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Dark matter direct detection searches for signals coming from dark matter scattering against nuclei at a very low recoil energy scale ∼ 10 keV. In this paper, a simple non-relativistic effective theory is constructed to describe interactions between dark matter and nuclei without referring to any underlying high energy models. It contains the minimal set of operators that will be tested by direct detection. The effective theory approach highlights the set of distinguishable recoil spectra that could arise from different theoretical models. If dark matter is discovered in the near future in direct detection experiments, a measurement of the shape of the recoil spectrum will provide valuable information on the underlying dynamics. We bound the coefficients of the operators in our non-relativistic effective theory by the null results of current dark matter direct detection experiments. We also discuss the mapping between the non-relativistic effective theory and field theory models or operators, including aspects of the matching of quark and gluon operators to nuclear form factors.

Based on observational constraints on large scale structure and halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component's interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.Comment: 37 pages, 13 figures; v2: references added, appearing in Physics of the Dark Univers

In this paper, we review recent theoretical progress and the latest experimental results in jet substructure from the Tevatron and the LHC. We review the status of and outlook for calculation and simulation tools for studying jet substructure. Following up on the report of the Boost 2010 workshop, we present a new set of benchmark comparisons of substructure techniques, focusing on the set of variables and grooming methods that are collectively known as 'top taggers'. To facilitate further exploration, we have attempted to collect, harmonize and publish software implementations of these techniques.

We point out that current constraints on dark matter imply only that the majority of dark matter is cold and collisionless. A subdominant fraction of dark matter could have much stronger interactions. In particular, it could interact in a manner that dissipates energy, thereby cooling into a rotationally-supported disk, much as baryons do. We call this proposed new dark matter component Double-Disk Dark Matter (DDDM). We argue that DDDM could constitute a fraction of all matter roughly as large as the fraction in baryons, and that it could be detected through its gravitational effects on the motion of stars in galaxies, for example. Furthermore, if DDDM can annihilate to gamma rays, it would give rise to an indirect detection signal distributed across the sky that differs dramatically from that predicted for ordinary dark matter. DDDM and more general partially interacting dark matter scenarios provide a large unexplored space of testable new physics ideas.Introduction. Most of the matter in the universe is dark, distributed in diffuse halos around galaxies. Even so, the subdominant component consisting of baryons, electrons, and photons-the stuff of everyday lifethough constituting only about 5% of the universe's energy density, gives rise to rich phenomena in the world around us. Our goal in this paper is to argue that dark matter too could contain a component exhibiting diverse and observable consequences: the dark world might even be as diverse and interesting as the visible world. This hypothesis is worth exploring as it can be tested in several complementary ways.The structure of our galaxy relies on interacting baryons that can cool. They do so by dissipating energy through photon emission as they collapse to form structure. Cooling is a prerequisite to baryonic structures occupying relatively small volumes and forming compact objects like stars and planets. On a larger scale, it is necessary for the formation of disk galaxies.In stark contrast to baryons, we typically assume that dark matter (DM) is cold and collisionless, distributed through a large halo in a random way. This paradigm is sometimes relaxed as in the cases of self-interacting dark matter (SIDM) [1] or warm dark matter [2], but such scenarios are bounded by observations of halo shapes and the Bullet Cluster that limit the amount by which dark matter can deviate from being cold and collisionless. These bounds are often thought to imply that the world of dark matter is much less rich and interesting than the world of visible matter, and as a result dark matter is usually assumed to be a single type of particle, like a WIMP.In this paper we propose that the dark world could be as complex as the visible world, with a simple assumption: while most of the dark matter is cold and collisionless, a subdominant fraction we call Partially Interacting Dark Matter (PIDM) could interact more strongly and even cool as baryons do. This subdominant fraction could have an energy density about as large as that of baryons, without having been noticed so far. ...