Annual Reviews OnlineSearch Annual ReviewsAnnual Review of Astronomy and Astrophysics OnlineMost Downloaded Astronomy and AstrophysicsReviewsAnnual Review of Astronomy and Astrophysics ErrataMost Cited Astronomy and Astrophysics ReviewsView Current Editorial CommitteeAll Articles in the Annual Review of Astronomy and Astrophysics, Vol. 48Searching for InsightCosmic SilicatesThe Birth Environment of the Solar SystemStrong Lensing by GalaxiesReionization and Cosmology with 21-cm FluctuationsInterstellar Dust in the Solar SystemThe Inner Regions of Protoplanetary DisksPhysical Processes in Magnetically Driven Flares on the Sun, Stars, and Young Stellar ObjectsLocal Helioseismology: Three-Dimensional Imaging of the Solar InteriorA Universal Stellar Initial Mass Function? A Critical Look at VariationsSmoothed Particle Hydrodynamics in AstrophysicsYoung Massive Star ClustersDark Matter Candidates from Particle Physics and Methods of DetectionMolecular Clouds in Nearby GalaxiesThe Ages of StarsExoplanet AtmospheresThe Hubble ConstantAA48CH13-Feng ARI 16 July 2010 22:3Dark Matter Candidates fromParticle Physics and Methodsof DetectionJonathan L. FengDepartment of Physics and Astronomy, University of California, Irvine, California 92697;email: jlf[at]uci.eduAnnu. Rev. Astron. Astrophys. 2010. 48:495–545First published online as a Review in Advance onMay 25, 2010The Annual Review of Astronomy and Astrophysics isonline at astro.annualreviews.orgThis article’s doi:10.1146/annurev-astro-082708-101659Copyrightc 2010 by Annual Reviews.All rights reserved0066-4146/10/0922-0495$20.00Key Wordsdark matter, weakly interacting massive particles (WIMPs), superWIMPs,light gravitinos, hidden dark matter, sterile neutrinos, axionsAbstractThe identity of dark matter is a question of central importance in both as-trophysics and particle physics. In the past, the leading particle candidateswere cold and collisionless, and typically predicted missing energy signals atparticle colliders. However, recent progress has greatly expanded the list ofwell-motivated candidates and the possible signatures of dark matter. Thisreview begins with a brief summary of the standard model of particle physicsand its outstanding problems. I then discuss several dark matter candidatesmotivated by these problems, including weakly interacting massive parti-cles (WIMPs), superWIMPs, light gravitinos, hidden dark matter, sterileneutrinos, and axions. For each of these, I critically examine the particlephysics motivations and present their expected production mechanisms, ba-sic properties, and implications for direct and indirect detection, particlecolliders, and astrophysical observations. Upcoming experiments will dis-cover or exclude many of these candidates, and progress may open up anera of unprecedented synergy between studies of the largest and smallestobservable length scales.495Annu. Rev. Astro. Astrophys. 2010.48:495-545. Downloaded from www.annualreviews.orgby California Institute of Technology on 05/02/11. For personal use only.Click here for quick links to Annual Reviews content online, including:• Other articles in this volume• Top cited articles• Top downloaded articles• Our comprehensive searchFurtherANNUALREVIEWSAA48CH13-Feng ARI 16 July 2010 22:31. INTRODUCTIONThe evidence that dark matter is required to make sense of our Universe has been building for sometime. In 1933, Fritz Zwicky found that the velocity dispersion of galaxies in the Coma cluster ofgalaxies was far too large to be supported by the luminous matter (Zwicky 1933). In the 1970s, VeraRubin and collaborators (Rubin & Ford 1970; Rubin, Thonnard & Ford 1980) and Albert Bosma(1978) measured the rotation curves of individual galaxies and also found evidence for nonluminousmatter. This and other “classic” evidence for nonluminous matter (see, e.g., Trimble 1987) hasnow been supplemented by data from weak (Refregier 2003) and strong (Tyson, Kochanski &Dell’Antonio 1998) lensing, hot gas in clusters (Lewis, Buote & Stocke 2003), the Bullet Cluster(Clowe et al. 2006), Big Bang nucleosynthesis (BBN) (Fields & Sarkar 2008), further constraintsfrom large scale structure (Allen et al. 2003), distant supernovae (Riess et al. 1998, Perlmutteret al. 1999), and the cosmic microwave background (CMB) (Komatsu et al. 2010).Together, these data now provide overwhelming evidence for the remarkable fact that not onlyis there nonluminous matter in our Universe, but most of it is not composed of baryons or anyof the other known particles. Current data imply that dark matter is five times more prevalentthan normal matter and accounts for about a quarter of the Universe. More precisely, these dataconstrain the energy densities of the Universe in baryons (B), nonbaryonic dark matter (DM), anddark energy () to be (Komatsu et al. 2010), respectively, B 0.0456 ± 0.0016, (1) DM 0.227 ± 0.014, (2)  0.728 ± 0.015. (3)Despite this progress, all of the evidence for dark matter noted above is based on its gravitationalinteractions. Given the universality of gravity, this evidence does little to pinpoint what dark matteris. At the same time, the identity of dark matter has far-reaching implications: In astrophysics, theproperties of dark matter determine how structure forms and impact the past and future evolutionof the Universe; in particle physics, dark matter is the leading empirical evidence for new particles,and there are striking hints that it may be linked to attempts to understand electroweak symmetrybreaking, the leading puzzle in the field today. The identity of dark matter is therefore of centralimportance in both fields and ties together studies of the Universe at both the largest and smallestobservable length scales.This review examines some of the leading dark matter candidates and their implications forexperiments and observatories. The wealth of recent cosmological data does constrain some darkmatter properties, such as its self-interactions and its temperature at the time of matter-radiationequality. Nevertheless, it is still not at all difficult to invent new particles that satisfy all the con-straints, and there are candidates motivated by minimality, particles motivated by possible exper-imental anomalies, and exotic possibilities motivated primarily by the desire of clever iconoclaststo highlight how truly ignorant we are about the nature of dark matter.Here I focus on dark matter candidates that are motivated not only by