arXiv subjects

S. Lee

Publications and source records attributed to S. Lee.

At least 163 records · Page 9Linked to original sources

arXiv2021

The JSNS^2 Detector

The JSNS^2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment aims to search for oscillations involving a sterile neutrino in the eV^2 mass-splitting range. The experiment will search for the appearance of electron antineutrinos oscillated from muon antineutrinos. The electron antineutrinos are detected via the inverse beta decay process using a liquid scintillator detector. A 1MW beam of 3 GeV protons incident on a spallation neutron target produces an intense and pulsed neutrino source from pion, muon, and kaon decay at rest. The JSNS^2 detector is located 24 m away from the neutrino source and began operation from June 2020. The detector contains 17 tonnes of gadolinium (Gd) loaded liquid scintillator (LS) in an acrylic vessel, as a neutrino target. It is surrounded by 31 tonnes of unloaded LS in a stainless steel tank. Optical photons produced in LS are viewed by 120 R7081 Hamamatsu 10-inch Photomultiplier Tubes (PMTs). In this paper, we describe the JSNS^2 detector design, construction, and operation.

physics.ins-det↗

arXiv2021

Bifurcation and Nonlinear Oscillation of the Bead Motion

This research focuses on the interesting physical phenomenon of the bead-hoop system. The bifurcation can be observed investigating the equilibrium point of the bead, and nonlinear oscillation also occurs from the bead's motion. This paper includes the theoretical investigation by setting the quantitative model and studying pitchfork bifurcation. Also, the equation of motion is derived by investigating resistance. Three parts of experiments were done and went through analysis by examining standard error, error of experiment, and the error of fitting.

physics.class-ph↗

arXiv2021

Mechanical Properties of Wilberforce Pendulum

This paper shows the study of interesting mechanical properties of Wilberforce pendulum. Analyzing qualitatively of the pendulum, it is able to know how the phenomenon occurs. By setting of the quantitative model, equation of the motion is derived. Considering the mass and moment of inertia of the spring, the experiment was done by changing the moment of inertia as the main parameter. The results were analyzed by defining oscillation ratio and conversion factor.

physics.class-ph↗

arXiv2021

Slow control and monitoring system at the JSNS$^{2}$

The JSNS$^2$ experiment is aimed to search for sterile neutrino oscillations using a neutrino beam from muon decays at rest. The JSNS$^2$ detector contains 17 tons of 0.1\% gadolinium (Gd) loaded liquid scintillator (LS) as a neutrino target. Detector construction was completed in the spring of 2020. A slow control and monitoring system (SCMS) was implemented for reliable control and quick monitoring of the detector operational status and environmental conditions. It issues an alarm if any of the monitored parameters exceed a preset acceptable range. The SCMS monitors the high voltage (HV) of the photomultiplier tubes (PMTs), the LS level in the detector, possible LS overflow and leakage, the temperature and air pressure in the detector, the humidity of the experimental hall, and the LS flow rate during filling and extraction. An initial 10 days of data-taking with a neutrino beam was done following a successful commissioning of the detector and SCMS in June 2020. In this paper, we present a description of the assembly and installation of the SCMS and its performance.

physics.ins-det↗

arXiv2021

Improved axion haloscope search analysis

One of the most significant and practical figures of merit in axion haloscope searches is the scanning rate, because of the unknown axion mass. Under the best experimental parameters, the only way to improve the figure of merit is to increase the experimentally designed signal to noise ratio in the axion haloscope search analysis procedure. In this paper, we report an improved axion haloscope search analysis using the data taken by the CAPP-8TB haloscope. By correcting for the background biased by the background parametrizations in the presence of axion signals, we realized a signal to noise ratio efficiency of about 100\%. Given the axion haloscope search analyses to date, the scanning rate can be improved by 21\%, with about a 10\% improvement in the signal to noise ratio. This improvement is another low cost innovation in axion haloscope searches, where all the experimental parameters are currently at their best.

astro-ph.CO↗

arXiv2021

Observation of Beam Spin Asymmetries in the Process $e p \rightarrow e π^{+}π^{-}X$ with CLAS12

The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function $e(x)$, which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function $G_1^\perp$. A clear sign change is observed around the $ρ$ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.

hep-ex↗

arXiv2021

DES Y1 results: Splitting growth and geometry to test $Λ$CDM

We analyze Dark Energy Survey (DES) data to constrain a cosmological model where a subset of parameters -- focusing on $Ω_m$ -- are split into versions associated with structure growth (e.g. $Ω_m^{\rm grow}$) and expansion history (e.g. $Ω_m^{\rm geo}$). Once the parameters have been specified for the $Λ$CDM cosmological model, which includes general relativity as a theory of gravity, it uniquely predicts the evolution of both geometry (distances) and the growth of structure over cosmic time. Any inconsistency between measurements of geometry and growth could therefore indicate a breakdown of that model. Our growth-geometry split approach therefore serves as both a (largely) model-independent test for beyond-$Λ$CDM physics, and as a means to characterize how DES observables provide cosmological information. We analyze the same multi-probe DES data as arXiv:1811.02375 : DES Year 1 (Y1) galaxy clustering and weak lensing, which are sensitive to both growth and geometry, as well as Y1 BAO and Y3 supernovae, which probe geometry. We additionally include external geometric information from BOSS DR12 BAO and a compressed Planck 2015 likelihood, and external growth information from BOSS DR12 RSD. We find no significant disagreement with $Ω_m^{\rm grow}=Ω_m^{\rm geo}$. When DES and external data are analyzed separately, degeneracies with neutrino mass and intrinsic alignments limit our ability to measure $Ω_m^{\rm grow}$, but combining DES with external data allows us to constrain both growth and geometric quantities. We also consider a parameterization where we split both $Ω_m$ and $w$, but find that even our most constraining data combination is unable to separately constrain $Ω_m^{\rm grow}$ and $w^{\rm grow}$. Relative to $Λ$CDM, splitting growth and geometry weakens bounds on $σ_8$ but does not alter constraints on $h$.

astro-ph.CO↗

arXiv2020

Proposal: JSNS$^2$-II

This article describes the goal and expected sensitivity of the JSNS$^2$-II experiment at J-PARC Materials and Life Science Experimental Facility (MLF). The JSNS$^2$-II experiment is the second phase of the JSNS$^2$ experiment (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) with two detectors which are located in 24 m (an existing detector) and 48 m (new one) baselines to improve the sensitivity of the search for sterile neutrinos, especially in the low $Δm^2$ region, which has been indicated by the global fit of the appearance mode. The new second detector has a similar structure as the existing JSNS$^2$ detector, which is already working. To compensate for the reduction of the neutrino flux due to the distance from the mercury target, the target mass of the Gd-loaded liquid scintillator which is the Linear AlkylBenzene (LAB) based liquid scintillator inside the acrylic vessel is 35 tons. To keep the same photo-coverage of the detector as the first detector, we will surround the acrylic vessel with 240 PMTs. With this experimental setup and 5 years (times 1 MW beam power) exposure, the sensitivity of the JSNS$^2$-II is significantly improved compared to the current JSNS$^2$, especially in the low $Δm^2$ oscillation parameter region. The JSNS$^2$-II can also confirm or refute the most of the oscillation parameters' space preferred by the previous experiments with 3 sigma C.L.. Considering these situations and world wide status of the sterile neutrino searches, we are eager to start the data taking with the two detector configuration from 2023. The fund to build the second detector was already secured.

hep-ex↗

arXiv2020

Two-magnon frequency-pulling effect in ferromagnetic resonance

We report the experimental observation in thin films of the hybridization of the uniform ferromagnetic resonance mode with nonuniform magnons as a result of the two-magnon scattering mechanism, leading to a frequency-pulling effect on the ferromagnetic resonance. This effect, when not properly accounted for, leads to a discrepancy in the dependence of the ferromagnetic resonance field on frequency for different field orientations. The frequency-pulling effect is the complement of the broadening of the ferromagnetic resonance lineshape by two-magnon scattering and can be calculated using the same parameters. By accounting for the two-magnon frequency shifts through these means, consistency is achieved in fitting data from in-plane and perpendicular-to-plane resonance conditions.

cond-mat.mtrl-sci↗

arXiv2020

Enriched Galerkin Discretization for Modeling Poroelasticity and Permeability Alteration in Heterogeneous Porous Media

Accurate simulation of the coupled fluid flow and solid deformation in porous media is challenging, especially when the media permeability and storativity are heterogeneous. We apply the enriched Galerkin (EG) finite element method for the Biot's system. Block structure used to compose the enriched space and linearization and iterative schemes employed to solve the coupled media permeability alteration are illustrated. The open-source platform used to build the block structure is presented and illustrate that it helps the enriched Galerkin method easily adaptable to any existing discontinuous Galerkin codes. Subsequently, we compare the EG method with the classic continuous Galerkin (CG) and discontinuous Galerkin (DG) finite element methods. While these methods provide similar approximations for the pressure solution of Terzaghi's one-dimensional consolidation, the CG method produces spurious oscillations in fluid pressure and volumetric strain solutions at material interfaces that have permeability contrast and does not conserve mass locally. As a result, the flux approximation of the CG method is significantly different from the one of EG and DG methods, especially for the soft materials. The difference of flux approximation between EG and DG methods is insignificant; still, the EG method demands approximately two and three times fewer degrees of freedom than the DG method for two- and three-dimensional geometries, respectively. Lastly, we illustrate that the EG method produces accurate results even for much coarser meshes.

cs.CE↗

arXiv2020

A Locally Conservative Mixed Finite Element Framework for Coupled Hydro-Mechanical-Chemical Processes in Heterogeneous Porous Media

This paper presents a mixed finite element framework for coupled hydro-mechanical-chemical processes in heterogeneous porous media. The framework combines two types of locally conservative discretization schemes: (1) an enriched Galerkin method for reactive flow, and (2) a three-field mixed finite element method for coupled fluid flow and solid deformation. This combination ensures local mass conservation, which is critical to flow and transport in heterogeneous porous media, with a relatively affordable computational cost. A particular class of the framework is constructed for calcite precipitation/dissolution reactions, incorporating their nonlinear effects on the fluid viscosity and solid deformation. Linearization schemes and algorithms for solving the nonlinear algebraic system are also presented. Through numerical examples of various complexity, we demonstrate that the proposed framework is a robust and efficient computational method for simulation of reactive flow and transport in deformable porous media, even when the material properties are strongly heterogeneous and anisotropic.

cs.CE↗

arXiv2020

Influence of magnetic ordering on the optical response of the antiferromagnetic topological insulator MnBi$_2$Te$_4$

The layered topological insulator MnBi$_2$Te$_4$ has attracted great interest recently due to its intrinsic antiferromagnetic order, potentially hosting various topological phases. By temperature-dependent infrared spectroscopy over a broad frequency range, we studied the changes in the optical conductivity of MnBi$_2$Te$_4$ at the magnetic ordering temperature. The temperature dependence of several optical parameters reveals an anomaly at the magnetic phase transition, which suggests the correlation between the bulk electronic band structure and the magnetism. We relate our findings to recent reports on the temperature dependence of the electronic band structure of MnBi$_2$Te$_4$.

cond-mat.mtrl-sci↗

arXiv2020

Charge collection properties of TowerJazz 180 nm CMOS Pixel Sensors in dependence of pixel geometries and bias parameters, studied using a dedicated test-vehicle: the Investigator chip

This paper contains a compilation of parameters influencing the charge collection process extracted from a comprehensive study of partially depleted Monolithic Active Pixel Sensors with small (<25 um$^2$) collection electrodes fabricated in the TowerJazz 180 nm CMOS process. These results gave guidance for the optimisation of the diode implemented in ALPIDE, the chip used in the second generation Inner Tracking System of ALICE, and serve as reference for future simulation studies of similar devices. The studied parameters include: reverse substrate bias, epitaxial layer thickness, charge collection electrode size and the spacing of the electrode to surrounding in-pixel electronics. The results from pixels of 28 um pitch confirm that even in partially depleted circuits, charge collection can be fast (<10 ns), and quantify the influence of the parameters onto the signal sharing and amplitudes, highlighting the importance of a correct spacing between wells and of the impact of the reverse substrate bias.

physics.ins-det↗

arXiv2020

Over 1% magnetoresistance ratio at room temperature in non-degenerate silicon-based lateral spin valves

To augment the magnetoresistance (MR) ratio of n-type non-degenerate Si-based lateral spin valves (Si-LSVs), we modify the doping profile in the Si layer and introduce a larger local strain into the Si channel by changing a capping insulator. The highest MR ratio of 1.4% is achieved in the Si-LSVs through these improvements, with significant roles played by a reduction in the resistance-area product of the ferromagnetic contacts and an enhancement of the momentum relaxation time in the Si channel.

physics.app-ph↗

arXiv2020

CAPP-8TB: Axion Dark Matter Search Experiment around 6.7 $μ$eV

CAPP-8TB is an axion dark matter search experiment dedicated to an axion mass search near 6.7 $μ$eV. The experiment uses a microwave resonant cavity under a strong magnetic field of 8 T produced by a superconducting solenoid magnet in a dilution refrigerator. We describe the experimental configuration used to search for a mass range of 6.62 to 6.82 $μ$eV in the first phase of the experiment. We also discuss the next phase of the experiment and its prospects.

physics.ins-det↗

arXiv2020

Axion Dark Matter Search around 6.7 $μ$eV

An axion dark matter search with the CAPP-8TB haloscope is reported. Our results are sensitive to axion-photon coupling $g_{aγγ}$ down to the QCD axion band over the axion mass range between 6.62 and 6.82 $μ$eV at a 90\% confidence level, which is the most sensitive result in the mass range to date.

hep-ex↗

arXiv2020

Resonant soft x-ray scattering from stripe-ordered La$_{2-x}$Ba$_x$CuO$_4$ detected by a transition edge sensor array detector

Resonant soft x-ray scattering (RSXS) is a leading probe of valence band order in materials best known for detecting charge density wave order in the copper-oxide superconductors. One of the biggest limitations on the RSXS technique is the presence of a severe fluorescence background which, like the RSXS cross section itself, is enhanced under resonant conditions. This background prevents the study of weak signals such as diffuse scattering from glassy or fluctuating order that is spread widely over momentum space. Recent advances in superconducting transition edge sensor (TES) detectors have led to major improvements in energy resolution and detection efficiency in the soft x-ray range. Here, we perform a RSXS study of stripe-ordered La$_{2-x}$Ba$_x$CuO$_4$ at the Cu $L_{3/2}$ edge (932.2 eV) using a TES detector with 1.5 eV resolution, to evaluate its utility for mitigating the fluorescence background problem. We find that, for suitable degree of detuning from the resonance, the TES rejects the fluorescence background, leading to a 5 to 10 times improvement in the statistical quality of the data compared to an equivalent, energy-integrated measurement. We conclude that a TES presents a promising approach to reducing background in RSXS studies and may lead to new discoveries in materials exhibiting valence band order that is fluctuating or glassy.

cond-mat.str-el↗

arXiv2020

Linear magneto-electric phase in ultrathin MnPS$_{3}$ probed by optical second harmonic generation

The transition metal thiophosphates $M$PS$_3$ ($M$ = Mn, Fe, Ni) are a class of van der Waals stacked insulating antiferromagnets that can be exfoliated down to the ultrathin limit. MnPS$_3$ is particularly interesting because its N$\acute{\textrm{e}}$el ordered state breaks both spatial-inversion and time-reversal symmetries, allowing for a linear magneto-electric phase that is rare among van der Waals materials. However, it is unknown whether this unique magnetic structure of bulk MnPS$_3$ remains stable in the ultrathin limit. Using optical second harmonic generation rotational anisotropy, we show that long-range linear magneto-electric type N$\acute{\textrm{e}}$el order in MnPS$_3$ persists down to at least 5.3 nm thickness. However an unusual mirror symmetry breaking develops in ultrathin samples on SiO$_2$ substrates that is absent in bulk materials, which is likely related to substrate induced strain.

cond-mat.str-el↗