title: Observation of Spin-Dependent Charge Symmetry Breaking in ΛN Interaction: Gamma-Ray Spectroscopy of _{Λ}^{4}He.
abstract: The energy spacing between the spin-doublet bound state of _{Λ}^{4}He(1^{+},0^{+}) was determined to be 1406±2±2  keV, by measuring γ rays for the 1^{+}→0^{+} transition with a high efficiency germanium detector array in coincidence with the ^{4}He(K^{-},π^{-})_{Λ}^{4}He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus _{Λ}^{4}H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0^{+} ground state but is vanishingly small in the 1^{+} excited state, demonstrating that the ΛN CSB interaction has spin dependence.
authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
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authors.affiliation: Dipartimento di Scienza Applicate e Tecnologica, Politecnico di Torino, Corso Duca degli Abruzzi, 10129 Torino, Italy.|INFN, Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy.
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authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
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authors.affiliation: Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan.
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authors.affiliation: INFN, Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy.|Dipartimento di Fisica, Universit di Torino, Via P. Giuria 1, 10125 Torino, Italy.
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authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
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authors.affiliation: INFN, Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy.
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authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
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authors.affiliation: Department of Physics, Tohoku University, Sendai 980-8578, Japan.
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authors.affiliation: INFN, Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy.|Dipartimento di Fisica, Universit di Torino, Via P. Giuria 1, 10125 Torino, Italy.
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