Transcript SUSY at LHC Bhaskar Dutta Texas A&M University SUSY Theory at the LHC

SUSY at LHC
Bhaskar Dutta
Texas A&M University
SUSY Theory at the LHC
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Discovery Time…
We are about to enter into an era of major discovery
Dark Matter: we need new particles to explain the content of the universe
Standard Model: we need new physics
Supersymmetry solves both problems!
The super-particles are distributed around the weak scale
Our best chance to observe SUSY is at the LHC
LHC: The only experiment which directly probes TeV scale
Future results from Planck, direct and
indirect detection in tandem with LHC
will confirm a model
SUSY Theory at the LHC
Model
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Collision of 2 Galaxy Clusters
splitting normal matter and dark matter apart
time
– Another Clear Evidence of Dark Matter –
(8/21/06)
Ordinary Matter
(NASA’s Chandra X
Observatory)
1
2
3
4
Dark Matter
(Gravitational Lensing)
Approximately
the same size as
the Milky Way
SUSY Theory at the LHC
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SUSY at the LHC
High PT jet
[mass difference is large]
DM
The pT of jets and leptons
depend on the sparticle
masses which are given by
models
Colored particles get
produced and decay into
weakly interacting stable
particles
DM
High PT jet
R-parity conserving
(or l+l-, t+t-)
The signal : jets + leptons + missing ET
SUSY Theory at the LHC
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Example Analysis
Kinematical Cuts, Event Selection - 4 jets +ETmiss
 PTj1 > 100 GeV, PTj2,3,4 > 50 GeV
 Meff > 400 GeV (Meff  PTj1+PTj2+PTj3+PTj4+ ETmiss)
 ETmiss > Max [100, 0.2 Meff]
Paige, Hinchliffe et al. , Phys. Rev. D 55 (1997) 5520
SUSY Theory at the LHC
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Background
Typical SUSY events are
105 events for 10 fb-1, while
BG rate is 109-8 for
W, Z, t tbar production.
The cuts need to be optimized
Large amount of missing
energy, high pT jets, large
numbers of jets and leptons
are good handles on signal
SUSY Theory at the LHC
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SUSY Models
MSSM has more than 100 parameters
The number of parameters can be reduced in different models
Minimal Model: minimal supergravity (mSUGRA)/CMSSM
Nonuniversal SUGRA model,
Anomaly mediated, NMSSM, Compressed- SUSY
Mixed Moduli, Gauge Mediated, non-critical string model, Split SUSY,
Long lived NLSP models, GUT less models, Planck scale SU(5), SO(10) models etc..
Once SUSY is discovered,
models will be searched
based on typical signals
These models also will be simultaneously tested at
the underground , satellite experiments from their
characteristic features.
Let LHC Decide
SUSY Theory at the LHC
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Minimal Supergravity (mSUGRA)
Let us use the simplest model to describe the reach of LHC
4 parameters + 1 sign
m1/2
Common gaugino mass at MG
m0
Common scalar mass at MG
A0
Trilinear couping at MG
tanb
<Hu>/<Hd> at the electroweak scale
sign(m) Sign of Higgs mixing parameter (W(2) = m Hu Hd)
Experimental Constraints
i.
ii.
iii.
iv.
MHiggs > 114 GeV
Mchargino > 104 GeV
2.2x10-4 < Br (b  s g) < 4.5x10-4
0 .094   ~0 h2  0 .129
(g-2)m
1
SUSY Theory at the LHC
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Reach at the LHC
Use Jets + leptons + ETmiss discovery channel.
5s
5s
ATLAS
ATLAS
Sensitivity only weakly dependent on A0, tan(b) and sign(m).
Tovey’02
SUSY Theory at the LHC
M. Tytgat (SUSY’07)
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Measurement of Masses
We need to measure the masses of the particles.
Model parameters need to be determined to check the
cosmological status.
[Allanach, Belanger, Boudjema and Pukhov’04]
If we observe missing energy, then we have a possible dark
matter candidate .
[ LHC experiments sensitive only to LSP lifetimes <1 ms (≪ tU ~ 13.7 Gyr) ]
Using the model parameters we need to calculate relic density
 CDM -1










+…



SUSY Theory at the LHC
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Dilepton Edge Measurement
• Deacy of  2 results into dilepton
invariant mass edge sensitive to
combination of masses of sparticles.
~0
Can perform SM &
SUSY background
subtraction using
distribution
e+e- + m+m- - e+m- - m+e-
e, m
e, m
e+e- + m+mPoint 5
ATLAS
Position of edge
measured with
precision ~ 0.5%
(30 fb-1).
~0

2
~
l
~0

1
•m0 = 100 GeV
•m1/2 = 300 GeV
•A0 = -300 GeV
•tan(b) = 6
•sgn(m) = +1
30 fb-1
atlfast
Physics
TDR
SUSY Theory at the LHC
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Measurements with Squarks




Use Dilepton edge for reconstruction of decay chain.
Make invariant mass combinations of leptons and jets.
multiple constraints on combinations of four masses.
Measurement of individual sparticle masses.
~
qL
~
q 0 2
l
~
l
~
0 1
l
~
qL
~
q 0 2
h
b
llq edge
lq edge
llq threshold
1% error
(100 fb-1)
1% error
(100 fb-1)
2% error
(100 fb-1)
ATLAS
Point
LHC Point 5
TDR,
Point 5
ATLAS
m0 m1/2 A0
100 300 300
TDR,
Point 5
TDR,
Point 5
ATLAS
~
0 1
b
bbq edge
1% error
(100 fb-1) TDR,
Point 5
ATLAS
tan(b) sign(m)
2
+1
SUSY Theory at the LHC
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Model Independent Masses
• Measurements from edges
from different jet/lepton
combinations to obtain
‘model-independent’ mass
measurements.
~
0
ATLAS
Mass (GeV)
~0
2
Sparticle Expected precision (100 fb-1)
~
qL
 3%
~
02
 6%
~
LHC
lR
 9%
Point 5
~
01
 12%
~
lR
1
ATLAS
Mass (GeV)
ATLAS
Mass (GeV)
~
q
L
ATLAS
Mass (GeV)
Accuracies using many of such observables:
2% (m0), 0.6% (m1/2), 9% (tanb), 16% (A0)
Similar analysis, P. Beatle (SUSY 07); M. Rauch (SUSY 07)
SUSY Theory at the LHC
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Higgsino vs Gaugino …
~
02 and ~
01 : Higgsinos, three gaugino masses are very close
~
02  ~01 l+lThe spectrum
terminates at
m(l+l-)max
Kitano, Nomura’06
~0
~
With M(  2 )-M(01) <MZ
Mslepton > Mz
Gaugino
~
Like 02 and
Higgsino
~
 01
Using other
observables like
Mllq Mlq, MT, it is
Possible to measure
squark and the
neutralino mass with
An accuracy of
2% and 10%
Shapes looks different, 2 scenarios can be distinguished
SUSY Theory at the LHC
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Dark Matter Allowed Regions
We choose mSUGRA model. However, the results can be
generalized.
[Focus point region]
the lightest neutralino has a
larger higgsino component
[A-annihilation funnel region]
This appears for large values of
m1/2
[Neutralino-stau
coannihilation region]
Bulk region-almost ruled out
SUSY Theory at the LHC
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Focus Point : Jets+leptons
Typical mSUGRA point: m0=2910; A0=0; m1/2=350; m>0; tanb=30;
Large sfermion mass, smaller gaugino masses comparatively
LHC events characterized by high jet, b-jet, isol. lepton
Baer, Barger, Shaughnessy, Summy, Wang ‘07
multiplicity _
_
Gluino decays into t t 0, t b +- (mostly) ]
Higher jet, b-jet, lepton multiplicity requirement increase the
signal over background rate
SUSY Theory at the LHC
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Focus Point : Jets+leptons…
Require cuts: n(j) ≥ 7, n(b) ≥ 2, AT ≥ 1400 GeV
Gluino mass can be measured with an accuracy 8%
ETmiss+SETjet+SETlepton
Baer, Barger, Shaughnessy, Summy, Wang ‘07
SUSY Theory at the LHC
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Focus Point: Leptons
•
•
•
•
Large m0  sfermions are heavy
m0=3550 GeV; m1/2=300 GeV; A0=0; tanß=10 ; μ>0
~ 0 +2 leptons
Direct three-body decays ~0n → 
1
Tovey, PPC’07
Edges give m(~0n)-m(~01)
~0 → ~
~
01 ll
 02 → ~
01 ll 
3
ATLAS
300 fb-1
Preliminary
Z0 → ll
Parameter Without
cuts
Exp.
value
M1
68±92
103.35
M2-M1
57.7±1.0
57.03
M3-M1
77.6±1.0
76.41
Similar analysis: Error (M2-M1)~ 0.5 GeV
G. Moortgat-Pick (SUSY 07)
SUSY Theory at the LHC
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Bulk Region
The most part of this region in mSUGRA is experimentally (Higgs mass
limit, bs g) ruled out
Relic density is satisfied by t channel selectron, stau and sneutrino exchange
Perform the end point analysis to determine the masses
mSUGRA point:
End pts
value
error
mass
mll
81.2
0.09
97.2
~0
Mlq((max)
365
2.1
398
266.9
1.6
~
Mlq(min)
l
189
425
2.5
~
g
~
uL
Mllq(max)
607
Mllq(min)
207
1.9
533
Mtt(max)
62.2
5.0
sparticle
~0

m0=70; A0=-300
m1/2=250; m>0;
tanb=10;

1
2
Nojiri, Polsello, Tovey’05
The error of relic density:
0.108 ± 0.01(stat + sys)
Includes: (+0.00,−0.002 )M(A); (+0.001, −0.011) tan β; (+0.002,−0.005) m(t~2)
[With a luminosity 300 fb-1, tt edge controlled to 1 GeV]
SUSY Theory at the LHC
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Coannihilation Signatures
Mass of another sparticle comes close to the neutralino:
both of them are thermally available.
This region appears for small m0 and m1/2 values and
therefore will be accessible within a short time
For smal tanb this region has e,m,t in the signals
For large tanb this region has t in the signals

 ~ 0
1



 ~
 t 1







2
e - ΔM / 20
SUSY Theory at the LHC
ΔM  Mt~1 - M ~0
1
Griest, Seckel ’91
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Coann. Signatures (tanb=10)
• Small slepton-neutralino mass difference gives soft leptons
– Low electron/muon/tau energy thresholds crucial.
• Study point chosen within region:
– m0=70 GeV; m1/2=350 GeV; A0=0; tanß=10 ; μ>0;
• Decays of 02 to both lL and lR kinematically allowed.
– Double dilepton invariant mass edge structure;
– Edges expected at 57 / 101 GeV
ATLAS
Preliminary
100 fb-1
• ETmiss>300 GeV
• 2 OSSF leptons
PT>10 GeV
• >1 jet with PT>150
GeV
• OSSF-OSOF
subtraction applied
Tovey, PPC’07
SUSY Theory at the LHC
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Coannihilation Region (tanb=40)
tanb = 40, m > 0, A0 = 0
M  M t~ - M ~
1
0
1
 5 ~ 15 GeV
t~1-  t - ~10
Can we measure M at colliders?
SUSY Theory at the LHC
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Coann. Signatures (tanb=40)
In Coannihilation Region of SUSY Parameter Space:
~

1

q
~
q
q
~
g
q
~
q
Soft t
q
~
g
p
p
t
p
q
q
t
2
t~
Soft t
~0

1
~0

1
t~
t
t
Hard t
Soft t
p
~
q
~0

Hard t t
~0

2
~0

1
t~
~
q
Soft t
~0

Hard t t
t
2
~0

1
t~
Final state: 3/4 ts+jets +missing energy M  M t~ - M ~

Use hadronically decaying t
1
0
1
 5 ~ 15 GeV
SUSY Theory at the LHC
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Four Observables
Sort τ’s by ET (ET1 > ET2 > …) and use OS-LS method to extract t
pairs from the decays
• NOS-LS
•
ditau invariant mass (Mtt)
• PT of the low energy t to estimate the mass difference M
• jet-t-t invariant mass: Mjtt
D. Toback’s talk, parallel session
Arnowitt, B.D., Kamon, Toback, Kolev,’06; Arnowitt, Arusano,B.D., Kamon,
Toback,Simeon,’06; Arnowitt,B.D., Gurrola, Kamon, Krislock, Toback, to appear; D. Toback,
talk [this conf]
SUSY Theory at the LHC
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SUSY Parameters
Since we are using 4 variables, we can measure M, Mgluino and the
universality relation of the gaugino masses
i.e.
M ~g ~ 2.8m 1/2 , M ~χ 0 ~ 0.8m 1/2 , M ~χ 0 ~ 0.4m 1/2
2
1
Mgluino measured from the Meff method may not be accurate for this
parameter space since the tau jets may pass as jets in the Meff
observable.
The accuracy of measuring these parameters are important for
calculating relic density.
EVENTS WITH CORRECT FINAL STATE : 2t + 2j + ETmiss
APPLY CUTS TO REDUCE SM BACKGROUND (W+jets, t-tbar,…)
ETmiss > 180 GeV, ETj1 > 100 GeV, ETj2 > 100 GeV, ETmiss + ETj1 + ETj2 > 600 GeV
ORDER TAUS BY PT & APPLY CUTS ON TAUS: WE EXPECT A SOFT t AND A HARD t
PTall > 20 GeV, PTt1 > 40 GeV
SUSY Theory at the LHC
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Mttvis in ISAJET
Version 7.69 (m1/2 = 347.88, m0 = 201.1)  Mgluino = 831
Number of Counts / 1 GeV
Chose di-t pairs from neutralino decays with
(a) |h| < 2.5
(b) t = hadronically-decaying tau
~20  tt~1  tt~10
( M  5.7 GeV)
~20  264.1
~10  137.4
t~1  143.1
End pont  62.0
ETvis(true) > 20, 20 GeV
ETvis(true) > 40, 20 GeV
ETvis(true) > 40, 40 GeV
ETt > 20 GeV is essential!
M tvist (GeV)
SUSY Theory at the LHC
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Determination of m0 , m1/2
M and Mgluino  m0 , m1/2,  ~ 0 h 2
1
(for fixed A0 and tanb
We determine dm0/m0 ~ 1.2% and dm1/2/m1/2 ~2 %
dh2/h2 ~ 7% (10 fb-1)
(for A0=0, tanb=40)
SUSY Theory at the LHC
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Higgs non-universality
The most common extension of mSUGRA
mH  m0 (1 + d1 )
2
2
1
Case 1.
mH  mH 2
mH 2  m0 (1 + d 2 )
2
2
Case 2.
mH  mH 2
1
1
Drees’00;
Baer
Belyaev,
Mustafayev,
Profumo,
Tata’05
Ellis,
Olive,
Santoso’03
LHC signal:
A, H and H+- will be relatively light, and more accessible to direct LHC searches
oi and +i
There can be light uR, cR squarks, small m: leads to light ~
SUSY Theory at the LHC
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Moduli-Mediation
KKLT model: type IIB string compactification with fluxes
MSSM soft terms have been calculated,
Choi, Falkowski, Nilles, Olechowski, Pokorski
Ratio of the modular mediated and anomaly mediated is given by
a phenomenological parameter a
Choi, Jeong, Okumura, Falkowski, Lebedev, Mambrini,Kitano, Nomura
Baer, Park, Tata, Wang’06,07
SUSY Theory at the LHC
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GUT-less and Moduli Mediation
Ellis,
Olive,
Sandick’07
m is smaller
in the GUT less case
for this
Example.
MM-AMSB
GUT-less
SUSY Theory at the LHC
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Other Examples…
Bino-wino Coannihilation,
Mixed Wino coannihilation
In these cases, the lightest chargino and the second lightest neutralino are
very close to the lightest neutralino
~
 02


~0
1
g : decay opens up along with other three
body decay modes
Baer et. al.’05
Long-lived charged particles:
Gravitino LSP (mass around 100 GeV…)
and sleptons NLSP
One can find that the sleptons to decay after a long time
Feng, Su, Takayama, ’04
Stop NLSP: stop charm+ ~
01
Gladyshev, Kazakov, Paucar’05’07
NMSSM: This model can have extra Z’, sneutrino as dark matter candidate,
In the context of of intersecting Brane Models [ Kumar, Wells’ 06]
Higgs signal at the LHC
Dermisek, Gunion’05
SUSY Theory at the LHC
Moretti et al ‘06
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Other Examples…
Martin,’07; Baer et al,’07
“Compressed” MSSM:
− m2Hu = 1.92 M 23 + 0.16 M2 M3 − 0.21 M 22 − 0.33 M3 At − 0.074 M2 At +…
Naturalness argument : M3 is small, use M3<(M2,M1) at the GUT scale
Relic density is satisfied by neutralino annihilation via t –t bar production,
stop coannihilation etc.
The GUT scale
A typical sample of
parameters are
``compressed"
M1,2,3= 500, 750, 250,
mass spectrum with
A0 = -500, m0 = 342GeV
 h2 = 0.11
Reduction of
leptons in the
signal.
Inflation and MSSM : Flat directions LLE, UDD etc. Smaller sparticle masses are
needed once the constraints from ns, dH are included
Allahverdi, Dutta, Mazumdar,07
Little Hierarchy : Smaller stop mass is needed
Ratazzi et al’06, Dutta, Mimura’07
SUSY Theory at the LHC
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EGRET-SUSY
EGRET excess of diffuse galactic gamma rays is explained as a
signal of supersymmetric dark matter annihilation
De Boer, Sander, Zhukov
Gladyshev, Kazakov’05,’06
Fitted SUSY parameters
m0=1400 GeV
tanβ=50
m1/2=180 GeV
A0=0.5m0
ATLAS
Gluino decays have a clear
signature (4μ + 4jets + PT +
up to 4 secondary vertices).
Expected # of events
for ATLAS after 1year
of running with LHC
luminosity 1034 cm-2s-1
is around 150
Bednyakov, Budagov, Gladyshev,
Kazakov, Khoriauli, Khramov,
Khubua’06’07
CMS tri-lepton discovery potential
of this region
DeBoer, Zhukov, Nigel ,Sander,’06, ‘07
SUSY Theory at the LHC
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Conclusion
LHC is a great machine to discover supersymmetry which would
solve problems in particle physics and cosmology
Signature contains missing energy (R parity conserving) many
jets and leptons : Discovering SUSY should not be a problem!
Once SUSY is discovered, attempts will be made to connect particle physics to
cosmology
The masses and parameters will be measured, models will be investigated
Four different cosmological motivated regions of the minimal SUGRA model
have distinct signatures
Based on these measurement, the dark matter content of the universe
will be calculated to compare with WMAP/PLANCK data.
SUSY Theory at the LHC
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Conclusion…
I hope not…
The search for Weapons of Mass Destruction
SUSY Theory at the LHC
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