The first observation of the neutron-rich hypernucleus

Physical Review Letters, 2013

EPJ Web of Conferences, 2016

Negatively charged pions from two-body decays of stopped 4 Λ H hypernuclei were studied in 2012 at the Mainz Microtron MAMI, Germany. The momenta of the decay-pions were measured with unprecedented precision by using high-resolution magnetic spectrometers. A challenge of the experiment was the tagging of kaons from associated K + Λ production off a Be target at very forward angles. In the year 2014, this experiment was continued with a better control of the systematic uncertainties, with better suppression of coincident and random background, improved particle identification, and with higher luminosities. Another key point of the progress was the improvement in the absolute momentum calibration of the magnetic spectrometers.

Physical Review C, 2016

The missing mass spectroscopy of the 7 Λ He hypernucleus was performed, using the 7 Li(e, e ′ K +) 7 Λ He reaction at JLab Hall-C. The Λ binding energy of the ground state (1/2 +) was determined with a smaller error than that of the previous measurement, being BΛ = 5.55 ± 0.10 stat. ± 0.11 sys. MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at BΛ = 3.65 ± 0.20 stat. ± 0.11 sys. MeV was observed and assigned as a mixture of 3/2 + and 5/2 + states, confirming the "glue-like" behavior of Λ, which makes an unstable state in 6 He stable against neutron emission.

Physics Letters B, 2011

Nuclear Physics A, 1996

We searched for neutron-rich A hypernuclei in the products of (K~,p~d, 7r +) reaction with 9Be, t2C and ~60 targets. No peaks were observed in the A hypernuclear region in the measured 7r + momentum spectra. We set upper limits of the formation probabilities for 9aHe, IZBe and !~C.

Nuclear Physics A, 2012

The FINUDA experiment has recently completed an extensive study of the weak decay of p-shell Λhypernuclei including both mesonic and non-mesonic modes. Charged mesonic decay rates have been determined based on the analysis of π − kinetic energy spectra, never measured before. The study of proton spectra from non-mesonic weak decay for p-shell hypernuclei, both single and in coincidence with a neutron, has triggered the investigation of the two-nucleon induced ΛN N → nN N decay channel: its weight has been evaluated to be Γ 2 /Γ NM = 0.21 ± 0.07 stat +0.03 sys −0.02 sys. Finally, a direct experimental evidence of the occurrence of the weak reaction Λnp → nnp in nuclei is presented for the first time. Three events have been found which can be attributed to 7 Λ Li and 9 Λ Be two-nucleon induced non-mesonic weak decay; the kinematical analysis is discussed here.

2006

The production of neutron rich Λ-hypernuclei via the (K− stop,π+) reaction has been studied using data collected with the FINUDA spectrometer at the DA NE φ-factory (LNF). The analysis of the inclusive π+ momentum spectra is presented and an upper limit for the production of 6 ΛH and 7 ΛH from 6Li and 7Li, is assessed for the first time. © 2006 Elsevier B.V. All rights reserved. * Corresponding author. Fax: +39 080 5443151. E-mail address: [email protected] (B. Dalena). This paper is dedicated to the memory of our colleague and friend Valerio Filippini. 0370-2693/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physletb.2006.07.051 146 FINUDA Collaboration / Physics Letters B 640 (2006) 145–149

Physical review letters, 2001

An experiment demonstrating the production of double-Lambda hypernuclei in (K(-),K(+)) reactions on (9)Be was carried out at the D6 line in the BNL alternating-gradient synchrotron. The technique was the observation of pions produced in sequential mesonic weak decay, each pion associated with one unit of strangeness change. The results indicate the production of a significant number of the double hypernucleus (4)(double Lambda)H and the twin hypernuclei (4)(Lambda)H and (3)(Lambda)H. The relevant decay chains are discussed and a simple model of the production mechanism is presented. An implication of this experiment is that the existence of an S = -2 dibaryon more than a few MeV below the double Lambda mass is unlikely.

Physical Review Letters, 2012

Evidence for the neutron-rich hypernucleus 6 Λ H is presented from the FINUDA experiment at DAΦNE, Frascati, studying (π + , π − ) pairs in coincidence from the K − stop + 6 Li → 6 Λ H+π + production reaction followed by 6 Λ H → 6 He + π − weak decay. The production rate of 6 Λ H undergoing this twobody π − decay is determined to be (2.9±2.0)·10 −6 /K − stop . Its binding energy, evaluated jointly from production and decay, is BΛ( 6 Λ H) = (4.0 ± 1.1) MeV with respect to 5 H + Λ. A systematic difference of (0.98 ± 0.74) MeV between BΛ values derived separately from decay and from production is tentatively assigned to the 6 Λ H 0 + g.s. → 1 + excitation.

Physical Review C, 2003

We have measured the neutron spectra emitted in the weak decay of ⌳ 12 C and ⌳ 89 Y over the energy region above 10 MeV in the ͑ + , K + ͒ reaction with better statistics and an improved signal-to-background ratio. The neutron yields in the nonmesonic weak decays were obtained from the spectra. By using the proton yield of ⌳ 12 C, the ⌫ n /⌫ p ratio was estimated to be 0.51±0.15 ͑stat͒ from the neutron-to-proton yield ratio for the first time, which suggests the ⌫ n /⌫ p ratio is significantly less than unity.

Few-Body Systems, 2012

We have investigated theoretically a feasible nuclear reaction to produce light double-Λ hypernuclei by choosing a suitable target. In the reaction from stopped Ξ − on 6 Li target light doubly-strange nuclei, 5 ΛΛ H and 6 ΛΛ He, are produced: we have calculated the formation ratio of 5 ΛΛ H to 6 ΛΛ He for Ξ − absorptions from 2S, 2P and 3D orbitals of Ξ −-6 Li atom by assuming a d-α cluster model for 6 Li. From this cluster model the d-α relative wave functions has a node due to Pauli exclusion among nucleons belonging to d and α clusters. Two kinds of d-α wave functions, namely 1s relative wave function with a phenomenological one-range Gaussian (ORG) potential and that of an orthogonality-condition model (OCM) are used. It is found that the probability of 5 ΛΛ H formation is larger than that of 6 ΛΛ He for all absorption orbitals: in the case of the major 3D absorption their ratio is 1.08 for ORG and 1.96 for OCM. The dominant low momentum component of the d-α relative wave function favors the 5 ΛΛ H formation with a low Q value compared to the 6 ΛΛ He formation with a high Q value. We have also calculated momentum distributions of emitted particles, d and n, displaying continuum spectra for single-Λ hypernuclei, 4 Λ H and 5 Λ He, and line spectra for the 5 ΛΛ H and 6 ΛΛ He nuclei. Thus, our present theoretical analysis would be a significant contribution to experiments in the strangeness-2 sector of hypernuclear physics.

2007

Exchange reactions with Dick Dalitz 11 A. Gal The hypernuclear physics heritage of Dick Dalitz (1925-2006) Spectroscopy of Hypernuclei 17 Y. Ma et al. γ-ray spectroscopy study of 11 Λ B and 12 Λ C* 21 M. Ukai et al. Observation of the 7 MeV excited spin-flip and nonspin-flip partners in 16 Λ O by γ-ray spectroscopy* 25 T. Koike et al. Next generation hypernuclear γ-ray spectrometer: Hyperball-J 29 J.J. LeRose et al. Hypernuclear spectroscopy in JLab's Hall A 33 S. Marrone et al. 9 Λ Li and 16 Λ N high resolution spectroscopy by electron scattering at Jefferson Lab in Hall A 37 F. Cusanno et al. High resolution hypernuclear spectroscopy at Jefferson Lab, Hall A: The experimental challenge 41 O. Hashimoto et al. Recent results of the JLab Hall C hypernuclear experiment E01-011 47 A. Margaryan RF picosecond timing technique and new possibilities for hypernuclear studies 51 S.N. Nakamura Future hypernuclear experiments at JLab 57 M. Agnello et al. The FINUDA Collaboration A study of 7 Λ Li production with FINUDA 61 P. Gianotti FINUDA: A hypernuclear factory 67 A. Feliciello One step beyond: Hypernuclear γ-ray spectroscopy with FINUDA 73 T. Nagae Strangeness nuclear physics at J-PARC 79 P. Achenbach Probing hypernuclei at PANDA and at MAMI-C 85 D.J. Millener Gamma decay studies of hypernuclei-Theoretical situation Weak Decays 93 M. Agnello et al. The FINUDA Collaboration Study of the proton weak decay of 12 Λ Cg.s. with FINUDA*

2012

An experiment with a newly developed high-resolution kaon spectrometer (HKS) and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab (JLab). The ground state of a neutron-rich hypernucleus, 7 Λ He, was observed for the first time with the (e, e ′ K +) reaction with an energy resolution of ∼0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The 7 Λ He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear iso-triplet, providing a new input for the charge symmetry breaking (CSB) effect of ΛN potential.

2011

A direct experimental evidence of the occurrence of the weak reaction $\Lambda np\rightarrow nnp$ in nuclei has been obtained by the FINUDA experiment. Three events have been found that can be attributed to $^{7}_{\Lambda}$Li and $^{9}_{\Lambda}$Be two nucleon-induced non mesonic weak decays. The kinematic analysis of such events is presented here.

Progress of Theoretical and Experimental Physics, 2018

A double-hypernucleus, Be, was observed by the J-PARC E07 Collaboration in nuclear emulsions tagged by the (K − , K +) reaction. This event was interpreted as the production and decay of 10 Be, 11 Be, or 12 Be * via − capture in 16 O. By assuming capture in the atomic 3D state, the binding energies of two hyperons (B) of these double-hypernuclei are obtained to be 15.05 ± 0.11 MeV, 19.07 ± 0.11 MeV, and 13.68 ± 0.11 MeV, respectively. Based on the kinematic fitting, 11 Be is the most likely explanation for the observed event.