title: Observation of Λ(4)H Hyperhydrogen by Decay-Pion Spectroscopy in Electron Scattering.
abstract: At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from decays of strange systems was performed by electron scattering off a (9)Be 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 10(3) pionic weak decays of hyperfragments and hyperons were observed. The pion momentum distribution shows a monochromatic peak at pπ≈133  MeV/c, corresponding to the unique signature for the two-body decay of hyperhydrogen Λ(4)H→(4)He+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 (3)H+Λ mass.
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Esser
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nagao
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Schulz
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Achenbach
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ayerbe Gayoso
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Böhm
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.|GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Borodina
authors.affiliation: Department of Physics, University of Zagreb, HR-10002 Zagreb, Croatia.
authors.forename: D
authors.initials: D
authors.lastname: Bosnar
authors.affiliation: GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Bozkurt
authors.affiliation: Department of Physics, University of Ljubljana, and Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia.
authors.forename: L
authors.initials: L
authors.lastname: Debenjak
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: M O
authors.initials: MO
authors.lastname: Distler
authors.affiliation: Department of Physics, University of Zagreb, HR-10002 Zagreb, Croatia.
authors.forename: I
authors.initials: I
authors.lastname: Friščić
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Gogami
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: O
authors.initials: O
authors.lastname: Hashimoto
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Hirose
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kanda
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kaneta
authors.affiliation: GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Kim
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: Y
authors.initials: Y
authors.lastname: Kohl
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Kusaka
authors.affiliation: Yerevan Physics Institute, 375036 Yerevan, Armenia.
authors.forename: A
authors.initials: A
authors.lastname: Margaryan
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Merkel
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Mihovilovič
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Müller
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: S N
authors.initials: SN
authors.lastname: Nakamura
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Pochodzalla
authors.affiliation: GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.|Helmholtz Institute Mainz, D-55099 Mainz, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Rappold
authors.affiliation: Department of Physics, Florida International University, Miami, Florida 33199, USA.
authors.forename: J
authors.initials: J
authors.lastname: Reinhold
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.|GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.|Helmholtz Institute Mainz, D-55099 Mainz, Germany.
authors.forename: T R
authors.initials: TR
authors.lastname: Saito
authors.affiliation: Helmholtz Institute Mainz, D-55099 Mainz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Sanchez Lorente
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Sánchez Majos
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: B S
authors.initials: BS
authors.lastname: Schlimme
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schoth
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Sfienti
authors.affiliation: Department of Physics, University of Ljubljana, and Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia.
authors.forename: S
authors.initials: S
authors.lastname: Širca
authors.affiliation: Department of Physics, Hampton University, Hampton, Virginia 23668, USA.
authors.forename: L
authors.initials: L
authors.lastname: Tang
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Thiel
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8571, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tsukada
authors.affiliation: Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Weber
authors.affiliation: GSI Helmholtz Centre for Heavy Ion Research, D-64291 Darmstadt, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Yoshida