and gluon-quark fusion.
chargino or neutralino together with a squark or gluino, but most mod
(of mixed electroweak and QCD strength) are much lower than for the
88 in (9.2) may be rather small at the Tevatron, but mig
production as
88
LHC [210]. Cross-sections
for sparticle production at hadron collider
88
have been incorporated in computer programs including [186],[212]-[2
The decays of the produced sparticles result in final states with tw
Heather Logan (Carleton U.)
SUSY
(3/4)
HCPSS 2010
the detector. The LSPs carry away at least 2mN! of missing ener
1
the component of the missing energy that is manifest in momenta t
15
(denoted E
/ T ) is observable. So, in general the observable signals for su
are n leptons + m jets + E
/ T , where either n or m might be 0. Ther
Shahram Rahatlou, Roma Sapienza & INFN
40
backgrounds to many of these signals, especially from processes
inv
Squark + gluino
g
q!
g
g
g
g!
etc.
LHC reach depends on mass spectrum.
Reach for gluinos & squarks is typically out to about 2 TeV.
• QCD production dominates but given heavy mass for SUSY, cross
section strongly depends on squark and gluino masses
Superparticle production at hadron colliders
SUSY
&PRODUCTION&VIA&ELECTROWEAK
Production via electroweak interactions is also possible.
q
C!i+
C!i+
u
C!i+
d
γ, Z
q
C!i+
C!i+
u
C!i+
!
d
!
u
d
L
L
γ, Z
+
+
+
q
C!−
C!−
u
C!−
d
!
i
i
!
i
u
dL
L
γ, Z
qq
C!C!j +
C!C!j +
C!C!j +
uu
dd
!
i
!L
i
u
dL
−
−i
!
!
γ, Z
q
C!j−
C
C
u
d
j
j
!
!L
u
d
−
−
L
!
!
!
q
Cj
Cj
Cj−
u
d
!!ij−
!!ij−
!!ij−
C
C
C
qq
qu
qd
N
N
N
Z
!i
!i
!i
q
q
q
N
N
N
q!L,R
q!L,R
Z
!i
!i
!i
q
q
q
N
N
N
!
!
q
q
L,R
L,R
!!j
!!j
!!j
qq
Z
qq
qq
N
N
N
Ni
Ni
Ni
!L,R
!L,R
q
q
!
!
!
Z
q
q
q
Nj
Nj
Nj
!L,R
!L,R
q
q
!j
!j
!j
q
q
q
N
N
N
+
+
!+j
!
!
!N
q
q
C!N
C!N
uq
u
u
C
j
j
i
i
i
+
+
+
W
C!i
C!i
u
u
u
C!i+
!
!L
u
d
+
L
W
!+
C!i+
C!i+
u
u
u
C
!
!
i
u
dL
L
!!j+
!!j+
!!j+
W+
du
N
N
N
d
d
C
C
u
u
C
!
i
i
!L
u
dL
!ji
!j
!j
W+
d
N
N
N
d
d
!L
u
d!L
!
!j
!j
d
Nj
N
N
d
d
+
+
!j
!j
qd
qd
ud
!!j
ℓ!N
ℓ!N
νN
i
i
+
γ, Z
Z
W
!+
q
q
u
ℓ!+
ℓ
ν!
i
i
+
γ, Z
Z
+
W
!
!
q
q
u
ℓ−i
ℓ+
ν!
i
+
qq
qq
γ, Z
Z
W
ℓ!ℓ!j+
ν!ℓ!ℓ+
du
ν!∗ν!
i
i
γ, Z
q
q
Z
W+
ℓ!−
ν!ℓ
d
ν!∗
j
q
q
Figure
9.1: Feynman diagrams
for electroweak
production of sparticles
at dhadron colliders from quarkℓ!−
ν!ℓ
ν!∗
j
−
!
q
qand neutralinos
ν!ℓ
antiquark
Theℓjcharginos
in the
t-channel
only couple
dhadron colliders
Figure
9.1:annihilation.
Feynman diagrams
for electroweak
production
of sparticles
atdiagrams
frombecause
quarkν!∗
Figure
Feynman
diagrams
for electroweak
production
of sparticles
atdiagrams
hadron
frombecause
quarkof
their 9.1:
gaugino
content,
for massless
initial-state
quarks,inand
so
are drawn
as wavycolliders
linescouple
superimposed
antiquark
annihilation.
The
charginos
and neutralinos
the
t-channel
only
Figure
9.1:annihilation.
Feynman
diagrams
for electroweak
production
of so
sparticles
at
hadron
frombecause
quarkantiquark
The
charginos
and neutralinos
the
t-channel
diagrams
only
on
solid.gaugino
of
their
content,
for massless
initial-state
quarks,inand
are drawn
as wavycolliders
linescouple
superimposed
antiquark
annihilation.
charginos
and neutralinos
thesot-channel
diagrams
because
of
their
content, The
for massless
initial-state
quarks,inand
are drawn
as wavyonly
linescouple
superimposed
on
solid.gaugino
of their
on
solid.gaugino content, for massless initial-state quarks, and so are drawn as wavy lines superimposed
on solid.
g!
g!
g!
g
g
g
g
g!
g!
g!
g
g
g
g!
g!
g
g!
g!
g!
g
g
g
!
g!
g
g
g
gg
gg
g!g!
g!g!
g!g!
g
Heather Logan (Carleton gU.)
SUSY
(3/4)
HCPSS
2010
!
!
g
g
g
g
Shahram Rahatlou, Roma Sapienza & INFN
g
g!
g!41
g!
Chargino pairs
etc.
Neutralino pairs
Chargino +
neutralino
Slepton pairs
Rates are smaller than for colored particles because production
cross sections involve EW couplings.
• Smaller cross section since EW coupling is smaller compared to
QCD
34
SUSY&CROSS&SECTION
Prospino2.1
SUSY
9
10
9
8
10
10
S = 7 TeV
8
10
1
!tot
7
10
10
q̃g̃
-1
q̃q̃
-2
*
100
200
300
400
500
10
600
2
10
700
800
900
maverage [GeV]
10
pp
g̃g̃, q̃q̃,
t̃1t̃1, ˜ o2 ˜ +1,
˜ ˜,
˜ o1g̃,
˜ +1q̃
3
!jet(ET
0
!jet(ET
jet
-4
10
200
-7
m [GeV]
Shahram Rahatlou, Roma Sapienza & INFN
300
350
400
450
0
-1
500
10
-3
10
!t
!jet(ET
jet
> "s/4)
-4
10
!Higgs(MH=120 GeV)
-5
10
200 GeV
10
˜ o1g̃
250
10
-2
-6
g̃g̃
150
!Z
10
-2
100
10
10
-3
-5
-3
1
!W
> 100 GeV)
10
q̃q̃
˜ +1q̃
2
10
-2
10
˜˜
> "s/20)
10
t̃1t̃1
˜ o2 ˜ +1
jet
1
10
NLO
LO
-1
4
10
10
10
-1
S = 2 TeV
1
10
!b
10
tot[pb]:
10
5
3
http://www.thphys.uni-heidelberg.de/~plehn/prospino/
10
5
10
! (nb)
10
6
4
˜ o2q̃LO
˜ e ˜e*
-3
10
10
˜ o2g̃
7
10
6
10
g̃g̃
t̃1t̃1*
LHC
10
q̃q̃
˜ o2 ˜ +1
10
Tevatron
WJS2009
0.1
-2 -1
pp
33
tot[pb]:
proton - (anti)proton cross sections
events / sec for L = 10 cm s
10
-6
10
500 GeV
-7
1
10
10
"s (TeV)
42
SUSY
&MASS&SPECTRUM
re is the resulting sparticle mass spectrum:
phenomenology depends on whether
mq̃ < mg̃ or mq̃ > mg̃
g̃
d˜L ,ũL
t̃2
b̃2
ũR ,d˜R
H
±
b̃1
˜44
Ñ
H 0 ,A0
Ñ
˜33
C̃2
Lightest squark
t̃1
Mass
Mass gaps between
other 4 Higgses
˜2
h
Ñ2
0
Lightest Higgs
similar to SM Higgs
˜Ñ11
C̃1
ẽL
τ̃2
ν̃e
ν̃τ
ẽR
τ̃1
Lightest slepton
Typical LSP candidates in several SUSY models
Shahram Rahatlou, Roma Sapienza & INFN
43
Sfermion decays: two possibilities: gauge interactions and Yukawa interactions
SPARTICLE&COUPLINGS
Yukawa interactions proportional to m2 of corresponding fermions: only relevant for third generation
For gauge interactions same couplings as corresponding SM vertexes:
qL
qL
qL(R)
qL′
qL(R)
qL
2gT 3
2g tan
g
Sparticle decays
W±
⇥
B
⇥
⇥3
W
WY
0
Cascade decays: decay
to
⇤
˜
kinematically favoured, but BR defined by neutralino
1 always
Sfermion decays:
two possibilities: gauge interactions and Yukawa interactions
composition and couplings,
decays proportional
into heavierto gauginos
may dominate.
Yukawa interactions
m2 of corresponding
fermions: only relevant for third generation
• Feynman rules: take any SM diagram and change R-parity of two
lines
For gauge interactions
samescouplings
as otherwise
corresponding
SM vertexes:
beacuse of
If q̃ ⌅ g̃q open: dominates
coupling,
weak
decays into gauginos
– Must conserve R-parity!
qL
Case: mZ ⇤ M1 < M2 < µmZ ; gaugino composition:
qL′
⇤˜01 ⇥ B,
⇥3
⇤˜01 ⇥ W
,
qL(R)
⇥±
⇤˜±
1 ⇥W
• Coupling constant
strength: typically
similar to SM 0to make sure
0
± ⇧
BR(q̃L ⌅ ⇤˜2q) = 30% BR(q̃L ⌅ ⇤˜1 q ) = 60% BR(q̃R ⌅ ⇤˜ q) = 100%
hierarchy problem is cured
qL
qL(R)
qL
2gT 3
2g tan
g
WY
• Yukawa interaction: coupling proportional to m2 of corresponding
Cascade decays: decay to ⇤˜ always kinematically favoured, but BR defined by neutralino
fermion
0
1
⇥
B
⇥±
W
⇥3
W
composition and couplings, decays into heavier gauginos may dominate.
– significant only
for third generationcoupling, otherwise weak decays into gauginos
If q̃ ⌅ g̃q open: dominates beacuse of
s
⇤˜ ⇥ B,
Case: m ⇤ M
< M <coupling
µm ; gaugino composition:
• Gauge interaction:
same
as in SM
Z
1
2
Z
BR(q̃L ⌅ ⇤˜02q) = 30%
Shahram Rahatlou, Roma Sapienza & INFN
0
1
⇧
BR(q̃L ⌅ ⇤˜±
1 q ) = 60%
⇥3
⇤˜01 ⇥ W
,
⇥±
⇤˜±
1 ⇥W
BR(q̃R ⌅ ⇤˜0q) = 100%
44
SPARTICLE&DECAYS
• mass difference between squarks and gluinos
Superparticle kinematically
decays
determines
allowed decays
Gluino decays: always to q q̃.
If Mg < Mq , then gluino will decay via an off-shell squark:
±
˜i
3-body decays, g ⇥ q q ⇥ qq̄ N
˜0i or qq̄ ⇤C
Squark decays:
To q g̃ (strong coupling) if kinematically allowed.
0
⇥
˜⇥
˜± or (for 3rd gen.) q H.
Otherwise q N
or q C
Decay branching fractions controlled by squark and -ino compositions.
±
0
⇥
˜
˜
Slepton decays: to ⇥ N or ⇥ C
(⇥ = ⇥± or
as appropriate)
Neutralino and chargino decays: to ⇥ ⇥˜ or q q̃,
or to gauge or Higgs boson + lighter neutral-/charg-ino
Typically get decay chains, which always end with the LSP.
q
q
Shahram Rahatlou, Roma Sapienza & INFN
q
q
f
f
45
SUSY&DECAY&CASCADECascade decays
Chains can be very
long.because
Extreme example,
if mass
• cascade decays through intermediate
states
of heavy
of SUSY particles
mg̃ > mq̃ > m ˜04 > m⌥˜L > m ˜02 > m⌥˜R :
• mass spectrum changes for
different breaking mechanism
• Exact chains must be determined
from measurements
g̃
|
⇤ q̃L q
|
⇤ ˜04 q
| ˜± ⇥
⇤ ⌥L ⌥
|
⇤ ˜02 ⌥±
| ˜± ⇥
⇤ ⌥R ⌥
|
⇤ ˜01 ⌥±
Final state from this leg includes 4 charged leptons, two je
• Often final states with at least 2 jets and 2 or more leptons
More typical
for the same
chain would involve 4 succ
– such final states suppressed
incase
Standard
Model
with can
four visible
particles inbut
final unlikely
state: 2 jets
two lepto
fake leptons
to+have
‣reconstruction effects
many real leptons produced in decay chains
Shahram Rahatlou, Roma Sapienza & INFN
46
EXPERIMENTAL&SIGNATURE&OF&SUSY
Jets of
~100’s GeV
jets
jets
Missing Energy
of 100’s GeV
Shahram Rahatlou, Roma Sapienza & INFN
Main Backgrounds:
ttbar
Z/W+jets
Z(νν)+jets
QCD
0,1,2
Leptons
of ~10’s GeV
47
GLUINO&DECAY&CHAIN
• Multiple decay paths leading to several leptons in final state
– peaks in invariant mass + multiple jets + large missing energy
Shahram Rahatlou, Roma Sapienza & INFN
48
EXPERIMENTAL&CHALLENGES
• Missing transverse energy (MET) measurement
– correct for instrumental effects and reduce tails
– verify correct MET resolution and tail description with known control
samples
‣ Electroweak events: small missing energy
‣ di-jet and QCD events: no intrinsic MET only instrumental effects
• Background estimation
– after kinematic requirements typically remain with
‣ t-tbar
‣ W/Z + jets
‣ WW and ZZ production
– Cross sections sometimes known at 5-10% level
‣ directly affects exclusion limits and discovery potential
– background kinematics also affected by PDF uncertainties
Shahram Rahatlou, Roma Sapienza & INFN
49
MISSINGTRANSVERSE&ENERGY
• D0 experiments in early part of Run II
– Lots of new physics caused by instrumental effects!
Shahram Rahatlou, Roma Sapienza & INFN
50
REAL&AND&FBkg
AKE&MET
&
B
ACKGROUND
To Fight
mismeasured jet
QCD with fake MET
related to pathological events
require understanding of rare
detector-related effects
_
Fake MET
ν
mismeasured jet
MET
SM processes with real MET, e.g. Z(νν)+jets
measurable from control samples defined
on data
ν
Wednesday, November 16, 11
Shahram Rahatlou, Roma Sapienza & INFN
51
MET&AT&LHC&AFTER&3&MONTHS!
1
1
0
10 20 30 40 50 60 70 80 90 100
0
Calo ΣET [GeV]
Calo ET [GeV]
106
Data
105
Simulation
104
(b) calo ET distribution
Number of Events / GeV
Number of Events / GeV
/ T distribution
(a) caloE
CMS Preliminary 2010
s=7 TeV
106
CMS Preliminary 2010
s=7 TeV
Data
5
10
Simulation
104
103
103
102
102
10
10
1
1
0
50 100 150 200 250 300 350 400 450 500
10 20 30 40 50 60 70 80 90 100
Tc ET [GeV]
0
10 20 30 40 50 60 70 80 90 100
Pf ET [GeV]
/ T distribution
/ T distribution
(c) tcE
(d) pfE
• Excellent understanding
of bulk and tails after
few
weeks of
operation
/ T (caloE
/ T ), calo ET , track-corrected E
/ T (tcE
/ T ), and particle-fl
Figure 3: calorimeter E
Very
promising for
SUSY
and Newdata
Physics
searches
already
/ T• (pfE
/ T ) distributions
E
in the
minimum-bias
compared
with Monte
Carlowith
simulation
50 pb-1
/ T ev
In addition to the event with anomalous HF signals mentioned above, the highest pfE
Shahram Rahatlou, Roma Sapienza & INFN
52
MET&AT&LHC&IN&2012
Shahram Rahatlou, Roma Sapienza & INFN
53
SPONTANEOUS&SUSY&BREAKING?
• Soft SUSY breaking in MSSM added explicitly to address our
original problems: hierarchy and naturalness
• Price to pay: > 100 free parameters to achieve SUSY breaking
• Strong constraints on SUSY breaking masses from precision
measurements and flavor violation
– SUSY breaking mass must be very heavy OR
– they must be insensitive to flavor since flavor violation highly constrained
from measurements
– reduce to 15 SUSY breaking parameters in addition to SM parameters
• Preferred solution would be to have spontaneous SUSY breaking
– and less parameters to measure
Shahram Rahatlou, Roma Sapienza & INFN
54
MESSENGERS&OF&DARK&SECTOR
The MSSM soft SUSY-breaking terms arise indirectly or radiatively, not from
tree-level renormalizable
couplings
directly to the terms
SUSY-breaking
sector.
The MSSM
soft SUSY-breaking
arise indirectly
or radia
tree-level renormalizable couplings directly to the SUSY-brea
Supersymmetry
breaking origin
(Hidden sector)
Flavor-blind
MSSM
sector)
Supersymmetry (Visible
Flavor-blind
interactions
breaking origin
(Hidden sector)
interactions
MSSM
(Visible sector)
breaking requires
occurs innon-vanishing
a “hidden sector”
of particles
with value
no
• Spontaneous
Spontaneous SUSY
SUSY breaking
vacuum
expectation
SUSY breaking occurs in a “hidden sector” of partic
(VEV)
forcouplings
some FSpontaneous
field
(or
tiny)<F>
direct
to the “visible
sector” chiral supermultiplets of the MSSM.
(or tiny) direct couplings to the “visible sector” chiral supermultiple
• However,
Add newthe
hidden
sector of
with mediating
non-zero <F>
two sectors
doparticles
share some
interactions that transmit
However, the two sectors do share some mediating interactions th
• SUSY-breaking
Small or no coupling
this sector
visible sector
of chiral multiplets
effectsofindirectly.
Asto
a bonus,
if the mediating
interactions are
SUSY-breaking effects indirectly. As a bonus, if the mediating inter
• flavor-blind,
Interaction then
of hidden
andSUSY-breaking
visible sectors terms
through
messenger
particles
the soft
of new
the MSSM
will be
also.
flavor-blind, then the soft SUSY-breaking terms of the MSSM will b
– flavor-blind interaction required by experimental constraints on flavor violation
Mediation between
visible
and hidden
sector occurs at certain scale M
By– dimensional
analysis,
By dimensional
analysis,
• soft breaking mass in visible sector generated
⟨F ⟩
through interaction with messengers
msoft ∼
msoft
⟨F ⟩
∼
M
M
– no SUSY breaking for <F> --> 0
where
is alarge
mass
associated
the physics
that mediat
– no SUSY
when
MM
is too
where
M is breaking
a mass scale
associated
withscale
the physics
thatwith
mediates
between
the
two sectors.
Shahram Rahatlou, Roma Sapienza & INFN
two sectors.
55
SUSY&BREAKING&STRUCTURE
performed through renormalisation group equations:
SUSY breaking structure
SUSY breaking communicated to visible sector at some high scale
running of different masses as a function of the gaugem quantum
numbers
, m , A , tan , sgn µ (mSUGRA)
0
1/2
0
rticles: splitting at the EW scale
Evolve down to EW scale through Renormalization Group Equations (RGE)
M1, M2, M3, m(f˜R ), m(f˜L), At, Ab, A⇤ , m(A), tan , µ
From ’soft’ terms derive mass eigenstates and sparticle couplings.
m(⌅˜0j ), m(⌅˜±
j ), m(q̃R ), m(q̃L ), m(b̃1 ), m(b̃2 ), m(t̃1 ), m(t̃2 )......
~
q
Structure enshrined in Monte Carlo generators (e.g ISAJET)
~
l
Task of experimental SUSY searches is to go up the chain, i.e. to measure enough
sparticles and branching ratios to infer information on the SUSY breaking
H
~
g
H
mechanism
two parameters determining
the mass of all scalars and
fermions: m0 and m1/2
ATLAS
~
W
~
B
Shahram Rahatlou, Roma Sapienza & INFN
ATLAS
56
mSUGRA&(MSSM&WITH&SUPERGRAVITY)
msoft
⟨F ⟩
∼
MP
This follows from dimensional analysis, since msoft must vanish in the limit that
SUSY breaking is turned off (⟨F ⟩
→ 0) and in the limit that gravity becomes
• Minimal model
gravity
irrelevantwith
(MP →
∞). as messenger of SUSY breaking at
GUT scaleSince we know msoft ∼ few hundred GeV, and MP ∼ 2.4 × 1018 GeV:
• Gravity
!
11 assumes
12 a “minimal” form for the kinetic
A dramatic simplification ⟨F
occurs
if10one
⟩
∼
or
10
GeV a “minimal”
A dramatic
simplification
becomes
relevant
onlyoccurs
nearif one
theassumes
Planck
scale form for the kinetic
A dramatic simplification occurs if one assumes a “minimal” form for the kinetic
(Whether
this this
terms and
gauge
interactions
in the in
underlying
supergravity
theory.
(Whether
terms
and gauge
interactions
the underlying
supergravity
theory.
terms and gauge interactions in the underlying supergravity theory. (Whether this
12 GeV
is reasonable
or not
remains
controversial.)
is
reasonable
or
not
remains
controversial.)
fewassumption
hundred
GeV
➞
<F>
∼
10
• For msoft ∼assumption
assumption is reasonable or not remains controversial.)
j
j
•
a
jj
45
This means
f
= ffafor
gauge
interactions,
ki =kkδ
fields,
andand
a all
This means
=
f for
all gauge
interactions,
=i for
kδ jjallforscalar
all scalar
fields,
This means f
= f for all gauge interactions, kii = kδii for all scalar fields, and
ijk generate
ijk
ij
ij
ijk
ij ijsoft
ij
mSUGRA αcan
MSSM
term
with
only
=αijk
αy
and
β
=
βM
.
Then
all
of all
the
MSSM
soft
terms
can can
be 5be
ijk
ijk
ij
=
αy
and
β
=
βM
. .Then
the
soft
can
befree
α = αy and β = βMbreaking
Then
allofof
theMSSM
MSSM
soft terms
terms
in written
terms
four
parameters:
parameterswrittenwritten
in of
terms
of
just
four
parameters:
in just
terms
of
just
four
parameters:
⟨F ⟩ ⟨F
⟨F⟩⟩
•
A
common
gaugino
mass:
m
=
f
• A common
gaugino gaugino
mass: m
f M=
• A common
mass:
m
f MPP
1/2
1/2
1/2 =
P M
– common gaugino mass
22
2
|⟨F
⟩|
|⟨F
⟩|
2
2
|⟨F
⟩|
2 m
A common
scalar
squared
mass:
m00==k2k M
• A• common
squared
22
common
scalar scalar
squared
mass:mass:
m
MP
0 =k
P
M
• A squared mass
– common scalar
– scalar
– tanβ
P
⟨F⟩⟩
3 3 coupling prefactor: A ⟨F=⟩ α⟨F
•
A
scalar
3
• A scalar
coupling
prefactor:
trilinear
term
• A scalar
coupling
prefactor:
A =Aα0 0= α MP
0
MP MP
⟨F⟩ ⟩
⟨F
2 2 prefactor B0
•
A
scalar
mass
=
β
⟨F
⟩
• A scalar
prefactor B0 = β MMP
• A scalar
mass2mass
prefactor
B0 = β MP P
This
simplified
parameter
spaceisisoften
oftencalled
called“Minimal
“Minimal Supergravity”
Supergravity” or
This
simplified
parameter
space
or
– sign(μ) (in
the
Higgs
potential)
This simplified parameter space is often called “Minimal Supergravity” or
“mSUGRA”.
“mSUGRA”.
Shahram Rahatlou, Roma Sapienza
& INFN
“mSUGRA”.
57
tralinos ⌅
˜0i (i = 1 - 4) and charginos ⌅
˜±
(i = 1, 2) are obtained after diagonalising their ma
i
The parameter M3 determines the gluino mass (after QCD corrections). The masses of ne
matrices 0which are a function of M1±
, M2 and µ. In the mSUGRA framework, the lighte
ralinos ⌅
˜i (i = 1 - 4) and charginos ⌅
˜i (i = 1, 2) are obtained after diagonalising their ma
chargino and the two lightest neutralinos are dominantly gaugino-like with masses close
matrices which are a function of M1 , M2 and µ. In the mSUGRA framework, the light
M1 and M2 .
chargino
and the
two lightest
neutralinos
are dominantly
• Highly
predictive
for squark
and gluino
masses ingaugino-like
terms of mwith
m1/2 close
0 andmasses
M
M2 .
The
sfermions
of the first two generations have masses given approximately by:
1 and
SPARTICLE&MASSES&IN&mSUGRA
2
2
The sfermions of the first two
have
masses
given
approximately
by:
m2ũ generations
⇤ m20 + 5.0m
+
0.35cos2⇥M
Z
1/2
L
2
22
m2ũ2d˜L ⇤
⇤m
m2020 +
+5.0m
5.0m21/2
0.42cos2⇥M
m
+
0.35cos2⇥M
Z
1/2
Z
L
2
22
m2d˜2ũR ⇤
⇤m
m2020 +
+5.0m
4.5m21/2
+
0.15cos2⇥M
m
0.42cos2⇥M
Z
Z
1/2
L
22 ⇤ m22 + 4.4m22
22
m
0.07cos2⇥M
mũd˜RR ⇤ m00 + 4.5m1/2
Z
1/2 + 0.15cos2⇥MZ
2
m
m2ẽ2d˜L ⇤
⇤m
m2020++0.49m
4.4m21/2
1/2
R
22
0.27cos2⇥MZZ
0.07cos2⇥M
2 2 ⇤ m22 + 0.49m22 + 0.50cos2⇥M 22
m
mẽL˜ ⇤ m00 + 0.49m1/2
0.27cos2⇥MZZ
1/2
2
2
22
m
⇤m
m2020 +
+0.49m
0.15m21/2
0.23cos2⇥M
mẽ2˜R ⇤
+
0.50cos2⇥M
Z
1/2
Z
(13
2
2
2
2
⇤
m
+
0.15m
0.23cos2⇥M
(13
By comparing with the m
gluino
mass,
these
relations
show
that
the latter cannot be mu
ẽR
0
Z
1/2
larger than the squark mass:
By comparing with the gluino mass, these relations show that the latter cannot be mu
arger than the squark mass:
Mg̃ 1.2mq̃
(13
(13
This relation (obtained for m0 = 0) M
is g̃not 1.2m
restricted
to the mSUGRA case, as it depen
q̃
primarily on the S contributions to the running down of the mass parameters from t
This relation (obtained for m0 = 0) is not restricted to the mSUGRA case, as it depen
GUT
scale.
Shahram
INFN
58
primarilyRahatlou,
on Roma
theSapienza &contributions
to the running down of the mass parameters from
t
no decays.
MSUGRA&MASS&SPECTRUM
he m0 versus m1/2 plane showing the production cross-sections and
uino decays.
, the
gluinos1:are
heavier
than any of the squarks. The decay
• Region
gluinos
heavier
areare
expected
to beany of the squarks. The decay
any
squark
n,sparticles
thethan
gluinos
heavier than
dion,
sparticles
are are
expected
tothan
be any of the squarks. The decay
the gluinos
heavier
g̃ ⇥ q̃ q̄ , q̃ ⇥ q
(13.5)
ced sparticles
g̃ ⇥ q̃are
q̄ , expected
q̃ ⇥ q to be
(13.5)
some squarks
other are lighter than the(13.5)
gluino.
g̃ ⇥ q̃are
q̄ , heavier,
q̃ ⇥ q
• decay
Region
2: some
squarks
arefor
n some
squarks
areare
heavier,
other
areinstance
lighter than the gluino.
ated
chains
possible,
ated
decay
chains
areheavier,
possible,
forare
instance
heavier
and are
some
are other
ion some
squarks
lighter than the gluino.
q̃Llighter
⇥decay
g̃q ,than
g̃ ⇥gluinos
b̃b̄are
, b̃possible,
⇥ b for instance
(13.6)
plicated
chains
q̃L ⇥ g̃q , g̃ ⇥ b̃b̄ , b̃ ⇥ b
(13.6)
o generations
expected
q̃L ⇥ g̃q are
, g̃ ⇥
b̃b̄ , b̃ ⇥tob be among the heaviest squarks
(13.6)
o generations are expected to be among the heaviest squarks
ong the lightest.
two
onggenerations
the lightest.are expected to be among the heaviest squarks
n,
the gluinos
are lighter than any of the squarks. A typical
among
the lightest.
n, the
gluinos3:are
lighter
• Region
gluinos
arethan any of the squarks. A typical
gion, the
gluinos
than any of the squarks. A typical
lighter
thanare
anylighter
squark
q̃q̃ ⇥
g̃q
,
g̃
⇥
q
q̄
(13.7)
⇥ g̃q , g̃ ⇥ q q̄
(13.7)
q̃ ⇥ g̃q , g̃ ⇥ q q̄
Shahram Rahatlou, Sh.
Roma
Sapienza & INFN
Rahatlou
(13.7)
59
• m(g̃) < m(q̃), hence g̃ ⌅ q̃q is forbidden except B(g̃ ⌅ b̃1,2 b) = 85%
± ˜0 ) = 100%
• B(⌃
˜02 ⌅ ll⌃
˜01 ) = 3.3%, B(⌃
˜02 ⌅ ⇧ ⇧ ⌃
˜01 ) = 2.2%, B(⌃
˜±
1
1 ⌅W ⌃
LM3
LM4
LM5
LM6
LM7
LM8
LM9
0
LM10
HM1
HM2
HM3
HM4
330
240
210
285
230
360
85
400
3000 230
500
300
1450 175
3000 1/2500
180
850
350
800
700
800
1350 600
20
10
10
10
10
10
50
10
10
35
10
10
TESTING&mSUGRA
• Point LM4 :
• Near NUHM point in the on-shell Z 0 decay region
• m(g̃) ⇤ m(q̃), hence g̃ ⌅ q̃q is dominant with g̃ ⌅ b̃1 b = 24%
± ˜0 ) = 100%
• B(⌃
˜02 ⌅ Z 0 ⌃
˜01 ) = 97%, B(⌃
˜±
1
1 ⌅W ⌃
+
+
+
+
+
+
+
+
+
+
+
+
0
0
0
0
0
-300
0
0
0
0
0
0
• •Given
continuous nature of free parameters and dramatic change of
Point LM5 :
• In the h decay region,
same as NUHM
⇥.
experimental
signatures
forpoint
specific
values of m and m one cannot
• m(g̃) ⇤ m(q̃), hence g̃ ⌅ q̃q is dominant with B(g̃ ⌅ b̃ b) = 19.7% and
explore
B(g̃ ⌅ t̃entire
t) = 23.4%parameter space
0
1
1
•
B(⌃
˜02
± ˜0 ) = 97%
⌅ h0 ⌃
˜01 ) = 85%, B(⌃
˜02 ⌅ Z 0 ⌃
˜01 ) = 11.5%, B(⌃
˜±
1
1 ⌅W ⌃
Point LM6 : solution: choose benchmark points with very different
• •Practical
• Same as post-WMAP benchmark point C’.
phenomenology
for event generation and feasibility studies with different
• m(g̃) ⇤ m(q̃), hence g̃ ⌅ q̃q is dominant
• B(⌃
˜ ⌅ ˜l l) = 10.8%, B(⌃
˜ ⌅ ˜l l) = 1.9%, B(⌃
˜ ⌅ ⇧˜ ⇧ ) = 14%,
MSUGRA, tanβ = 10, A = 0, µ > 0
detectors
B(⌃
˜ ⌅ ⌅˜ l) = 44%
1
• Point LM8 :
•
•
•
•
Gluino lighter than squarks, except b̃1 and t̃1
m(g̃) = 745 GeV/c2 , M (t̃1 ) = 548 GeV/c2 , g̃ ⌅ t̃1 t is dominant
B(g̃ ⌅ t̃1 t) = 81%, B(g̃ ⌅ b̃1 b) = 14%, B(q̃L ⌅ q ⌃
˜02 ) = 26 27%,
± ˜0 ) = 100%
B(⌃
˜02 ⌅ Z 0 ⌃
˜01 ) = 100%, B(⌃
˜±
1
1 ⌅W ⌃
• Point LM9 :
1000
1200
1400
1600
2000
1400
GeV
m h = 122
(g~
)
7
1200
1000
8
HM1
800
HM2
mh = 120 GeV
HM3
Br(
600
~
0~
χ02→h χ01)
> 0.5
HM4
<
t 1)
(
m
400
800
9
~
600
~
g)
m(
LM10
400
LM6
LM5
LM2
LM4
LM1
LM3
5
200 4
6
~
Teva
l
tron
0
1800
>m
1200
800
1000
• Heavy squarks, light gluino. Consistent with EGRET data on diffuse
gamma ray spectrum, WMAP results on CDM and mSUGRA [674].
Similar to LM7.
• m(g̃) = 507 GeV/c2 , hence g̃ ⌅ 3-body is dominant
• B(⌃
˜02 ⌅ ll⌃
˜01 ) = 6.5%, B(⌃
˜±
˜01 ) = 22%
1 ⌅ ⌅l⌃
• Point LM10 :
~
τ1 LSP
600
L)
Very heavy squarks, outside reach, but light gluino.
m(g̃) = 678 GeV/c2 , hence g̃ ⌅ 3-body is dominant
B(⌃
˜02 ⌅ ll⌃
˜01 ) = 10%, B(⌃
˜±
˜01 ) = 33%
1 ⌅ ⌅l⌃
EW chargino-neutralino production cross-section is about 73% of total.
m1/2 (GeV)
•
•
•
•
1400
400
m
• Point LM7 :
200
(u~
0
l
0
(χ 0)
2
0
2
L )<m
R
m(e~
0
2
0.15
L
Br( χ~0 ~
2 →l l)
>
0
2
±
1
0
200
400
LM8
~
~
Br( χ02→Z0χ01) > 0.5
LM7
mh = 114 GeV
mχ = 103 GeV
200
LM9
NO EWSB
600
800
1000
1200
1400
1600
m0 (GeV)
• Similar to LM7, but heavier gauginos.
• Very Roma
heavySapienza
squarks,
outside reach, but light gluino.
Shahram Rahatlou,
& INFN
Figure 13.3: Position of the test points in the m0 versus m
1800
0
2000
plane.60The l
SUSY&SPECTRUM&(SPS1A)
Use the famous SPS1a benchmark point for illustration!
[m0=100, m12=250, tanβ=10, A0=-100, μ>0] !
Mass / GeV
EPS 2013 Direct SUSY Searches, O. Buchmüller
A “typical” SUSY Spectrum"
gluino/
squarks
700
g̃
q̃L
q̃R
600
charginos/
neutralinos
500
400
300
H0
A0
H±
Higgs
sector
200
100
CMSSM!
m0 , m1/2 , tan β , A0 , sign( µ )
h0
0
c̃04
c̃03
c̃2±
b̃2
b̃1
t̃1
Advantage:!
!  Only four free
parameters (when
sign(μ) fixed) !
!  One of the most
studied incarnations
of the MSSM!
!
Disadvantage:!
sleptons
`˜ L
ñL
`˜ R
t̃2
t̃2
ñt
t̃1
c̃02
c̃1±
c̃01
LSP
!  Not generally
representative of
SUSY (e.g. fixed
mass relation
between Mgluion and
MLSP) !
4
Shahram Rahatlou, Roma Sapienza & INFN
61
SIGNATURE8BASED&SEARCH&STRATEGY
• Do not relay on your best theory friend to define signatures
– Variety of creative models sometimes with very specific predictions
– Fine tuning of search strategy for model A dangerous and counterproductive
‣ If model A is incorrect you will see nothing
‣ If model A prediction very different from models B and C, you might not be even sensitive
to B and C predictions. Waste of time!
• Experimental approach: define categories of events that could be predicted by
different models for different corners of phase space
–
–
–
–
–
–
MET + 1 jet
MET + n jet
MET + 1 lepton
MET + dilepton (same sign and opposite sign treated differently)
MET + multi-leptons
MET + high pt photon
• Model-independent strategy potential rules out some or even classes of
models with individual measurement
Shahram Rahatlou, Roma Sapienza & INFN
62
SIMPLIFIED&MODELS&(SMS)
Simplified Models for LHC New Physics Searches, arxiv:1105.2838
Shahram Rahatlou, Roma Sapienza & INFN
63
INTERPRETATION&OF&SMS
EPS 2013 Direct SUSY Searches, O. Buchmüller
Interpretation in Simplified Models"
CMSSM!
What the individual searches
are sensitive to is much more
simple…!
Simplified model spectrum (SMS)!
with 3 particles, 2 decay modes!
12
Shahram Rahatlou, Roma Sapienza & INFN
64
DIRECT&SQUARK&PRODUCTION
Direct squark!
mSU SY = mq̃
<
!
m
t
CMS-SUS-PAS-13-012"
Signature: Jets + Etmiss!
LS
P
Limit assumes only one light !
squark (e.g. uL) and decoupled!
gluino (as before).!
!
~!*
u L!
500!
600
0
pp → ~
q~
q, ~
q → q∼
χ NLO+NLL exclusion
10
1
Observed ± 1 σtheory
Expected ± 1 σexperiment
500
~ ~
~
q +~
q (~
u,d,~
s,c)
400
L
1
R
!
10-1
300
BR=100%!
one light ~
q
200
all
alllimits
limitsare
are!!
-2
observed
observed10
nominal
nominal!!
95%
95%CLs
CLslimits
limits!!
100
250!
95% C.L. upper limit on cross section (pb)
~!
u L!
CMS Preliminary, 19.5 fb-1, s = 8 TeV
mLSP (GeV)
SU
SY
750!
0
1 CMS-PAS-SUS-13-012 (8x mass deg.) !
0
1 CMS-PAS-SUS-13-012!
0
1 ATLAS-CONF-2013-053 !
0 ATLAS-CONF-2013-037 !
1
m
q̃ ! q
ũL ! q
b̃ ! b
t̃ ! t
1000!
m
EPS 2013 Direct SUSY Searches, O. Buchmüller
mLSP!
[GeV]!
300
400
500
600
700
800
900 1000
10-3
m~q (GeV)
mSUSY!
[GeV]!
0!
0!
Shahram Rahatlou, Roma Sapienza & INFN
250!
500!
750!
1000!
1250!
1500!
19
65
GLUINO8MEDIATED&PRODUCTION
EPS 2013 Direct SUSY Searches, O. Buchmüller
Gluino mediated squark production – limits chosen"
g̃ ! q q̄
0
1
g̃ ! bb̄
m
1
m
t
m
<
m LS P
< 2! m t
CMS-SUS-PAS-13-012"
500!
Signature: Jets + HT + Etmiss!
!
!
CMS-SUS-PAS-12-024"
!
Signature:
: Jets + b-tag + Etmiss!
See also parallel talk:!
C. Autermann !
!
250!
!
See parallel talk for details: !
S. Sekmen !
!
!
!
Observed limit ± 1
SUSY
Theory
-1
0
!g̃ ! bb̄ 1
en
CMS-PAS-SUS-12-024!
idd
0
0
= mg̃
exp
0-l + 3 b-jets, 12.8 fb
g̃! ! q q̄ 01 All limits at 95% CL
CMS-PAS-SUS-13-012 !
400
!
int
L = 20.1 fb-1, s=8 TeV
1
0 and 1 leptonSU
+ 3 b-jets
SYchannels
600
200
0
tt+ , m(~q) >> m(~g)
Expected limit ±1
ATLAS
Preliminary
Gluino
mediated
!
P
LS
SU
mSU SY
1000
800
SY
750!
0
1 CMS-PAS-SUS-13-012!
0
1CMS-PAS-SUS-13-012!
0
1 ATLAS-CONF-2013-053 !
0 ATLAS-CONF-2013-037 !
1
m
q̃ ! q
u˜L ! u
b̃ ! b
t̃ ! t
1000!
0
Direct squark!
mSU SY = mq̃
m
EPS 2013 Direct SUSY Searches, O. Buchmüller
[GeV]
~g~g production, ~g
mLSP!
[GeV]!
0
1
g̃ ! tt̄
0
1
~g
t t+
b
for
1
0
!g̃ ! tt̄ 1
ATLAS-CONF-2013-061!
600
800
1000
1200
1400
m~g [GeV]
ATLAS-CONF-2013-061"
Signature: 0/1 Leptons +!
mis!
3 b-tag + EBR=100%!
t
See parallel
talk are
for! details: !
all limits
observed nominal !
D. Cote ! 95% CLs limits!
21
RP conserved !
!
!
mSUSY!
[GeV]!
0!
0!
Shahram Rahatlou, Roma Sapienza & INFN
250!
500!
750!
1000!
1250!
1500!
22
66
THIRD&GENERATION
Think$carefully$about$predicHons$
f
H$
H
f$
2
H
Δm =
λf
16π
2
2
[−2Λ
2
UV
]
+ 6m 2f ln(ΛUV m f ) +…
S$
mf2$
€
H$
λs
2
2
Δm =
Λ
−
2m
s ln(ΛUV m s ) + …]
2 [ UV
16π
2
H
Shahram Rahatlou, Roma Sapienza & INFN
Dominant+loop+is+from+top:+only+
need+third+genera'on+squarks+to+be+
really+light.++
3rd+genera'on+cross+sec'on+is+
reduced+(no+t/b+content+in+proton):+
exis'ng+limits+don’t+apply!+
15$
67
SEARCH&FOR&STOP
EPS 2013 Direct SUSY Searches, O. Buchmüller
mLSP!
[GeV]!
Direct squark!
Mind the gap! "
1st & 2nd squarks: CMS-12-028!
1000!
ONE uL squark: CMS-12-028!
sbottom: ATLAS-CONF-2013-053 !
stop: ATLAS-CONF-2013-037 !
750!
mSUSY = msq!
!
!
!
500!
!
edicated searches for direct stop-pair production"
±
b
1
,
±
W
1
rnal
0
(*)
Status: July 2013
1
Lint = 20-21 fb-1 s=8 TeV
+ 5 GeV
06 GeV
0 GeV
- 10 GeV
×m0
all limits are !
observed nominal !
95% CLs limits!
RP conserved !
250!
Lint = 4.7 fb-1 s=7 TeV
0L ATLAS-CONF-2013-053
-
-
2L [1208.4305], 1-2L [1209.2102]
1L ATLAS-CONF-2013-037
-
2L ATLAS-CONF-2013-048
-
1L CONF-2013-037, 2L CONF-2013-048
1-2L [1209.2102]
mSUSY!
[GeV]!
1
limits
Observed limits (-1
theo)
Expected limits
0
b ˜±
1 ! bW ˜1
0
+5
G
0!
)
eV
1
m~t 1
+m
< mb
(m
±
=2
×m
0
)
m ± = m 0 + 5 GeV
1
1
250!
500!
750!
1000!
1250!
1500!
24
1
Lint = 20.1 fb-1
1
1
m ± = 2× m
1
±
0!
BR=100%!
0
1
Lint = 20-21 fb-1
10 GeV
m = m -Rahatlou,
Shahram
Roma Sapienza & INFN
L = 20.7 fb
±
1
int
m ± < 103.5 GeV
~
t1
1
-1
68
CONSTRAINTS&FROM&STOP
Direct squark!
mSU SY = mq̃
750!
m
<
P
LS
m
m
m!S U S Y
m LS P
0
1
CMS-PAS-SUS-13-012 !
!
0
g̃
! ! bb̄ 1
CMS-PAS-SUS-12-024!
g̃! ! q q̄
0
!g̃ ! tt̄ 1
ATLAS-CONF-2013-061!
!
< 2! m t
!
m
W
500!
SU
Direct stop in “gap”!
mSU SY = mt̃
t̃ ! c 01 LEPSUSYWG!
CDF: 1203.4171!
t̃ ! c 01 D0: 0803.2263!
t̃ ! c 01 ATLAS-CONF-!
2013-068!
t
0
1 CMS-PAS-SUS-13-012!
0
1CMS-PAS-SUS-13-012!
0
1 ATLAS-CONF-2013-053 !
0 ATLAS-CONF-2013-037 !
1
SY
q̃ ! q
u˜L ! u
b̃ ! b
t̃ ! t
1000!
Gluino mediated !
mSU SY = mg̃
<
EPS 2013 Direct SUSY Searches, O. Buchmüller
mLSP!
[GeV]!
t
m
<
L
L
m
b
S
P
m
all limits are !
observed nominal !
95% CLs limits!
RP conserved !
t˜
m
m
t˜
250!
BR=100%!
m
CMS-PAS!
-SUS-13-011!
SP
0
1
t̃ ! W b
mSUSY!
[GeV]!
0!
0!
Shahram Rahatlou, Roma Sapienza & INFN
250!
500!
750!
1000!
1250!
1500!
30
69
EPS 2013 Direct SUSY Searches, O. Buchmüller
BENEFITS&OF&
IGHER&
E"NERGY
Outlook: 8 H
TeV
vs 14 TeV
Use parton luminosities to illustrate the gain of 14 vs 8 TeV !
Higgs:!
pp " H, H"WW, ZZ and γγ
mainly gg: factor ~2
SUSY – 3rd Generation:
Mass scale ~ 500 GeV
qq and gg: factor ~3 to 6
SUSY – Squarks/Gluino:
Higgs!
Mass scale ~ 1.5 TeV
125 GeV!
qq,gg,qg: factor ~40 to 80
!
Z :!
Mass scale ~ 5 TeV
qq: factor ~1000
Increase in energy will help a lot!
Z !
~5.0 TeV!
SUSY!
squarks/Gluino !
~1.5 TeV!
SUSY!
3rd Gen!
~500 GeV!
Not just for SUSY...
44
Shahram Rahatlou, Roma Sapienza & INFN
70
CONSTRAINTS&ON&CMSSM
Constrained Minimal Supersymmetry: unification of superpartner masses and Gauge
couplings at GUT scale
• G.&Kane&et&al.,&“Study&of&constrained&minimal&supersymmetry”,&
h\p://arxiv.org/abs/hep8ph/9312272
Shahram Rahatlou, Roma Sapienza & INFN
71
HEAVY&STABLE&PARTICLES
HEAVY&STABLE&CHARGED&PARTICLES
• In many flavors of SUSY, LSP is a heavy charged particle, stau, stop, gluino
– split SUSY, GMSB, KK tau from some universal extra dimension models
• Behave like very
heavy muon
through
tracking
and muons detectors
Muon
Drift
Tube
system
– β<1 so later time of arrival in detectors compared to common relativistic
particles fromCMS
collisions
muon system has Drift Tube (DT) in the barrel region
– Smaller velocity
larger ionization
loss
Theimplies
DT staggered
pattern canenergy
be exploited
Muon Drift Tube system
to measure
the time
of measure
flight
• Search
for muon
like
particles
dE/dx
CMS
muon
system
hasand
Drift
Tube (DT)
in the barrel region
DT are timed so that particle, produced in pp
energy loss
The DT staggered
pattern
can
beof exploited
interaction give
an aligned
pattern
hits
• Dedicated
muon reconstruction
because of late
to measure
the time of flight
arrival compared to standard muon
DT are timed so that particle, produced in pp
interaction givestandard
an aligned
pattern of hits
muon
heavy muon
A “slow” particle produce a zigzag pattern with offsets
proportional to the deltaT
Up to 44 measurement per track (if all four
stations are crossed)
Shahram Rahatlou, Roma Sapienza & INFN
73
ANALYSIS&METHOD
• Discriminating variables
– High pt tracks
– ionization energy loss
– time of flight
Shahram Rahatlou, Roma Sapienza & INFN
74
Aisstudy
performed
on MC indicates
that
a selection
Ias discriminator
in the
place
shown
in Fig. 4 (right).
The known
values
of thethat
kaonuses
andthe
proton
masses are also
indicated
ofas
the
Ih estimator
increases
theThe
signal-to-noise
ratio by awith
factor
The not
division
in subsamples
vertical
lines on
the figure.
histogram obtained
MC3.does
display
the deuteron
according
to thePYTHIA
track number
of hits
(⇥) brings
an additional
by[9].
a factor 8 (1.3).
peak because
does not
produce
such particles
in ppincrease
collisions
MASS&MEASUREMENT&FROM&dE/dX
s = 7 TeV
10
Ionization-based Mass Reconstruction
#Tracks
6
CMS Preliminary 2010
5
Data
MC
The most probable value of the particle dE/dx is estimated
using a harmonic estimator Ih of
104
grade k = 2:
Ih =
1
N
i
⇥1/k 103
cik
with k =
2
(2)
102
where ci is the charge per unit path length of the i-th hit attached to a given reconstructed track.
In order to estimate the mass of highly ionizing particles, the following relationship between
10
Ih , p and m is assumed in the momentum region below that corresponding to the minimum of
ionization:
0
m2
0.5
1
1.5
2
2.5
3
2
Mass (GeV/c )
Ih = K p 2and
+ CI for all reconstructed tracks with at leas
(3)
Figure 4: Left: Distribution of the measured
h
p
12 hits in the silicon strip detector and good primary vertex compatibility from a data sample
• Quadratic relation between measured energy loss Ih and mass
collected3 with
a minimum
biasaccuracy
trigger. of
Right:
reconstructed
spectrum
in datainand
fo
Equation
reproduces
with an
better
than 1% the mass
Bethe-Bloch
formula
the MC
interall
tracks
forand
theCfigure
on
theknown
left,
with ionizations
Ih(pions,
> 5 MeV/cm
and
p < of
2.01.1
GeV/c.
Deuteron
•0.4
Determine
K
from
fit to
particles
kaons,
val
< used
< 0.9,
which
corresponds
tobut
specific
in protons)
the
range
to 4 times
the
production
is not simulated in PYTHIA [9].
MIP
specific ionization.
• Determine mass of heavy particles based on measured Ih and momentum p
Figure
4 (left) shows the distribution of Ih versus p for all reconstructed tracks with at least
Shahram Rahatlou, Roma Sapienza & INFN
75
#HSCP}
MASS&OF&HEAVY&PARTICLES
1
CMS Preliminary 2010
s = 7TeV 198 nb -1
Tracker - Only
Stop130
Stop200
Stop300
Stop500
Stop800
10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
10-9
0
200
400
600
800
1000
Reconstructed Mass (GeV/c 2)
Figure 5: Left: Distribution of the reconstructed p and Ih for all tracks passing the pre-sele
and matched to HSCP particles in the t̃1 MC samples. The curves Ih = Km2 /p2 + C, fo
5 nominal values of the t̃1 mass, are also drawn. Right: reconstructed mass spectra for
• Not enough data yet to measure precisely the mass of the heavy
racks.
7
particle
Background Determination and Search Optimization
Shahram Rahatlou, Roma Sapienza & INFN
76
HSCP&MASS
Shahram Rahatlou, Roma Sapienza & INFN
77
EXCLUSION&LIMITS
Shahram Rahatlou, Roma Sapienza & INFN
78
LONG8LIVED&SEARCHES
GAUGE&MEDIATED&SUSY&BREAKING&(GMSB)
Gauge-Mediated SUSY Breaking (GMSB) models
Gauge-Mediated SUSY Breaking (GMSB) models
The idea: SUSY breaking is transmitted from a hidden secto
• SUSY breaking
transmitted
ordinaryfrom a hidden
gauge
SU (3)Csector
× SUby
(2)the
U (1)Y gauge
interactions. This m
L ×ordinary
The idea: SUSY
breaking via
is transmitted
automatically flavor-blind!
interactions
SU (3)C × SU (2)L × U (1)Y gauge interactions.
This makes them
To do this, introduce new, heavy, chiral supermultiplets, calle
automatically flavor-blind!
which
couple to ⟨F ⟩ and also to the MSSM gauge bosons a
• New fields F with non-zero VEV <F> in hidden
sector
To do this, introduce new, heavy, chiral supermultiplets, called messengers,
If the typical messenger particle masses are Mmess , the MS
which messengers
couple to ⟨F ⟩ and
also toM
the
MSSM
gaugebetween
bosons and hidden
gauginos.sector and gauge
• New heavy
of mass
mediate
mess
αa ⟨F ⟩
msoft ∼
and gaugino
particles
in visible
sector
If the typical
messenger
particle
masses are Mmess , the MSSM soft terms are: 4π Mmess
• soft SUSY breaking scale
msoft
αa ⟨F ⟩ The αa /4π is a one-loop factor for diagrams involving gaug
∼
follows by dimensional analysis, since msoft must vanish as
4π Mmess
messengers become very heavy.
• If
! 4interactions. This 4
4
The
α
/4π
is
a
one-loop
factor
for
diagrams
involving
gauge
a
Mmess ⁓ 10 GeV then comparable VEV of <F>
⁓ 10
GeV
Note that
⟨F ⟩ can
be as low as 10 GeV, if M
mess is com
follows by dimensional analysis, since msoft must vanish as ⟨F ⟩
→ 0, or as the
This is much lower than in Planck-scale Mediated SUSY Bre
become
heavy.
– SUSYmessengers
breaking at
muchvery
lower
energy scale compared
tosometimes
mSUGRA
and
otherSUSY breaking”
these are also
called
“low-scale
!
models
4 gravitino (with mass denoted m
GMSB
models
predict
that
Note that
⟨F typically
⟩ can be as
low as
10the
GeV, if M
is comparable.
3/2 ) is the
mess
6
e Gauge Mediated
Supersymmetry
Breaking
LSP.
This
is because,
provided
that MMediated
MP , Breaking. Therefore,
mess ≪ SUSY
This
is
much
lower
than
in
Planck-scale
• Important feature of GMSB: gravitino as LSP and lightest neutralino as NLSP
model
these are also sometimes called “low-scale SUSY breaking” models.
αa ⟨F ⟩
⟨F ⟩
≪ msoft ∼
m3/2 ∼
MP is considered:
4π Mmess
ated Supersymmetry Breaking model
6
∼
G is the LSP
!
0
4
⟨F
⟩
∼
10
In
fact,
m
can
be
as
low
as
0.1
eV,
for
GeV.
⇥
˜
!
G̃
+
• Enhanced
mode: decay: 1
3/2
+ photon
produceddecay
by neutralino
Shahram Rahatlou,The
Roma lightest
Sapienza & INFN
of the
MSSM superpartner states is then the Next-to-Lightest
80
GMSB&PARAMETERS
• Only 6 free parameters to provide SUSY
breaking
–N: number of messengers
–messenger mass scale Mmess
–SUSY breaking scale
– tanβ
hF i
⇤=
Mmess
– sign(μ) (in the Higgs potential)
– Cgrav: determines lifetime of neutralino
• For N > 1 stau becomes the NLSP
Shahram Rahatlou, Roma Sapienza & INFN
81
HIGH&PT&PHOTON(S)&+&MET&+&JETS
Neutralino lifetime depends
on parameters of theory!
γ
jet
Search strategy must be sensitive
to both scenarios
q
p
q
…
q
jet
p
…
q
jet
γ"
Shahram Rahatlou, Roma Sapienza & INFN
jet
82
Experimental
signature
E
XPERIMENTAL&SIGNATURE
Experimental
signature
Experimental signature
Two high-PT !
Jet
Jet
q
˜10
q
˜10
qq
q
γ
γγ
γ q
G̃
G̃ q
G̃
Jet
Jet
= Interaction Point
=
= Interaction
Interaction Point
Point
Shahram
Rahatlou, Roma Sapienza
& INFN
= Interaction
Point
Jet
q
G̃
G̃ G̃
G̃
✓
MET
MET
MET
in-time !
off-time !
Jet
EHC EECC L
CAA AA
H HHC LL LL
CACAA
L LL
Jet
˜˜100
1
EC
A
γ
γ
γγ
Jet
cτ∼0
Two✓
high-P
✓ ✓cτ>0
undetectable G̃
Two Two
undetectable
✓ ✓Energy imbalance
✓ ✓Missing ET
Many high-PT quarks
jet multiplicity
✓High
Many high-PT quarks
✓High jet multiplicity
83
STANDARD&
M
ODEL&BACKGROUND
SM backgrounds
QCD events:
!Large cross section
!Fake photons from jets
!Mis-identified MET
Rejected by γ isolation and MET
jet
jet
Photon+Jet:
!Real photon in the final state
!Mis-identified MET
!Low jet multiplicity
jet
Rejected by jet multiplicity
t t events:
!Fake photons from electrons
!Real MET from neutrinos
!High jet multiplicity
Rejected by γ isolation
Shahram Rahatlou, Roma Sapienza & INFN
84
IMPACT&OF&NEUTRALINO&LIFETIME
Zero vs non-zero lifetime
Non-zero lifetime
De
te
ct
or
y
y
De
te
ct
or
wer
γ sho
γs
how
er
Zero lifetime
δ
γ
γ
X
IP
In-time photon
x
!Arrival time compatible with that of a
relativistic particle from the IP
Shahram Rahatlou, Roma Sapienza & INFN
IP
x
Off-time photon
!Arrival time sensibly increases with
parent particle lifetime
!ΔT∼O(ns)
85
Cluster shape
S
HAPE&OF&
P
HOTONS&IN&
C
ALORIMETER
Cluster shape described by the covariance matrix
Several clustering algorithms are used in CMS:
index
! Energy fully recovered (ECLU = ∑Ei) ECAL cluster from a pointing photon
! Precise position measurement
30
29
! Time from the hottest crystal
COV⌘ =
✓
S⌘⌘
S ⌘
S⌘
S
◆
28
with
Sµ =
PN
27
i=126wi
hµi) (
(µi
25
h i)
i
24
✓Eigenvectors: principal axes of the energy distribution
✓Eigenvalues: energy spread along the principal axes
23
22
11
index
index
13
14
15
16
17
18
19
index
ECAL cluster from an off-pointing photon
ECAL cluster from a pointing photon
Pointing photon
30
12
37
Off-pointing photon
36
29
28
SMAJOR
35
34
27
SMINOR
26
33
25
32
24
31
23
30
22
29
11
12
13
14
15
Shahram Rahatlou, Roma Sapienza & INFN
16
17
18
19
index
26
27
28
29
30
31
32
33
34
index
86
MISSING&TRANSVERSE&ENERGY
• Select events with at least 3 jets and isolated high pT photon
• Low MET populated by SM while signal dominates at high MET
Shahram Rahatlou, Roma Sapienza & INFN
87
EXCLUSION&LIMITS
Shahram Rahatlou, Roma Sapienza & INFN
88
REFERENCES
• Prospino: program for the PROduction of Supersymmetric Particles In Next-to-leading Order qcd
– http://www.thphys.uni-heidelberg.de/~plehn/prospino/
• G. Kane et al., “Study of constrained minimal supersymmetry”, http://arxiv.org/abs/hep-ph/9312272
– Phys. Rev. D49 (1994) 6173. doi:10.1103/PhysRevD.49.6173
• Simplified Models for LHC New Physics Searches, arXiv:1105.2838
• Natural Supersymmetry: LHC, dark matter and ILC searches, arXiv:1203.5539
• Missing transverse energy performance of the CMS detector, JINST 6 (2011) 09001
• ATLAS JetMET page:
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/JetEtMissPublicCollisionResults
• ATLAS SUSY:
https://twiki.cern.ch/twiki/bin/view/AtlasPublic/
SupersymmetryPublicResults
• CMS SUSY:
https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS
• Search for heavy long-lived charged particles in pp collisions, arXiv:1205.0272
• Search for Long-Lived Particles using Displaced Photons in pp Collisions, CMS-PAS-EXO-11-035
Shahram Rahatlou, Roma Sapienza & INFN
89