The document discusses the search for dark matter and dark energy, which together make up 95% of the universe. Dark energy is theorized to drive the accelerated expansion of the universe and accounts for 68.3% while dark matter accounts for 26.8% through its gravitational interactions. One theory for dark energy is chameleon fields, which change their properties based on local density. The XENON Collaboration experiments search for dark matter in the form of weakly interacting massive particles using a liquid xenon detector. Their XENON100 project ruled out some potential dark matter models and long-standing claims from other experiments. The ongoing search for dark matter and dark energy through laboratory experiments brings scientists closer to answering fundamental cosmological questions.

1. The Search for Dark Matter
and Dark Energy
By Zoe Zontos

2. Road Map
• What are dark matter/energy?
• The search for dark matter/energy
• Dark energy – chameleon fields
• Dark matter – the XENON Collaboration
• Impact of searches

3. The universe consists of two components on unknown
origin known as dark matter and dark energy.
• Dark energy – drives the accelerated expansion of the universe
• Dark energy = 68.3%
• Chameleon field search theory
• Dark matter – weakly interacting massive particles (WIMPs)
• Responsible for excess of gravitational interactions
• Dark matter = 26.8%
• XENON Collaboration experiment

4. One theory for dark energy research are
chameleon fields.
• Suppresses effects in regions of high density
• Mass depends on ambient matter density
• Light, mediates a long-range force
• In sparse environments (cosmos)
• Massive, mediates a short-range force
• In high-density environments (laboratory)

5. Searching for chameleon fields using a cesium
interferometer and vacuum chamber.
Image Source: http://arxiv.org/pdf/1502.03888.pdf

6. The XENON100 project rules out the possibility of
three potential dark matter models.
• WIMPs interacting with regular matter
• Create recoiling charged particles
• Can be detected
• XENON100 detector
• liquid xenon target
• Results in prompt scintillation signal and delayed ionization signal
• Minimizes background signals

7. The goal of XENON100 is to look for the effects of dark
matter other than gravity through interactions of WIMPs.
Image source: http://xenon.astro.columbia.edu/XENON100_Experiment/

8. The XENON100 project rules out long-standing
information from DAMA/LIBRA collaboration.
Image Source: http://inspirehep.net/record/1385287/files/figure1.png

9. The experiments encourage the effort to
search for dark matter and dark energy.
• Shows how to address cosmological questions in a laboratory setting
• Brings scientists closer to probing hard to reach energy ranges
• Pushes sensitivity of types of experiments
• Many are performed at university level
• A deep understanding of very broad aspects of physics

10. Questions?

11. References
• Hamilton, P., et al. “Atom-interferometry constraints on dark energy.”
Science. Vol. 349, Issue 6250, pp. 849-851. 21 Aug. 2015.
• Schmiedmayer, Jorg and Abele Hartmut. ”Probing the dark side.”
Science. Vol. 349, Issue 6250, pp. 849-851. 21 Aug. 2015.
• The XENON Collaboration. “Exclusion of leptophilic dark matter
models using XENON100 electronic recoil data.” Science. Vol.
349, Issue 6250, pp. 849-851. 21 Aug. 2015.