Amplitude analysis of the $K^{-}{K}^{+}$ system produced in the reactions ${\pi }^{-}p\to K^{-}{K}^{+}n$ and $K^{-}{K}^{+}$ at 6 GeV/c

We have carried out an amplitude analysis of the $K^{-}{K}^{+}$ system produced in the reactions ${\pi }^{+}p\to K^{-}{K}^{+}n$ and ${\pi }^{+}n\to K^{-}{K}^{+}p$ using data from a high-statistics experiment performed with the Argonne effective-mass spectrometer. Combining the results from the two reactions allows us to analyze the $\overline{K}K$ production amplitudes in terms of their isospin-zero and -one components. We use phenomenological arguments based on $t$ dependence and on the expected properties of the $P$ and $D$ waves to resolve ambiguities. Our favored solution exhibits an enhancement around 1300 MeV in the isospin-zero $S$ wave produced by $\pi$ exchange. In this solution the Argand plot for the $\pi \pi \to \overline{K}KS$ wave changes rapidly above 1300 MeV, consistent with a resonance at 1425±15 MeV with width 160±30 MeV. We show that our solution is consistent with the features of neutral and charged $\overline{K}K$ systems found in other experiments.