Observation of e+ e- → pp(p)over-bar(p)over-barπ- +c.c *

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, the process e(+)e(-) -> pp (p) over bar(p) over bar 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 +/- 5.7 +/- 1.2) fb, fb and (59.0 +/- 9.4 +/- 3.2)fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the (p) over bar(n) over bar and pp pi(-) invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.

Automated summary

Using the BESIII detector, data collected at 29 different center-of-mass energies between 4.16 and 4.70 GeV shows the first observation of the process e(+)e(-) -> pp (p) over bar(p) over bar pi(-) +c.c with a statistical significance of 11.5 sigma. The measurements of the average Born cross sections in different energy ranges indicate that no hexaquark or di-baryon state is observed.