The Role of a1 (1260) in π−p → a1−(1260)p and π−p → π−ρ0p Reactions Near Threshold**Supported by the National Natural Science Foundation of China under Grant Nos. 11475227 and 11475015, and the Youth Innovation Promotion Association CAS under Grant No. 2016367

Abstract

We report on a theoretical study of the π− p → a1−(1260)p and π−p → π− ρ0p reactions near threshold within an effective Lagrangian approach. The production process is described by t-channel ρ0 meson exchange. For the π−p → π−ρ0p reaction, the final π−p0 results from the decay of the a1(1260) resonance, which is assumed as a dynamically generated state from the K*K̄ and ρπ coupled channel interactions. We calculate the total cross section of the π−p → a1−(1260)p reaction. It is shown that, with the coupling constant of the a1(1260) to ρπ channel obtained from the chiral unitary theory and a cut off parameter Λρ ∼ 1.5 GeV in the form factors, the experimental measurement can be reproduced. Furthermore, the total and differential cross sections of π−p → a1−(1260)p → π−ρ0p reaction are evaluated, and it is expected that our model calculations can be tested by future experiments. These reactions are important for the study of the a1(1260) resonance and would provide further constraints on the properties of the a1(1260) state.