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interactions at
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have been studied by means of a self-shunted streamer chamber filled with helium at atmospheric pressure. This technique allowed reconstruction of the complete kinematics of the nuclear events under analysis, since tracks of slow
p,
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, tritium and
3He are readily measurable. The study revealed that the
4He nucleus behaves as a Planck radiator, emitting a
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Planck-like spectrum of high energy
γs, when hit by a
π beam of
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. A resonant behaviour in the
π−n invariant mass spectrum has been observed, with
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and
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in the
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neutron knockout reaction: we consider this to be the first experimental evidence for the existence of the
Δ−. The observed mass shift and width narrowing are compatible with the activation of an isobaric collective resonance in the
4He nucleus. The collaboration has also observed a resonant behaviour in the
π−pp invariant mass spectrum in the
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pp double-charge-exchange reaction, on nuclear photoemulsion, compatible with the activation of the
JP=0−d′ dibaryonic resonance with a strong p–p final state interaction. A new direct measured upper limit for the
νμ mass has been derived by measuring a complete decay
π–μ–e event recorded at the CERN PS179 experiment (
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Ne scattering): at a 90%confidence level,
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.