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SUSY at LHC

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m(l l-)max. Using other. observables like. Mllq Mlq, MT, it is ... Baer, Barger, Shaughnessy, Summy, Wang 07. Gluino decays into t t c0, t b c - (mostly) ... – PowerPoint PPT presentation

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Title: SUSY at LHC


1
SUSY at LHC
Bhaskar Dutta Texas AM University
2
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
Model
3
Collision of 2 Galaxy Clusters
splitting normal matter and dark matter apart
Another Clear Evidence of Dark Matter (8/21/06)
Ordinary Matter (NASAs Chandra X Observatory)
time
Approximately the same size as the Milky Way
Dark Matter (Gravitational Lensing)
3
4
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
R-parity conserving
DM
(or ll-, tt-)
High PT jet
The signal jets leptons missing ET
5
Example Analysis
Kinematical Cuts, Event Selection - 4 jets ETmiss
  • PTj1 gt 100 GeV, PTj2,3,4 gt 50 GeV
  • Meff gt 400 GeV (Meff ? PTj1PTj2PTj3PTj4
    ETmiss)
  • ETmiss gt Max 100, 0.2 Meff

Paige, Hinchliffe et al. , Phys. Rev. D 55 (1997)
5520
6
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
7
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
8
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 ltHugt/ltHdgt at the electroweak
scale sign(m) Sign of Higgs mixing parameter
(W(2) m Hu Hd)
Experimental Constraints
  • MHiggs gt 114 GeV Mchargino gt 104 GeV
  • 2.2x10-4 lt Br (b ? s g) lt 4.5x10-4
  • (g-2)m

9
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).
Tovey02
M. Tytgat (SUSY07)
10
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 Pukhov04
If we observe missing energy, then we have a
possible dark matter candidate . LHC
experiments sensitive only to LSP lifetimes lt1 ms
( tU 13.7 Gyr)
Using the model parameters we need to calculate
relic density
11
Dilepton Edge Measurement
  • Can perform SM SUSY background subtraction
    using distribution
  • ee- mm- - em- - me-
  • Position of edge measured with precision 0.5
    (30 fb-1).
  • m0 100 GeV
  • m1/2 300 GeV
  • A0 -300 GeV
  • tan(b) 6
  • sgn(m) 1

ee- mm-
Point 5
ATLAS
30 fb-1 atlfast
Physics TDR
12
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.

bbq edge
llq threshold
1 error (100 fb-1)
2 error (100 fb-1)
TDR, Point 5
TDR, Point 5
TDR, Point 5
TDR, Point 5
ATLAS
ATLAS
ATLAS
ATLAS
13
Model Independent Masses
  • Measurements from edges from different jet/lepton
    combinations to obtain model-independent mass
    measurements.



c01
lR
ATLAS
ATLAS
Mass (GeV)
Mass (GeV)


c02
qL
ATLAS
ATLAS
LHC Point 5
Mass (GeV)
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)
14
Higgsino vs Gaugino
and Higgsinos, three gaugino masses
are very close
Kitano, Nomura06
ll-
Mslepton gt Mz
With M( )-M( ) ltMZ
Gaugino Like and
The spectrum terminates at m(ll-)max
Using other observables like Mllq Mlq, MT, it
is Possible to measure squark and the
neutralino mass with An accuracy of 2 and 10
Higgsino
Shapes looks different, 2 scenarios can be
distinguished
15
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
16
Focus Point Jetsleptons
Typical mSUGRA point m02910 A00 m1/2350
mgt0 tanb30 Large sfermion mass, smaller
gaugino masses comparatively
LHC events characterized by high jet, b-jet,
isol. lepton multiplicity
Baer, Barger, Shaughnessy, Summy, Wang 07
_
_
Gluino decays into t t c0, t b c- (mostly)
Higher jet, b-jet, lepton multiplicity
requirement increase the
signal over background rate
17
Focus Point Jetsleptons
Require cuts n(j) 7, n(b) 2, AT 1400 GeV
ETmissSETjetSETlepton
Gluino mass can be measured with an accuracy 8
Baer, Barger, Shaughnessy, Summy, Wang 07
18
Focus Point Leptons
  • Large m0 ? sfermions are heavy
  • m03550 GeV m1/2300 GeV A00 tanß10 µgt0
  • Direct three-body decays c0n ? c01 2 leptons
  • Edges give m(c0n)-m(c01)





Tovey, PPC07
Similar analysis Error (M2-M1) 0.5 GeV
G. Moortgat-Pick (SUSY 07)
19
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

m070 A0-300 m1/2250 mgt0 tanb10
Nojiri, Polsello, Tovey05
The error of relic density 0.108 0.01(stat
sys)

Includes (0.00,-0.002 )M(A) (0.001, -0.011)
tan ß (0.002,-0.005) m(t2)
With a luminosity 300 fb-1, tt edge controlled
to 1 GeV
20
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
21
Coann. Signatures (tanb10)
  • Small slepton-neutralino mass difference gives
    soft leptons
  • Low electron/muon/tau energy thresholds crucial.
  • Study point chosen within region
  • m070 GeV m1/2350 GeV A00 tanß10 µgt0
  • Decays of c02 to both lL and lR kinematically
    allowed.
  • Double dilepton invariant mass edge structure
  • Edges expected at 57 / 101 GeV

Preliminary
ATLAS
100 fb-1
  • ETmissgt300 GeV
  • 2 OSSF leptons PTgt10 GeV
  • gt1 jet with PTgt150 GeV
  • OSSF-OSOF subtraction applied

Tovey, PPC07
22
Coannihilation Region (tanb40)
tanb 40, m gt 0, A0 0
Can we measure DM at colliders?
23
Coann. Signatures (tanb40)
In Coannihilation Region of SUSY Parameter Space
Soft t
Soft t
Final state 3/4 tsjets missing energy Use
hadronically decaying t
24
Four Observables
  • Sort ts by ET (ET1 gt ET2 gt ) 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 DM
  • jet-t-t invariant mass Mjtt

D. Tobacks 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
25
SUSY Parameters
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 (Wjets,
t-tbar,) ETmiss gt 180 GeV, ETj1 gt 100 GeV,
ETj2 gt 100 GeV, ETmiss ETj1 ETj2 gt
600 GeV
ORDER TAUS BY PT APPLY CUTS ON TAUS WE EXPECT
A SOFT t AND A HARD t PTall gt 20 GeV, PTt1 gt
40 GeV
26
Mttvis in ISAJET
Version 7.69 (m1/2 347.88, m0 201.1) ?
Mgluino 831
Chose di-t pairs from neutralino decays with (a)
h lt 2.5 (b) t hadronically-decaying tau
27
Determination of m0 , m1/2
DM and Mgluino ? m0 , m1/2, (for fixed A0 and
tanb)
We determine dm0/m0 1.2 and dm1/2/m1/2 2
dWh2/Wh2 7 (10 fb-1) (for A00, tanb40)
28
Higgs non-universality
The most common extension of mSUGRA
Case 2.
Case 1.
Drees00 Baer Belyaev, Mustafayev, Profumo,
Tata05
Ellis, Olive, Santoso03
LHC signal
A, H and H- will be relatively light, and more
accessible to direct LHC searches

There can be light uR, cR squarks, small m
leads to light and
?oi
?i
29
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, Wang06,07
30
GUT-less and Moduli Mediation
Ellis, Olive, Sandick07
m is smaller in the GUT - less case for this
Example.
MM-AMSB
GUT-less
31
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
decay opens up along with other three body
decay modes
Baer et. al.05
Gravitino LSP (mass around 100 GeV) and
sleptons NLSP
Long-lived charged particles
One can find that the sleptons to decay after a
long time
Feng, Su, Takayama, 04
Gladyshev, Kazakov, Paucar0507
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
Moretti et al 06
Dermisek, Gunion05
32
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
M3lt(M2,M1) at the GUT scale
Relic density is satisfied by neutralino
annihilation via t t bar production, stop
coannihilation etc.
The GUT scale parameters are M1,2,3 500, 750,
250, A0 -500, m0 342GeV
A typical sample of compressed" mass spectrum
with W 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
Dutta, Mimura07
Ratazzi et al06,
33
EGRET-SUSY
EGRET excess of diffuse galactic gamma rays is
explained as a signal of supersymmetric dark
matter annihilation
Fitted SUSY parameters m01400 GeV
tanß50 m1/2180 GeV A00.5m0
De Boer, Sander, Zhukov Gladyshev, Kazakov05,06
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
CMS tri-lepton discovery potential of this region
DeBoer, Zhukov, Nigel ,Sander,06, 07
Bednyakov, Budagov, Gladyshev, Kazakov,
Khoriauli, Khramov, Khubua0607
34
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.
35
Conclusion
I hope not
                                                
                                             The
search for Weapons of Mass Destruction
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