A double-hyperfragment event has been found in a hybrid-emulsion experiment. It is identified uniquely as the sequential decay of ( 6)(LambdaLambda)He emitted from a Xi(-) hyperon nuclear capture at rest. The mass of ( 6)(LambdaLambda)He and the Lambda-Lambda interaction energy DeltaB(LambdaLambda) have been measured for the first time devoid of the ambiguities due to the possibilities of excited states. The value of DeltaB(LambdaLambda) is 1.01+/-0.20(+0.18)(-0.11) MeV. This demonstrates that the Lambda-Lambda interaction is weakly attractive.
In Fig. 3 and its inset the vertical scales should be reduced by a factor of 4. This plotting error affects only the figure. All relevant quantities in the text and in the table are correct as published. We regret the oversight.The corrected version of Fig. 3 is reproduced here. This correction does not affect any results or conclusions of the published paper.FIG. 3. Inclusive ÿ ; K spectrum on Si at K 6 2 . The curves are the calculated spectra for the repulsive (solid) and shallow (dashed) -nucleus potentials, fitted to the measured spectrum. A value of the scaling factor and 2 per degree of freedom are shown for each fitting.
The experimental data obtained from the reaction of 6 Li projectiles at 2A GeV on a fixed graphite target were analyzed to study the invariant mass distributions of d + π − and t + π − . Indications of a signal in the d + π − and t + π − invariant mass distributions were observed with significances of 5.3 σ and 5.0 σ , respectively, when including the production target, and 3.7 σ and 5.2 σ , respectively, when excluding the target. The estimated mean values of the invariant mass for d + π − and t + π − 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 + π − and t + π − final states were deduced to be as 181 +30 −24 ± 25 ps and 190 +47 −35 ± 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 hyperon, 3 n.A hypernucleus, a subatomic system with at least one bound hyperon, is studied in order to deduce the information about fundamental hyperon (Y )-nucleon (N) and Y -Y interactions. Hypernuclei have been mainly studied by means of the missing-mass experiments with secondary-meson and primary-electron beams [1] and earlier with emulsion techniques and bubble chambers [2]. In these experiments, a variety of hypernuclei with the lightest hyperon, the hyperon, were produced and identified. However, the isospin of the produced hypernuclei is similar to that of the target nucleus in these experiments, since they are produced by the elementary process of converting one nucleon in the target nucleus into a hyperon.Information on the Λ-N interaction was already inferred from the hypernuclei in the vicinity of the β stability line * c.rappold@gsi.de † t.saito@gsi.de [3][4][5][6]. The nature of the Λ-N interaction for neutron-rich hypernuclei, in which the ΛN -ΣN coupling three-body force may play a role as described theoretically in Refs. [7-11], has not yet been studied in detail since only a few cases were observed, 10 Li [12], 7 He [13], and 6 H [14]. We thus search for other neutron-rich hypernuclei by means of induced reactions of heavy-ion beams.Neutron-and proton-rich hypernuclei can be indeed studied by using projectile fragmentation reactions of heavy-ion beams. In such reactions, a projectile fragment can capture a hyperon produced in the hot participant region to produce a hypernucleus [15][16][17][18][19]. They might also be produced in a multistage process, such as through a Fermi breakup decay of excited heavier hypernuclear spectators, possibly formed in peripheral collisions [19][20][21].We, the HypHI Collaboration, have proposed a series of experiments at the GSI Helmholtz Centre for Heavy Ion Research that would use induced reactions of stable heavy-ion beams and rare-isotope beams to produce 041001-1 0556-2813/2013/88(4)/041001 (6)
The solid state morphology of the main-chain liquid crystal BB-6
polyester was studied by
the small angle X-ray scattering (SAXS) method. The BB-6 polyester
forms isotropic, smectic A, and
crystal phases in the order of decreasing temperature; thereby its
crystallization is taking place from the
smectic A phase. The SAXS for the crystalline specimens prepared
by cooling the isotropic melt at a
rate of 10 °C min-1 shows the well-defined
reflection maxima which are attributable to the stacked
lamellar
structure. The lamellar spacings are distributed around 250 Å so
that an appreciable number of chain
foldings are included in a chain. The lamellar size is increased
by annealing the crystal like in other
crystallizable polymers. In contrast, it is not essentially
altered by annealing the smectic A phase. The
results show that the chain foldings exist at a thermodynamic
equilibrium in the smectic A phase. The
correlation length between the chain foldings is assumed approximately
to be 250 Å, which corresponds
to 15 times the length of the repeat unit.
A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy-ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear products of 6 Li projectiles on a carbon target at 2 A GeV was performed. Signals of the Λ-hyperon and 3 Λ H and 4 Λ H hypernuclei were observed for final states of p+π − , 3 He+π − and 4 He+π − , respectively, with significance values of 6.7, 4.7 and 4.9σ. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be 262 +56 −43 ± 45 ps for Λ, 183 +42 −32 ± 37 ps for 3 Λ H, and 140 +48 −33 ± 35 ps for 4 Λ H.
We have measured the asymmetric emission of protons from the nonmesonic decay of polarized (5)(Lambda)He produced by the (pi(+), K+) reaction. (5)(Lambda)He is an s-shell hypernucleus and its polarization is due to the Lambda. One expects to obtain direct information on the elementary weak Lambda-->p-->np process. The asymmetry parameter has been determined to be 0.24+/-0.22. The implication of the result is discussed.
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