Opening Remark

• Hong Joo Kim (Kyungpook National University)

Novel hermetic detector for KAPAE

• Hyeoung Woo Park (Kyungpook National University)

The KNU Advanced Positronium Annihilation Experiment (KAPAE) explores new physics such as visible and invisible exotic decay on a laboratory scale. The KAPAE phase I aims to improve the sensitivity of CPT violation in the lepton sector using a novel trigger system. Furthermore, the KAPAE phase II has been developed to focus on invisible decay measurement. We will present KAPAE detector configuration and based on the preliminary results, discuss about the intensification of KAPAE.

Search for Elementary Magnetic Monopoles in Electron-Positron At Rest

• Sehwook Lee (Kyungpook National University)

Dark matter axion search at IBS-CAPP

• Sungwoo Youn (CAPP, IBS)

The axion is a hypothetical elementary particle which can address two fundamental questions in modern physics - CP problem in the strong interactions and mystery of dark matter. The most sensitive searches rely on the haloscope technique that utilizes the axion-photon conversion under a strong magnetic field. The key elements of experimental setup include a high-field magnet in a cryogenic refrigerator, a large-volume high-quality microwave resonator, and a quantum noise limited amplifier. Most of experiments are performed on a small scale in laboratories and IBS-CAPP, established in 2013 based on the similar concept, has played critical roles in this business. In this talk, we present the past, present, and future of dark matter axion searches at IBS-CAPP.

Distinguishing axion models with running axion couplings

• Sang Hui Im (CTPU, IBS)

We examine the possibility to experimentally distinguish three different classes of axion models, i.e. KSVZ-like, DFSZ-like, and string-theoretic axions by observing a different pattern of low energy couplings to the photons, nucleons and electrons. For this purpose, we study the renormalization group running of axion couplings at leading order. We find that the low energy couplings of string-theoretic axions have a similar pattern as those of KSVZ-like axions but yet reveal a sizable difference which might be testable in future axion search experiments. We also note that the coupling of KSVZ-like QCD axions to the electron is dominated by a three-loop contribution involving the exotic heavy quark, gluons, top quark and Higgs field.

Sterile neutrino dark matter with dipole interaction

• Ki Young Choi (SKKU)

Supernova-scope for the Direct Search of Supernova Axions

• Koichi Hamaguchi (University of Tokyo)

This talk is based on [arxiv:2008.03924]. If a supernova explosion occurs within a few hundred parsecs from the Earth, a huge number of axions, in addition to neutrinos, may arrive at the Earth. We discuss the prospect of detecting those supernova axions by an axion helioscope. With the help of a pre-supernova neutrino alert system, it is possible to point a helioscope at an exploding supernova in advance. The supernova axions can then be detected by a gamma-ray detector installed at the end of the helioscope. We call such a detection system an axion supernova-scope (SNscope). We propose a conceptual design for an axion SNscope, where the gamma-ray detector is installed at the opposite end to the X-ray detector for the solar axion. It still functions as an axion helioscope during the normal operation time, and once a pre-SN neutrino alert is received, the scope is temporarily turned around and targeted to a SN candidate, waiting for the supernova axions. We estimate the sensitivity of supernova axion detection and find that SNscopes based on the next-generation axion helioscopes, such as IAXO, have potential to explore the invisible axions.

The μ → eγ decay in an EW- scale non-sterile RH neutrino model

• Dinh Nguyen Dinh (Institute of Physics)

In this report, we briefly introduce an extended model with non-sterile RH neutrino at EW scale by P.Q. Hung. Then the branching ratio of μ → eγ decay will be derived at one- loop approximation with the participation of W gauge boson, neutral and singly charged Higgs scalars. We set constraints on relevant parameters and predict the sensitivities of the decay channel with the present and future experiments.

Light dark matter in cosmological relaxation scenario

• Hyungjin Kim (DESY)

I will discuss how light dark matter can arise from cosmological relaxation scenarios, which provides an alternative solution to the electroweak hierarchy problem. This dark matter candidate is lighter than eV-scale, and at the same time, couples to the standard model particles in the same way that the Higgs does. I will discuss the related phenomenology.

Discussion

Direct Detection of Dark Energy

• Surjeet Rajendran (Johns Hopkins University)

If dark energy evolves in time, its dynamical component could be tested in the laboratory. There are two kinds of tests. First, the coherent motion of the dark energy can lead to precession of spins of particles that are coupled to the dark energy. This leads to a dc precession of particle spins and it can be probed in storage ring experiments as well as experiments that search for Lorentz violation. Second, the dark energy can convert into a bath of dark radiation. Within current constraints this radiation could have up to ~ 10^3 timesmore energy density than the cosmic microwave background. In particular models, a rolling scalar field can generate different forms of dark radiation such as hidden photons, milli-charged particles and even Standard Model neutrinos. The leading effect on the late-time cosmological expansion history depends on a single parameter beyond Lambda CDM - namely the temperature of the dark radiation today. Cosmological observations of this modified expansion rate could provide a striking signature of this scenario. The dark radiation itself could even be directly detectable in laboratory experiments, suggesting a broader experimental program into the nature of dark energy.

The Migdal effect in semi-conductors

• Simon Knapen (CERN)

Engineering graphene Josephson junction for sensitive photon detector

• Gil-Ho Lee (POSTECH)

Sensitive microwave detectors are essential in radioastronomy, dark-matter axion searches and superconducting quantum information science. The conventional strategy to obtain higher-sensitivity bolometry is the nanofabrication of ever smaller devices to augment the thermal response. However, it is difficult to obtain efficient photon coupling and to maintain the material properties in a device with a large surface-to-volume ratio owing to surface contamination. Here we present an ultimately thin bolometric sensor based on monolayer graphene. To utilize the minute electronic specific heat and thermal conductivity of graphene, we develop a superconductor–graphene–superconductor Josephson junction bolometer embedded in a microwave resonator with a resonance frequency of 7.9 gigahertz and over 99 per cent coupling efficiency. The dependence of the Josephson switching current on the operating temperature, charge density, input power and frequency shows a noise-equivalent power of 7 × 10 −19 watts per square-root hertz, which corresponds to an energy resolution of a single 32-gigahertz photon, reaching the fundamental limit imposed by intrinsic thermal fluctuations at 0.19 kelvin. We also discuss our experimental demonstration of 1,550-nm infrared single photon detector as well as theoretical modelling for ultra-light dark matter search using graphene-based sensor.

Detection of Super-light Dark Matter Using Graphene Josephson Junction

• Jong-Chul Park (CNU)

We propose a new dark matter detection strategy that will enable the search of keV-range super-light dark matter, representing an improvement of the minimum detectable mass by more than three orders of magnitude over the ongoing experiments. This is possible by integrating intimately the target material, π-bond electrons in graphene, into a Josephson junction to achieve a high sensitivity detector that can resolve a small energy exchange from dark matter as low as ~0.1 meV. We investigate detection prospects with pg-, ng-, and 𝜇g-scale detectors by calculating the scattering rate between dark matter and the free electrons confined in two-dimensional graphene with Pauli blocking factors included. We find not only that the proposed detector can serve as a complementary probe of super-light dark matter but also achieve higher experimental sensitivities than other proposed experiments, i.e. in having a low detectable threshold provided the same target mass, thanks to the extremely low energy threshold of our Josephson junction sensor.

NaI detector for rare event searches

• Hyun Su Lee (CUP, IBS)

A NaI is conventional detector with a very long history and are still widely used. In particular, since the DAMA experiment claimed an observation of dark matter with the NaI(Tl) detector, the development of a low background and high scintillation efficiency detectors were widely researched. In Korea, the COSINE experiment to verify the DAMA experiment by developing a high-purity NaI detector at the Center for Underground Physics in IBS is being operated at the Yangyang Underground Laboratory and reported interesting results. In addition, COSINE collaboration is preparing for the next phase COSINE-200 experiment by developing the world's best performing high-purity NaI detector. In addition, several efforts are underway to increase the light yield and the detector performances. Based on the results of these efforts, the NEON experiment, an experiment to observe the neutrino-nucleus coherent scattering from the electron antineutrinos in a nuclear power plant that requires an extremely low energy threshold, was started. In this presentation, we want to show the efforts and achievements on the development of high-purity NaI detectors for dark matter and neutrino experiments.

A small cryogenic detector for low mass WIMPs search

• Hyelim Kim (CUP, IBS)

The focusing mass of the present WIMPs (weakly interacting massive particles) search is going down. For the low mass WIMP search, we studied a low threshold cryogenic particle detector using an MMC (Metallic Magnetic Calorimeter) sensor and a pure CaF2 crystal as a particle absorber. The spin (l/2) of 19F has a large cross section for axial coupled WIMPs. The fast response time of a MMC sensor and good thermal connection of the crystal and the sensor made a 76 us rise time and a 67 eV of FWHM baseline energy resolution. The luminescence of the CaF2 crystal has a main emission band at 280 nm and 60% light yield of CaWO4 at 8 K. The UV scintillation light can make large light signals at the cryogenic light detector, which will make powerful particle discrimination. Here, I will talk about the prospect of the MMC based cryogenic particle detector using CaF2 for the low mass WIMP search.

A lab-scale experiment for keV sterile neutrino search from tritium beta decay spectrum

• Yong Chang Lee (SNU)

We developed a simple small-scale detection method for beta decay spectrum of 3H. This research is motivated to investigate the presence of sterile neutrinos in keV region. In our experiment, tritium nuclei are embedded in a 1x1x1 cm^3 LiF crystal from 6Li(n,3H)4He reaction. The beta energy spectrum is measured with an MMC sensor, one of the high-resolution microcalorimeters operating at mK temperatures. We present the method for the sample preparation and the experiment together with the physics result from the first measurement set. Moreover, an expected sensitivity to search for the heavy neutrino is discussed for one year measurement with the setup.

Semiempirical calculation of quenching factors for ions in scintillators

• Volodymyr Tretyak (Institute of Nuclear Physics)

Discussion

Background particle rate of an Axion-like Particle Search at the DAMSA experiment

• Min Sang RYU (CHEP)

With the 2012 discovery of the Higgs-like particle at CERN and its increasingly Standard Model-like properties, the primary interests of the field of particle physics are shifting to the study of the remaining 95% of the matter and energy in the universe, using accelerators. The so-called unseen aboriginal particles (UAPs) that make up a large fraction of the 95% could be produced and discovered in particle accelerators with high-intensity beams. Rare nuclear isotope accelerator facility, such as Rare isotope Accelerator complex for ON-line experiment (RAON) provides an excellent opportunity for discovery of UAPs. The axion-like particle (ALP) is a good candidate for the UAP and thus provides an excellent case study at the DAMSA (Dump produced Aboriginal Matter Searches at an Accelerator) experiment, a 610-ton liquid argon time projection chamber (LArTPC) detector at the immediate downstream of the beam dump, as a part of the proposed ARI AA (A Research Innovation and Infrastructure Initiative for the discovery of unseen Aboriginal particles at Accelerators) project. The primary background to the charge-neutral UAP searches at DAMSA, using the RAON facility, would be the secondary electromagnetic particles produced in the interactions of neutrons that come from the high-intensity 600MeV proton beams impinging on the iron dump, given the proximity of the detector to the source of the beam. In this talk, I will present a detailed GEANT4 based study on the production rate of background particles to the ALP search case study and a potential strategy to minimize the impact of the background from the secondary neutron interactions in the DAMSA detector.

Relic neutrino detection

• Yeongduk Kim (CUP, IBS)

PTOLEMY is an experiment trying to detect the relic neutrinos with Tritium target of 100 g mass. I will present another targets which try to use the resonant interaction of neutrino induced electron capture. Though none of the candidate nuclei seem to be better than the Tritium target, there are rooms to investigate further the masses more precisely. There is another proposal to use accelerator to make the resonant condition with the relic neutrinos. I will try to describe these ideas.

Summary

• Yeongduk Kim (CUP, IBS)

Discussion