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The existence of a charge-symmetry-breaking (CSB) term in the lambda-nucleon (Λ−N) interaction is shown to produce an admixture of a T=1 state to the predominant isospin singlet state in ΛH3. The present analysis shows that a CSB term constructed to fit light hypernuclear and Λ−p scattering data is poorly determined (∼4%-25% of the total Λ−p singlet and ∼4%-15% of the total Λ−p triplet interaction), but is strongly correlated with the Λ-separation energy, BΛ, from ΛH3, and that isospin mixing in ΛH3 can lead to significant adjustments of the deduced Λ−N interaction strengths. The mixed-symmetry T=0 state in ΛH3 is seen to have a small effect. Data employed include Λ−p total cross sections, σp), for total c.m. energy Ec.m.MeV, published values of BΛ, and a theoretical determination by Herndon and Tang of the relative magnitudes of the Λ−N potentials responsible for the mean binding and the ground-state splitting of ΛHe4 and ΛHe4. The two hypotheses that the spin, I, of ΛHe4 is 0 and 1 are studied. Nonlocal separable, spin-dependent central interactions of the Yamaguchi form are used, and all range parameters in the Λ−N interaction are constrained to be equal. A search of fits to σp) is made with intrinsic ranges in the interval 1.5 F to 2.3 F. Self-consistent CSB potentials are found for I=0 and I=1. The deduced singlet Λ−p CSB interaction is attractive in all cases, in disagreement with predictions of the SU3 particle-mixing model of Downs.

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©1971 American Physical Society