The Role of a ₁ (1260) in π ⁻ p → a ₁ ⁻ (1260) p and π ⁻ p → π ⁻ ρ

Abstract

We report on a theoretical study of the π − p → a − 1 (1260)p and π − p → π − ρ 0 p reactions near threshold within an effective Lagrangian approach. The production process is described by t-channel ρ 0 meson exchange. For the π − p → π − ρ 0 p reaction, the final π − ρ 0 results from the decay of the a1(1260) resonance, which is assumed as a dynamically generated state from the K * K and ρπ coupled channel interactions. We calculate the total cross section of the π − p → a − 1 (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 → a − 1 (1260)p → π − ρ 0 p 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.

Hadronic molecules

“…It should be noted that in Refs. Cheng et al, 2016;Debastiani et al, 2017a) the a 1 (1420) enhancement is proposed to be caused by the a 1 (1260) together with the TS mechanism and similarly f 1 (1420) is produced by f 1 (1285). However, as shown by the convincing experimental data from MARK-III, BESII, BESIII, and the detailed partial wave analysis of Ref.…”

Theoretical description of the J/ψ→η(η′)hWu1, Sakai2, Oset3 2019Phys. Rev. D11190View full textAdd to dashboardCite

“…[23], the π − p → a 1 ð1260Þp reaction studied in Ref. [33], the e þ e − → f 1 ð1285Þγða 1 ð1260ÞγÞ reactions studied in Ref. [34], and the K − p → f 1 ð1285ÞΛ reaction studied in Ref.…”

Role of the $Λ(1600)$ in the $K^-p \to Λπ^0π^0$ reaction

“…The combination of the resonance model and the effective Lagrangian approach is an important theoretical tool in describing the various scattering processes in the resonance production region [30][31][32][33]. In this section, we introduce the theoretical formalism and ingredients to study the K − p → Λπ 0 π 0 reaction by using the effective Lagrangian approach and resonance model.…”