Professor Neal Weiner at NYU

Over the past several years, we have become aware that the majority of mass in the universe is unseen. Of the total energy of the universe, we believe ~73% of it is in the form of “dark energy”, ~23% in the form of  “dark matter” and only 4% in the form of ordinary matter. Ordinary matter would comprise protons, neutrons, electrons, atoms, and really almost any matter that we have created in the lab. Neutrinos appear to have mass but are believed to contribute only a tiny fraction of the energy of the universe.

So what is this dark matter?

There are a wide range of theoretical candidates, from axions to neutralinos to qballs. Much of my research effort focuses on
WIMPs or Weakly Interacting Massive Particles. These particles are ones that would have been in equilibrium with ordinary matter in the early universe, but long ago decoupled. The leftover particles would make up the dark matter of the universe.

Such particles are exciting candidates for a number of reasons. First: they appear ubiquitously in our theories of physics at the TeV scale, such as supersymmetry, extra dimensions, or strong dynamics. Second: they process that maintains equilibrium in the early universe gives a means of detecting dark matter today. This can come in many ways: dark matter could be colliding and producing high energy cosmic rays in the Milky Way, it could collide with nuclei in underground direct detection experiments, or it could be produced at a collider, such as the Tevatron or LHC.

Remarkably, some hints have arisen that could be arising from dark matter. The
DAMA collaboration has seen an annual variation in rate at their experiment in Gran Sasso. PAMELA has seen a significant excess of cosmic ray positrons that could be coming from dark matter annihilation in the galactic halo. CoGeNT has seen an interesting excess at low energies that might be arising from dark matter. INTEGRAL has seen significant 511 keV radiation in the galactic center beyond what is expected from

While it remains to be seen whether any of these is indeed arising from dark matter, they have motivated broad thinking about new ideas of dark matter. New results from PLANCK,
XENON100, KIMS and others will continue to inform this rapidly changing field.

Selected Publications:

Photo of superimposed lensing DM map and X-ray map of the Bullet Cluster.