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Potential of the reaction $e^{+} e^{-} \to p \bar{p} π^{0}$ for constructing higher $ρ$ -meson spectroscopy above 2.4 GeV

Dan Guo

Jun-Zhang Wang ^*

Qin-Song Zhou^†

School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, People’s Republic of China

Department of Physics, Chongqing University, Chongqing 401331, People’s Republic of China and School of Physics and Center of High Energy Physics, Peking University, Beijing 100871, People’s Republic of China

School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, People’s Republic of China; Research Center for Quantum Physics and Technologies, Inner Mongolia University, Hohhot 010021, People’s Republic of China and Inner Mongolia Key Laboratory of Microscale Physics and Atomic Manufacturing, Hohhot 010021, People’s Republic of China

^*Contact author: wangjzh@cqu.edu.cn
^†Contact author: zhouqs@imu.edu.cn

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Phys. Rev. D 112, 114029 – Published 18 December, 2025

DOI: https://doi.org/10.1103/w5gh-lq88

Abstract

The spectrum of light unflavored vector mesons above 2.4 GeV has not yet been firmly established experimentally. In this work, we demonstrate that the process $e^{+} e^{-} \to p \bar{p} π$ serves as a particularly promising channel as a probe for higher isovector $ρ$ excitations. In contrast to typical electron-positron annihilation processes into purely light-meson final states, the reaction $e^{+} e^{-} \to p \bar{p} π$ benefits from a relatively low continuum background, on the order of $(50 \sim 100) pb$ around 2.4 GeV, which enhances the visibility of even modest resonance contributions. In addition, the comparatively high production threshold further suppresses potential contamination from lower $ρ$ -meson excitations. Our analysis based on effective Lagrangian approach indicates that the observed line shape of the $e^{+} e^{-} \to p \bar{p} π$ cross section measured by the Beijing Spectrometer (BESIII) Experiment can be naturally interpreted by including the $ρ (5 S)$ and $ρ (6 S)$ contributions, namely the fourth and fifth radial excitations of $ρ (770)$ . In particular, the pronounced rise of the cross section near 2.4 GeV provides strong evidence for the contribution of $ρ (5 S)$ signal. Their branching ratios to the $p \bar{p} π$ final state are found to be below 4%, which do not contradict with usual expectations. In addition, we evaluate pion-induced production of these two $ρ$ -meson states as a complementary probe, offering useful guidance for the relevant experiments such as the Common Muon and Proton Apparatus for Structure and Spectroscopy.

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Phys. Rev. D 112, 114029– Published 18 December, 2025

Vol. 112, Iss. 11 — 1 December 2025

Received 11 September 2025
Accepted 1 December 2025

DOI: https://doi.org/10.1103/w5gh-lq88

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Potential of the reaction $e^{+} e^{-} \to p \bar{p} π^{0}$ for constructing higher $ρ$ -meson spectroscopy above 2.4 GeV

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Potential of the reaction e+e−→pp¯π0 for constructing higher ρ-meson spectroscopy above 2.4 GeV

Abstract

Physics Subject Headings (PhySH)

Article Text

References (48)

Potential of the reaction $e^{+} e^{-} \to p \bar{p} π^{0}$ for constructing higher $ρ$ -meson spectroscopy above 2.4 GeV