Sub-GeV Dark Matter Searches and Electric Field Studies for the LUX and LZ Experiments. (arXiv:1904.08979v1 [astro-ph.IM])

Sub-GeV Dark Matter Searches and Electric Field Studies for the LUX and LZ Experiments. (arXiv:1904.08979v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Tvrznikova_L/0/1/0/all/0/1">Lucie Tvrznikova</a>

The nature of dark matter (DM) remains a mystery since it has so far eluded
detection in the laboratory. To that end, the Large Underground Xenon (LUX)
experiment was built to directly observe the interaction of DM with xenon
target nuclei. LUX acquired data from April 2013 to May 2016 at SURF in South
Dakota, which led to publications of many world-leading exclusion limits that
probe much of the unexplored DM parameter space. This manuscript describes two
novel direct detection methods that used the first LUX dataset to place limits
on sub-GeV DM. The Bremsstrahlung and Migdal effects consider electron recoils
that accompany the standard DM-nucleus scattering, thereby extending the reach
of the LUX detector to lower DM masses. The spin-independent DM-nucleon
scattering was constrained for four different classes of mediators for DM
particles with masses of 0.4-5 GeV/c$^{2}$. The detector conditions changed
significantly before its final 332 live-days of data acquisition. The electric
fields varied in a non-trivial non-symmetric manner, which triggered a need for
a fully 3D model of the electric fields inside the LUX detector. The successful
modeling of these electric fields, described herein, enabled a thorough
understanding of the detector throughout its scientific program and
strengthened its sensitivity to DM. The LUX-ZEPLIN (LZ) experiment is a
next-generation xenon detector soon to start searching for DM. However,
increasingly large noble liquid detectors like LZ are facing challenges with
applications of high voltage (HV). The Xenon Breakdown Apparatus (XeBrA) at the
Lawrence Berkeley National Laboratory was built to characterize the HV behavior
of liquid xenon and liquid argon. Results from XeBrA will serve not only to
improve our understanding of the physical processes involved in the breakdown
but also to inform the future of noble liquid detector engineering.

The nature of dark matter (DM) remains a mystery since it has so far eluded
detection in the laboratory. To that end, the Large Underground Xenon (LUX)
experiment was built to directly observe the interaction of DM with xenon
target nuclei. LUX acquired data from April 2013 to May 2016 at SURF in South
Dakota, which led to publications of many world-leading exclusion limits that
probe much of the unexplored DM parameter space. This manuscript describes two
novel direct detection methods that used the first LUX dataset to place limits
on sub-GeV DM. The Bremsstrahlung and Migdal effects consider electron recoils
that accompany the standard DM-nucleus scattering, thereby extending the reach
of the LUX detector to lower DM masses. The spin-independent DM-nucleon
scattering was constrained for four different classes of mediators for DM
particles with masses of 0.4-5 GeV/c$^{2}$. The detector conditions changed
significantly before its final 332 live-days of data acquisition. The electric
fields varied in a non-trivial non-symmetric manner, which triggered a need for
a fully 3D model of the electric fields inside the LUX detector. The successful
modeling of these electric fields, described herein, enabled a thorough
understanding of the detector throughout its scientific program and
strengthened its sensitivity to DM. The LUX-ZEPLIN (LZ) experiment is a
next-generation xenon detector soon to start searching for DM. However,
increasingly large noble liquid detectors like LZ are facing challenges with
applications of high voltage (HV). The Xenon Breakdown Apparatus (XeBrA) at the
Lawrence Berkeley National Laboratory was built to characterize the HV behavior
of liquid xenon and liquid argon. Results from XeBrA will serve not only to
improve our understanding of the physical processes involved in the breakdown
but also to inform the future of noble liquid detector engineering.

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