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

A Review of Basic Energy Reconstruction Techniques in Liquid Xenon and Argon Detectors for Dark Matter and Neutrino Physics Using NEST

Detectors based upon the noble elements, especially liquid xenon as well as liquid argon, as both single- and dual-phase types, require reconstruction of the energies of interacting particles, both in the field of direct detection of dark matter (Weakly Interacting Massive Particles or WIMPs, axions, etc.) and in neutrino physics. Experimentalists, as well as theorists who reanalyze/reinterpret experimental data, have used a few different techniques over the past few decades. In this paper, we review techniques based on solely the primary scintillation channel, the ionization or secondary channel available at non-zero drift electric fields, and combined techniques that include a simple linear combination and weighted averages, with a brief discussion of the applications of profile likelihood, maximum likelihood, and machine learning. Comparing results for electron recoils (beta and gamma interactions) and nuclear recoils (primarily from neutrons) from the Noble Element Simulation Technique (NEST) simulation to available data, we confirm that combining all available information generates higher-precision means, lower widths (energy resolution), and more symmetric shapes (approximately Gaussian) especially at keV-scale energies, with the symmetry even greater when thresholding is addressed. Near thresholds, bias from upward fluctuations matters. For MeV-GeV scales, if only one channel is utilized, an ionization-only-based energy scale outperforms scintillation; channel combination remains beneficial. We discuss here what major collaborations use.Comment: 42 Pages, 2 Tables, 11 Figures, 13 Equation

Snowmass CF1 Summary: WIMP Dark Matter Direct Detection

As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.Comment: Snowmass CF1 Final Summary Report: 47 pages and 28 figures with a 5 page appendix on instrumentation R&

After LUX: The LZ Program

The LZ program consists of two stages of direct dark matter searches using liquid Xe detectors. The first stage will be a 1.5-3 tonne detector, while the last stage will be a 20 tonne detector. Both devices will benefit tremendously from research and development performed for the LUX experiment, a 350 kg liquid Xe dark matter detector currently operating at the Sanford Underground Laboratory. In particular, the technology used for cryogenics and electrical feedthroughs, circulation and purification, low-background materials and shielding techniques, electronics, calibrations, and automated control and recovery systems are all directly scalable from LUX to the LZ detectors. Extensive searches for potential background sources have been performed, with an emphasis on previously undiscovered background sources that may have a significant impact on tonne-scale detectors. The LZ detectors will probe spin-independent interaction cross sections as low as 5E-49 cm2 for 100 GeV WIMPs, which represents the ultimate limit for dark matter detection with liquid xenon technology.Comment: Conference proceedings from APS DPF 2011. 9 pages, 6 figure