Speaker
Description
Although nucleon resonances (N and $\Delta$) have been studied for a long time, there are still many resonances which have not been established experimentally, which were measured mostly using $\gamma N\rightarrow \pi N$. $\pi N \rightarrow \pi N$, and $\gamma N \rightarrow \pi\pi N$ data. On the other hand, there are only a limited number of events of $\pi N \rightarrow \pi\pi N$ data, which was mainly measured in 1970’s. Thus, we proposed an experiment E45 to study nucleon resonances in N→N reactions with high-intensity ± beams injected on the liquid hydrogen target at J-PARC. We aim at establishing experimentally the nucleon resonances with the mass up to 2 GeV/c$^{2}$ using the measured $\pi N \rightarrow \pi\pi N$ data in higher statistics than the existing data by two-orders of magnitude. We measure reactions of $\pi^{−}p \rightarrow \pi^{+}\pi^{−}n$, $\pi^{0}\pi^{−}p$ and $\pi^{+}p \rightarrow \pi^{0}\pi^{+}p$, $\pi^{+}\pi^{+}n$, as well as $\pi^{−}p \rightarrow K^{0}\Lambda$ and $\pi^{+}p \rightarrow K^{+}\Sigma^{+}$ in a large acceptance Time Projection Chamber (HypTPC) inside a superconducting Helmholtz magnet. We will measure these reactions in small momentum steps in the center-of-mass energy range of 1.5-2.1 GeV. Then, we perform partial-wave analysis to extract properties of resonances. The first physics run of E45 is planned in 2026 for the energy range of 1.66-1.75 GeV. In this presentation, we will show the status and the preliminary results of the first physics run.