Speaker
Description
J-PARC E16 and E88 experiments aim to study the in-medium modification of $\phi$ mesons in $e^+e^-$ and $K^+K^-$ decays in proton-nucleus collisions to study the effect of the chiral-symmetry restoration. In the past KEK-E325 experiment, the mass reduction of ϕ was observed at low velocity in p+Cu collisions in the $e^+e^-$ decay. E16 will measure several thousand $\phi \rightarrow e^+e^-$ events in p+C and p+Cu in the first physics run planned in 2026-2027. E88 will measure about one million $\phi \rightarrow K^+K^-$ events in p+C, p+Cu, and p+Pb collisions complementarily. By measuring the mass dependence on the momentum (dispersion relation) in both experiments, the $\bar{s}s$ condensate in nucleons will be evaluated by evaluating the mass shift at zero momentum. E88 also aims to measure the dependence of the mass shifts on the ϕ polarity for the first time.
E16 and E88 share part of the experimental setup. Electron identification performance has been evaluated in the E16 commissioning runs. In the trigger-study run in 2024, the $\omega$ and $\phi$ peaks in the $e^+e^-$ invariant mass spectra have been observed. Kaon identification performance for E88 was also evaluated.
In this talk, we will show the physics goals, the experimental design, the feasibility, and the status of both experiments.