Sin Kyu Kang
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
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Research Interests
Sin Kyu Kang has a total of 124 co-authors. Here are the top co-authors by number of shared publications:
- Choong Sun Kim
Yonsei University
18 shared publications - Arnab Dasgupta
University of Pittsburgh
14 shared publications - Debasish Borah
Indian Institute of Technology Guwahati
8 shared publications - Oleg Popov
Shenzhen MSU-BIT University
7 shared publications - Yang Hwan Ahn
School of Liberal Arts Seoul National University of Science and Technology 232 Gongneung-ro Nowon-gu 01811 Seoul Korea
7 shared publications - Hwa Sung Cheon
Institute of Convergence Fundamental Studies Seoul National University of Science and Technology 139-743 Seoul Korea
6 shared publications
Latest Publications
- Open Access
- 23 October 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (10) , 1220
Searching for dark photon tridents through primordial black hole signatures
The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling evidence for their role as a dark matter candidate, particularly through the observation of their Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-the-SM particle emissions. A particularly promising avenue involves production of dark photons by PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the trident decay of dark photons with mass $$m_{A'}\le 1$$ MeV focusing on their primary emission from asteroid-mass PBHs. We assume that the dark photons produced via Hawking radiation decay into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The energy spectrum of the photons decaying from the dark photons is distinct from that of direct Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in the gamma-ray signal. Using the asteroid-mass PBHs as a case study, we demonstrate that future gamma-ray missions could detect dark-photon signatures and distinguish them from conventional Hawking radiation. This approach enables the exploration of previously inaccessible parameter spaces in dark photon mass $$m_{A'}\le 1$$ MeV and their coupling to photons, offering a viable avenue to uncover the properties of dark sectors and the nature of asteroid-mass PBHs.- 23 October 2026
- Published by Springer Nature in The European Physical Journal C
- Vol. 86 (10) , 1220
Open AccessSearching for dark photon tridents through primordial black hole signatures
The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling evidence for their role as a dark matter candidate, particularly through the observation of their Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-the-SM particle emissions. A particularly promising avenue involves production of dark photons by PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the trident decay of dark photons with mass $$m_{A'}\le 1$$ MeV focusing on their primary emission from asteroid-mass PBHs. We assume that the dark photons produced via Hawking radiation decay into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The energy spectrum of the photons decaying from the dark photons is distinct from that of direct Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in the gamma-ray signal. Using the asteroid-mass PBHs as a case study, we demonstrate that future gamma-ray missions could detect dark-photon signatures and distinguish them from conventional Hawking radiation. This approach enables the exploration of previously inaccessible parameter spaces in dark photon mass $$m_{A'}\le 1$$ MeV and their coupling to photons, offering a viable avenue to uncover the properties of dark sectors and the nature of asteroid-mass PBHs. - Open Access
- 17 September 2026
- Published by Elsevier in SSRN Electronic Journal
Distinguishing Multi-Modal Primordial Black Hole Populations with Future Gamma-Ray Observations
Primordial black holes (PBHs) are a well-motivated dark matter (DM) candidate and, if sufficiently light, can be probed through gamma rays produced by Hawking radiation. In the asteroid-mass window, $10^{15}$--$10^{17}$ g, the resulting photon spectrum peaks in the MeV--GeV range, placing it within the reach of next-generation gamma-ray observatories such as e-ASTROGAM.In this work, we investigate the observational signatures of multi-modal PBH mass distributions that can arise in inflationary scenarios containing multiple localized features in the primordial curvature power spectrum. Such scenarios can produce gamma-ray spectra with multiple spectral peaks associated with distinct PBH mass populations. Using a likelihood-based statistical analysis, we perform an explicit model-comparison study to determine the regions of parameter space in which these multi-component PBH signals can be distinguished from both astrophysical backgrounds and the best-fitting single-component PBH interpretation.We show that spectral-shape information provides a sensitive probe of multi-modal PBH populations and quantify the capability of future gamma-ray experiments to resolve such features. Our results establish a framework for testing single- versus multi-modal PBH dark matter scenarios with high-precision gamma-ray observations, extending beyond existing single-population analyses and providing a new observational handle on nontrivial PBH mass distributions.- 17 September 2026
- Published by Elsevier in SSRN Electronic Journal
Open AccessDistinguishing Multi-Modal Primordial Black Hole Populations with Future Gamma-Ray Observations
Primordial black holes (PBHs) are a well-motivated dark matter (DM) candidate and, if sufficiently light, can be probed through gamma rays produced by Hawking radiation. In the asteroid-mass window, $10^{15}$--$10^{17}$ g, the resulting photon spectrum peaks in the MeV--GeV range, placing it within the reach of next-generation gamma-ray observatories such as e-ASTROGAM.In this work, we investigate the observational signatures of multi-modal PBH mass distributions that can arise in inflationary scenarios containing multiple localized features in the primordial curvature power spectrum. Such scenarios can produce gamma-ray spectra with multiple spectral peaks associated with distinct PBH mass populations. Using a likelihood-based statistical analysis, we perform an explicit model-comparison study to determine the regions of parameter space in which these multi-component PBH signals can be distinguished from both astrophysical backgrounds and the best-fitting single-component PBH interpretation.We show that spectral-shape information provides a sensitive probe of multi-modal PBH populations and quantify the capability of future gamma-ray experiments to resolve such features. Our results establish a framework for testing single- versus multi-modal PBH dark matter scenarios with high-precision gamma-ray observations, extending beyond existing single-population analyses and providing a new observational handle on nontrivial PBH mass distributions. - Open AccessRadiative Dirac Neutrino Masses from Modular $S_3$ Symmetry in an Axion ModelWe present a unified axion model framework that simultaneously addresses the origin of neutrino masses, leptonic flavor structure, the strong CP problem, and dark matter. The model is based on a global $U(1)_{\rm PQ}$ symmetry combined with a modular $S_3$ symmetry and is realized within a novel class of KSVZ-type axion model. Exotic colored fermions and scalars mediate radiative neutrino mass generation at the one loop-level. The PQ charge assignment forbids tree-level neutrino masses and leaves a residual $Z_3$ symmetry that ensures the Dirac nature of neutrinos. In the minimal realization, the neutrino mass matrix is of rank two, predicting one massless neutrino. Consequently, the sum of neutrino masses is constrained for both the normal and inverted hierarchies. We analyze the implications for charged lepton flavor violation and the lepton $g-2$. The axion emerging from this framework dynamically resolves the strong CP problem and accounts for the observed dark matter abundance. Notably, the predicted axion-photon coupling is within reach of upcoming experiments and consistent with existing astrophysical and cosmological bounds.Open AccessRadiative Dirac Neutrino Masses from Modular $S_3$ Symmetry in an Axion ModelWe present a unified axion model framework that simultaneously addresses the origin of neutrino masses, leptonic flavor structure, the strong CP problem, and dark matter. The model is based on a global $U(1)_{\rm PQ}$ symmetry combined with a modular $S_3$ symmetry and is realized within a novel class of KSVZ-type axion model. Exotic colored fermions and scalars mediate radiative neutrino mass generation at the one loop-level. The PQ charge assignment forbids tree-level neutrino masses and leaves a residual $Z_3$ symmetry that ensures the Dirac nature of neutrinos. In the minimal realization, the neutrino mass matrix is of rank two, predicting one massless neutrino. Consequently, the sum of neutrino masses is constrained for both the normal and inverted hierarchies. We analyze the implications for charged lepton flavor violation and the lepton $g-2$. The axion emerging from this framework dynamically resolves the strong CP problem and accounts for the observed dark matter abundance. Notably, the predicted axion-photon coupling is within reach of upcoming experiments and consistent with existing astrophysical and cosmological bounds.
- Open Access
Neutrino Dipole Portal
The neutrino dipole portal (NDP) is a minimal and predictive extension of the Standard Model, in which a transition magnetic moment operator couples an active neutrino to a heavy neutral lepton via the electromagnetic field. This higher-dimensional interaction gives rise to distinctive processes such as neutrino up-scattering, radiative decays, meson transitions, and modifications of recoil spectra, offering multiple avenues for discovery. In this review, we discuss the theoretical foundations of the NDP, its ultraviolet completions, and the associated production and decay mechanisms across laboratory, astrophysical, and cosmological settings. Current constraints arise from accelerator searches, recoil-based detectors, collider studies, and high energy neutrino observatories, complemented by robust bounds from Big Bang Nucleosynthesis, the Cosmic Microwave Background, and supernova cooling. Future experimental and observational efforts, including next-generation neutrino experiments, multi-ton dark matter detectors, and improved cosmological and astrophysical probes, are anticipated to test the remaining allowed regions. The NDP thus provides a simple, well-motivated, and broadly testable framework at the intersection of particle physics, astrophysics, and cosmology.
Open AccessNeutrino Dipole Portal
The neutrino dipole portal (NDP) is a minimal and predictive extension of the Standard Model, in which a transition magnetic moment operator couples an active neutrino to a heavy neutral lepton via the electromagnetic field. This higher-dimensional interaction gives rise to distinctive processes such as neutrino up-scattering, radiative decays, meson transitions, and modifications of recoil spectra, offering multiple avenues for discovery. In this review, we discuss the theoretical foundations of the NDP, its ultraviolet completions, and the associated production and decay mechanisms across laboratory, astrophysical, and cosmological settings. Current constraints arise from accelerator searches, recoil-based detectors, collider studies, and high energy neutrino observatories, complemented by robust bounds from Big Bang Nucleosynthesis, the Cosmic Microwave Background, and supernova cooling. Future experimental and observational efforts, including next-generation neutrino experiments, multi-ton dark matter detectors, and improved cosmological and astrophysical probes, are anticipated to test the remaining allowed regions. The NDP thus provides a simple, well-motivated, and broadly testable framework at the intersection of particle physics, astrophysics, and cosmology.
- Open Access
A two scalar triplets model as common origin for dark matter, neutrino masses, baryon asymmetry and inflation
We propose an extension of the standard model (SM) by two SU(2) triplet scalars and an inert SU(2) doublet. We demonstrate that this setup can simultaneously produce an inflaton and baryon asymmetry in the early universe, provide a dark matter candidate and explain the smallness of neutrino masses. The two triplets are particularly important as they become mediators for the production of dark matter and the generation of lepton asymmetry, as well as contribute an inflaton. The inert doublet results in a dark matter candidate. The required CP-violation for lepton asymmetry is obtained by interference between the triplet mediators that communicate the dark sector to the SM sector. More precisely, the complex Breit-Wigner propagators of the triplets and their mixing, result in an asymmetric production of leptons and antileptons that is boosted before dark matter freeze-out. In this case, simultaneously achieving enough dark matter relic abundance and proper matter-antimatter asymmetry limits the available parameter space of the model. Moreover, the scalar triplets are coupled non-minimally to gravity and give rise to the inflaton. We calculate the inflationary parameters and check that we can obtain predictions consistent with Planck constraints from 2018. We also perform an analysis of the reheating for the inflaton decays/annihilations to relativistic SM particles.
Open AccessA two scalar triplets model as common origin for dark matter, neutrino masses, baryon asymmetry and inflation
We propose an extension of the standard model (SM) by two SU(2) triplet scalars and an inert SU(2) doublet. We demonstrate that this setup can simultaneously produce an inflaton and baryon asymmetry in the early universe, provide a dark matter candidate and explain the smallness of neutrino masses. The two triplets are particularly important as they become mediators for the production of dark matter and the generation of lepton asymmetry, as well as contribute an inflaton. The inert doublet results in a dark matter candidate. The required CP-violation for lepton asymmetry is obtained by interference between the triplet mediators that communicate the dark sector to the SM sector. More precisely, the complex Breit-Wigner propagators of the triplets and their mixing, result in an asymmetric production of leptons and antileptons that is boosted before dark matter freeze-out. In this case, simultaneously achieving enough dark matter relic abundance and proper matter-antimatter asymmetry limits the available parameter space of the model. Moreover, the scalar triplets are coupled non-minimally to gravity and give rise to the inflaton. We calculate the inflationary parameters and check that we can obtain predictions consistent with Planck constraints from 2018. We also perform an analysis of the reheating for the inflaton decays/annihilations to relativistic SM particles.
- Open Access
- 29 August 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (8) , 1-17
Neutrino masses and mixing in an axion model
We propose a novel framework that simultaneously addresses three critical issues: tiny neutrino masses and their mixing patterns, dark matter, and the strong CP problem. Our model extends the Peccei–Quinn (PQ) symmetry by incorporating modular $$S_3$$ symmetry, which plays a central role in explaining the observed neutrino mixing structure. The field content includes two vector-like colored fermions and three colored scalars as $$S_3$$ singlets, an isospin doublet inert scalar and a singlet PQ scalar, each assigned appropriate modular weights. We show that such an extension, together with a suitable assignment of modular weights to the fields, can lead to holomorphic modular forms of Yukawa interactions, which can be derived from a superpotential. Furthermore, we explore an extension of the model to include non-holomorphic Yukawa interactions in the non-supersymmetric framework and show that the results are distinct from the holomorphic case. Tiny neutrino masses are generated radiatively through colored mediators, while the KSVZ-type axion appears to dynamically resolve the strong CP problem. We investigate the phenomenology of lepton flavor violation and the muon $$g-2$$ anomaly within this framework. Additionally, we explore the axion’s properties and its role as dark matter.- 29 August 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (8) , 1-17
Open AccessNeutrino masses and mixing in an axion model
We propose a novel framework that simultaneously addresses three critical issues: tiny neutrino masses and their mixing patterns, dark matter, and the strong CP problem. Our model extends the Peccei–Quinn (PQ) symmetry by incorporating modular $$S_3$$ symmetry, which plays a central role in explaining the observed neutrino mixing structure. The field content includes two vector-like colored fermions and three colored scalars as $$S_3$$ singlets, an isospin doublet inert scalar and a singlet PQ scalar, each assigned appropriate modular weights. We show that such an extension, together with a suitable assignment of modular weights to the fields, can lead to holomorphic modular forms of Yukawa interactions, which can be derived from a superpotential. Furthermore, we explore an extension of the model to include non-holomorphic Yukawa interactions in the non-supersymmetric framework and show that the results are distinct from the holomorphic case. Tiny neutrino masses are generated radiatively through colored mediators, while the KSVZ-type axion appears to dynamically resolve the strong CP problem. We investigate the phenomenology of lepton flavor violation and the muon $$g-2$$ anomaly within this framework. Additionally, we explore the axion’s properties and its role as dark matter. - Open Access
Probing Double-Peaked Gamma-Ray Spectra from Primordial Black Holes with Next-Generation Gamma-Ray Experiments
Primordial black holes (PBHs), hypothesized to form in the early universe from gravitational collapse of density fluctuations, represent a well-motivated dark matter (DM) candidate. Their potential detection through gamma-ray signatures arising from Hawking radiation would provide definitive evidence for their existence and constrain their contribution to the DM abundance. Unlike conventional DM candidates, PBHs emit a unique, thermal-like spectrum of particles as they evaporate, including photons, neutrinos, and possible beyond-the-Standard Model particles. Future high-sensitivity gamma-ray observatories, such as e-ASTROGAM and other next-generation telescopes, will play a pivotal role in this search. With improved energy resolution and sensitivity, these missions can disentangle PBH-originating photons from astrophysical backgrounds, probe subtle spectral features such as multi-peak structures, and test exotic evaporation models. Such observations could either confirm PBHs as a viable DM component or place stringent limits on their abundance across critical mass windows. In this work, we explore the distinguishing features of a double-peaked gamma-ray spectrum produced by PBHs, focusing on the asteroid-mass window ($10^{15}$ g to $10^{17}$ g), where Hawking radiation peaks in the MeV to GeV range. Using a likelihood-based analysis, we demonstrate how future missions could discriminate between single- and double-peaked PBH scenarios, the latter arising in cosmological models predicting multi-modal PBH mass distributions. Our results highlight the diagnostic power of spectral shape analysis in identifying PBH populations and constrain the parameter space for which a double-peaked signal could be detectable above background.Open AccessProbing Double-Peaked Gamma-Ray Spectra from Primordial Black Holes with Next-Generation Gamma-Ray Experiments
Primordial black holes (PBHs), hypothesized to form in the early universe from gravitational collapse of density fluctuations, represent a well-motivated dark matter (DM) candidate. Their potential detection through gamma-ray signatures arising from Hawking radiation would provide definitive evidence for their existence and constrain their contribution to the DM abundance. Unlike conventional DM candidates, PBHs emit a unique, thermal-like spectrum of particles as they evaporate, including photons, neutrinos, and possible beyond-the-Standard Model particles. Future high-sensitivity gamma-ray observatories, such as e-ASTROGAM and other next-generation telescopes, will play a pivotal role in this search. With improved energy resolution and sensitivity, these missions can disentangle PBH-originating photons from astrophysical backgrounds, probe subtle spectral features such as multi-peak structures, and test exotic evaporation models. Such observations could either confirm PBHs as a viable DM component or place stringent limits on their abundance across critical mass windows. In this work, we explore the distinguishing features of a double-peaked gamma-ray spectrum produced by PBHs, focusing on the asteroid-mass window ($10^{15}$ g to $10^{17}$ g), where Hawking radiation peaks in the MeV to GeV range. Using a likelihood-based analysis, we demonstrate how future missions could discriminate between single- and double-peaked PBH scenarios, the latter arising in cosmological models predicting multi-modal PBH mass distributions. Our results highlight the diagnostic power of spectral shape analysis in identifying PBH populations and constrain the parameter space for which a double-peaked signal could be detectable above background. - Open Access
- 2 April 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (4) , 1-27
Unveiling the invisible: ALPs and sterile neutrinos at the LHC and HL-LHC
We investigate the potential of using the signature of mono-Higgs plus large missing energies to constrain on two new ph ysics models, namely the model of an axion-like particle (ALP) and the model of sterile neutrinos. We focus on the Higgs-ALP interactions starting at dimension-six and the Higgs-sterile neutrino interactions starting at dimension-five, via the processes pp → haa for ALP production and pp → hNN for sterile neutrinos at the LHC and High Luminosity LHC (HL-LHC), followed by the Higgs decay $$ h\to b\overline{b} $$ . We establish bounds on the ALP-Higgs coupling $$ \frac{C_{aH}}{\Lambda^2} $$ and sterile neutrino-Higgs coupling $$ \frac{\lambda_3}{M_{\ast }} $$ , respectively, for ALP and sterile-neutrino mass ranging from 1 to 60 GeV, using the recent ATLAS data on mono-Higgs plus missing energies at the LHC ( $$ \sqrt{s} $$ = 13 TeV and $$ \mathcal{L} $$ = 139 fb−1). The most stringent constraint occurs in the missing transverse energy M ET range 200 < M ET ≤ 350 GeV. We also estimate the sensitivities that we can achieve at the HL-LHC ( $$ \sqrt{s} $$ = 14 TeV and $$ \mathcal{L} $$ = 3000 fb−1). We obtain improved sensitivities across various missing energy regions. The ALP model exhibits better sensitivities, particularly at lower mass range, compared to the sterile neutrino model, which shows weaker sensitivities across similar mass and energy ranges. Our results underscore the potential of the mono-Higgs signature as a robust probe for physics beyond the Standard Model.- 2 April 2025
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2025 (4) , 1-27
Open AccessUnveiling the invisible: ALPs and sterile neutrinos at the LHC and HL-LHC
We investigate the potential of using the signature of mono-Higgs plus large missing energies to constrain on two new ph ysics models, namely the model of an axion-like particle (ALP) and the model of sterile neutrinos. We focus on the Higgs-ALP interactions starting at dimension-six and the Higgs-sterile neutrino interactions starting at dimension-five, via the processes pp → haa for ALP production and pp → hNN for sterile neutrinos at the LHC and High Luminosity LHC (HL-LHC), followed by the Higgs decay $$ h\to b\overline{b} $$ . We establish bounds on the ALP-Higgs coupling $$ \frac{C_{aH}}{\Lambda^2} $$ and sterile neutrino-Higgs coupling $$ \frac{\lambda_3}{M_{\ast }} $$ , respectively, for ALP and sterile-neutrino mass ranging from 1 to 60 GeV, using the recent ATLAS data on mono-Higgs plus missing energies at the LHC ( $$ \sqrt{s} $$ = 13 TeV and $$ \mathcal{L} $$ = 139 fb−1). The most stringent constraint occurs in the missing transverse energy M ET range 200 < M ET ≤ 350 GeV. We also estimate the sensitivities that we can achieve at the HL-LHC ( $$ \sqrt{s} $$ = 14 TeV and $$ \mathcal{L} $$ = 3000 fb−1). We obtain improved sensitivities across various missing energy regions. The ALP model exhibits better sensitivities, particularly at lower mass range, compared to the sterile neutrino model, which shows weaker sensitivities across similar mass and energy ranges. Our results underscore the potential of the mono-Higgs signature as a robust probe for physics beyond the Standard Model. - Open Access
Searching for Dark Photon Tridents Through Primordial Black Hole Signatures
The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling evidence for their role as a dark matter candidate, particularly through the observation of their Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-the-SM particle emissions. A particularly promising avenue involves production of dark photons by PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the trident decay of dark photons focusing on their primary emission from PBHs. We assume that the dark photons produced via Hawking radiation decay into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The energy spectrum of the photons decaying from the dark photons is distinct from that of direct Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in the gamma-ray signal. Using the asteroid-mass PBHs as a case study, we demonstrate that future gamma-ray missions could detect dark-photon signatures and distinguish them from conventional Hawking radiation. This approach enables the exploration of previously inaccessible parameter spaces in dark photon mass $m_{A^{\prime}}$ and their coupling to photons, offering a novel pathway to uncover the properties of dark sectors and the nature of PBHs.Open AccessSearching for Dark Photon Tridents Through Primordial Black Hole Signatures
The detection of gamma-ray signals from primordial black holes (PBHs) could provide compelling evidence for their role as a dark matter candidate, particularly through the observation of their Hawking radiation. Future gamma-ray observatories, such as e-ASTROGAM, and the next-generation telescopes, are poised to explore this possibility by measuring both Standard Model (SM) and beyond-the-SM particle emissions. A particularly promising avenue involves production of dark photons by PBHs, which is a hypothetical particle that decays into photons. In this work, we investigate the trident decay of dark photons focusing on their primary emission from PBHs. We assume that the dark photons produced via Hawking radiation decay into photons well before reaching Earth, thereby enhancing the detectable gamma-ray flux. The energy spectrum of the photons decaying from the dark photons is distinct from that of direct Hawking-radiated photons due to higher degree of freedom, leading to observable modifications in the gamma-ray signal. Using the asteroid-mass PBHs as a case study, we demonstrate that future gamma-ray missions could detect dark-photon signatures and distinguish them from conventional Hawking radiation. This approach enables the exploration of previously inaccessible parameter spaces in dark photon mass $m_{A^{\prime}}$ and their coupling to photons, offering a novel pathway to uncover the properties of dark sectors and the nature of PBHs.