Bhaskar Dutta

1
23 of the Universe at the Large Hadron Collider
Colloquium, 03/13/08 Texas Tech University
Bhaskar Dutta Texas AM University
Supported by
2
Collision of 2 Galaxy Clusters
splitting normal matter and dark matter apart
Another Clear Evidence of Dark Matter
(8/21/06)
3
Contents of the Universe
4
The 23 is not observed in the laboratory.. This
new matter can not be seen visually! Cold Dark
Matter (CDM)
23 of the Universe at the LHC
3
4
What is Dark Matter?
MENU
SPECIALS Dark Energy Power Drink .. 73 -
Chefs choice Dark Matter Sandwich 23 -
Neutral, long-lived Atomic Soup . 4 - All
elements in one
Cafe Universe
Can it be one of the known particles?
5
CDM in The Standard Model?
The Standard Model (SM) describes all these
particles and 3 of 4 forces. We have confirmed
the existence of those in the laboratory
experiments.
6
No!
Quarks, electron, muon, tau particles, and force
carriers can not be the dark matter, since their
interactions are stronger than what we
expect. Neutrinos can, but they are too light!
X
We need new idea, based on a new symmetry.
Supersymmetry or SUSY
7
New Model

• The Standard Model
• Cannot provide a dark matter candidate.
• Has a serious Higgs mass divergence problem due
  to quantum correction.
• Cannot accommodate masses for neutrinos.
• Cannot provide enough matter-antimatter
  asymmetry.
• ?Standard Model has fallen!

• Supersymmetry
• Provides a candidate for dark matter
  neutralino.
• Solves the Higgs mass problem in a very elegant
  way.
• Supersymmetric grand unified models include
  neutrinos!
• Dutta, Mimura, Moahapatra, PRL 96,
  (2006) 061801 94, (2005) 091804 PRD 72 (2005)
  075009 (2004) 115014
• Can produce correct matter-antimatter asymmtery
• Dutta, Kumar, Leblond, JHEP 0707 (2007) 045
  Dutta, Kumar, PLB 643 (2006) 284

• What is the new model?
• Can the neutralino be detected and consistent
  with the dark matter content of the Universe?

23 of the Universe at the LHC
7
8
Higgs and Fermion Masses

• 1 The Higgs Mass (Mh) has the following bounds
  
• 114 GeV lt Mh lt 182 GeV in the SM
• 114 GeV lt Mh lt 150 GeV in minimal SUSY model
• Tevatron and/or LHC will probe this Higgs mass.
• 2 In SM, there also exists a tremendous
  hierarchy among the fermion masses, e.g.,
  mt/me105.
• ? Attempts are being made to understand the
  origin of these hierarchies in the context of
  string motivated SUSY models.

23 of the Universe at the LHC
8
9
Particle Physics and Cosmology
LHC
LHC
LHC
SUSY is an interesting class of models to provide
a weakly interacting massive neutral particle (M
100 GeV).
LHC
23 of the Universe at the LHC
9
10
When Were the DM Particles Created?
Now
380,000 years
CMB
0.0000001 seconds
23 of the Universe at the LHC
10
11
Supersymmetrized SM

• The fundamental law(s) of nature is hypothesized
  to be symmetric between bosons and fermions.
• Fermion ? Boson
• Have they been observed? ? Not yet.

12
SUSY Transition Diagrams
SUSY partner of W boson chargino
SUSY partner of t lepton stau
SUSY partner of Z boson neutralino
Lightest neutralinos are always in the final
state! This neutralino is the dark matter
candidate!!
13
Dream of the Unification
Grand Unified Theory GUT
The grand unification of forces occur in SUSY
models.
14
Minimal Supergravity (mSUGRA)
SUSY model in the framework of unification

Key Experimental Constraints
4 parameters 1 sign tanb ltHugt/ltHdgt at
MZ m1/2 Common gaugino mass at MGUT m0
Common scalar mass at MGUT A0
Trilinear couping at MGUT sign(m) Sign of
m in W(2) m Hu Hd

• MHiggs gt 114 GeV
• Mchargino gt 104 GeV
• 2.2x10-4 ltB(b ? s g) lt4.5x10-4
• (g-2)m 3 s deviation from SM

Arnowitt, Chamesdinne, Nath, PRL 49 (1982) 970
NPB 227 (1983) 121. Barbieri, Ferrara, Savoy,
PLB 119 (1982) 343. Lykken, Hall, Weinberg, PRD
27 (1983) 2359.
15
Anatomy of WCDM
.
Co-annihilation Process
Griest, Seckel 91

.
Use well motivated mSUGRA as a benchmark model
16
Dark Matter Allowed Regions
Focus-point Region
Arnowitt, Dutta, Santoso, NPB 606 (2001)
59 Arnowitt, Dutta, Hu, Santoso, PLB 505 (2001)
177 Allahverdi, Dutta, Mazumdar, PRD 75 (2007)
075018
Co-annihilation Region
17
Dark Matter Allowed Region
Co-annihilation Region
23 of the Universe at the LHC
17
18
Probing the susy Dark Matter
LHC, Tevatron - Accelerator
Wc ? 0.23
Production Decay
Direct Detection of DM ! _at_ LUX, XENON 100,
CDMS etc
Detector
DM Hunters
19
Model Parameters and Expts.
SUSY Particles can be directly produced at the
colliders

• Colliders
• Large Hadron Collider (pp) (In a year),
• Tevatron (pp) (running),
• International Linear Collider (ee-) (future?)

Indirect effects

• Rare Decays of B meson at Tevatron B factories
• Arnowitt, Dutta, Hu, Oh, PLB 641 (2006) 305 PLB
  633 (2006) 748 Dutta, Kim, Oh, PRL 90 (2003)
  011801
• Dark Matter Detection Experiments

20
Tevatron and Cosmology
Tevatron and Cosmological Connection
SUSY particles can be directly produced at the
Tevatron
We found the reach is not high! Krutelyov,
Arnowitt, Dutta, Kamon, McIntyre, Santoso, Phys.
Lett. B505, (2001) 161 But, we propose a
promising experimental signal Arnowitt Dutta,
Kamon, Tanaka, Phys. Lett. B 538 (2002) 121 Bs
? m m -
21
Rare Decay Bs ? mm-
Within the SM, we will not see any events even
with 100 x 1012 collisions. In the SUSY models
(large tanb), which are cosmologically
consistent, the decay can be enhanced by up to
1,000.
22
23 of the Universe at the LHC
23
LHC and Cosmological Connection
mSUGRA at tanb 50 Arnowitt, Dutta, et al., PLB
538 (2002) 121
mSUGRA signal at the LHC
24
LHC Large Hadron Collider
()
Two large international collaborations. () TAMU
is a CMS member institution.
blue and red dots and yellow lines are studied to
figure out what happens in the collision!
PHYSICS is extracted out of many trillion pp
collisions.
Arnowitt, Dutta, Kamon, Kolev, Toback, PLB 639
(2006) 46 Arnowitt, Arusano, Dutta, Kamon, Kolev,
Simeon, Toback, Wagner, PLB 649 (2007)
73 Arnowitt, Dutta, Gurrola, Kamon, Krislock,
Toback, arXiv0802.2968
23 of the Universe at the LHC
24
25
First Analysis at the LHC
Kinematical Cuts to Establish SUSY

• PTj1 gt 100 GeV, PTj2,3,4 gt 50 GeV
• Meff gt 400 GeV (Meff is a scalar sum of
  PTj1,2,3,4 and PTmiss)
• PTmiss gt max 100, 0.2 Meff

Hinchliffe, Paige, Phys. Rev. D 55 (1997) 5520
The heavy SUSY particle mass is measured by
combining the final state particles
q
q
q
q
26
Meff and Relic Density
SUSY scale is measured with an accuracy of 10-20

• This measurement does not tell us whether the
  model can generate the right amount of dark
  matter
• The dark matter content is measured to be 23
  with an accuracy of around 3 at WMAP

• Questions

How can we establish the dark matter allowed
regions?
To what accuracy can we calculate the relic
density based on the measurements at the LHC?
27
Coannihilation Region at the LHC
One of the key reactions
Unique kinematics
gt3 jet PTmiss gt2t
28
Coannihilation Region (tanb40)
tanb 40, m gt 0, A0 0
Phys. Lett. B 649 (2007) 73
Can we measure DM at the LHC?
29
Anatomy Mass Distribution
Phys. Lett. B 639 (2006) 46
Mmax(true) 78.7 GeV
Mpeak 47.1 GeV
SUSY 125 counts (Mtt lt 100 GeV)
23 of the Universe at the LHC
29
30
Anatomy Mass Distribution (2)
GOAL Establish the path for a well motivated
SUSY scenario before the experiment starts in
2008.
Probing squark mass
23 of the Universe at the LHC
30
31
Five Observables

• Sort ts by ET (ET1 gt ET2 gt )
• Use OS-LS method to extract t pairs from the
  decays

SMSUSY Background gets reduced

• Ditau invariant mass Mtt
• Jet-t-t invariant mass Mjtt
• Jet-t invariant mass Mjt
• PT of the low energy t
• Meff 4 jets missing energy
• Meff (b) 4 jets (leading jet is a b quark)
  missing energy

All these variables depend on masses gt model
parameters

Since we are using 6 variables, we can measure
the model parameters and the grand unified scale
symmetry (a major ingredient of this model)
32
How to Establish the Discovery

• Phys. Lett. B 639 (2006) 46 Phys. Lett. B 649
  (2007) 73 arXiv0802.2968
• 1 Low energy ts are crucial to discover the DM
  allowed region.
• 2 We construct different observables involving
  these ts.
• 3 We study Mjtt, Mtt etc distributions and
  their properties
• e.g., Peak(Mtt) f (Msquark, Mstau, M , M
  )
• 4 Squark and stau masses can be expressed in
  terms of m0, m1/2, A0, tanb. Note our observables
  are not that sensitive to A0 and tanb in the dark
  matter allowed region
• 5 We use these observables to solve for m0 ,
  m1/2, A0, tanb
• 6 We can now calculate the dark matter content

33
Dark Matter at TAMU
Kamon, Safonov, and Toback will use the path to
accurately measure the model parameters from the
detailed features of the signals (real data) when
the LHC will start.
Synergism between the theorists and the
experimentalists
We then calculate the relic density and compare
with WMAP.
34
Determining Model Parameters
The Model parameters are solved by inverting the
following functions
(in GeV)
35
GUT Scale Symmetry
We can also probe the physics at the Grand
unified theory (GUT) scale
Use the masses measured at the LHC and evolve
them to the GUT scale using mSUGRA
The masses , , unify at the grand
unified scale in SUGRA models
We can measure this unification to an accuracy of
lt5
Another evidence of a symmetry at the grand
unifying scale!
36
Relic Density and Luminosity

• How does the uncertainty in the Dark
• Matter relic density change with Luminosity?

• dWh2/Wh2 6 (30 fb-1)

37
DM Particle Direct Detection?
The measurement at the LHC will pinpoint the
parameters of SUSY models. We can predict the
direct detection probability of dark matter
particles.
µ
()
Complementary measurements !
detector
Dark Matter particle
() The TAMU group is one of the leading
institutions in the US.
23 of the Universe at the LHC
37
38
Status - Direct Detection

• Ongoing/future projects CDMS, ZEPLIN, XENON10,
  LUX
• Status
• DAMA group (Italy) claims to have observed some
  events.
• CDMS, ZEPLIN, XENON10 dispute their claim.

CDMS
DAMA
ZEPLIN
XENON10
DAMA
10-8 pb
Accomando, Arnowitt, Dutta, Santoso, NPB 585
(2000) 124
Cross section lt 9 x 10-8 pb for 100 GeV
neutralino
Close to the current sensitivity
39
International Linear Collider (ILC)
CDM Allowed Region and Kinematical Reach for
t1t1- c20c10
The plan is to build an ILC after the LHC starts
running! Dark matter content will be known with
higher precision. The parameters of SUSY models
can be measured with a greater accuracy
Khotilovich, Arnowitt, Dutta, Kamon, PLB 618
(2005) 182
23 of the Universe at the LHC
39
40
Conclusion

• SM of particle physics has fallen.
• Supersymmetry seems to be natural in the rescue
  act and the dark matter content of the universe
  can be explained in this theory.
• The minimal SUGRA model is consistent with the
  existing experimental results.
• 1 LHC can probe the minimal SUGRA model
  directly.
• The dark matter content can be measured with a
  high accuracy .
• 2 Direct detection experiments will
  simultaneously confirm the existence of these
  models.
• 3 Future international linear collider will
  shed further light!

23 of the Universe at the LHC
40
41
My Vision Diagram
23 of the Universe at the LHC
41
42
Conclusion
23 of the Universe at the LHC
42
43
Backups
44
mSUGRA Case Study at tanb 40
45
180
23 of the Universe at the LHC
45
46
Meff Distribution 4j ETmiss

• ETj1 gt 100 GeV, ETj2,3,4 gt 50 GeV No es,
  ms with pT gt 20 GeV
• Meff gt 400 GeV (Meff ? ETj1ETj2ETj3ETj4
  ETmiss No b jets eb 50)
• ETmiss gt max 100, 0.2 Meff

At Reference Point
Meffpeak 1220 GeV (m1/2 335 GeV)
Meffpeak 1331 GeV (m1/2 365 GeV)
Meffpeak 1274 GeV
47
Meff(b) Distribution

• ETj1 gt 100 GeV, ETj2,3,4 gt 50 GeV No es,
  ms with pT gt 20 GeV
• Meff(b) gt 400 GeV (Meff(b) ? ETj1bETj2ETj3ETj
  4 ETmiss j1 b jet)
• ETmiss gt max 100, 0.2 Meff

At Reference Point
Meff(b)peak 933 GeV (m1/2 335 GeV)
Meff(b)peak 1122 GeV (m1/2 365 GeV)
Meff(b)peak 1026 GeV
Meff(b) can be used to determine A0 and tanb even
without measuring stop and sbottom masses