Pentaquark ${\Theta }^{+}$ search at HERMES

Abstract

The earlier search at HERMES for narrow baryon states excited in quasi-real photoproduction, decaying through the channel $p{K}_S^0\to p{\pi }^{+}{\pi }^{-}$, has been extended with improved decay-particle reconstruction, more advanced particle identification, and increased event samples. The structure observed earlier at an invariant mass of 1528 MeV shifts to 1522 MeV and the statistical significance drops to about 2$\sigma$ for data taken with a deuterium target. The number of events above background is $68_{-31}^{+98}\text{(stat)}\pm 13\text{(sys)}$. No such structure is observed in the hydrogen data set.

References in corpus (9)

• Evidence for Narrow S=+1 Baryon Resonance in Photo-production from Neutron
• Exotic Anti-Decuplet of Baryons: Prediction from Chiral Solitons
• Quark helicity distributions in the nucleon for up, down, and strange quarks from semi--inclusive deep--inelastic scattering
• Evidence for a narrow |S|=1 baryon state at a mass of 1528 MeV in quasi-real photoproduction
• The HERMES Dual-Radiator Ring Imaging Cerenkov Detector
• Pentaquark in the Skyrme Model
• The HERMES Polarized Hydrogen and Deuterium Gas Target in the HERA Electron Storage Ring
• Azimuthal distributions of charged hadrons, pions, and kaons produced in deep-inelastic scattering off unpolarized protons and deuterons
• Present status on experimental search for pentaquarks