Data Reduction with the MIKE Spectrometer

This manuscript describes the design, usage, and data-reduction pipeline developed for the Magellan Inamori Kyocera Echelle (MIKE) spectrometer used with the Magellan telescope at the Las Campanas Observatory. We summarize the basic characteristics of the instrument and discuss observational procedures recommended for calibrating the standard data products. We detail the design and implementation of an IDL based data-reduction pipeline for MIKE data (since generalized to other echelle spectrometers, e.g. Keck/HIRES, VLT/UVES). This includes novel techniques for flat-fielding, wavelength calibration, and the extraction of echelle spectroscopy. Sufficient detail is provided in this manuscript to enable inexperienced observers to understand the strengths and weaknesses of the instrument and software package and an assessment of the related systematics.

The Physics and Nuclear Nonproliferation Goals of WATCHMAN: A WAter CHerenkov Monitor for ANtineutrinos

This article describes the physics and nonproliferation goals of WATCHMAN, the WAter Cherenkov Monitor for ANtineutrinos. The baseline WATCHMAN design is a kiloton scale gadolinium-doped (Gd) light water Cherenkov detector, placed 13 kilometers from a civil nuclear reactor in the United States. In its first deployment phase, WATCHMAN will be used to remotely detect a change in the operational status of the reactor, providing a first- ever demonstration of the potential of large Gd-doped water detectors for remote reactor monitoring for future international nuclear nonproliferation applications. During its first phase, the detector will provide a critical large-scale test of the ability to tag neutrons and thus distinguish low energy electron neutrinos and antineutrinos. This would make WATCHMAN the only detector capable of providing both direction and flavor identification of supernova neutrinos. It would also be the third largest supernova detector, and the largest underground in the western hemisphere. In a follow-on phase incorporating the IsoDAR neutrino beam, the detector would have world-class sensitivity to sterile neutrino signatures and to non-standard electroweak interactions (NSI). WATCHMAN will also be a major, U.S. based integration platform for a host of technologies relevant for the Long-Baseline Neutrino Facility (LBNF) and other future large detectors. This white paper describes the WATCHMAN conceptual design,and presents the results of detailed simulations of sensitivity for the projects nonproliferation and physics goals. It also describes the advanced technologies to be used in WATCHMAN, including high quantum efficiency photomultipliers, Water-Based Liquid Scintillator (WbLS), picosecond light sensors such as the Large Area Picosecond Photo Detector (LAPPD), and advanced pattern recognition and particle identification methods.

Level densities and thermodynamical properties of Pt and Au isotopes

The nuclear level densities of $^{194-196}$Pt and $^{197,198}$Au below the neutron separation energy have been measured using transfer and scattering reactions. All the level density distributions follow the constant-temperature description. Each group of isotopes is characterized by the same temperature above the energy threshold corresponding to the breaking of the first Cooper pair. A constant entropy excess $Delta S=1.9$ and $1.1$ $k_B$ is observed in $^{195}$Pt and $^{198}$Au with respect to $^{196}$Pt and $^{197}$Au, respectively, giving information on the available single-particle level space for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is revealed by sequential peaks in the microcanonical caloric curve.

First measurement of the ionization yield of nuclear recoils in liquid argon

This Letter details a measurement of the ionization yield ($Q_y$) of 6.7 keV $^{40}Ar$ atoms stopping in a liquid argon detector. The $Q_y$ of 3.6-6.3 detected $e^{-}/mbox{keV}$, for applied electric fields in the range 240--2130 V/cm, is encouraging for the use of this detector medium to search for the signals from hypothetical dark matter particle interactions and from coherent elastic neutrino nucleus scattering. A significant dependence of $Q_y$ on the applied electric field is observed and explained in the context of ion recombination.

Coherent Scattering Investigations at the Spallation Neutron Source: a Snowmass White Paper

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. In this white paper, we describe how the SNS source can be used for a measurement of coherent elastic neutrino-nucleus scattering (CENNS), and the physics reach of different phases of such an experimental program (CSI: Coherent Scattering Investigations at the SNS).

Chemical Abundance Evidence of Enduring High Star Formation Rates in an Early Type Galaxy: High [Ca/Fe] in NGC 5128 Globular Clusters

We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between -1.6 to -0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H]<-0.4 is +0.37$pm$0.07, while the average [Ca/Fe] in our MW and M31 GC samples is +0.29 $pm$0.09 and +0.24 $pm$0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the Milky Way or M31.This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the Milky Way. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope.

Extragalactic Globular Cluster Populations from High Resolution Integrated Light Spectra

We present a comparison of high-resolution, integrated-light, detailed chemical abundances for Galactic and extragalactic globular clusters in both massive galaxies and dwarf galaxies. We include measurements of Fe, Ca, Si, Na, and Al for globular cluster samples in the Milky Way, M31, Large Magellanic Cloud, and NGC 5128. These and other recent results from our group on M31 and NGC 5128 are the first chemical abundances derived from discrete absorption features in old stars beyond the Milky Way and its nearest neighbors. These abundances can provide both galaxy enrichment histories and constraints on globular cluster formation and evolution.

First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber

We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37, respectively. The Ar-37 source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed Fe-55 x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies.

Discovering the New Standard Model: Fundamental Symmetries and Neutrinos

This White Paper describes recent progress and future opportunities in the area of fundamental symmetries and neutrinos.

Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors

Cherenkov detectors employ various methods to maximize light collection at the photomultiplier tubes (PMTs). These generally involve the use of highly reflective materials lining the interior of the detector, reflective materials around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the use of water-soluble wavelength-shifters has been explored to increase the measurable light yield of Cherenkov radiation in water. These wave-shifting chemicals are capable of absorbing light in the ultravoilet and re-emitting the light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we have characterized the increase in light yield from three compounds in water: 4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in PMT response at a concentration of 1 ppm as: 1.88 $pm$ 0.02 for 4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 $pm$ 0.03 for Carbostyril-124, and 1.20 $pm$ 0.02 for Amino-G Salt. The response of 4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of the experimental gain at 1 ppm concentration. Finally, we report an increase in neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.