Evidence for an Anti-charmed Baryon State

TL;DR

This paper reports the discovery of a narrow resonance in deep-inelastic ep scattering at HERA, interpreted as an anti-charmed baryon with a specific quark composition, providing evidence for an exotic baryon state.

Contribution

First observation of a narrow anti-charmed baryon resonance in deep-inelastic scattering, with precise mass measurement and interpretation as a $uudd\bar c$ state.

Findings

Resonance mass measured at 3099 MeV

Resonance width compatible with experimental resolution

Evidence supporting an exotic anti-charmed baryon state

Abstract

We report on the observation of a narrow resonance in D^{*-}p and D^{*+} pbar invariant mass combinations in deep-inelastic ep scattering at centre-of-mass energies of 300 and 320 GeV at HERA. The mass of the resonance is measured to be 3099 +- 3 (stat.) +- 5 (syst.) MeV, the Gaussian width of 12 +- 3 (stat.) MeV is compatible with the experimental resolution. The state can be interpreted as an anti-charmed baryon with minimal constituent quark composition $uudd\bar c$, together with the charge conjugate.