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M. MacCormick

Publications and source records attributed to M. MacCormick.

20 records · Page 2Linked to original sources

πN and ηp deexcitation channels of the N^* and Δbaryonic resonances between 1470 and 1680 MeV

Two reactions, pp->ppX and pp->pπ^+X, are used to study the 1.47<M<1.68 GeV baryonic mass range. Three different final states are considered in the invariant masses: N^* or Δ^+, pπ^0, and pη. The last two channels are defined by software cuts applied to the missing mass of the first reaction. Several narrow structures are extracted with widths σ(Γ) varying between 3 and 9 MeV. Some structures are observed in one channel but not in others. Such nonobservation may be due either to the spectrometer momenta limits or to the physics (e.g. no such disintegration channel is allowed from the narrow state considered). We tentatively conclude that the broad Particle Data Group (PDG) baryonic resonances N(1520)D13, N(1535)S11, Delta(1600)P33, and N(1675)D15 are collective states built from several narrow and weakly excited resonances, each having a (much) smaller width than the one reported by PDG.

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Possible Indication of Narrow Baryonic Resonances Produced in the 1720-1790 MeV Mass Region

Signals of two narrow structures at M=1747 MeV and 1772 MeV were observed in the invariant masses M_{pX} and M_{π^{+}X} of the pp->ppX and pp->pπ^{+}X reactions respectively. Many tests were made to see if these structures could have been produced by experimental artefacts. Their small widths and the stability of the extracted masses lead us to conclude that these structures are genuine and may correspond to new exotic baryons. Several attempts to identify them, including the possible "missing baryons" approach, are discussed.

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