$K^{+}$-nucleon scattering and exotic $S=+1$ baryons

The $K^{+}$-nucleon elastic scattering process has been reexamined in light of recent measurements which have found a narrow exotic $S=+1$ resonance in their $KN$ invariant mass distributions. We have analyzed the existing database in order to consider the effect of a narrow state on fits to $K^{+}$-nucleon observables.

Figure 1

Change of overall ${\chi }^2$ due to insertion of a resonance into $P_{01}$ for $M=1520–1560\text{MeV}$ with (a) $\Gamma =2$ and $5\text{MeV}$ and (b) $\Gamma =0.3$ and $0.7\text{MeV}$, using $KN$ plane wave approximation (PWA) [1]. Energies where measurements exist are labeled by vertical bars (for references, see Ref. 1). In Fig. 1b the $1535\text{−}\text{MeV}$ values for $\Delta {\chi }^2$ are off scale.

Figure 2

Change of overall ${\chi }^2$ due to insertion of a resonance into (a) $S_{01}$ and (b) $P_{03}$ for $M=1520–1560\text{MeV}$ with $\Gamma =0.3$ and $0.7\text{MeV}$ using $KN$ PWA [1]. Energies where measurements exist are labeled by vertical bars (for references, see Ref. 1).