1. Dark Matter at the LHC Bhaskar Dutta Texas A&M University
Texas Cosmology Network Meeting, UT, Austin
12/17/07
30th Oct ’ 09
Dark Matter at the LHC
Cosmological Connection at the LHC: Stau Neutralino Coannihilation Case 1 1

2. Dark Matter and SUSY
+ ….
We need to observe the new layer of matter in order
to establish this explanation
Dark Matter at the LHC 2 2

3. SUSY at the LHC The signal : jets + leptons + missing ET
(or l+l-, t+t-)
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
R-parity conserving
(or l+l-, t+t-)
High PT jet
The signal : jets + leptons + missing ET
Dark Matter at the LHC 3

4. mSUGRA: Minimal Scenario
SUSY Models
Minimal Supersymmetry Standard Model has more than
100 parameters
We may not have enough observables to establish them
We start with a simple scenario and go to complicated cases
mSUGRA: Minimal Scenario
4 parameters
+ 1 sign
Dark Matter at the LHC 4 4 4

5. Dark Matter Allowed Regions
tanb = 40
A0 = 0, m > 0
FP/HB Region 3 c
m0 (GeV)
Over-dense DM Region 2 a b
m1/2 (GeV)
Coannihilation Region 1
Excluded by
Rare B decay b  sg
No CDM candidate
Muon magnetic moment a b c
Dark Matter at the LHC 5 5 5

6. Observables at the LHC SUSY Masses The observables include:
Z, h, W, t, t, b, jet, l and
missing energy
Mjtt
&Mjt
97%
SUSY Masses
(CDM)
pTt > 40 GeV
pTt > 20 GeV
ETjet > 100 GeV
Mtt
& pT(t)
100%
The observables are
determined by the
underlying physics of
the model
Dark Matter at the LHC

7. Case 1. Coannihilation Region
Griest, Seckel ’91
+ ….
Low energy taus
characterize the CA region
However, one needs to
measure the model
parameters to predict the
dark matter content in this
scenario
SUSY Masses
97%
100%
(CDM)
2 quarks+2 t’s
+missing energy
Arnowitt, Dutta, Kamon,Toback’08 7
Dark Matter at the LHC 7

8. Determining mSUGRA Parameters
Solved by inverting the following functions:
10 fb-1
Dark Matter at the LHC 8 8
Phys.Rev.Lett.100:231802,2008.

9. Case 2 : Over-dense region
m1/2=440, m0=471, tanb=40, mtop=175
87%
1041
1044
500
393
181
341
114
462
13% 91
ETmiss > 180 GeV;
N(jet) > 2 with ET > 200 GeV;
ETmiss + ETj1 + ETj2 > 600 GeV
N(b) > 2 with
PT > 100 GeV; 0.4< DRbb < 1
Dark Matter at the LHC 9 9 9

10. Determining Wh2 Solved by inverting the following functions: 1000 fb-1
Dutta, Kamon,Nanopoulos etal ’09
Phys.Rev.D79:055002,2009
Dark Matter at the LHC 10 10

11. Case 3 : Focus Point /HB M4x4 (m1/2, m, tanb ) Prospects at the LHC:
m0, A0, m, tanb Z
Prospects at the LHC:
A few mass measurements are available: 2nd and 3rd neutralinos, and gluino
m1/2, m, tanb
M4x4 (m1/2, m, tanb )
Dark Matter at the LHC 11 11

12. Case 4 : Non-U SUGRA Steps:
Nature may not be so kind … Our studies have been done based on a minimal scenario (= mSUGRA). …
Let’s consider a non-universal scenario: Higgs non-universality: mHu, mHd m0
Steps:
Reduce Higgs coupling parameter, m, by increasing
mHu, …  More annihilation (less abundance)
 correct values of Wh2
3) Find smoking gun signals  Technique to calculate Wh2
SUGRA Models at the LHC 12 12

13. Extraction of Model Parameters
Dark Matter at the LHC 13 13

14. End-points-nonuniversal
We have 3 (4) parameters in the
chargino-neutralino system:
m1/2, m, tanb (m1,m2, m, tanb)
M(jW) [ ] = GeV
M(jW) [ ] = GeV
[use 2 t’s since ]
M(jW)[ ] = GeV
[use Z since ]
M(jW) [ ] = GeV
We can use stop decay chain
In this case we use a b/t
~500 GeV
M(bW)
Theory:738.8
Similarly, M(tZ) =338 GeV
M(jW)
Mttt, Mjtt etc can also be constructed
Dark Matter at the LHC

15. Conclusion 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
measure the sparticle masses (highly non trivial!),
establish the model and make connection between
particle physics and cosmology
Different cosmologically motivated regions of the
minimal model have distinct signatures.
It is possible to determine model parameters and
the relic density based on the LHC measurements
Work is in progress to determine non-universal model
Parameters----looks promising
Dark Matter at the LHC