Role of the resonance in the reaction

Abstract

New measurement by CELSIUS-WASA Collaboration on the pp → pnπ + reaction reveals clear evidence for the presence of the Roper resonance N * (1440) which has been ignored in previous theoretical calculations. In this article, based on an effective Lagrangian approach and available knowledge on the Roper resonance, we investigate the role of the Roper resonance for the pp → pnπ + reaction. It is found that the contribution from the Roper resonance N * (1440) becomes significant for kinetic energy above 1.1 * Corresponding author. ouyangzh@impcas.ac.cn; Tel: +86-10-88236162; fax: +86-10-88233085 † xiejujun@mail.ihep.ac.cn ‡ zoubs@mail.ihep.ac.cn § hushan@impcas.ac.cn 1 GeV, consistent with the new experimental observation. The t-channel σ-meson exchange is dominant for the production of the Roper resonance.

Phenomenological study on the reactions

“…Other resonances give negligible contributions so we can safely ignore them. The effective Lagrangians for the relevant resonance couplings are [15,16],…”

“…This may be due to the fact that we have not treated the initial state interactions (ISI) properly. The ISI usually has a weak energy dependence for the meson production processes, so adjusting cutoff parameters in the form factors may partly account for it effectively as for the pp collision [2,16]. However, while thepn is a pure isospin-vector state, thepp is a mixture of isospin-scalar and isospin-vector.…”

Proposal for studyingN*resonances with thep¯p→pWu1, Ouyang2, Zou3 2009Phys. Rev. CSelf Cite461560View full textAdd to dashboardCite

“…A difficulty in extracting the N * information from these experiments is the isospin decompo-sition of 1/2 and 3/2 [18]. Recently, the J /ψ →NNπ and pp → pnπ + reactions have been used to study N * resonances with claimed observation of the Roper resonance peak [19,20] due to their isospin filter effect [21,22]. However, because of the presence of large interfering contributions from other resonances, there is still considerable model dependence in extracting its properties.…”

N[sup ∗] production from pp and p̄p collisions

“…[10,11], there are two points in the full analysis of pp → pnπ + . First, the role of N * (1440)Nσ is very important at beam energies above 1.1 GeV.…”