Observation of H Λ4 hyperhydrogen by decay-pion spectroscopy in electron scattering

A. Esser, S. Nagao, F. Schulz, P. Achenbach, C. Ayerbe Gayoso, R. Böhm, O. Borodina, D. Bosnar, V. Bozkurt, L. Debenjak, M. O. Distler, I. Friščić, Yu Fujii, T. Gogami, O. Hashimoto, S. Hirose, H. Kanda, M. Kaneta, E. Kim, Y. KohlJ. Kusaka, A. Margaryan, H. Merkel, M. Mihovilovič, U. Müller, S. N. Nakamura, J. Pochodzalla, C. Rappold, J. Reinhold, T. R. Saito, A. Sanchez Lorente, S. Sánchez Majos, B. S. Schlimme, M. Schoth, C. Sfienti, S. Širca, L. Tang, M. Thiel, K. Tsukada, A. Weber, K. Yoshida

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58 Citations (Scopus)

Abstract

At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a Be9 target in order to study the Λ binding energy of light hypernuclei. Positively charged kaons were detected by a short-orbit spectrometer with a broad momentum acceptance at 0° forward angles with respect to the beam, efficiently tagging the production of strangeness in the target nucleus. Coincidentally, negatively charged decay pions were detected by two independent high-resolution spectrometers. About 103 pionic weak decays of hyperfragments and hyperons were observed. The pion momentum distribution shows a monochromatic peak at pπ≈133MeV/c, corresponding to the unique signature for the two-body decay of hyperhydrogen HΛ4→He4+π-, stopped inside the target. Its Λ binding energy was determined to be BΛ=2.12±0.01(stat)±0.09(syst)MeV with respect to the H3+Λ mass.

Original languageEnglish
Article number232501
JournalPhysical review letters
Volume114
Issue number23
DOIs
Publication statusPublished - 2015 Jun 9

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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