C. Rappold

Observation of H Λ 4 Hyperhydrogen by Decay-Pion Spectroscopy in Electron Scattering

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.

HYPERNUCLEAR SPECTROSCOPY WITH HEAVY ION BEAMS: THE HypHI PROJECT AT GSI AND FAIR

The HypHI experiment for precise hypernuclear spectroscopy with induced reactions of stable heavy ion beams and rare isotope beams is currently under preparation at GSI. The main goal of the HypHI project is to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments at GSI and FAIR. In the first HypHI experiment (Phase 0) planned in 2009, the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π- decay channels of , and with 6Li projectiles at 2 A GeV impinging on a 12C target. An overview of the HypHI project and the details of the Phase 0 experiment will be discussed.

Recent Progress of the HypHI Project at GSI and Its Perspective at FAIR

The data analysis for the Phase 0 experiment has been already completed, and the results on the invariant mass reconstruction and lifetime values for the observed ΛH and 3 ΛH hypernuclei as well as the Λ-hyperon have been published [1]. In addition to these known hypernuclei, we have also observed signals in the d+π− + t+π− invariant mass distributions, and the lifetime measurements of the state associated with these final states have revealed that it decays with a strangeness-changing weak interaction [2]. Analyses on the production cross section as well as on the kinematics variables have also been completed [3], and the results will be also discussed. The analysis for the Phase 0.5 experiment are to be completed [4], and preliminary results will be also discussed.

Hypernuclear Decay Pion Spectroscopy at Mainz Microtron

Sho NAGAO1∗, Patrick ACHENBACH2, Naoki ARAI1, Carlos Ayerbe GAYOSO2, Ralph BOHM2, Olga BORODINA2,3, Damir BOSNAR4, Vakkas BOZKURT3, Luka DEBENJAK5, Michael O. DISTLER2, Anselm ESSER2, Ivica FRISCIC4, Yuu FUJII1, Toshiyuki GOGAMI1, Mar GOMEZ RODRIGUEZ2, Satoshi HIROSE1, Hiroki KANDA1, Masashi KANETA1, Eunhee KIM3, Junichiro KUSAKA1, Amur MARGARYAN6, Harald MERKEL2, Ulrich MULLER2, Satoshi N. NAKAMURA1, Josef POCHODZALLA2, Christophe RAPPOLD3, Joerg REINHOLD7, Takehiko R. SAITO2,3,8, Alicia Sanchez LORENTE8, Salvador Sanchez MAJOS2, Bjorn Soren SCHLIMME2, Matthias SCHOTH2, Florian SCHULZ2, Concettina SFIENTI2, Simon SIRCA5, Liguang TANG9, Michaela THIEL2, Kyo TSUKADA1, Daisuke UCHIYAMA1 A1 hypernuclear collaboration

Recent Studies of the Strangeness Physics at MAMI-C

Kyo Tsukada1, Patrick Achenbach2, Naoki Arai1, Carlos Ayerbe Gayoso2, Ralph Bohm2, Olga Borodina2,3, Damir Bosnar4, Vakkas Bozkurt3, Luka Debenjak5, Michael O. Distler2, Anselm Esser2, Ivica Friscic3, Yuu Fujii1, Toshiyuki Gogami1, Mar Gomez Rodriguez2, Osamu Hashimoto1, Satoshi Hirose1, Hiroki Kanda1, Masashi Kaneta1, Eunhee Kim3, Junichiro Kusaka1, Kazushige Maeda,1 Amur Margaryan6, Harald Merkel2, Ulrich Muller2, Sho Nagao1, Satoshi N. Nakamura1, Josef Pochodzalla2, Christophe Rappold3,7, Joerg Reinhold8, Takehiko R. Saito2,3,7, Alicia Sanchez Lorente7, Salvador Sanchez Majos2, Bjorn Soren Schlimme2, Matthias Schoth2, Florian Schulz2, Concettina Sfienti2, Simon Sirca5, Liguang Tang9, Michaela Thiel2 A1 hypernuclear collaboration

Experimental Setup for hypernuclear study at the Super-FRS

The first experiment of the HypHI collaboration aimed to demonstrate the feasibility of the hypernuclear spectroscopy by means of heavy ion beam induced reactions. The final results show that the experimental method is viable for the study of hypernuclei [1, 2, 3]. The study of exotic hypernuclei which can not be produced in typical missing mass experiments involved at JPARC or JLab and MamiC is the topic of the future phases of the project[4]. The use of rare-isotope beams is mandatory to the study of exotic hypernuclei toward the protonand neutron-drip line. The Super-FRS is crucial to the future phases of the HypHI project at FAIR, a feasibility study of the Super-FRS capability toward high energy of several GeV had to be achieved. A dedicated apparatus for exclusive measurement can be set up within the fragment separator Super-FRS, as an alternative to the experimental apparatus devoted to inclusive measurement as it was performed during the first experiments of the HypHI project. A detection apparatus consisting of an additional set magnetic optics could be install in order to separate the π− meson of the mesonic weak decay of produced hypernuclei, while the second part of the Super-FRS is used as a fragment spectrometer to determine precisely the momentum of the fragment of hypernucleus of interest. Two different strategies have been investigated. The first strategy is to use a couple of dipole magnets in order to deflect the π− meson from the positively charged particles and fragments with a first dipole magnet. The induced deflection to the fragments is then compensated with the second magnet in order to allow them to enter appropriately the second part of the Super-FRS. The second approach consists of using a solenoid magnet in order to analyze the momentum of the π− meson while the fragments is to enter the second part of the Super-FRS as in the case of first approach. The detection apparatus is then to be considered to allow the vertex reconstruction of the hypernuclear decay. In the first case, detectors already developed and used in the first experiment of the HypHI project such as the fiber detectors can used in a similar way to track charged particles around the decay volume and in the upstream of the dipole magnets. π− meson are then detected with a set of a hodoscope wall and drift chambers already available from the first HypHI experiment in order to complete the information needed for the track reconstruction. In solenoid magnet approach, a dedicated detection apparatus has to be developed in order to perform the position and energy-loss measurements

High precision mass measurements of hypernuclei achievements and perspectives

A. Essera, S. Nagaoe, F. Schulza, P. Achenbacha, C. Ayerbe Gayosoa, R. Bohma, O. Borodinaa,b, D. Bosnarc, A. Botvinag, V. Bozkurtb, L. Debenjakd , M.O. Distlera, I. Friscicc, Y. Fujiie, T. Gogamie, M. Gomez Rodrigueza, O. Hashimotoe∗, S. Hirosee, H. Kandae, M. Kanetae, E. Kimb, Y. Kohla, J. Kusakae, A. Margaryan f , H. Merkela, M. Mihovilovicd , U. Mullera, S.N. Nakamurae, J. Pochodzalla†a,g, C. Rappoldb, J. Reinholdh, T.R. Saitoa,b,g, A. Sanchez Lorenteg, S. Sanchez Majosa, B.S. Schlimmea, M. Schotha, C. Sfientia, S. Sircad , L. Tangi, M. Thiela, K. Tsukadae, A. Webera, K. Yoshidab

Search for evidence ofΛ3nby observingd+π−andt+π−final states in the reaction of6Li+12C at2AGeV

The experimental data obtained from the reaction of Li-6 projectiles at 2A GeV on a fixed graphite target were analyzed to study the invariant mass distributions of d + pi(-) and t + pi(-). Indications of a signal in the d + pi(-) and t + pi(-) invariant mass distributions were observed with significances of 5.3 sigma and 5.0 sigma, respectively, when including the production target, and 3.7 sigma and 5.2 sigma, respectively, when excluding the target. The estimated mean values of the invariant mass for d + pi(-) and t + pi(-) signal were 2059.3 +/- 1.3 +/- 1.7 MeV/c(2) and 2993.7 +/- 1.3 +/- 0.6 MeV/c(2) respectively. The lifetime estimation of the possible bound states yielding to d + pi(-) and t + pi(-) final states were deduced to be as 181(-24)(+30) +/- 25 ps and 190(-35)(+47) +/- 36 ps, respectively. Those final states may be interpreted as the two-body and three-body decay modes of a neutral bound state of two neutrons and a Lambda hyperon, (3)(Lambda)n.

Search for evidence of

The experimental data obtained from the reaction of Li-6 projectiles at 2A GeV on a fixed graphite target were analyzed to study the invariant mass distributions of d + pi(-) and t + pi(-). Indications of a signal in the d + pi(-) and t + pi(-) invariant mass distributions were observed with significances of 5.3 sigma and 5.0 sigma, respectively, when including the production target, and 3.7 sigma and 5.2 sigma, respectively, when excluding the target. The estimated mean values of the invariant mass for d + pi(-) and t + pi(-) signal were 2059.3 +/- 1.3 +/- 1.7 MeV/c(2) and 2993.7 +/- 1.3 +/- 0.6 MeV/c(2) respectively. The lifetime estimation of the possible bound states yielding to d + pi(-) and t + pi(-) final states were deduced to be as 181(-24)(+30) +/- 25 ps and 190(-35)(+47) +/- 36 ps, respectively. Those final states may be interpreted as the two-body and three-body decay modes of a neutral bound state of two neutrons and a Lambda hyperon, (3)(Lambda)n.