A measurement of the K + total cross sections on carbon and deuterium and their ratios from 450 to 740 MeV/c has been carried out at the Brookhaven Alternating Gradient Synchrotron. The observed ratios depart significantly from those expected from conventional nuclear physics calculations. The data are compared with models of nucleon "swelling," which ascribe the effect to quark deconfinement or, alternatively, to vector-meson exchange with density-dependent masses.PACS numbers: 25.80.Nv, 12.40.Aa, 13.75.Jz The low-momentum AT + holds a very special position as the weakest of any available strongly interacting probes. It has a mean free path in the nucleus larger than 6 fm. Thus the K + is capable of probing the entire volume of the nucleus. l Single scattering of the K + with a nucleon in the nucleus dominates scattering, and only small and calculable higher-order corrections are needed. These properties make the K + the ideal hadronic probe of nuclear-medium effects, and a useful complement to leptonic or electromagnetic probes. The nucleon is a dynamical entity and its internal structure can, in principle, be altered by its surrounding nuclear environment. This work reports an experiment in which the K + is used to compare the nucleon in the nucleus with a free nucleon.Siegel, Kaufmann, and Gibbs, 2 recognizing the special properties of the K + probe and its analogy to the leptonic probes of the European Muon Collaboration (EMC) effect, argued that if the nucleons in the nucleus "swell" (partial deconfinement), the effect could be detected by measuring the ratio of the K + total cross section on carbon to that on deuterium. At low momenta ( < 800 MeV/c) the K*N interaction is dominated by the S\\ channel. The authors predicted that a 10% increase in nucleon size carries with it a (5-10)% increase in Ss n . Such an increase would be consistent with that of the quark-confinement scale predicted by Close et al. 3 Siegel, Kaufmann, and Gibbs calculated the abovementioned ratio in an optical model and concluded that an increase of 10% in the S\\ K*N phase shift would result in ratios significantly higher than the upper limits of the calculation with free K~*~N phase shifts and conventional medium corrections which do not include nucleon "swelling."Brown, Dover, Siegel, and Weise 4 took another view of the swelling effect and pointed out that in mesonexchange models of the K + N interaction, p and co exchanges play a dominant role. The vector-meson mass is density dependent which in turn implies a densitydependent K + N scattering amplitude. The elastic scattering and reaction cross sections were then calculated in an optical potential derived from the scattering amplitude. They also calculated the ratio of total cross sections of K*C to K*d, with the result that a reasonable density parameter produced an increase in the ratio similar to the predictions of Siegel, Kaufmann, and Gibbs. Weise 5 has compared these alternative models and discussed their interpretation in terms of nucleon swelling. In this paper, the ...

1. Until recently studies of intestinal aluminium absorption used pharmacological amounts of stable 27Al. 2. To examine the intestinal absorption of trace amounts of different chemical compounds of aluminium, in the present study we have employed the long half-life isotope of aluminium, 26Al, and accelerator mass spectrometry. Trace amounts of 26Al (2.7-12.1 ng) as the hydroxide, citrate, citrate plus 1 mmol/kg sodium citrate, or maltolate respectively, were administered to four groups of rats (n = 9 per group) by gavage. Blood and urine samples were collected for 5 h and the 26Al content (as a percentage of the administered dose) determined by accelerator mass spectrometry. 3. The 5 h urinary 26Al excretion amounted to 0.1 +/- 0.02, 0.7 +/- 0.2, 5.1 +/- 1.5 and 0.1 +/- 0.1% of administered dose in the four groups respectively. There was a strong positive correlation between peak plasma 26Al (r = 0.98) and urinary 26Al excretion in individual animals (P < 0.001). 4. We conclude that the fractional intestinal absorption of trace oral doses of aluminium hydroxide is at least 0.1% (compared with the previous estimate of 0.01% using large 27Al oral loads). Absorption of aluminium citrate given alone is significantly greater (0.7%) and is further increased to 5% by the accompanying sodium citrate, consistent with an enhancing effect of added citrate upon mucosal aluminium permeability. Aluminium maltolate absorption approximates that of aluminium hydroxide (0.1%).

Pion absorption in He was studied at T =62.5 and 82.8 MeV using nucleon-nucleon coincidences, For~+ absorption on proton-neutron pairs the differential cross section is the same as that for n. ++d~p+p except for an increase by a factor of about 1.5. For m absorption on the proton-proton pair, the differential cross section is asymmetric about 90', indicating possible isospin mixing. The total cross sections Op, (m+) are 10.2%0.9 mb and 13.5+1.3 mb at 62.5 and 82.8 MeV and for opp(~) are 0 70%0 07 mb and 0 92+0 10 mb at 62 5 and 82 8 MeV The three body absorption cross sections for m+ and n are found to be comparable to each other and show no strong energy dependence. The three-body absorption cross section 03(m+) is 6.7%2.5 mb and 5.7+2.3 mb and for m, a3(m ) is 8.7+1.4 mb and 6.5+2.0 mb at 62.5 and 82.8 MeV, respectively.

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