arXiv subjects
Publications and source records attributed to Seon-Hee Seo.
This is the report from the 2023 Particle Physics Project Prioritization Panel (P5) approved by High Energy Physics Advisory Panel (HEPAP) on December 8, 2023. The final version was made public on May 8, 2024 and submitted to DOE SC and NSF MPS.
The demand for underground labs for neutrino and rare event search experiments has been increasing over the last few decades. Yemilab, constructed in October 2022, is the first deep ($\sim$1~km) underground lab dedicated to science in Korea, where a large cylindrical cavern (D: 20~m, H: 20~m) was excavated in addition to the main caverns and halls. The large cavern could be utilized for a low background neutrino experiment by a liquid scintillator-based detector (LSC) where a 2.26 kiloton LS target would be filled. It's timely to have such a large but ultra-pure LS detector after the shutdown of the Borexino experiment so that solar neutrinos can be measured much more precisely. Interesting BSM physics searches can be also pursued with this detector when it's combined with an electron linac, a proton cyclotron (IsoDAR source), or a radioactive source. This article discusses the concept of a candidate detector and the physics potential of a large liquid scintillator detector.
We investigate the sensitivities of the liquid scintillator counter (LSC) at Yemilab and JUNO to solar neutrino oscillation parameters, focusing on $θ_{12}$ and $Δm^2_{21}$. We compare the potential of JUNO with LSC at Yemilab utilizing both reactor and solar data in determining those parameters. We find that the solar neutrino data of LSC at Yemilab is highly sensitive to $θ_{12}$ enabling its determination with exceptional precision. Our study also reveals that if $Δm^2_{21}$ is larger, with a value close to the best fit value of KamLAND, JUNO reactor data will have about two times better precision than the reactor LSC at Yemilab. On the other hand, if $Δm^2_{21}$ is smaller and closer to the best fit value of solar neutrino experiments, the precision of the reactor LSC at Yemilab will be better than JUNO.
IsoDAR@Yemilab is a novel isotope-decay-at-rest experiment that has preliminary approval to run at the Yemi underground laboratory (Yemilab) in Jeongseon-gun, South Korea. In this technical report, we describe in detail the considerations for installing this compact particle accelerator and neutrino target system at the Yemilab underground facility. Specifically, we describe the caverns being prepared for IsoDAR, and address installation, hielding, and utilities requirements. To give context and for completeness, we also briefly describe the physics opportunities of the IsoDAR neutrino source when paired with the Liquid Scintillator Counter (LSC) at Yemilab, and review the technical design of the neutrino source.
This review demonstrates the unique role of the neutrino by discussing in detail the physics of and with neutrinos. We deal with neutrino sources, neutrino oscillations, absolute masses, interactions, the possible existence of sterile neutrinos, and theoretical implications. In addition, synergies of neutrino physics with other research fields are found, and requirements to continue successful neutrino physics in the future, in terms of technological developments and adequate infrastructures, are stressed.
Dark photons are well motivated hypothetical dark sector particles that could account for observations that cannot be explained by the standard model of particle physics. A search for dark photons that are produced by an electron beam striking a thick tungsten target and subsequently interact in a 3 kiloton-scale neutrino detector in Yemilab, a new underground lab in Korea, is proposed. Dark photons can be produced by "darkstrahlung" or by oscillations from ordinary photons produced in the target and detected by their visible decays, "absorption" or by their oscillation to ordinary photons. By detecting the absorption process or the oscillation-produced photons, a world's best sensitivity for measurements of the dark-photon kinetic mixing parameter of $ε^2 > 1.5 \times 10^{-13} (6.1 \times 10^{-13})$ at the 95\% confidence level (C.L.) could be obtained for dark photon masses between 80 eV and 1 MeV in a year-long exposure to a 100 MeV-100 kW electron beam with zero ($10^3$) background events. In parallel, the detection of $e^+e^-$ pairs from decays of dark photons with mass between 1 MeV and $\sim$86 MeV would have sensitivities of $ε^2 > \mathcal{O}(10^{-17}) (\mathcal{O}(10^{-16}))$ at the 95% C.L. with zero ($10^3$) background events.
There are $\sim3σ$ or more evidence of eV-scale sterile neutrinos from several different measurements. Many dedicated experiments are (being) created and (will) take data to confirm or refute the eV-scale sterile neutrinos. In this talk, a mini review is presented on current experimental efforts and status on sterile neutrino search, especially using reactor and accelerator neutrinos.
There is a well known 2$σ$ tension in the measurements of the solar $Δm^2$ between KamLAND and SNO/Super-KamioKANDE. Precise determination of the solar $Δm^2$ is especially important in connection with current and future long baseline CP violation measurements. Reference \cite{Seo:2018rrb} points out that currently running short baseline reactor neutrino experiments, Daya Bay and RENO, can also constrain solar $Δm^2$ value as demonstrated by a GLoBES simulation with a limited systematic uncertainty consideration. In this work, the publicly available data, from Daya Bay (1,958 days) and RENO (2,200 days) are used to constrain the solar $Δm^2$. Verification of our method through $Δm^2_{ee}$ and $\sin^2 θ_{13}$ measurements is discussed in Appendix A. Using this verified method, reasonable constraints on the solar $Δm^2$ are obtained using above Daya Bay and RENO data, both individually and combined. We find that the combined data of Daya Bay and RENO set an upper limit on the solar $Δm^2$ of 18 $\times 10^{-5}$ eV$^2$ at the 95% C.L., including both systematic and statistical uncertainties. This constraint is slightly more than twice the KamLAND value. As this combined result is still statistics limited, even though driven by Daya Bay data, the constraint will improve with the additional running of this experiment.
We present neutrino-based options for verifying that the nuclear reactors at North Korea's Yongbyon Nuclear Research Center are no longer operating or that they are operating in an agreed manner, precluding weapons production. Neutrino detectors may be a mutually agreeable complement to traditional verification protocols because they do not require access inside reactor buildings, could be installed collaboratively, and provide persistent and specific observations. At Yongbyon, neutrino detectors could passively verify reactor shutdowns or monitor power levels and plutonium contents, all from outside the reactor buildings. The monitoring options presented here build on recent successes in basic particle physics. Following a dedicated design study, these tools could be deployed in as little as one year at a reasonable cost. In North Korea, cooperative deployment of neutrino detectors could help redirect a limited number of scientists and engineers from military applications to peaceful technical work in an international community. Opportunities for scientific collaboration with South Korea are especially strong. We encourage policymakers to consider collaborative neutrino projects within a broader program of action toward stability and security on the Korean Peninsula.
A new underground lab, Yemilab, is being constructed in Handuk iron mine, Korea. The default design of Yemilab includes a space for a future neutrino experiment. We propose to build a water-based liquid scintillator (WbLS) detector of 4$\sim$5 kiloton size at the Yemilab. The WbLS technology combines the benefits from both water and liquid scintillator (LS) in a single detector so that low energy physics and rare event searches can have higher sensitivities due to the larger size detector with increased light yield. No experiment has ever used a WbLS technology since it still needs some R&D studies, as currently being performed by THEIA group. If this technology works successfully with kiloton scale detector at Yemilab then it can be applied to future T2HKK (Hyper-K 2$^{nd}$ detector in Korea) to improve its physics potentials especially in the low energy region.
We demonstrate that the currently running short baseline reactor experiments, especially Daya Bay, can put a significant upper bound on $Δm^2_{21}$. This novel approach to determining $Δm^2_{21}$ can be performed with the current data of both Daya Bay \& RENO and provides additional information on $Δm^2_{21}$ in a different $L/E$ range ($\sim$ 0.5 km/MeV) for an important consistency check on the 3 flavor massive neutrino paradigm. Upper limits by Daya Bay and RENO and a possible lower limit from Daya Bay, before the end of 2020, will be the only new information on this important quantity until the medium baseline reactor experiment, JUNO, gives a very precise measurement in the middle of the next decade. In this study $θ_{12}$ value is fixed since its impact on the $Δm^2_{21}$ measurement is relatively small as discussed in the Appendix.
Hyper-Kamiokande (Hyper-K) succeeds the very successful Super-K experiment and will consist of a large detector filled with 260~kton purified water and equipped with 40\% photo-coverage. Physics program of Hyper-K is broad, covering from particle physics to astrophysics and astronomy. The Hyper-K 1$^{st}$ detector will be built in Japan, and the 2$^{nd}$ detector is considered to be built in Korea because locating the 2$^{nd}$ detector in Korea improves physics sensitivities in most cases thanks to the longer baseline ($\sim$1,100~km) and larger overburden ($\sim$1,000~m) for Korean candidate sites. In this talk, we present overview and physics potentials of the Hyper-K 2$^{nd}$ detector in Korea.
We describe the open-source global fitting package GAMBIT: the Global And Modular Beyond-the-Standard-Model Inference Tool. GAMBIT combines extensive calculations of observables and likelihoods in particle and astroparticle physics with a hierarchical model database, advanced tools for automatically building analyses of essentially any model, a flexible and powerful system for interfacing to external codes, a suite of different statistical methods and parameter scanning algorithms, and a host of other utilities designed to make scans faster, safer and more easily-extendible than in the past. Here we give a detailed description of the framework, its design and motivation, and the current models and other specific components presently implemented in GAMBIT. Accompanying papers deal with individual modules and present first GAMBIT results. GAMBIT can be downloaded from gambit.hepforge.org.
RENO (Reactor Experiment for Neutrino Oscillation) is the first reactor neutrino experiment which began data-taking in 2011 with two identical near and far detectors in Yonggwang, Korea. Using 1500 live days of data, sin^2(2θ_13) and |Δm^2_ee| are updated using spectral measurements: sin^2(2θ_13) = 0.086 +/- 0.006 (stat.) +/- 0.005 (syst.) and |Δm^2_ee| = 2.61+0.15-0.16 (stat.) +/- 0.09 (syst.) (x10^-3 eV^2). The correlation between the 5 MeV excess rate and the reactor thermal power is again clearly observed with the increased data set.
The successful measurements of the smallest neutrino mixing angle, $θ_{13}$, in 2012 by the short (1$\sim$2 km) baseline reactor neutrinos experiments, Daya Bay, RENO, and Double Chooz, have triggered a golden age of neutrino physics. The three experiments have been improving the $θ_{13}$ measurements by accumulating event statistics and reducing systematic uncertainties. Now the $θ_{13}$ measurement is the most precise one among the mixing angles in the Pontecorvo-Maki-Nakagawa-Sakata matrix. The most updated $θ_{13}$ and $Δm^{2}_{ee}$ measurements from these experiments are reported here as well as the 5 MeV excess, absolute reactor neutrino flux and sterile neutrino search. The best final precision on the sin$^{2}2θ_{13}$ ($|Δm^2_{ee}|$) measurement is expected to be $\sim$3\% ($\sim$3\%). A combined analysis from the three experiments will reduce the uncertainty and the relevant activity has started recently.
One of the main goals of RENO (Reactor Experiment for Neutrino Oscillation) is to measure the smallest neutrino mixing angle θ13 using reactor neutrinos in Korea. RENO is the first reactor experiment taking data with two identical detectors in different locations (Near and Far), which is critical to reduce systematic uncertainty in reactor neutrino flux. Our data taking has been almost continuous since Aug. 2011 and we have collected about 434,000 (54,000) electron anti-neutrinos in the Near (Far) detector by 2013. Using this data (about 800 live days) we present a new result on θ13: sin22θ13 = 0.101 +/- 0.008 (stat.) +/- 0.010 (syst.). We also report the 5 MeV excess present in the prompt signal spectrum in our data, and its correlation with our reactor thermal power.
RENO (Reactor Experiment for Neutrino Oscillation) is an experiment dedicated to measure the smallest neutrino mixing angle θ_13 using reactor neutrinos in Korea. Our first result measured in 2012 using about 220 live days of data showed non-zero θ_13 value with 4.9 σ significance. In March 2013 we updated our first result with improvements in both statistical and systematic errors using 403 live days of data. The measured value using rate-only analysis is sin^2(2θ_13) = 0.100 +/- 0.010 (stat) +/- 0.015 (sys.) corresponding to 6.3 σ significance. RENO has been taking data almost continuously since August 2011 and we have reached more than 800 live days of data that is currently being analyzed.