THE BINDING ENERGY DIFFERENCE BETWEEN THE HYPERNUCLIDES 4HE SUB LAMBDA AND 4H SUB LAMBDA.
CHICAGO UNIV ILL ENRICO FERMI INST FOR NUCLEAR STUDIES
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Experimental and theoretical studies indicate a departure from charge symmetry for the mirror hypernuclides 4He sub lambda and 4He sub lambda amounting to a few tenths of a MeV in the binding energies. A nuclear emulsion experiment utilizing 45 newly measured pion- mesic decays of 4He sub lambda and 4H sub lambda is reported to give delta B sub lambda B sub lambda 4He sub lambda -B sub lambda 4H sub lambda 0.550.26 MeV. Contamination by other hypernuclides probably 5He sub lambda was eliminated from the 4He sub lambda sample by a strict recoil-range requirement R or 10 micro. m, while, on the other hand, no contaminants were found among the 4H sub lambda decays. The binding energy discrepancy between the pion-r and pion-pr decays of 4H sub lambda was found to be due to pion range measurement losses which are important mainly for the pion-r events R sub pi 4 cm. The final value of delta B sub lambda for the latter sample is 0.300.14 MeV. Because a negative term in the theoretical calculation of delta B sub lambda is expected from a Coulomb energy increase in the 3He core of 4He sub lambda, this positive experimental result is a strong indication of charge-symmetry violation in the lambda hyperon N interaction compatible with estimates of the virtual electromagnetic effects in lambda hyperon to lambda hyperon pion suggested by theoretical workers.