A Xenon Bubble Chamber for Direct Dark Matter Detection

With the lack of discovery of WIMPs at high mass, and hints of signals at low masses, it is becoming increasingly important for direct dark matter detectors to set low thresholds. With a hypothetically completely tuneable threshold based on pressure and temperature, a bubble chamber could be the ideal detector to search for sub-GeV WIMPs and other light exotica. However, this technology has its own drawbacks, such as an unknown recoil energy on an event-by-event basis. By combining this technology with that of the xenon time-projection chamber, however, the strengths of both of these approaches are merged, leading to a bubble chamber with energy reconstruction combined with excellent discrimination of nuclear versus electron recoils, critical for rejecting the most common radiogenic and cosmogenic backgrounds. A sketch of how such a device could be constructed will be presented

Grasping the Fundamental Physics of Xenon

Direct searches for dark matter using noble liquids, especially liquid xenon in recent years, have obtained the best sensitivities in the field for moderate to high-mass dark-matter WIMPs. Along with the development of this technology, there has been a continued effort in the community to better understand the detailed scintillation and ionization responses of noble liquids in the presence of low-energy ionizing radiation. As this body of knowledge is reaching a mature state, a unified software framework for simulating scintillation and ionization production in these detectors is strongly needed. In this talk, I introduce NEST: Noble Element Simulation Technique, which is an open-source simulation package based on physics models informed by the world\u27s best data on the subject. I additionally present the method used for modeling electronic recoils, which comprise most of the background in a dark-matter search, and nuclear recoils (which dark matter should produce), and compare with available data

US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Enhancement of NEST Capabilities for Simulating Low-Energy Recoils in Liquid Xenon

The Noble Element Simulation Technique (NEST) is an exhaustive collection of models explaining both the scintillation light and ionization yields of noble elements as a function of particle type (nuclear recoil, electron recoil, alphas), electric field, and incident energy or energy loss dE/dx. It is packaged as C++ code for Geant4 that implements said models, overriding the default model which does not account for certain complexities, such as the reduction in yields for nuclear recoils (NR) compared to electron recoils (ER). We present here improvements to the existing NEST models and updates to the code which make the package even more realistic and turn it into a more full-fledged Monte Carlo simulation. All available liquid xenon data on NR and ER to date have been taken into consideration in arriving at the current models. Furthermore, NEST addresses the question of the magnitude of the light and charge yields of nuclear recoils, including their electric field dependence, thereby shedding light on the possibility of detection or exclusion of a low-mass dark matter WIMP by liquid xenon detectors