16 papers
Revisiting the limits on dark matter annihilation cross-section and decay lifetime in light of electron and positron fluxes
Nagisa Hiroshima, Kazunori Kohri, Partha Kumar Paul +1
We revisit the upper bound on the annihilation cross-section, of a stable dark matter (DM) of mass GeV by considering five different channels: $W^+…
EMPRESS. XV. A New Determination of the Primordial Helium Abundance Suggesting a Moderately Low Value
Hiroto Yanagisawa, Masami Ouchi, Akinori Matsumoto +18
We present a new constraint on the primordial helium abundance, , based on Subaru observations. A major source of uncertainty in previous determination…
Primordial black holes save inflation
Xinpeng Wang, Kazunori Kohri, Tsutomu T. Yanagida
In light of the latest Planck and Atacama Cosmology Telescope (P-ACT) joint results on the primordial scalar power spectrum, we show that the inflation model extended with a…
GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts
LST Collaboration, K. Abe, S. Abe +328
GRB 221009A is the brightest gamma-ray burst (GRB) observed to date. Extensive observations of its afterglow emission across the electromagnetic spectrum were performed, providing…
Verifying the failing supernova constraint on dark photons with two-dimensional hydrodynamic simulations
Kanji Mori, Tomoya Takiwaki, Kazunori Kohri
Recent studies on the dark photon (DP) production in collapsing stars argue that the cooling effect induced by DPs can hinder supernova explosions and lead to a ``failing supernova…
Primordial Black Holes as Dark Matter and the Tachyonic Trap During Inflation
Yuma S. Furuta, Mindaugas KarÄiauskas, Kazunori Kohri +1
We show that resonant processes during multi-field inflation can generate a large curvature perturbation on small scales. This perturbation naturally leads to the formation of prim…