Observation of $e^+e^- \to p p \bar{p} \bar{n} \pi^{-} + c.c.$

TL;DR

This paper reports the first observation of the process $e^+e^- o p p ar{p} ar{n} ar{ ext{pi}}^{-} + c.c.$ at various energies, measuring cross sections and analyzing invariant mass spectra, with no evidence of exotic states.

Contribution

First experimental observation of the specified multi-baryon production process in electron-positron collisions, with detailed cross section measurements across energy ranges.

Findings

Measured cross sections increase with energy.

Invariant mass spectra are consistent with phase space.

No evidence of hexaquark or di-baryon states.

Abstract

Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 $\rm fb^{-1}$, the process $e^+e^- \to p p \bar{p} \bar{n} \pi^{-} + c.c.$ is observed for the first time with a statistical significance of $11.5\sigma$. The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be $(21.5\pm5.7\pm1.2)$ fb, $(46.3\pm10.6\pm2.5)$ fb and $(59.0\pm9.4\pm3.2)$ fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the $\bar{p}\bar{n}$ and $pp\pi^-$ invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.