Interactions of Negative<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>Mesons

Abstract

A detailed analysis of events in nuclear emulsions caused by ${K}^{\ensuremath{-}}$ mesons is given. Of 39 ${K}^{\ensuremath{-}}$ mesons observed, 8 produced stars in flight, 1 underwent nuclear scattering, and 30 were captured at rest. The ${K}^{\ensuremath{-}}$ mean free path for inelastic collisions in emulsion is 17\ifmmode\pm\else\textpm\fi{}5 cm, at most geometric. Charged hyperons and hyperfragments were seen in 12 stars; in all others, emission of a neutral hyperon is allowed by energy balance. In $\frac{2}{5}$ of the stars, a charged pion was emitted; half of the pions had kinetic energy \ensuremath{\geqslant} 100 Mev. 3 stars consisted only of a $\ensuremath{\Sigma}$ hyperon and a pion, of such momenta as to make it obvious that ${K}^{\ensuremath{-}}$ capture proceeded according to: ${K}^{\ensuremath{-}}+N\ensuremath{\rightarrow}Y+\ensuremath{\pi}$. Kinematic analysis shows that this reaction was the most likely process in almost all of the other captures. In 5 of the captures at rest, the pion energies were \ensuremath{\geqslant} 100 Mev, compatible only with $Y={\ensuremath{\Lambda}}^{0}$. One ${K}^{\ensuremath{-}}$ capture reaction (and possibly a few more) was: ${K}^{\ensuremath{-}}+2N\ensuremath{\rightarrow}Y+N$. In this one capture, the hyperon is either ${\ensuremath{\Sigma}}^{\ifmmode\pm\else\textpm\fi{}}$ decaying by an unusual mode, possibly into an electron, or else is a hitherto unknown particle.