Workshop on Physics of Dark Cosmos: dark matter, dark energy, and all

Lavalse Hotel Busan 2F

Lavalse Hotel Busan 2F

Seong Chan Park (Yonsei University)

Welcome to the workshop on the physics of Dark Cosmos hosted by APCTP, Lab of Dark Universe (Yonsei BRL), and Center for Cosmological Constant Problem (PNU BRL). The workshop venue is located in the beautiful island, Young-do in Busan. We aim to discuss physics to understand our Universe, which strongly suggests new physics beyond the Standard Model. Various related topics ranging from collider physics, astrophysics and cosmology will be intensively discussed and new research results will be shared among participants. 

- Place: Lavalse Hotel Busan (

- Date: 10/21, 22, 23 (Fri~Sun) 



To speakers,

Please send your talk file to
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  • Adriana Guerrero Menkara
  • Anna Antonova
  • chanho Kim
  • Chanyoung Lee
  • Choong Sun Kim
  • Deog Ki Hong
  • Dhong Yeon Cheong
  • Dong-han Yeom
  • Dong-Won Jung
  • Doojin Kim
  • Erdenebulgan Lkhagvadorj
  • Eung Jin Chun
  • Gansukh Tumurtushaa
  • Hang Bae Kim
  • Hyun A Kim
  • Hyun Min Lee
  • Ingu Jeong
  • JaeHoon Jeong
  • Jie Jiang
  • Jihn Kim
  • Jong-Chul Park
  • Jong-Wan Lee
  • Junewoo Park
  • Kang Young Lee
  • Kayoung Ban
  • Ki-Young Choi
  • Kimiko Yamashita
  • Kiwoon Choi
  • Kwang Sik Jeong
  • Meshkat Rajaee
  • Minseok Ryu
  • Myeongnun Park
  • Natsumi Nagata
  • Pouya Bakhti
  • Pyungwon Ko
  • Sang Chul Hyun
  • Sang Hui Im
  • SangHwan Kim
  • Seodong Shin
  • Seong Chan Park
  • Seong Moon Yoo
  • Seong Youl Choi
  • Seongsik Kim
  • Shu-Yu Ho
  • Shun Watanuki
  • Shuntaro Aoki
  • Stephen Lonsdale
  • Sungjin Cho
  • Sunny Seo
  • Tae Geun Kim
  • Wan-Il Park
  • Wanda Isnard
  • Wei-Chen Lin
  • Yeji Park
  • Yeong Gyun Kim
  • Yongkyu Kim
  • Youngjoon Kwon
  • Youngsub Yoon
    • 15:00 15:30
      Registration & Discussion 30m
    • 15:30 17:00
      BSM & Cosmology: 1
      Convener: Prof. Seong Chan Park
      • 15:30
        Some thoughts on natural models for inflation 30m

        We present some of the recent developments on natural models for inflation, with a focus on Higgs inflation and hybrid inflation with a pseudo-scalar field. Implications of new symmetry/particles in each of scenarios will be discussed.

        Speaker: Prof. Hyun Min Lee
      • 16:00
        Reheating and Dark Matter Freeze-in in the Higgs-R2 Inflation Model 30m

        The Higgs inflation perfectly agrees with the CMB observation, but suffers from a unitarity problem due to a large non-minimal coupling of Higgs field to the Ricci scalar. Recently, it has been shown that introducing a Ricci square term (R2 term) in the Higgs inflation can solve this problem. In this talk, we discuss the post-inflationary dynamics for reheating and freeze-in dark matter in the Higgs-R2 model. Analyzing the temperature evolution of the Universe carefully, we evaluate the abundance of dark matter produced both from the non-thermal scattering during reheating and the thermal scattering after reheating. An application to leptogenesis scenario will also be discussed.

        Speaker: Dr Shuntaro Aoki
      • 16:30
        Quintessential axion 30m

        I will talk on quintessential axions.

        Speaker: Prof. Jihn E. Kim
    • 17:00 19:00
      Dinner 2h LAVALSE SKY CAFE&BAR 28F


    • 19:00 20:00
      Convener: Dr Doojin Kim
      • 19:00
        Flavor anomalies and other highlights from Belle and Belle II 30m

        In this talk, we present recent highlights from the Belle and Belle II experiments, focusing on the latest progress on flavor anomalies. We also discuss selected results on searches for dark sector from both experiments, including the B and D meson decays to invisible and semi-invisible decays.

        Speaker: Prof. Youngjoon Kwon (Yonsei University)
      • 19:30
        Riemannian Data preprocessing in Machine Learning to focus on QCD color structure 30m

        We provide a simple but a novel data preprocessing method using a Riemann sphere to utilize a full phase space by decorrelating QCD structure from a kinematics. We can achieve a statistical stability by enlarging the size of testable data set with focusing on QCD structure effectively

        Speaker: Prof. Myeonghun Park
    • 20:00 21:00
      Student Session: 1
      Convener: Prof. Youngjoon Kwon
      • 20:00
        Constraining ALPs from PBH with time-varying decay process 15m

        Axion-like particles (ALPs) are one of the well-known particles beyond the standard model, so understanding its properties and interactions with standard model particles is important. In this study, we constrain the mass ($m_a$) and the photon coupling constant ($g_{a\gamma\gamma}$) of ALPs through light particle emission from primordial black holes (PBHs). To achieve this, we focus on the photon decay process of axion-like particle (ALP) which were continuously emitted from extragalactic primordial black holes (PBHs). Our research is divided into two parts. First, by comparing the direct photon spectrum from PBH with the sensitivity of e-ASTROGAM, the next generation of gamma-ray detectors, we obtain an upper limit of the PBH dark matter fraction. Second, we compute the upper limit of the PBH dark matter fraction again, but now with the total photon spectrum - a direct photon plus additional photon from the ALP decay. Next, we plot the two upper limit differences in the $m_a$-$g_{a\gamma\gamma}$ plane and get the region with significant differences. In this presentation, we will focus on the second part, the decay process of ALPs from PBH.

        Speaker: Tae Geun Kim
      • 20:15
        Sterile Neutrino Dark Matter with PTOLEMY-like Experiment 15m

        We study the detection prospect of the cosmic background of sterile neutrinos in PTOLEMY-like experiments. The sterile neutrino with mass ranges between sub-eV - 10 keV may contribute to the local number density of dark matter candidates. While, in the literature, 100% of the sterile neutrino dark matter was assumed, however we assume that sterile neutrino could be sub-component of dark matter. In this study, we calculate the capture rate for different models consistent with other constraints as dark matter in the PTOLEMY-like experiments. We show the results in the parameter space of active-sterile neutrino mixing and mass of sterile neutrinos consistent with the current constraints of other experiments. Our preferred mass range of the sterile neutrinos could reach a sensitivity of PTOLEMY in the near future.

        Speaker: Erdenebulgan Lkhagvadorj
      • 20:30
        Unifying flavor and Dark Matter puzzles with SU(2)D lepton portals 15m

        We propose a novel model for lepton flavor and dark matter based on an SU(2)D gauge symmetry and vector-like leptons in their fundamental representations. We introduce a dark SU(2)D Higgs doublet and a Higgs bi-doublet for the mass mixing between the vector-like lepton and the lepton, leading to small seesaw lepton masses. The SU(2)D gauge bosons and the vector-like lepton contribute to the muon g−2 as indicated in Fermilab E989, while the tree-level mass mixing between the Z boson and the new isospin neutral gauge boson (V^0) shifts the W boson mass consistently with the recent Tevatron CDFII measurement. Furthermore, the isospin charged gauge boson of SU(2)D becomes a plausible candidate for dark matter with a small mass splitting dependent on the W boson mass. We find viable parameter space where the favored corrections to the muon g-2, the W boson mass and dark matter constraints are simultaneously fulfilled.

        Speaker: Adriana Guerrero Menkara
      • 20:45
        Models for Self-resonant Dark Matter 15m

        We consider a new mechanism for enhancing the self-scattering and annihilation cross sections for dark matter with multiple components but without a light mediator. The lighter dark matter component plays a role of the u-channel pole in the elastic co- scattering for dark matter, leading to a large self-scattering cross section and a Som- merfeld enhancement for semi-annihilation processes. Taking the effective theory ap- proach for self-resonant dark matter, we present various combinations of multiple dark matter components with spins and parities that show a u-channel pole in the co- scattering processes. Adopting dark photon and dark Higgs portals for self-resonant dark matter, we impose the relic density condition and indirect detection bounds on semi-annihilation channels with Sommerfeld enhancement and discuss potential signals for direct detection experiments.

        Speaker: Seongsik Kim
    • 09:30 10:30
      Dark Matter: 1
      Convener: Prof. Jong-Chul Park
      • 09:30
        On the WIMP dark matter signature in old neutron stars 30m

        Weakly Interacting Massive Particles (WIMPs) in the Universe accumulate in neutron stars (NSs) through their interactions with ordinary matter, and their annihilation inside the NS core causes late-time heating. It has been argued that this heating effect maintains the surface temperature of old NSs to be a few thousand K, which can be regarded as a smoking gun signature of dark matter (DM) heating in NSs. This conclusion is, however, drawn based on the assumption that the beta equilibrium is sustained in NSs throughout their life, which turns out to be invalid for real pulsars. If a NS is out of beta equilibrium, then there is another heating effect due to the dissipation of the excessive energy stored in the imbalance in the chemical potentials, which may conceal the DM heating effect. In fact, such an “out-of-equilibrium heating” effect is favored by recent observations. In this talk, we show that the signature of DM heating can still be detected in old ordinary pulsars even in the presence of the out-of-beta-equilibrium effect, whereas it is hidden in millisecond pulsars. We also discuss that an observation of a NS with the surface temperature lower than a thousand K imposes a stringent limit on a variety of WIMP DM candidates, such as the electroweak multiplet DM particles.

        Speaker: Prof. Natsumi Nagata
      • 10:00
        Dark matter signals from charged mesons in neutrino experiments 30m

        Neutral mesons such as pi0 and eta have played a role of an important source of dark sector particles including dark matter in the beam-dump type and neutrino experiments. We point out that charged mesons are another important but overlooked source of dark sector particles especially in the beam-focused neutrino experiments. The idea is that a charged meson decays to a charged lepton, a neutrino counterpart, and a dark-sector mediator. As this three-body decay is helicity-unsuppressed unlike the corresponding two-body decay and the charged mesons are focused by the magnetic horn, we expect an enhanced dark-sector signal flux. We discuss two examples: a dark-matter solution to the MiniBooNE low energy excess and the light dark matter search at SBND.

        Speaker: Dr Doojin Kim
    • 10:30 11:00
      Tea Break and Photo session 30m
    • 11:00 12:30
      Dark Matter: 2
      Convener: Prof. Hyun Min Lee
      • 11:00
        Cosmic-ray-induced Boosted Dark Matter 30m

        In this talk, we review boosted dark matter (BDM) production mechanisms via extended dark sectors and charged cosmic rays. Next, we propose a novel dark-matter boosting mechanism by cosmic-ray neutrinos. The new mechanism is so significant that the arriving flux of cosmic-ray neutrino BDM (νBDM) lighter than O(1-10) MeV on Earth is substantially larger than the one of the cosmic-ray electron BDM. Therefore, νBDM can dominantly contribute in direct detection experiments. We derive conservative but still stringent bounds and future sensitivity limits for νBDM from advanced underground dark matter and neutrino experiments such as XENON1T/nT and JUNO.

        Speaker: Prof. Jong-Chul Park
      • 11:30
        Manifesting hidden dynamics of a sub-component dark matter 30m

        A distinctive cosmological dynamics of a sub-component dark matter will be discussed. The thermal evolution of the sub-component is significantly affected by the sizable self-scattering and the required annihilation cross section of the sub-component sharply increases as we consider a smaller relative abundance fraction among the dark-matter species. Therefore, contrary to a naive expectation, it can be easier to detect the sub-component with smaller abundance fractions in direct/indirect-detection experiments and cosmological observations.

        Speaker: Prof. Seodong Shin
      • 12:00
        Detecting axion dark matter with chiral magnetic effects 30m

        We show that dark matter axions or axion-like particles (ALP) induce non-dissipative alternating electric currents in conductors along the external magnetic fields due to the axial anomaly, realizing the chiral magnetic effects. We propose a new experiment to measure this current to detect the dark matter axions or ALP. This non-dissipative currents are the electron medium effects, directly proportional to the axion or ALP coupling to electrons, which depends on their microscopic physics.

        Speaker: Prof. Sang Hui Im
    • 12:30 16:00
      Lunch 3h 30m
    • 16:00 18:00
      Dark Matter: 3
      Convener: Prof. Sang-hui Im
      • 16:00
        Positivity bounds for scalar dark matter 30m

        We study the positivity bounds implication on dimension-8 Higgs-portal dark matter production in the early universe. The relevant operators are subject to satisfying positivity bounds when the UV physics follows the S-matrix based on the fundamental pillars of quantum field theory. We present how positivity bounds limit the model parameter space of dark matter production and show the interplay from the direct detection constraint on the model parameter space. We also include dark matter and quark interactions as counter terms and revisit dark matter production. The future HL-LHC search on the dark matter production induced by the dimension-8 Higgs portal operators is suggested and demonstrated.

        Speaker: Dr Kimiko Yamashita
      • 16:30
        An Asymmetric SIMP Dark Matter Model 30m

        In this talk, we will show for the first time an asymmetric strongly interacting massive particles (SIMP) dark matter (DM) model, where a new vector-like fermion and a new complex scalar both having nonzero chemical potentials can be asymmetric DM particles. After the spontaneous breaking of a U(1)𝖣 dark gauge symmetry, these two particles can have accidental ℤ4 charges making them stable. By adding one more complex scalar as a mediator between the SIMP DM, the relic density of DM is determined by 3→2 and two-loop induced 2→2 annihilations in this model. On the other hand, the SIMP DM can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the new gauge interaction. Interestingly, this model can have a bouncing effect on DM, whereby the DM number density rises after the chemical freeze-out of DM. With this effect, the prediction of the DM self-interacting cross section in this model can be consistent with astrophysical observations, and the ratio of the DM energy density to the baryonic matter energy density can be explained by primordial asymmetries. We also predict the DM-electron elastic scattering cross section that can be used to test this model in future projected experiments.

        Speaker: Dr Shu-Yu Ho
      • 17:00
        Positronium decays with a dark Z and fermionic dark matter 30m

        We investigate the invisible decay of positronium to probe the fermionic light dark matter mediated by the dark Z boson. The invisible decay rate of positronium through weak interaction in the standard model is too small to be detected in the experiment. We show that it can be enhanced to be observed in the future if the dark matter is lighter than the electron in the dark Z model. We also compute the relic abundance of such light dark matter and discuss the big bang nucleosynthesis constraint with an alternative thermal history scenario.

        Speaker: Dr Dong-Won Jung
      • 17:30
        Cosmology in a SUSY B-L model 30m

        I will discuss some cosmological implications of a SUSY B-L model, including dark matter and gravitational waves

        Speaker: Prof. Wan-Il Park
    • 18:00 20:00
      Dinner 2h 3F


    • 20:00 21:00
      Student Session: 2
      Convener: Prof. Hang Bae Kim
      • 20:00
        FIMP dark matter from a hidden effective supersymmetric theory 15m

        In this study, we present a dark matter model relying on hidden supersymmetric sectors such that dark matter particles are then decoupled from the SM. We will consider dark matter as massive bound states of gluons and gluinos called glueballs and gluinoballs. We will discuss the possibility to produce such dark matter particles with a freeze-in mechanism.

        Speaker: Isnard Wanda
      • 20:15
        Revisit the gravitational lensing effect using radio wave polarization 15m

        Gravitational lensing effect analysis allows us to find the matter distribution in galactic clusters. For example, such an analysis at the Bullet Cluster suggested convincingly in favor of the existence of dark matter. However, in this analysis, it was assumed that the average of the original orientation of galaxies in a small patch of sky is zero. While this assumption is reasonable, it can lead to some errors, if there are not enough many galaxies in each patch, or the orientation of each galaxy is not random. Luckily, it is now possible to measure the orientation of each galaxy, as the polarization of radio waves from each galaxy correlates with its orientation. In this talk, we will derive formulas that can be directly applied to the re-analysis of the gravitational lensing effect using polarization data.

        Speaker: Youngsub Yoon
      • 20:30
        Non-minimally assisted chaotic inflation 15m

        Conventional wisdom says that a chaotic inflation model with a power-law potential is ruled out by the recent Planck-BICEP/Keck results. We find, however, that the model can be assisted by a non-minimally coupled scalar field and still provides a successful inflation. Considering a power-law chaotic inflation model of the type $V \sim \varphi^n$ with $n$ = {2, 4/3, 1, 2/3, 1/3}, we show that $n$ = 1/3 ($n$ = {2/3, 1/3}) may be revived with the help of the quadratic (quartic) non-minimal coupling of the assistant field to gravity.

        Speaker: Sang Chul Hyun
      • 20:45
        Primordial Black Holes and Gravitational Waves from the Tachyonic Instability in Higgs-$R^2$ Inflation 15m

        The running of the Higgs self coupling may lead to numerous phenomena in early universe cosmology. In this paper we introduce a scenario where the Higgs running induces turns in the trajectory passing a region with tachyonic mass, leading to a temporal tachyonic growth in the curvature power spectrum. This effect induced by the Higgs leaves phenomena in the form of primordial black holes and stochastic gravitational waves, where proposed GW observatories will be able to probe in the near future.

        Speaker: Dhong Yeon Cheong
    • 09:30 10:30
      Neutrino: 1
      Convener: Prof. Seodong Shin
      • 09:30
        New Particle Searches at Yemilab Large Neutrino Detector 30m

        In thisIn this talk, I will introduce Yemilab, 1st deep underground laboratory dedicated to science in Korea, and present new particle searches using a large neutrino detector to be proposed at the Yemilab.

        Speaker: Prof. Sunny Seo
      • 10:00
        Neutrino transition in dark matter 30m

        An ultralight dark matter may have interesting implications in neutrino physics which have been studied actively in recent years. There can occur yet unexplored medium effect of neutrino transition which must be taken into account when describing the oscillations of neutrinos propagating through dark matter. Strong constraints on the model parameters are obtained considering the solar neutrino oscillation.

        Speaker: Prof. Eung Jin Chun
    • 10:30 11:00
      Tea Break 30m
    • 11:00 12:30
      Neutrino: 2
      Convener: Prof. Sunny Seo
      • 11:00
        Probing the non-standard neutrino interactions using quantum statistics 30m

        I will talk on BSM neutrino interactions, which can be probed by quantum statistics.

        Speaker: Prof. Choong Sun Kim
      • 11:30
        Solar neutrinos and future experiments 30m

        In this talk, we review the production of solar neutrinos and their propagation within the Sun and the Earth. The LMA-MSW solution explains the flavor change of solar neutrinos. However, there are some tensions between the data and predictions. In order to resolve these tensions, new physics such as Non-Standard neutrino Interaction (NSI) or the presence of a new sterile neutrino are proposed. Moreover, we are moving to a phase of sub-percent precision with future solar neutrino experiments. In this talk, I will discuss how we will be sensitive to the Earth tomography using day-night asymmetry of solar neutrinos and new physics such as NSI and super-light sterile neutrino scenarios.

        Speaker: Dr Pouya Bakhti
      • 12:00
        Non-Standard Interaction of atmospheric neutrino in future experiments 30m

        We discuss the prospects of probing neutral-current non-standard interaction (NSI) in the propagation of atmospheric neutrinos in future large-volume neutrino experiments including DUNE, HK, KNO, and ORCA. For DUNE, we utilize its ability of identifying the tau neutrino event and combine the $\nu_\tau$ appearance with the $\nu_\mu$ disappearance. Based on our simulated results, the ten years of data taking of the atmospheric neutrinos can enormously improve the bounds on the NSI parameters $\varepsilon_{\mu \tau}, | \varepsilon_{\mu \mu} - \varepsilon_{\tau \tau} |$, $\varepsilon_{e \mu }$, $\varepsilon_{e \tau}$ and $| \varepsilon_{\mu \mu} - \varepsilon_{e e} |$ by a couple of orders of magnitudes. In addition, we show the expected correlations between the CP-violation phase $\delta_{CP}$ and the NSI parameters $\varepsilon_{e\mu}, \varepsilon_{e\tau}$, and $|\varepsilon_{ee} - \varepsilon_{\mu \mu}|$ and confirm the potentials of DUNE, HK, KNO (combined with HK) in excluding the ``No CP violation" hypothesis at 1$\sigma$, 2$\sigma$, and 3$\sigma$, respectively.

        Speaker: Dr Meshkat Rajaee
    • 12:30 14:00
      Lunch 1h 30m
    • 14:00 15:30
      BSM & Cosmology: 2
      Convener: Prof. Kwangsik Jeong
      • 14:00
        All the covariant tensor currents of massless particles in the covariant formulation 30m

        We present an efficient algorithm for constructing all the covariant tensor currents of massless particles of arbitrary spins in the covariant formulation. This algorithm enables us to construct all the matrix elements as well as covariant three-point vertices simply by assembling the basic building blocks,
        leading to the direct construction of tensor currents. We revisit the restrictions on massless particles called the Weinberg-Witten (WW) theorem in terms of arbitrary spins. We find the covariance conditions on form factors leading to the corresponding tensor currents to be covariant and verify that the continuity assumption of matrix elements taken for obtaining the WW theorem in the original paper is correct at least in the quantum field theory involving conventional high-spin massless fields.

        Speaker: Dr JaeHoon Jeong
      • 14:30
        Trouble with geodesics in black-to-white hole bouncing scenarios 30m

        By utilizing the thin shell approximation, we investigate the behavior of radial timelike geodesics in a black hole to white hole bouncing scenario with a mass (de-)amplification relation. We show that those geodesics lose energy after crossing the transition surface if the white hole mass is less than the black hole mass and vice versa. That is, the bounded timelike radial geodesics become closer to the event horizon in the mass decreasing direction. We then show that by tracing a finite amount of bouncing cycles along the mass decreasing direction, all bounded radial geodesics can be squeezed into the range of the stretched horizon while the black hole and white hole are still massive. Those highly squeezed geodesics are problematic since there exists a Planck-scale blueshift between them and the regular infalling trajectories. We also discuss the possible implication and rescues.

        Speaker: Dr Wei-Chen Lin
      • 15:00
        Hartle-Hawking wave function beyond the instanton approach 30m

        We discuss the no-boundary wave function by numerically solving the Wheeler-DeWitt equation. We report some interesting new observations.

        Speaker: Prof. Dong-han Yeom
    • 15:30 16:00
      Discussion on various topics in Dark Cosmos, and final remark 30m
      Speaker: Seong Chan Park (Yonsei University)