The "neutron lifetime puzzle" arises from the discrepancy between neutron lifetime measurements obtained using the beam method, which measures decay products, and the bottle method, which measures the disappearance of neutrons. To resolve this puzzle, we conducted an experiment using a pulsed cold neutron beam at J-PARC.
In this experiment, the neutron lifetime is determined from the ratio...
Recent accelerator experiments have reported unexpected states known as exotic hadrons, whose properties cannot be explained by the conventional picture, mesons and baryons. In the heavy quark sector, $XYZ$, $T_{cc}$, $P_c$ etc. have been reported since the discovery of $X(3872)$. There have been many exotic hadrons located near the hadron threshold, and thus loosely hadron bound states called...
Ultra-high energy cosmic rays are the highest energy particles arriving at the Earth and measured using an extensive air shower induced by them. In 2025, the Pierre Auger Observatory reported an excess of the number of muons in an extensive air shower than that expected in simulations. This indicates a puzzle, a muon puzzle, suggesting the interactions in an extensive air shower are not...
