Experimental study of the inclusiveη-spectrum fromp \bar p annihilations at rest in liquid hydrogen

The inclusive η-momentum spectrum from \(\bar p\) annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for $$\begin{gathered} p\bar p \to \eta \omega \left( {1.04_{ - 0.10}^{ + 0.09} } \right)\% ,\eta \rho ^0 \left( {0.53_{ - 0.08}^{ + 0.20} } \right)\% , \hfill \\ \pi a_2 \left( {8.49_{ - 1.10}^{ + 1.05} } \right)\% ,\eta \pi ^0 \left( {1.33 \pm 0.27} \right) \times 10^{ - 4} , \hfill \\ \end{gathered} $$ , and ηη(8.1±3.1)×10^?5. An upper limit for \(p\bar p \to \eta \eta '\) of 1.8×10^?4 at 95% CL was found. The ratio of the branching ratios is BR(η?)/BR(ηω)=0.51 _?0.06 ^+0.20 . For the ratio of branching ratios into two pseudoscalar mesons, we have BR(ηπ⁰)/BR(π⁰π⁰)=0.65±0.14, BR(ηη)/BR(π⁰π⁰), BR(η η ^′ )/BR(π⁰π⁰) at 95% CL, and BR(ηη)/BR(ηπ⁰).     

Experimental determination of the branching ratiosp\bar p \to 2\pi ^0 ,\pi ^0 \gamma,and 2γ at rest

The branching ratios of \(p\bar p\) annihilations into the neutral final states 2π⁰, π⁰γ, and 2γ are measured by stopping antiprotons in liquid hydrogen. They are \(B_{2\pi ^0 } = \left( {2.06 \pm 0.14} \right) \times 10^{ - 4} \) , \(B_{\pi ^0 \gamma } = \left( {1.74 \pm 0.22} \right) \times 10^{ - 5} \) , andB _γγ<1.7×10^?6 (95% c.l.).     

Interaction of food packaging material and selected food components under high pressure

Abstract

Interactions between ethanolic solutions of p-cymene and acetophenone and different polymer packaging materials. were studied at 500 MPa and 25° C. p-Cymene solution, filled into low-density polyethylene bags, lost 30% of its aroma concentration after 24 h at 500 MPa compared to a 60% loss at atmospheric pressure. The decrease was strongest within the first 15 min. Using LDPE/HDPE/LDPE bags, losses were 20% and 30%, resp. Applying the “bag in the bag” method, p-cymene concentrations measured inside and outside the inner bag has shown sorption by the pressurized film to be one third of that by the non-pressurized. In PET/AI/LDPE bags impermeable to p-cymene, sorption was confined to the inner LDPE layer and caused higher loss in the non-pressurized sample. Acetophenone has not been found to interact with the polymer during pressure treatment, while at atmospheric pressure sorption loss in aroma concentration was nearly 70% after 60 h.     

Combined stereoscopic particle image velocimetry and line integral convolution methods

The flow fields for a sphere sedimenting through a Newtonian and two non-Newtonian liquids near a wall in a square tank are investigated using 3-D stereoscopic particle image velocimetry (PIV) and line integral convolution (LIC) methods. The PIV data were taken using an angular stereoscopic configuration with tilt and shift arrangements for the Scheimpflug condition and a pair of liquid correction prisms. Data were recorded from planes perpendicular and parallel to the wall for each fluid case over a range of distances from the wall. The PIV and LIC results highlight significant differences in the wake structure for all three cases. Out of plane flow was also found to persist up to two sphere diameters downstream in the wake for all cases.     

Pionic and muonic X-ray transitions in liquid helium

Energies and intensities of pionic and muonic X-rays in liquid ⁴He have been measured with a Si (Li) detector. The energy shift due to strong interaction effects of the pionic 1s level in ⁴He was determined to be ?75.7±2.0 eV. The natural line width of this level is 45±3 eV. These values are compared with different theoretical predictions. Cascade calculations, including external Auger effect and sliding transitions, have been performed to reproduce the yields of the muonic and pionic transitions. The pionic 2p level width is deduced: $\text{Γ}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext>}}\text{= (1.1 ± 0.5) × 10}{}^{12}\text{sec}{}^{\mathrm{?1}}\text{=}\text{(7.2±3.3) × 10}{}^{\mathrm{?4}}\text{eV}$.     

Precision determination of the difference of the charge radii of 16O and 18O

The difference of the rms radii of the charge distribution of the oxygen isotopes was determined by a relative measurement of the muonic K-series X-rays. It is $\text{r(}{}^{18}\text{O) ? r(}{}^{16}\text{O) = (0.076 ± 0.005)}\text{fm}$.     

Optical potential calculations for the 1s level in pionic atoms

The Ericson-Ericson optical potential for theπ-nucleuss-wave interaction was extended to be applicable also for light nuclei. In particular, terms of order A^?1 were evaluated and the (π2N) dispersion was considered. From comparison with experimental data we found that considerable improvement could be achieved by introducing terms of order A^?1. The (π2N) dispersion was found to be repulsive and of the same magnitude as the absorption. The (πN) scattering lengths were deduced to be α₃?α₁=0.258±0.008m _π ^?1 and α₁+2α₃=?0.018±0.008m _π ^?1 .     

Pionic x-ray transitions in 3He

Pionic ³He atoms have been produced in a gaseous target. Energies and strong absorption broadening of the 2 → 1 and the 3 → 1 transition lines have been measured. The 1s level is shifted by 44 ± 5 eV by the (attractive) strong interaction, and the natural 1s level width is 42 ± 14 eV.     

Non-linear density dependence of the Δ-self-energy in nuclear matter and its implications in pionic atoms

The $\text{Δ(}\text{3}\text{2}\text{,}\text{3}\text{2}$) self-energy in a nuclear medium is shown to be highly non-linear in density, when proper care is taken of the virtual meson propagation in the medium and retardation effects. As a consequence the p-wave absorptive potential for pionic atoms diverges appreciably from the standard ρ² form. A fit to the existing data on pionic atoms is carried out with the new functional of the density and turns out to be as good as those with the ρ² functional. The successful fits with such different density functionals are due to a very narrow range of nuclear effective densities felt by the pion in the observed pionic atoms. The influence of these effects in related problems is discussed along with the suggestion to widen the range of nuclear densities felt by the pions by looking at other nuclear phenomena.     

Results on the measurement ofK-series X-rays from antiprotonic hydrogen

The X-ray spectrum emerging from a liquid-hydrogen target when stopping antiprotons was measured with high resolution in order to determine the strong interaction shift and width of the atomic 1s level. Owing to strong Stark quenching only weak structures could be observed. The upper limit of the yield of any one of theK-series transitions is 3.5×10^?4 (95% C.L.) per stopped antiproton, assuming no broadening of the 1s level. Possible identifications of the weak lines with theK-series transitions are discussed.