arXiv subjects

R. Lee

Publications and source records attributed to R. Lee.

12 recordsLinked to original sources

arXiv2025

Decadal upgrade strategy for KAGRA toward post-O5 gravitational-wave astronomy

The KAGRA Collaboration has investigated a ten-year upgrade strategy for the KAGRA gravitational wave detector, considering a total of 14 upgrade options that vary in mirror mass, quantum noise reduction techniques, and the quality of cryogenic suspensions. We evaluated the scientific potential of these configurations with a focus on key targets such as parameter estimation of compact binary coalescences, binary neutron star post-merger signals, and continuous gravitational waves. Rather than aiming to improve all science cases uniformly, we prioritized those most sensitive to the detector configuration. Technical feasibility was assessed based on required hardware developments, associated R\&D efforts, cost, and risk. Our study finds that a high-frequency upgrade plan that enhances sensitivity over a broad frequency range above ~200 Hz offers the best balance between scientific return and technical feasibility. Such an upgrade would enable sky localization of binary neutron star mergers at 100 Mpc to better than 0.5 deg$^2$ in a LIGO-Virgo-KAGRA network, and improve the measurement precision of tidal deformability parameter by approximately 10% at median, compared to a network without KAGRA.

gr-qc↗

arXiv2025

Identification of Noise-Associated Glitches in KAGRA O3GK with Hveto

Transient noise ("glitches") in gravitational wave detectors can mimic or obscure true signals, significantly reducing detection sensitivity. Identifying and excluding glitch-contaminated data segments is therefore crucial for enhancing the performance of gravitational-wave searches. We perform a noise analysis of the KAGRA data obtained during the O3GK observation. Our analysis is performed with hierarchical veto (Hveto) which identifies noises based on the statistical time correlation between the main channel and the auxiliary channels. A total of 2,531 noises were vetoed by 28 auxiliary channels with the configuration (i.e., signal-to-noise threshold set to 8) that we chose for Hveto. We identify vetoed events as glitches on the spectrogram via visual examination after plotting them with Q-transformation. By referring to the Gravity Spy project, we categorize 2,354 glitches into six types: blip, helix, scratchy, and scattered light, which correspond to those listed in Gravity Spy, and dot and line, which are not found in the Gravity Spy classification and are thus named based on their spectrogram morphology in KAGRA data. The remaining 177 glitches are determined not to belong to any of these six types. We show how the KAGRA glitch types are related to each subsystem of KAGRA. To investigate the possible correlation between the main channel and the round winner - an auxiliary channel statistically associated with the main channel for vetoing purposes - we visually examine the similarity or difference in the glitch pattern on the spectrogram. We compare the qualitative correlation found through visual examination with coherence, which is known to provide quantitative measurement for the correlation between the main channel and each auxiliary channel. Our comprehensive noise analysis will help improve the data quality of KAGRA by applying it to future KAGRA observation data.

gr-qc↗

arXiv2022

Noise subtraction from KAGRA O3GK data using Independent Component Analysis

In April 2020, KAGRA conducted its first science observation in combination with the GEO~600 detector (O3GK) for two weeks. According to the noise budget estimation, suspension control noise in the low frequency band and acoustic noise in the middle frequency band are identified as the dominant contribution. In this study, we show that such noise can be reduced in offline data analysis by utilizing a method called Independent Component Analysis (ICA). Here the ICA model is extended from the one studied in iKAGRA data analysis by incorporating frequency dependence while linearity and stationarity of the couplings are still assumed. By using optimal witness sensors, those two dominant contributions are mitigated in the real observational data. We also analyze the stability of the transfer functions for whole two weeks data in order to investigate how the current subtraction method can be practically used in gravitational wave search.

astro-ph.IM↗

arXiv2022

Performance of the KAGRA detector during the first joint observation with GEO 600 (O3GK)

KAGRA, the kilometer-scale underground gravitational-wave detector, is located at Kamioka, Japan. In April 2020, an astrophysics observation was performed at the KAGRA detector in combination with the GEO 600 detector; this observation operation is called O3GK. The optical configuration in O3GK is based on a power recycled Fabry-P\'{e}rot Michelson interferometer; all the mirrors were set at room temperature. The duty factor of the operation was approximately 53%, and the strain sensitivity was $3\times10^{-22}~/\sqrt{\rm{Hz}}$ at 250 Hz. In addition, the binary-neutron-star (BNS) inspiral range was approximately 0.6 Mpc. The contributions of various noise sources to the sensitivity of O3GK were investigated to understand how the observation range could be improved; this study is called a "noise budget". According to our noise budget, the measured sensitivity could be approximated by adding up the effect of each noise. The sensitivity was dominated by noise from the sensors used for local controls of the vibration isolation systems, acoustic noise, shot noise, and laser frequency noise. Further, other noise sources that did not limit the sensitivity were investigated. This paper provides a detailed account of the KAGRA detector in O3GK including interferometer configuration, status, and noise budget. In addition, strategies for future sensitivity improvements such as hardware upgrades, are discussed.

astro-ph.IM↗

arXiv2021

Panoramic SETI: on-sky results from prototype telescopes and instrumental design

The Panoramic SETI (Search for Extraterrestrial Intelligence) experiment (PANOSETI) aims to detect and quantify optical transients from nanosecond to second precision over a large field-of-view ($\sim$4,450 square-degrees). To meet these challenging timing and wide-field requirements, the PANOSETI experiment will use two assemblies of $\sim$45 telescopes to reject spurious signals by coincidence detection, each one comprising custom-made fast photon-counting hardware combined with ($f/1.32$) focusing optics. Preliminary on-sky results from pairs of PANOSETI prototype telescopes (100 sq.deg.) are presented in terms of instrument performance and false alarm rates. We found that a separation of $>$1 km between telescopes surveying the same field-of-view significantly reduces the number of false positives due to nearby sources (e.g., Cherenkov showers) in comparison to a side-by-side configuration of telescopes. Design considerations on the all-sky PANOSETI instrument and expected field-of-views are reported.

astro-ph.IM↗

arXiv2021

ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides

The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project makes the best use of all available resources, i.e., observations from ground telescopes, mid-time values from the literature and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85\% of the currently known Ariel candidate targets. This work includes the results of $\sim$1600 observations obtained up to the 31st of December 2020 from the ExoClock network. These data in combination with $\sim$2350 mid-time values collected from the literature are used to update the ephemerides of 180 planets. The analysis shows that 40\% of the updated ephemerides will have an impact on future scheduling as either they have a significantly improved precision, or they have revealed biases in the old ephemerides. With the new observations, the observing coverage and rate for half of the planets in the sample has been doubled or more. Finally, from a population perspective, we identify that the differences in the 2028 predictions between the old and the new ephemerides have an STD that is double what is expected from gaussian uncertainties. These findings have implications for planning future observations, where we will need to account for drifts potentially greater than the prediction uncertainties. The updated ephemerides are open and accessible to the wider exoplanet community both from our Open Science Framework (OSF) repository and our website.

astro-ph.EP↗

arXiv2019

An arm length stabilization system for KAGRA and future gravitational-wave detectors

Modern ground-based gravitational wave (GW) detectors require a complex interferometer configuration with multiple coupled optical cavities. Since achieving the resonances of the arm cavities is the most challenging among the lock acquisition processes, the scheme called arm length stabilization (ALS) had been employed for lock acquisition of the arm cavities. We designed a new type of the ALS, which is compatible with the interferometers having long arms like the next generation GW detectors. The features of the new ALS are that the control configuration is simpler than those of previous ones and that it is not necessary to lay optical fibers for the ALS along the kilometer-long arms of the detector. Along with simulations of its noise performance, an experimental test of the new ALS was performed utilizing a single arm cavity of KAGRA. This paper presents the first results of the test where we demonstrated that lock acquisition of the arm cavity was achieved using the new ALS and residual noise was measured to be $8.2\,\mathrm{Hz}$ in units of frequency, which is smaller than the linewidth of the arm cavity and thus low enough to lock the full interferometer of KAGRA in a repeatable and reliable manner.

physics.ins-det↗

arXiv2018

Diagnosing numerical Cherenkov instabilities in relativistic plasma simulations based on general meshes

Numerical Cherenkov radiation (NCR) or instability is a detrimental effect frequently found in electromagnetic particle-in-cell (EM-PIC) simulations involving relativistic plasma beams. NCR is caused by spurious coupling between electromagnetic-field modes and multiple beam resonances. This coupling may result from the slow down of poorly-resolved waves due to numerical (grid) dispersion and from aliasing mechanisms. NCR has been studied in the past for finite-difference-based EM-PIC algorithms on regular (structured) meshes with rectangular elements. In this work, we extend the analysis of NCR to finite-element-based EM-PIC algorithms implemented on unstructured meshes. The influence of different mesh element shapes and mesh layouts on NCR is studied. Analytic predictions are compared against results from finite-element-based EM-PIC simulations of relativistic plasma beams on various mesh types.

physics.comp-ph↗

arXiv2018

Standard Model Theory for the FCC-ee Tera-Z stage

The future 100-km circular collider FCC at CERN is planned to operate in one of its modes as an electron-positron FCC-ee machine. We give an overview comparing the theoretical status to the experimental demands of one of four foreseen FCC-ee operating stages, Z-boson resonance energy physics, called the FCC-ee Tera-Z stage for short. The FCC-ee Tera-Z will deliver the highest integrated luminosities as well as very small systematic errors for a study of the Standard Model (SM) with unprecedented precision. In fact, the FCC-ee Tera-Z will allow the study of at least one more perturbative order in quantum field theory compared to the LEP/SLC precision. The real problem is that the present precision of theoretical calculations of the various SM observables does not match that of the anticipated experimental measurements. The bottle-necks to overcoming this situation are identified. In particular, the issues of precise QED unfolding and the correct calculation of SM pseudo-observables are critically reviewed. In an Executive Summary, we specify which basic theoretical calculations are needed to meet the strong experimental expectations at the FCC-ee Tera-Z. Several methods, techniques and tools needed for higher-order multi-loop calculations are presented. By inspection of the Z-boson partial and total decay width analyses, it is argued that at the beginning of operation of the FCC-ee Tera-Z, the theory predictions may be tuned to be precise enough not to limit the physics interpretation of the measurements. This statement is based on anticipated progress in analytical and numerical calculations of multi-loop and multi-scale Feynman integrals and on the completion of two-loop electroweak radiative corrections to the SM pseudo-observables this year. However, the above statement is conditional as the theoretical issues demand a very dedicated and focused investment by the community.

hep-ph↗

arXiv2003

A straw drift chamber spectrometer for studies of rare kaon decays

We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5 mm diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-intensity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds.

physics.ins-det↗

arXiv2000

A Perturbative SU(3) Casson Invariant

A perturbative SU(3) Casson invariant $Λ_{SU(3)}(X)$ for integral homology 3-spheres is defined. Besides being fully perturbative, it has nice properties: (1) $4 . Λ_{SU(3)}(X)$ is an integer. (2) It is preseved under orientation change. (3) A connected sum formula holds. Explicit calculations of the invariant for $1/k$ surgery on $(2,q)$ torus knots are made and compared with a different generalization of Casson's invariant to SU(3) by Boden and Herald. For those cases computed, the invariant defined here is a quadratic polynomial in k for k>0 and a quadratic polynomial for k<0.

math.DG↗

arXiv1998

First Observation of the Rare Decay Mode K-long -> e+ e-

In an experiment designed to search for and study very rare two-body decay modes of the K-long, we have observed four examples of the decay K-long -> e+ e-, where the expected background is 0.17+-0.10 events. This observation translates into a branching fraction of 8.7^{+5.7}_{-4.1} X 10^{-12}, consistent with recent theoretical predictions. This result represents by far the smallest branching fraction yet measured in particle physics.

hep-ex↗