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1
Bhaskar Dutta
Texas A&M University
Search for DM at the LHC using
Vector Boson Fusion
CETUP: SOUTH DAKOTA
2
(i) Cascade Decays of squarks and Dark Matter Search
Outline
(ii) Direct Production Dark Matter Sector at the LHC
Via Vector Boson Fusion
(iii) Conclusion
3
LHC and Dark Matter
Usual method to probe these non-colored particles:
LHC is very efficient in producing
colored particles
Annihilation cross-section
of dark matter particles generates dark
matter content of the universe
Annihilation cross-section strength mostly depend on the
colorless particles, e.g., sleptons, staus, charginos, neutralinos, etc.
Cascade decays of squarks and gluinos
4
The signal :
jets + leptons+ t’s +W’s+Z’s+H’s + missing ET
Via Cascade decays at the LHC
(or l+l-, t+t-)
DM
DM
Colored particles are
produced and they
decay finally into the
weakly interacting stable
particle
High PT jet
High PT jet
[mass difference is large]
The pT of jets and leptons
depend on the sparticle
masses which are given by
models
R-parity conserving
(or l+l-, t+t-)
5
DM at the LHC
Ambitious Goal: Final states Masses Model Parameters
Calculate dark matter density
We may not be able to
solve for masses of all the
sparticles in a model
Solving for the MSSM : Very difficult
0
1~~++ lqQ
0
1~~+ lL
0
1
0
4,3,2~,,~ + llhZ etc.
Identifying one side
is very tricky!
Not all the sparticles
appear in cascade
decays
Problem 1:
Problem 2:
Apply :
Bi-Event Subtraction
Technique (BEST) Dutta, Kamon,
Krislock, ‘12
6
1fb 10
-L
1fb 50
-
6 6
Determining Dark Matter Content mSUGRA Non Universal Higgs Model
@ 200 fb-1
1fb 001 -
Mirage Mediation Model
Determine DM content at
14 TeV LHC with high luminosity
Dutta, Kamon, Kolev, Krislock, Oh,
Phys.Rev. D82 (2010) 115009
Dutta, Kamon, Krislock, Sinha, Wang,
Phys.Rev. D85 (2012) 115007
Arnowitt, Dutta, Gurrola, Kamon, Krislock, Toback,
Phys.Rev.Lett. 100 (2008) 231802
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Dark Matter at the LHC
For simple model: the model parameters can be
determined
nature of dark matter candidate
Is the neutralino a Bino, Wino or
Higgsino?
Very difficult to establish!
We need to produce them directly!
For a general model:
(Bino: Smaller annihilation cross-section
Wino/Higgsino: Larger annihilation cross-section)
Are there sleptons around to increase
the annihilation cross-sections?
2. DM via Stop at the LHCLHC
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Utilize Stop decay modes to search charginos, sleptons, neutralinos
Existence and type of DM particle, hard to calculate the DM content
2 jets+ 2 leptons (OSSF-OSDF)
+missing energy
Ex. 3 is mostly Bino-Higgsino
Correct relic density
0
1
For lighter sleptons
Dutta, Kamon, Kolev,Wang, Wu,
Phys. Rev. D 87, 095007 (2013)
Ex. 1 is mostly bino and is wino
Topness variable to identify stops
Stop can identified via fully hadronic or
1 lepton plus multijet final states
Ex. 2 are mostly Higgsino 0
2,1
0
1 0
2
[Yang Bai, Cheng, Gallichio, Gu, 1203.4813;Han,
Katz, Krohn, Reece, 1205.5808;Plehn, Spannowsky,
Takeuchi, 1205.2696;Kaplan, Rehermann, Stolarski,
1205.5816; Dutta, Kamon, Kolev, Sinha, Wang,
1207.1893]
Grasser, Shelton, arXiv:1212.4495
[More in Kuver’s talk]
DM at the LHC Via VBF
9 Dutta, Gurrola, Johns, Kamon, Sheldon, Sinha, Phys. Rev. D 87, 035029 (2013)
Direct probes of charginos, neutralinos and sleptons
P + P
Two high ET forward jets in opposite hemispheres
with large dijet invariant mass
VBF studies
10
jjjjjjjjpp0
2
0
2
0
211111~~,~~,~~,~~
jjpp0
1
0
1~~
jjvjjvjjjjjjeepp ~~,~~,~~,~~,~~ ttt
1.
2.
3.
jjttpp 11
~~4. : Kuver’s talk
VBF studies
11
jjjjjjjjpp0
2
0
2
0
211111~~,~~,~~,~~
1.
Background: W + jets, Z + jets, WW, ZZ, etc.
Signal: missing energy, ++ t22 j missing energy ++ 22 j
For : 01
021
~,
mmmml
For Heavy Sleptons:
Signal: 2 j + W W, W Z, Z Z + missing energy,
tt
1. Charginos, Neutralinos via VBF
GeV 75 MET GeV; 650)(
0 ;24
GeV 75 )(jp GeV; 50(j)p with jets 2
21
21
1TT
j,jM
.
2 Benchmark Scenarios
30 GeV 30 GeV
12
180 GeV
90 GeV 90 GeV
180 GeV
VBF Kinematics
Signal Characteristics:
Large MET, large Mjj, large pT jets
Phys. Rev. D 87, 035029 (2013)
)( 21 j,jMTE
)( 1jpT
GeV 30)()(
GeV 90)(
GeV 180)()(
011
01
021
-t
+
+
~M~M
~M
~M~~M
13
Signal: ≥ 2j+2t+missing energy
14
2 jets each with pT>50 GeV, leading pT>75 GeV
|(j1,j2)|>4.2, j1j2<0, Mj1j2>650 GeV
TeV
Lum: 25 fb-1
Signal: missing energy
8s
++ t22 j
Two t 's with pT >20 GeV in < 2.1, with R(tt ) > 0:3. All t's are hadronic
The t ID efficiency is assumed to be 55% and the jett Mis-
identification rate is taken to be 1%,
GeV,180~ 021
~~ mm
15
Signal: ≥ 2j+2t+missing energy
2.4 s
Signal: ≥ 2j+2+missing energy
16
2 jets each with pT>50 GeV, leading pT>75 GeV
|(j1,j2)|>4.2, j1j2<0, Mj1j2>650 GeV
TeV
Lum: 25 fb-1
8s
Signal: missing energy ++ 22 j
Two isolated 's with pT >20 GeV in < 2.1
For 3s :
GeV,180~ 021
~~ mm
GeV330~ 021
~~ mm
17
Signal: ≥ 2j+2+missing energy
6 s
18
Cross Sections via VBF 2. Lightest neutralinos via VBF jjpp
0
1
0
1~~
CDM
19
Cross Sections via VBF 2. Lightest neutralinos via VBF
Pure Wino/Higgsino dark matter scenarios are special
20
Cross Sections via VBF
LHC8 LHC14
2. Lightest neutralinos via VBF jjpp
0
1
0
1~~
21
Cross Sections via VBF 2. Lightest neutralinos via VBF
Missing ET (GeV)
22
Wino-DM MET
Delannoy, Dutta, Gurrola, Johns, Kamon, Luiggi, Melo,Sheldon, Sinha, 1304.7779
23
Wino-DM Missing Energy
Delannoy, Dutta, Gurrola, Johns, Kamon, Luiggi, Melo,Sheldon, Sinha, 1304.7779
24
Wino-DM MET Preselection:
missing ET > 50 GeV,
2 leading jets (j1,j2) :pT (j1),pT(j2) >30 GeV ,
|(j1, j2)| > 4.2 and j1j2 < 0.
Optimization:
Tagged jets : pT > 50 GeV, Mj1j2 > 1500 GeV;
Events with loosely identified leptons(l = e; ; th) and b-quark jets: rejected.
Missing ET : optimized for different value of the LSP mass.
Jet energy scale uncertainty ~20% change the significance by 4%
25
Wino-DM MET
Simultaneous fit of the observed rate,
shape of missing energy distribution:
26
Conclusion • Annihilation cross-section of DM particles is mostly
dominated by the particles without any color charge
• These particle are mostly studied from the cascade decays
of new colored particle since direct production is small and
the signal suffers from large background
• We use VBF production of charginos, neutralinos,
sleptons etc. utilizing two high ET jets in opposite
hemispheres
• It is possible to determine the dark matter content with
high accuracy
27
Backup
28
Sleptons via VBF
Chaudhuri, Datta, Huitu, Konar, Moretti, Mukhopadhyaya hep-ph/0304192
DY
VBF