A5082599586- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Neutrino Physics Research
- Relativity and Gravitational Theory
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- International Science and Diplomacy
- Scientific Research and Discoveries
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Atmospheric Ozone and Climate
- Spacecraft and Cryogenic Technologies
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Aerospace Engineering and Energy Systems
- Radiation Detection and Scintillator Technologies
University of Toyama
2020-2024
RIKEN
2019-2024
Yokohama National University
2024
National Academy of Sciences of Ukraine
2023
TU Dortmund University
2023
University of Łódź
2023
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2023
University of Turku
2023
Niels Brock
2023
University of Copenhagen
2023
From a theoretical point of view, there is strong motivation to consider an MeV-scale reheating temperature induced by long-lived massive particles with masses around the weak scale, decaying only through gravitational interaction. In this study, we investigate lower limits on imposed big-bang nucleosynthesis assuming both radiative and hadronic decays such particles. For first time, effects neutrino self-interactions oscillations are taken into account in thermalization calculations. By...
We study evolution of dark matter substructures, especially how they lose mass and change density profile after fall in gravitational potential larger host halos. develop an analytical prescription that models the subhalo calibrate it to results $N$-body numerical simulations various scales from very small (Earth size) large (galaxies clusters) then combine with halo accretion histories calculate function is physically motivated down Earth-mass scales. Our results---valid for arbitrary...
The presence of dark matter substructure will boost the signatures annihilation. We review recent progress on estimates this subhalo factor—a ratio luminosity from annihilation in subhalos to that originating smooth component—based both numerical N-body simulations and semi-analytic modelings. Since all scales, ranging Earth mass (as expected, e.g., supersymmetric neutralino, a prime candidate for cold matter) galaxies or larger, give substantial contribution rate, it is essential understand...
Dwarf spheroidal galaxies that form in halo substructures provide stringent constraints on dark matter annihilation. Many ultrafaint dwarfs discovered with modern surveys contribute significantly to these constraints. At present, because of the lack abundant stellar kinematic data for ultrafaints, noninformative prior assumptions are usually made parameters density profiles. Based semianalytic models subhalos and their connection satellite galaxies, we present more informative realistic...
We revisit constraints on small-scale primordial power from annihilation signals dark matter minihalos. Using gamma rays and neutrinos extragalactic minihalos assuming the delta-function spectrum, we show dependence of modes, mass matter, cross section. report conservative by are fully destructed when becoming part halos originating standard almost-scale invariant spectrum optimistic neglecting destruction.
Since the report of PeV--TeV neutrinos by IceCube Collaboration, various particle physics models have been proposed to explain neutrino spectrum dark matter particles decaying into and other standard model particles. In such scenarios, simultaneous $\ensuremath{\gamma}$-ray emission is commonly expected. Therefore, multimessenger connections are generally important for indirect searches matters. The recent development astronomy puts stringent constraints on properties matter, especially...
The Fermi Large Area Telescope (Fermi-LAT) has been widely used to search for Weakly Interacting Massive Particle (WIMP) dark matter signals due its unparalleled sensitivity in the GeV energy band. leading constraints WIMP by Fermi-LAT are obtained from analyses of dwarf spheroidal galaxies within Local Group, which compelling targets searches their relatively low astrophysical backgrounds and high content. In meantime, heavy with masses above TeV remains a unexplored frontier. this study,...
We investigate how sterile neutrinos with a range of masses influence cosmology in MeV-scale reheating temperature scenarios. By computing the production through combination mixing and scattering early Universe, we find that light neutrinos, mixings as inferred from short-baseline neutrino oscillation experiments, are consistent big-bang nucleosynthesis (BBN) cosmic microwave background (CMB) radiation for (1) MeV if parent particle responsible decays into electromagnetic components...
We investigate the primordial curvature perturbation by observation of dark matter substructure. Assuming a bump in spectrum wave number $k>1\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$, we track evolution host halo and subhalos semianalytic way. Taking into account possible uncertainties evaluation tidal stripping effect on subhalo growth, find new robust bound with from observed dwarf spheroidal galaxies our Galaxy observations stellar stream. The upper limit amplitude is...
We revisit constraints on annihilating dark matter based the global 21cm signature observed by EDGES. For this purpose, we used numerical data of latest N-body simulation performed state-of-the-art standard in order to estimate boost factor at high redshifts ($z$ = 10 - 100), which enhances annihilation course structure formation. By taking into account what fraction injected energy from contributes ionization, excitation and heating intergalactic medium during ages, estimated how large...
Dwarf spheroidal galaxies are excellent targets in $\ensuremath{\gamma}$-ray searches for dark matter. We consider matter dwarf (dSphs) with the Cherenkov Telescope Array (CTA). The aim of this work is to reveal a quantitative and precise dependence accessible annihilation cross sections on density profiles dSphs distance them. In most data analyses, researchers have assumed pointlike signals from because it difficult resolve expected emission current observatories. future however, CTA will...
Substructures of dark matter halo, called subhalos, provide important clues to understand the nature matter. We construct a useful model describe properties subhalo mass functions based on well-known analytical prescriptions, extended Press-Schechter theory. The unevolved at arbitrary scales become describable without introducing free parameters. different host halo evolution histories are directly recast their functions. As applications, we quantify effects from (i) Poisson fluctuation,...
Abstract The Fermi Large Area Telescope ( -LAT) has been widely used to search for Weakly Interacting Massive Particle (WIMP) dark matter signals due its unparalleled sensitivity in the GeV energy band. leading constraints WIMP by -LAT are obtained from analyses of dwarf spheroidal galaxies within Local Group, which compelling targets searches their relatively low astrophysical backgrounds and high content. In meantime, heavy with masses above TeV remains a unexplored frontier. this study,...
GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation proposed balloon-borne/satellite-based mission aimed at high sensitivity MeV gamma-ray astrophysical observations background-free indirect dark matter search via hadronic antiparticles. The main detector of meter-scale liquid argon time projection chamber (LArTPC). adoption as material allows us to produce an unprecedentedly large effective area instrument both for cosmic gamma rays 0.5-20 antiparticles origin. This area, which...
Recent James Webb Space Telescope observations of high-redshift massive galaxy candidates have initiated renewed interest in the important mystery around formation and evolution our Universe's largest supermassive black holes (SMBHs). We consider possibility that some them were seeded by direct collapse primordial density perturbations from inflation into analyze consequences this on current dark matter substructures assuming non-Gaussian curvature perturbation distributions. derive bounds...
Abstract GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite experiment utilizing LArTPC (Liquid Argon Time Projection Chamber), to simultaneously target astrophysical observations of cosmic MeV gamma-rays conduct an indirect dark matter search using antimatter. While LArTPCs are widely used in particle physics experiments, they have never been operated at balloon altitudes. An engineering flight with small-scale (eGRAMS) was conducted on July 27th, 2023, establish...
The Crab pulsar and its nebula are very luminous variable. Since 1982, random fluctuations of the dispersion measure (DM) have been recorded. Also in 2011, Fermi-LAT telescope detected $γ$-ray flux variation nebula. No correlation between these phenomena considered although their fluctuating patterns look similar. We propose a model which connects DM fluctuation, motivated by recently reported braking index variability. Considering electrons within inner shock region produced breaking change...
Many models of dark matter (DM) are now widely considered and probed intensively with accelerators, underground detectors, astrophysical experiments. Among the various approaches, high-energy observations extremely useful to complement laboratory searches for some DM candidates. In near future, Cherenkov Telescope Array (CTA) should enable us access much heavier weakly interacting massive particles, as well a broad range other this talk, we describe CTA.
Abstract The structure of dark matter halo is hierarchical. Among them, small-scale structures in (so-called subhalos) can enhance annihilation signals. It necessary to quantify boost factors by those subhalos derive the property with current/future gamma-ray observations. In order subhalo factors, calculations covering more than 20 orders-of-magnitude mass up a redshift z ˜ 10 are required. This beyond capability current state-of-art cosmological N-body simulation which widely-adopted...
We investigate the primordial curvature perturbation by observation of dark matter substructure. Assuming a bump in spectrum wavenumber k>1 Mpc^{-1}, we track evolution host halo and subhalos semi-analytic way. Taking into account possible uncertainties evaluation tidal stripping effect on subhalo growth, find new robust bound with from number observed dwarf spheroidal galaxies our Galaxy observations stellar stream. The upper limit amplitude is O(10^{-7}) for k~10^3 Mpc^{-1}. Furthermore...
Substructures of dark matter halo, called subhalos, provide important clues to understand the nature matter. We construct a useful model describe properties subhalo mass functions based on well-known analytical prescriptions, extended Press-Schechter theory. The unevolved at arbitrary scales become describable without introducing free parameters. different host halo evolution histories are directly recast their functions. As applications, we quantify effects from (i) Poisson fluctuation,...