Evidence of Pentaquark States from KN Scattering Data?

Motivated by the recent experimental evidence of the exotic B = S = +1 baryonic state Θ (1540), we examine the older existing data on KN elastic scattering through the time delay method. We find positive peaks in time delay around 1.545 and 1.6 GeV in the D03 and P01 partial waves of K N scattering respectively, in agreement with experiments. We also find an indication of the J = 3/2 Θ∗ spin-orbit partner to the Θ, in the P03 partial wave at 1.6 GeV. We discuss the pros and contras of these findings in support of the interpretation of these peaks as possible exotics. PACS numbers: 13.75.Jz, 13.85.Dz, 13.60.Rj In a recent letter by Nakano et al. [1], strong experimental evidence for the exotic state, characterized by the quantum numbers B = S = +1, with a mass and width of 1.54±0.01 and 0.025 GeV respectively, was reported. This could be interpreted as a molecular meson-baryon resonance (see e.g. [2]) or a pentaquark baryon [3, 4, 5], hence its importance. It was actually since the late sixties that such a state was predicted [6]. Some other groups [7] also reported similar results which shifts the evidence for the new state from plausibility to certainty. In this note, we would like to shed some light on these findings by examining whether this exotic state around 1.54 GeV is actually supported by phase shifts [8] obtained from older data on kaon-nucleon elastic scattering. If our analysis is taken in support of the experimental interpretation, we can assign or speculate about the L2I,2J quantum numbers. Indeed, according to our analysis, the exotic state found in [1] and [7] is likely to be either a P01 (this would be in agreement with the prediction made in [9] which actually prompted the experiments) or D03 (or maybe even P03).