SEARCH FOR (SIGMA-N) AND (SIGMA-NN) BOUND STATES

In an experiment involving K- capture in helium, a search was made for (Î<>-n) and (Î<>-nn) bound states as produced by the following reactions: K-+He4→(Î<>-n)+π++d; K-+He4→(Î<>-nn)+π++p. We did not find any unambiguous examples of these reactions among the interactions of 8370 stopping K- mesons. Upper limits on the rates for the production of these bound hyperon states are determined, relative to various K- capture reactions. With respect to stopping K- mesons, an upper limit on the bound-state production rate is ≤0.02%, using one ambiguous bound-state event for calculational purposes. In addition, for these data, we do not find evidence for a maximally strong (Î<>-n) final-state interaction. © 1969 The American Physical Society.