Study of the ReactionK−n→Λπ−at 3.9 and 3.6 GeV/c: Test of Exchange Degeneracy in thetregion and an observation of a Backward Peak in theuRegion

Abstract

Angular distributions in the low-$\mathrm{}\left|t\right|\mathrm{}$ region in the reaction $K^{-}n\to \Lambda {\pi }^{-}$ and in the linereversed reaction ${\pi }^{-}p\to \Lambda K^0$ and from other complementary experiments do not support the predictions of exchange degeneracy between the ${K_{\frac{1}{2}}}^{*}\mathrm{}\left(890\right)\mathrm{}$ and the ${K_{\frac{1}{2}}}^{*}\mathrm{}\left(1420\right)\mathrm{}$ up to $s\sim 11$ ${\mathrm{GeV}}^2$. In the low-$\mathrm{}\left|u\right|\mathrm{}$ region of the reaction $K^{-}n\to \Lambda {\pi }^{-}$ at 3.9 GeV/c, we observe a peak with a slope of 10±3 ${\mathrm{GeV}}^{-2\mathrm{}}$ followed by a valley from $u=-0.15\mathrm{} \mathrm{to} -0.4\mathrm{}$ ${\mathrm{GeV}}^2$. A simple Regge-pole fit to this backward-scattering region using the $N_{\alpha }$ trajectory is presented.