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This thesis covers several theoretical aspects of WIMP (weakly interacting massive particles) dark matter searches, with a particular emphasis on colliders. It mainly focuses on the use of effective field theories as a tool for Large Hadron Collider (LHC) searches, discussing in detail the issue of their validity, and on simplified dark matter models, which are receiving a growing attention from the physics community. It highlights the theoretical consistency of simplified models, which is essential in order to correctly exploit their potential and for them to be a common reference when comparing results from different experiments. This thesis is of interest to researchers (both theorists and experimentalists) in the field of dark matter searches, and offers a comprehensive introduction to dark matter and to WIMP searches for students and non-experts.
Dark matter is a frequently discussed topic in contemporary particle physics. Written strictly in the language of particle physics and quantum field theory, these course-based lecture notes focus on a set of standard calculations that students need in order to understand weakly interacting dark matter candidates. After introducing some general features of these dark matter agents and their main competitors, the Higgs portal scalar and supersymmetric neutralinos are introduced as our default models. In turn, this serves as a basis for exploring four experimental aspects: the dark matter relic density extracted from the cosmic microwave background; indirect detection including the Fermi galactic center excess; direct detection; and collider searches. Alternative approaches, like an effective theory of dark matter and simplified models, naturally follow from the discussions of these four experimental directions.
The possible gamma-ray excess in the inner Galaxy and the Galactic center (GC) suggested by Fermi-LAT observations has triggered a large number of studies. It has been interpreted as a variety of different phenomena such as a signal from WIMP dark matter annihilation, gamma-ray emission from a population of millisecond pulsars, or emission from cosmic rays injected in a sequence of burst-like events or continuously at the GC. We present the first comprehensive study of model systematics coming from the Galactic diffuse emission in the inner part of our Galaxy and their impact on the inferred properties of the excess emission at Galactic latitudes 2°>
Dark Matter and the Dinosaurs by Lisa Randall | Key Takeaways, Analysis & Review Preview: Dark Matter and the Dinosaurs by Lisa Randall proposes to explain the causes of the meteoroid that wiped out the dinosaurs using a dark matter model. It also describes a wide range of scientific findings to illustrate the interconnectedness of the cosmos to life on Earth… PLEASE NOTE: This is key takeaways and analysis of the book and NOT the original book. Inside this Instaread of Dark Matter and the Dinosaurs: · Overview of the book · Important People · Key Takeaways · Analysis of Key Takeaways
If dark matter is embedded in a non-trivial dark sector, it may annihilate and decay to lighter dark-sector states which subsequently decay to the Standard Model. Such scenarios - with annihilation followed by cascading dark-sector decays - can explain the apparent excess GeV gamma-rays identified in the central Milky Way, while evading bounds from dark matter direct detection experiments. Each 'step' in the cascade will modify the observable signatures of dark matter annihilation and decay, shifting the resulting photons and other final state particles to lower energies and broadening their spectra. We explore, in a model-independent way, the effect of multi-step dark-sector cascades on the preferred regions of parameter space to explain the GeV excess. We find that the broadening effects of multi-step cascades can admit final states dominated by particles that would usually produce too sharply peaked photon spectra; in general, if the cascades are hierarchical (each particle decays to substantially lighter particles), the preferred mass range for the dark matter is in all cases 20-150 GeV. Decay chains that have nearly-degenerate steps, where the products are close to half the mass of the progenitor, can admit much higher DM masses. We map out the region of mass/cross-section parameter space where cascades (degenerate, hierarchical or a combination) can fit the signal, for a range of final states. In the current paper, we study multi-step cascades in the context of explaining the GeV excess, but many aspects of our results are general and can be extended to other applications.
We provide conservative bounds on the dark matter cross-section and lifetime from final state radiation produced by annihilation or decay into charged leptons, either directly or via an intermediate particle [phi]. Our analysis utilizes the experimental gamma-ray flux upper limits from four Milky Way dwarf satellites: HESS observations of Sagittarius and VERITAS observations of Draco, Ursa Minor, and Willman 1. Using 90% confidence level lower limits on the integrals over the dark matter distributions, we find that these constraints are largely unable to rule out dark matter annihilations or decays as an explanation of the PAMELA and ATIC/PPB-BETS excesses. However, if there is an additional Sommerfeld enhancement in dwarfs, which have a velocity dispersion ≈ 10 to 20 times lower than that of the local Galactic halo, then the cross-sections for dark matter annihilating through [phi]'s required to explain the excesses are very close to the cross-section upper bounds from Willman 1. Dark matter annihilation directly into [tau]'s is also marginally ruled out by Willman 1 as an explanation of the excesses, and the required cross-section is only a factor of a few below the upper bound from Draco. Finally, we make predictions for the gamma-ray flux expected from the dwarf galaxy Segue 1 for the Fermi Gamma-ray Space Telescope. We find that for a sizeable fraction of the parameter space in which dark matter annihilation into charged leptons explains the PAMELA excess, Fermi has good prospects for detecting a gamma-ray signal from Segue 1 after one year of observation.
The current major problems in particle physics and astrophysics are the source of possible new features: of The Standard Model, of the nature of Dark Matter, of the nature of Dark Energy, and of the nature of the Big Bang. In this book we propose an extended version of The Standard Model based on earlier work that adds another SU(2)X U(1) symmetry to the usual Standard Model, and an accompanying set of particles that we propose are the constituents of Dark Matter. This additional symmetry follows directly from a geometrical foundation for space-time within a 16 dimensional flat space that we call the Flatverse. Upon introducing a form of quantum coordinates we find that The Standard Model in those coordinates has no infinities, that the Big Bang is finite (no singularity), and that the Dark Energy that fuels the expansion of the universe has inflatons that consist of the imaginary part of the quantum coordinates - a free abelian gauge field. This field first stabilizes the universe in the Big Bang period and then causes a massive inflationary expansion. The complete theory has a remarkable convergence of features that remove infinities, identify the nature of Dark Matter and of Dark Energy, specify a physically acceptable Big Bang, and predict the observed expansion of the universe. In addition we address the recently reported discovery of the Higgs particle that "explains" the origin of the masses of the other elementary particles but does not explain the origin of the Higgs particle mass terms and thus leaves open the ultimate question - What is the origin of mass and inertia? We show that the only final answer can be that it arises as a separation constant in Higgs dynamic equations that include coordinates of this universe and a sister universe. These two 8-dimensional universes are embedded in the 16-dimensional Flatverse. Thus the sister universe is the ultimate source of mass and inertia for our universe. The Flatverse is an absolute reference frame that is consistent with Einstein's General Relativity according to General Relativists. The Flatverse very nicely provides an environment for the two universes - joining them together to provide mass and inertia at their most fundamental level as well as providing, at last, a concrete definition of inertial reference frames. Result: a fundamental synergy between mass, inertia, and inertial frames. In recent weeks major experimental findings on Dark Matter have been presented that at last begin to clarify the nature of Dark Matter and its interactions with "normal" matter. These findings are consistent with a Dark Matter SU(2) X U(1) set of interactions that parallels, to a great extent, the known ElectroWeak interactions of normal matter. We will explore a detailed theory of Dark Matter interactions, and their relation to ElectroWeak interactions in this book. It is based on our previous work. In the previous work we did not specify a relation between ElectroWeak and "DarkWeak" interactions due to the absence of experimental data. With the information now in hand we can develop a detailed relationship. Lastly, the book emphasizes again our belief that the origin of particle physics lies in a combination of Asynchronous Logic and space-time geometry."
There is overwhelming evidence that non-baryonic dark matter constitutes ~ 27% of the energy density of the Universe. Weakly Interacting Massive Particles (WIMPs) are promising dark matter candidates that may produce [gamma] rays via annihilation or decay detectable by the Fermi Large Area Telescope (LAT). A detection of WIMPs would also indicate the existence of physics beyond the Standard Model. We present recent results from the two cleanest indirect WIMP searches by the Fermi-LAT Collaboration: searches for [gamma]-ray spectral lines and [gamma]-ray emission associated with Milky Way dwarf spheroidal satellite galaxies.