Neutron and muon-induced background studies for the AMoRE double-beta decay experiment

AMoRE (Advanced Mo-based Rare process Experiment) is an experiment to search a neutrinoless double-beta decay of $^{100}$Mo in molybdate crystals. The neutron and muon-induced backgrounds are crucial to obtain the zero-background level (<$10^{-5}$ counts/(keV$\cdot$kg$\cdot$yr)) for the AMoRE-II experiment, which is the second phase of the AMoRE project, planned to run at YEMI underground laboratory. To evaluate the effects of neutron and muon-induced backgrounds, we performed Geant4 Monte Carlo simulations and studied a shielding strategy for the AMORE-II experiment. Neutron-induced backgrounds were also included in the study. In this paper, we estimated the background level in the presence of possible shielding structures, which meet the background requirement for the AMoRE-II experiment

Spontaneous phase oscillation induced by inertia and time delay

We consider a system of coupled oscillators with finite inertia and time-delayed interaction, and investigate the interplay between inertia and delay both analytically and numerically. The phase velocity of the system is examined; revealed in numerical simulations is emergence of spontaneous phase oscillation without external driving, which turns out to be in good agreement with analytical results derived in the strong-coupling limit. Such self-oscillation is found to suppress synchronization and its frequency is observed to decrease with inertia and delay. We obtain the phase diagram, which displays oscillatory and stationary phases in the appropriate regions of the parameters.Comment: 5 pages, 6 figures, to pe published in PR

Production and optical properties of liquid scintillator for the JSNS2^{2} experiment

The JSNS$^{2}$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment will search for neutrino oscillations over a 24 m short baseline at J-PARC. The JSNS$^{2}$ inner detector will be filled with 17 tons of gadolinium-loaded liquid scintillator (LS) with an additional 31 tons of unloaded LS in the intermediate $\gamma$-catcher and outer veto volumes. JSNS$^{2}$ has chosen Linear Alkyl Benzene (LAB) as an organic solvent because of its chemical properties. The unloaded LS was produced at a refurbished facility, originally used for scintillator production by the RENO experiment. JSNS$^{2}$ plans to use ISO tanks for the storage and transportation of the LS. In this paper, we describe the LS production, and present measurements of its optical properties and long term stability. Our measurements show that storing the LS in ISO tanks does not result in degradation of its optical properties.Comment: 7 pages, 4 figures

Spatiotemporal Stochastic Resonance in Fully Frustrated Josephson Ladders

We consider a Josephson-junction ladder in an external magnetic field with half flux quantum per plaquette. When driven by external currents, periodic in time and staggered in space, such a fully frustrated system is found to display spatiotemporal stochastic resonance under the influence of thermal noise. Such resonance behavior is investigated both numerically and analytically, which reveals significant effects of anisotropy and yields rich physics.Comment: 8 pages in two columns, 8 figures, to appear in Phys. Rev.

Evaluation of cognitive function in adult rhesus monkeys using the finger maze test

In research on cognitive function, the use of experimental animals is essential for the study of human cognitive processes and mechanisms. Furthermore, non-human primates are necessary for understanding higher cognitive functions in humans. However, there are few cognitive function tests available for non-human primates, Thus, we modified a finger maze test for application to non-human primates. In this study, we assessed learning and memory in 12 adult rhesus monkeys using a finger maze test that was developed to assess cognitive functions in captive non-human primates. The monkeys were trained with moving rewards indicating the correct direction, which allowed the monkeys to obtain the reward. Following training, subjects completed a learning trial and a memory trial two months later. Although the time required for training varied among the monkeys, 11 out of 12 monkeys completed the training and achieved a high success rate in the learning trial as well as in the memory trial conducted 2 months later. This is the first study to apply the finger maze test to adult rhesus monkeys. The finger maze test enabled us to assess learning and memory in several adult rhesus monkeys simultaneously

Performance of a prototype active veto system using liquid scintillator for a dark matter search experiment

We report the performance of an active veto system using a liquid scintillator with NaI(Tl) crystals for use in a dark matter search experiment. When a NaI(Tl) crystal is immersed in the prototype detector, the detector tags 48% of the internal K-40 background in the 0-10 keV energy region. We also determined the tagging efficiency for events at 6-20 keV as 26.5 +/- 1.7% of the total events, which corresponds to 0.76 +/- 0.04 events/keV/kg/day. According to a simulation, approximately 60% of the background events from U, Th, and K radioisotopes in photomultiplier tubes are tagged at energies of 0-10 keV. Full shielding with a 40-cm-thick liquid scintillator can increase the tagging efficiency for both the internal K-40 and external background to approximately 80%.Comment: Submitted to Nuclear Instruments and Methods in Physics Research Section

A combined variation of the musculocutaneous nerve associated with a supernumerary head of the biceps brachii muscle

Single anatomical variation in the upper limb is common, but the coexistence of neuromuscular anomalies is still rare. We found a combined neuromuscular variation in the upper limb in a 61-year-old Korean male cadaver, whose cause of death was laryngeal carcinoma, during a routine dissection course for medical students. In his left arm, a supernumerary head of the biceps brachii muscle attached to the anteromedial surface of mid-humerus and united distally with the long and short heads of the biceps brachii muscle (BBM). The musculocutaneous nerve, which did not pierce the coracobrachialis muscle but gave 2 muscular branches, had a communicating branch to the median nerve. Since the presence of the supernumerary head of the BBM might affect the course and branching of the musculocutaneous nerve, knowing different patterns of the musculocutaneous variation associated with the BBM variations is essential for anatomists and clinicians