Speaker
Description
We present Proposal P111 for a new experiment that will investigate $J/\psi$ production in $\pi^-p$ reactions near threshold at the $\pi$20 beamline of J-PARC. Studying $J/\psi$ production in $\pi^−p$ collisions will offer valuable insights into the mechanism of $c\bar{c}$ pair creation in pion-induced reactions, with particular focus on hidden-charm pentaquark states. This measurement seeks to deliver the world’s first data on total and differential cross sections for the exclusive $\pi^-p\to J/\psi n$ reaction from threshold up to W = 4.65 GeV, thereby spanning the full mass region for $P_c$ states—from $\bar{D}\Lambda_c$ to $\bar{D}^\ast\Sigma^\ast_c$ thresholds. Polarization measurements will also be possible. The P111 proposal includes the development of a dedicated lepton detector for measuring $J/\psi$ leptonic decays, to be incorporated into the MARQ spectrometer. This presentation will highlight the current status and future prospects of the proposal.
