engleski

The re-analysis of the 1700 MeV structure of the P_11 partial wave using the pi N-->KLambda production data

Abstract. We have used the Breit-Wigner resonance model with S_11, P_11, and P_13 resonances in the s-channel to reanalyze the old pi N&#8594; K&#923; data with the aim to establish the origin of the prominent structure in the total cross section in the vicinity of 1700&#8201; MeV. We have found a new set of resonance parameters enforcing the experimentally observed structure of the total cross-section data simultaneously with the linear dependence of the differential cross sections with cos&#8201; theta in the energy range 1650 MeV < W < 1800 MeV. Owing to the differential cross-section linearity, the P_13 partial wave has been strongly attenuated in this model, and the total cross-section structure is attributed to the resonant behavior of the P_11 partial wave. In this paper we show that, at least in the Breit-Wigner resonance model, it is not possible to achieve a detailed reproduction of the narrow 1700 MeV total cross-section peak using the standard partial widths. To understand the phenomenon, a much narrower width of a resonant state, the N(1710) P_11 in our case, is required (&#915; &#8776; 68 MeV), but then the agreement of the model predictions with the total cross-section data at higher energies is lost. One way out is to allow for the existence of another P_11 resonance in that energy range. The same feature is shown by the polarization data: The introduction of a much narrower resonance spoils the level of agreement which the Breit-Wigner resonance model is able to achieve with experiment, but the consistency is restored when another resonance is introduced. Analyzing the qqq or qqqq\bar nature of the recommended narrow P_11 structure in the neighborhood of 1700&#8201; MeV we reopen (remind of) the possibility that another P 11 resonant state exists in addition to the standard N(1710) P_11 PDG-resonance, and that one of the two states can be identified with the yet undiscovered cryptoexotic pentaquark state. To clarify the situation, we strongly recommend a remeasurement of the pi N&#8594; K&#923; process in the energy range 1650 MeV<W<1800 MeV.

P_11 resonance; pentaquark

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