Effective Theories of Gamma-ray Lines from Dark Matter Annihilation

We explore theories of dark matter in which dark matter annihilations produce mono-energetic gamma rays ("lines") in the context of effective field theory, which captures the physics for cases in which the particles mediating the interaction are somewhat heavier than the dark matter particle itself. Building on earlier work, we explore the generic signature resulting from SU(2)xU(1) gauge invariance that two (or more) lines are generically expected, and determine the expected relative intensities, including the possibility of interference between operators.Comment: 11 pages, 0 figure

Particle Physics Implications and Constraints on Dark Matter Interpretations of the CDMS Signal

Recently the CDMS collaboration has reported an excess of events in the signal region of a search for dark matter scattering with Silicon nuclei. Three events on an expected background of 0.4 have a significance of about 2 sigma, and it is premature to conclude that this is a signal of dark matter. Nonetheless, it is important to examine the space of particle theories capable of explaining this excess, to see what theories are capable of explaining it, and how one might exclude it or find corroborating evidence in other channels. We examine a simplified model containing a scalar mediator particle, and find regions consistent with the CDMS observations. Bounds from colliders put important restrictions on the theory, but viable points, including points leading to the observed thermal relic density, survive.Comment: 16 pages, 6 figure

CoGeNT, DAMA, and Light Neutralino Dark Matter

Recent observations by the CoGeNT collaboration (as well as long standing observations by DAMA/LIBRA) suggest the presence of a $\sim 5$-10 GeV dark matter particle with a somewhat large elastic scattering cross section with nucleons ($\sigma\sim 10^{-40}$ cm$^2$).Within the context of the minimal supersymmetric standard model (MSSM), neutralinos in this mass range are not able to possess such large cross sections, and would be overproduced in the early universe. Simple extensions of the MSSM, however, can easily accommodate these observations. In particular, the extension of the MSSM by a chiral singlet superfield allows for the possibility that the dark matter is made up of a light singlino that interacts with nucleons largely through the exchange of a fairly light ($\sim$30-70 GeV) singlet-like scalar higgs, \hi. Such a scenario is consistent with all current collider constraints and can generate the signals reported by CoGeNT and DAMA/LIBRA. Furthermore, there is a generic limit of the extended model in which there is a singlet-like pseudoscalar higgs, \ai, with \mai\sim \mhi and in which the $\chi^0\chi^0$ and b\anti b, s\anti s coupling magnitudes of the \hi and \ai are very similar. In this case, the thermal relic abundance is automatically consistent with the measured density of dark matter if \mchi is sufficiently small that \chi^0\chi^0\to b\anti b is forbidden.Comment: 6 pages, published versio

MAT-761: THE EFFECT OF TEMPERATURE ON THE LATERAL RESPONSE OF UNBONDED FIBER-REINFORCED ELASTOMERIC ISOLATORS

Base isolation is a method that can be employed to significantly reduce the demands on a structure during a seismic event. This method has shown considerable success in reducing the adverse effects of earthquakes, including damage and loss of life. The main concept of base isolation is to reduce the seismic demand on a structure by placing isolators beneath the superstructure at points where load is transferred to the foundation. One of the most commonly used types of isolator is the elastomeric isolator. These isolators are traditionally comprised of layers of elastomer and steel. More recently, research has been completed on the use of fibers as a replacement to the steel reinforcement layers, in order to reduce weight and potentially reduce costs. Fiber reinforced elastomeric isolators (FREI) can be placed (unbonded) between the superstructure and its foundation. This research investigates the behaviour of unbonded fiber-reinforced elastomeric isolators (U-FREI) under lateral deformations expected during seismic events. The objective of this study is to investigate the lateral behaviour of FREI under a range of temperatures, representative of those expected in various regions throughout Canada. Results from preliminary experimental tests show that the influence of temperature on the lateral response of U-FREI is negligible under the range of temperatures considered

LHC Bounds on Interactions of Dark Matter

We derive limits on the interactions of dark matter with quarks from ATLAS null searches for jets + missing energy based on ~1 fb^-1 of integrated luminosity, using a model-insensitive effective theory framework. We find that the new limits from the LHC significantly extend limits previously derived from CDF data at the Tevatron. Translated into the parameter space of direct searches, these limits are particularly effective for ~GeV mass WIMPs. Our limits indicate tension with isospin violating models satisfying minimal flavor violation which attempt to reconcile the purported CoGeNT excess with Xenon-100, indicating that either a light mediator or nontrivial flavor structure for the dark sector is necessary for a viable reconciliation of CoGeNT with Xenon.Comment: 20 pages, 11 figure

NDM-563: THE VERTICAL, ROTATIONAL AND LATERAL RESPONSE OF UNBONDED FIBER REINFORCED ELASTOMERIC ISOLATORS

Bridge structures often experience damage during an earthquake, which is one of the most devastating types of natural disasters. Base isolation can be employed to mitigate earthquake-induced damage. The main concept of base isolation is to reduce the seismic demand on the structure by shifting its fundamental time period away from the predominant periods associate with earthquakes. Base isolation involves placing horizontally flexible isolators between the bridge superstructure (i.e. deck/girder) and the substructure (i.e. pier/column). There are two main types of seismic isolators: (1) elastomeric, and (2) sliding. A fiber reinforced elastomeric isolator (FREI) is a particular type of reinforced elastomeric isolator. In an FREI the steel reinforcement used in a traditional elastomeric isolator is replaced with fiber fabric, which results in a reduction in the weight and potentially the manufacturing cost. FREI can be either bonded (B-FREI) or unbonded (U-FREI) to the substructure and superstructure. This paper investigates the behaviour of U-FREI under combined vertical, rotational, and lateral loading, as bridge bearings are expected to experience this combination of loads. Accordingly, the test program includes different vertical loads, angles of rotation, as well as a number of lateral sinusoidal input motions varying in both frequency and amplitude. The objective of this study is to investigate the response of U-FREI under serviceability and extreme loading conditions. The findings of this paper also address the feasibility of using U-FREI as bridge bearings/isolators

Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond

In this report we summarize the many dark matter searches currently being pursued through four complementary approaches: direct detection, indirect detection, collider experiments, and astrophysical probes. The essential features of broad classes of experiments are described, each with their own strengths and weaknesses. The complementarity of the different dark matter searches is discussed qualitatively and illustrated quantitatively in two simple theoretical frameworks. Our primary conclusion is that the diversity of possible dark matter candidates requires a balanced program drawing from all four approaches.Comment: Report prepared for the Community Summer Study (Snowmass) 2013, on behalf of Cosmic Frontier Working Groups 1-4 (CF1: WIMP Dark Matter Direct Detection, CF2: WIMP Dark Matter Indirect Detection, CF3: Non-WIMP Dark Matter, and CF4: Dark Matter Complementarity); published versio