Search

We have measured a proton energy from the stopped K- reaction on 4He to search for strange tribaryon states at KEK 12 GeV PS. No statistically significant signal was observed in the missing mass spectrum obtained by the inclusive 4He(stopped K-, p) measurement. Upper limits of the formation branching ratio at the 95 % C.L. were derived for neutral tribaryon states with strangeness -1 to be (0.4 ~ 6) × 10-4, (0.2 ~ 6) × 10-3 and (0.06 ~ 5) × 10-2/(stopped K-) for assumed natural widths of 0, 20 and 40 MeV/c2, respectively. [ABSTRACT FROM AUTHOR]

Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope 23O. The 22O fragments produced in one-nucleon removal from 23O at 938 MeV/nucleon in a carbon target were detected in coincidence with de-exciting γ rays, allowing to discern between 22O ground-state and excited-states contributions. From the comparison of exclusive experimental momentum distributions for the one-neutron removal channel to theoretical momentum distributions calculated in an Eikonal model for the knockout process, and spin and parity assignment of Iπ = 1/2+ was deduced for the 23O ground state. This result solved the existent experimental discrepancy. [ABSTRACT FROM AUTHOR]

The DEAR (DAΦNE Exotic Atom Research) experiment1 measured the energy of X-rays emitted in the transitions to the ground states of kaonic hydrogen. The shift ∊ and the width Γ of the 1s state are sensitive quantities for tests of the current understanding of the low energy antikaon-nucleon interaction. We obtain ∊1s=-193±37 (stat.)±6 (syst.) and Γ1s=249±112 (stat.)±30 (syst.). [ABSTRACT FROM AUTHOR]

The objective of DEAR (DAΦNE Exotic Atom Research) is the measurement of the Kα line shift and width, due to the strong interaction, in kaonic hydrogen and a similar measurement - the first one - in kaonic deuterium. The aim is a precision determination of the antikaon-nucleon isospin dependent scattering lengths in order to obtain the kaon nucleon sigma terms. In a first phase, dedicated to the calibration and optimization of the setup, the experiment collected data on kaonic nitrogen: for the first time a complex of three transitions (7 → 6 at 4.6 keV, 6 → 5 at 7.6 keV and 5 → 4 at 14 keV) was measured, and the corresponding yields obtained. The kaonic hydrogen measurement was performed for a total integrated luminosity of about 60 pb-1 in the last months of the 2002 year. Data analyses are in progress, preliminary results being hereby presented, together with those on kaonic nitrogen. [ABSTRACT FROM AUTHOR]

Abstract: Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon obtained in KEK PS-E471. In contrast to the previous proton spectrum, no narrow (∼20 MeV) peak structure was found either in the inclusive 4He(stopped , p) or in the semi-inclusive 4He(stopped , ) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to , has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure. [Copyright &y& Elsevier]

Abstract: We have measured proton and neutron energy spectra by means of time-of-flight (TOF) from 4He() reactions (KEK PS E471 experiment). In the proton spectrum, a clear mono-energetic peak was observed under semi-inclusive condition, which was assigned to the formation of a strange tribaryon S0(3115) with isospin . The mass and width of the state were deduced to be and , respectively, and its main decay mode was . In the neutron spectrum, a mono-energetic peak was found as the result of a detailed analysis, which was assigned to the formation of another kind of strange tribaryon S+(3140). The mass and width of the state were deduced to be and , respectively, and its main decay mode was . The isospin of the state is assigned to be 0. The results are compared with recent theoretical calculations. [Copyright &y& Elsevier]

The recent progress of a feasibility study at the RIKEN-RAL muon facility using the cold hydrogen film method to extend muonic atom spectroscopy to the use of radioactive isotope beams is being reported. This would allow studies of the nuclear properties and nuclear sizes of unstable nuclei by means of the muonic X-ray method at facilities where both intense negative muon and RI beams would be available. The first experimental results have just been obtained with stable argon ions implanted in solid deuterium films. [Copyright &y& Elsevier]

One-nucleon removal reactions at relativistic energies have been used as a spectroscopic tool to characterise the ground state properties of several neutron-rich isotopes in the sd-shell. Using the FRS at GSI, the longitudinal momentum distributions of the emerging fragments after one-nucleon removal were measured. The relative contributions of the remaining fragments in their ground and excited states have been determined from measurements of γ rays in coincidence with the longitudinal momentum distributions. In particular the breakup of 23O has been investigated. The interpretation of our measurements, in the framework of a simple theoretical model, favours a spin and parity assignment of 1/2+ for the 23O ground state in agreement with shell model predictions. [Copyright &y& Elsevier]

One-proton removal reactions of 936 MeV/u 8B have been studied with carbon and lead as breakup targets. Using the FRS at GSI, the longitudinal momentum distributions of the 7Be fragments and the one-proton removal cross section of 8B were measured. The relative contributions of the breakup channels leading to 7Be in its ground state and excited state at 429 keV (7Be*) have been determined from measurements of γ rays in coincidence with the fragments from the one-proton removal reaction. The experimental breakup data are discussed in the context of a theoretical (α+3He+p) three-body model. The combined data from the two targets allow a determination of the weight of the 7Be* component in the 8B ground state wave function as (13.3±2.2%) [Copyright &y& Elsevier]