Particle Physics and Cosmology (PPC)
[PPC 2012 (???)] [PPC 2011 (CERN)] [PPC 2010 (Univ. of Torino/INFN)] [PPC 2009 (Univ. of Oklahoma)] [PPC 2008 (Univ. of New Mexico)] [PPC 2007 (TAMU)] [Big Bang Theory ]
This program at Texas A&M aims to solve the mysterious dark matter puzzle of the universe, one of the major unresolved questions in astronomy. With signals from the collider and the Milky Way, one can understand the nature of the early universe at a ten billionth of a second after the Big Bang, and thus unify the two fields of particle physics and early universe cosmology. The program is possible by a unique collaboration between the phenomenology theory group of Arnowitt, Dutta, and Nanopoulos and three distinct international experimental programs: (a) Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) by Kamon, Safonov, and Toback; (b) the Large Underground Xenon (LUX) dark matter experiment at the new Deep Underground Science and Engineering Laboratory (DUSEL) by Mohapatra, Webb, and White; (c) and the Alpha Magnetic Spectrometer (AMS) experiment at the International Space Station by McIntyre. Further, McIntyre has proposed the "100-TeV collider," which is seven times more powerful than the LHC, to enhance the future PPC program.
"Partcle Physics and Cosmology (PPC)" - T. Kamon designed this "PPC" cube for the 2nd international conference on PPC (PPC08)(*) to visualize the interconnection between particle physics and cosmology. See public talks for more details. If you are interested in more scientific talks, see here. (BTW: This cube was inspired by my 12-yrs. old daughter who was watching "Transformers Movie" with me.) See also the "Standard Model" cube (Window Movie).
(*) The PPC conference was founded by Arnowitt, Dutta and Kamon in 2007, where Dutta and Kamon were co-chairs of PPC07.
Cosmology at Colliders
- Hunting for Dark Matter at the LHC -
There is enough evidence for the existence of the dark matter (DM) in the universe. A recent precision astromonical measurement by Wilkinson Microwave Anisotropy Probe (WMAP) reveals that 23% of the universe (or Ω = 0.23) is composed of cold dark matter (CDM). However, we still don't known what the CDM is. Particle physics theorists have been trying to construct new models that are consistent with the Standard Model (SM), but includes a CDM candidate paricle.

Supersymmetry (SUSY) uniquely opens the possibility to directly connect the SM with an ultimate unification of the fundamental interactions. When combined with supergravity grand unification (SUGRA GUT), it resolves a number of problems inherent in the SM and predicts grand unification at the GUT scale MGUT ~ 1016 Giga-electron-Volts (GeV), subsequently verified at LEP.

A minimal framework of supergravity model (the minimal supergravity or mSUGRA model) is consistent with all existing experimenatal data and provides a leading candidate for CDM observed in universe. Ω = 0.23 constrains mSUGRA model, suggesting four distinct parameter regions: coannhilation (CA) region, focus point (FP) region, A-funnel region, and bulk region. "SUSY mass" spectra in each region are unique. This means we have to employ different experimental techniques to probe all four.

Can we search for dark matter in laboratories? Yes. If SUSY is correct, the Large Hadron Collider (LHC) at CERN is powerful enough to produce SUSY paricles including the SUSY dark matter particle in proton-proton (pp) collisions at 14 Tera-electron-Volts (TeV). Two detectors (ATLAS and CMS) will be ready to detect the collisions in fall 2008. Each experimentist must be a super-detective who can solve the mysterious dark matter puzzle from millisons of trillions of pp collisions.

In 2002, R. Arnowitt, B. Dutta, and T. Kamon launched a global phenomenology project to study cosmologically-motivated SUSY signals at 3 colliders: (a) Tevatron, (b) ILC and (c) LHC.

Within the mSUGRA model in standard cosmology, there are four regions that are equally motivated. Taking into account the measurements of anomalous muon magnetic moment and Br(b → s γ), they began with the CA region at the Tevatron and the ILC in 2002, followed by studies at the LHC in 2004. Further in 2007, their studies were expanded by including mSUGRA signals in non-standard cosmology. Fruitful collaboration with other colleagues amplified the publication productivity. Below are papers and progress:

Standard cosmology
[1] Coannihilation case

  • [#7 of TeV Pheno Project] R. Arnowitt, B. Dutta, T. Kamon, and M. Tanaka, Phys. Lett. B538 (2002) 121
  • [#2 of ILC Pheno Project] V. Khotilovich, R. Arnowitt, B. Dutta, and T. Kamon, Phys.Lett. B618 (2005) 182
  • [#1 of LHC Pheno Project] R. Arnowitt, B. Dutta, T. Kamon, N. Kolev, and D. Toback, Phys. Lett. B 639 (2006) 46
  • [#2 of LHC Pheno Project] R. Arnowitt, A. Aurisano, B. Dutta, T. Kamon, N. Kolev, P. Simeon, D. Toback, and P. Wagner, Phys. Lett. B. 649 (2007) 73
  • [#3 of LHC Pheno Project] R. Arnowitt, B. Dutta, A. Gurrola, T. Kamon, A. Krislock, and D. Toback, Phys. Rev. Lett. 100 (2008) 231802

[2] Non-universarity case

  • [#5 of LHC Pheno Project] B. Dutta, T. Kamon, N. Kolev, A. Krislock, Y. Oh, accepted for publication in PRD (Nov 2010).

[3] "Focus Point" case

  • [#6 of LHC Pheno Project] B. Dutta, W. Flanagan, A. Gurrola, T. Kamon, N. Kolev, A. Krislock, and M. VanDyke, coomplted and unpublished.

[4] "Mirage-mediation" case

  • [#7 of LHC Pheno Project] B. Dutta, T. Kamon, A. Krislock, K. Sinha, K. Wang in progress

Non-standard cosmology
[1] "Overdensed Dark Matter" case

  • [#4 of LHC Pheno Project] B. Dutta, A. Gurrola, T. Kamon, A. Krislock, A.B. Lahanas, N.E. Mavromatos, and D. Nanopoulos, Phys. Rev. D 79 (2009) 055002.


Mysterious universe: Dark energy (73%), dark matter (23%), and nomal matter (4%).

Standard Model (SM): The SM particles (6 quarks, 6 leptons, 3 gauge particles) are just accounted for 4% of universe. [Window Movie]

Cold Dark Matter: 23% of universe is composed of cold dark matter. If cold dark matter is an elementary particle, we need a new particle theory since none of the SM particles possess the dark matter properties. Such a new theory guides us how to search it at various experiments at colliders and underground labs. Two of leading theories are Supersymmetry (SUSY) or Extra Dimension.

Grand Unified Theories (GUTs): Particle physics theories that explain the unification of three of four fundamental forces in nature: strong, weak and electromagnetic forces. The Standard Model (SM) is known to have its structural defects to prevent from explaining physics at much higher energy than ~100 GeV. Supersymmetry (SUSY) rescues us to be able to construct a theory that can explain physics up to the GUT scale (~1016 GeV).

mSUGRA: The minimal supergravity (or mSUGRA) model is a leading theory of particle physics which connects the SM with two Higgs doublets and universality. Since it is a minimal framework, the model is specified by 4 parameters (m0, m1/2, A0, tanβ) plus one sign (a sign of μ) and has been used as many benchmark studies at the Tevatron, at the ILC, and at the LHC.

What is the universality? Like in the unification of fundamental forces, there is a concept of a common value for each physics parameter at the GUT scale. This is called a universality. The mSUGRA model, for example, introduvces three common values for a spin-1/2 paricle mass (m1/2), a spin-0 paricle mass (m0), and a coupling (A0).

mSUGRA Parameters:

m0   = common scalar mass at GUT scale
m1/2 = common gaugino mass at GUT scale
A0   = common trilinear couping at GUT scale
tanβ = ratio of two Higgs vacuum expectation values
μ    = Higgsio mixing parameter

Compact Muon Solenoid (CMS): The CMS (21 m x 15 m x 15 m, 12,500 tonnes) is one of two super-fast & super-sensitive detectors, consisting of 15 heavy elements, collecting derbies from the collision and converting a visual image for us. Shown is such a visual, called an event display, from one of "cosmic ray" runs in July. You see a nice straight-line "track" (muon) hitting various components of the CMS detector. The Texas A&M University (TAMU) experimental "Collder Physics" group is a member institution.

Dark Matter Hunters: The Texas A&M university High Energy group has extensively searched for the dark matter particle at the Tevatron, and is searching for at the LHC. For example, Dr. Weinberger, one of our post-docs, is featured for his search for dark matter through Bs → μμ events at Science Grid This Week Feature - Computing the unseen: the search for dark matter (2/06/08).

Why ILC? The International Linear Collider (ILC) is proposed to do precision measurements. The power of the collider machine is complementary to the LHC.