122861815
Beam test of the CsI(Tl) calorimeter for the BELLE detector at the KEK-B factory
We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25-3.5 GeV. The prototype consisted of an array of 6 x 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm x 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/pi separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector.
121190690
Study of the radiation hardness of CsI(Tl) crystals for the BELLE detector
Abstract The radiation hardness of prototype CsI(Tl) crystals has been tested for the barrel electromagnetic calorimeter for the BELLE detector of the KEK B factory. Although samples made by one of the producers were found to be soft under irradiation, the problem was quickly improved when this information was fed back. All the tested crystals were found to meet our requirement. The light output was found to be almost uniform along a crystal, even when the front part was damaged by radiation. The damage causes a degradation of the attenuation length due to the formation of color centers; this conclusion was confirmed by a Monte Carlo ray-tracing study.
120641266
$K^-$-Nuclear Bound States in Relativistic Mean-Field Theory
118925554
Lambda Lambda interactions in finite-density QCD sum rules
The properties of Lambda hyperons in pure Lambda matter are studied with the finite-density quantum chromodynamics (QCD) sum rule approach. The first-order quark and gluon condensates in Lambda nuclear matter are deduced from the chiral perturbation theory. The sum-rule predictions are sensitive to the four-quark condensates, (2)(rho) and (rho) (rho), and the pi N sigma term. When (2)(rho) is nearly independent of density and (rho) (rho) depends strongly on density, we can obtain weakly attractive Lambda Lambda potentials (about several MeV) in the low Lambda density region, which agrees with the information from the latest double Lambda hypernucleus experiments. The nearly no-density dependence of (2)(rho) and strong density dependence of (rho) (rho) can be explained naturally if the properties of (2)(rho) and rho (rho) are assumed to be similar to those of pi pi and (K) over barK in nuclear medium, respectively.