Study of baryonic resonances and ρ meson production in the reaction pp → ppπ+π− at 3.5 GeV with HADES

We report on measurements of baryon resonance and ρ meson production in the exclusive pp → ppπ+π− channel at a beam kinetic energy of 3.5 GeV measured with the HADES experimental setup. The differential distributions are compared to Monte Carlo simulations based on a resonance model assuming an incoherent sum of contributions of various baryonic resonances with masses below 2 GeV and using inputs from one pion production measured in the same experiment. A very good description of the two pion production is achieved allowing for an estimate of the contribution of one and double baryon-resonance excitation. Using appropriate kinematical cuts the ρ meson signal could also be extracted.

The High-Energy Photoproduction of Light-Quark Pseudoscalar and Scalar Meson at GlueX

The high-energy photoproduction of light-quark pseudoscalar and scalar mesons is an effective tool for understanding the properties of strong interaction in the nonperturbative regime. It has been investigated theoretically using Regge-cut phenomenology with massive quasi-particle exchange in the high-energy regime, and the linearly polarized photon beam asymmetry [Formula: see text] can provide insight into the dominant production mechanism. In the low-energy region, it can provide constraints on ”background” to baryon resonance extraction. With an almost 50-year history, intensive experiments on meson photoproduction are growing vigorously at several international laboratories, such as JLab, ELSA, and MAMI. Recently the beam asymmetry [Formula: see text] in high-energy [Formula: see text] photoproduction has been measured at GlueX, which is the first measurement both from the GlueX experiment and the 12 GeV upgraded JLab. The highest precision measurement of the [Formula: see text] asymmetry and the first measurement of [Formula: see text] beam asymmetry at a beam energy above 3 GeV are presented. A broad meson photoproduction project, including scalar meson [Formula: see text], is under way at GlueX. In the proceedings, we report the beam asymmetry results for [Formula: see text] photoproduction at GlueX, as well as preliminary results for scalar meson photoproduction in the [Formula: see text] and [Formula: see text] channels.