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The measurement of strong interaction effects in high-Z sigma hyperonic atoms
Phillips, William Clarke
Phillips, William Clarke
Abstract
Strong-interaction effects have been observed in the X-ray spectra of atoms formed with {dollar}\Sigma\sp-{dollar} in lead and tungsten.;In the experiment, performed at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, negative kaons were brought to rest in a novel laminar target consisting of thin sheets of high-Z material in a liquid hydrogen bath. The geometry of the target was designed to optimize the production of high-Z {dollar}\Sigma\sp-{dollar} atoms and the detection of their subsequent de-excitation X rays. A method of identifying the energetic {dollar}\pi\sp+{dollar} from the production reaction K{dollar}\sp-{dollar}+ p {dollar}\to\Sigma\sp- +\pi\sp+{dollar} resulted in a factor of 15 improvement in the signal-to-noise ratio of the {dollar}\Sigma\sp-{dollar} atom X-rays over that of previous experiments. The X-ray spectra were recorded by three high-resolution intrinsic Ge detectors and analyzed for shifts, broadenings, and yield reductions of the final X-ray transitions before absorption of the {dollar}\Sigma\sp-{dollar} into the nucleus. A lineshape function which reflected the non-Gaussian response of the X-ray spectroscopy system was developed for this analysis. The results are(UNFORMATTED TABLE OR EQUATION FOLLOWS){dollar}{dollar}\eqalign{lcub}\rm \Sigma\sp- - W (10\to9): \varepsilon = 650 \pm 30 eV,&\quad\rm \Gamma = 380 \pm 70 eV,\quad \%Y = .98 \pm .04\cr \rm \Sigma\sp- - Pb (10\to9): \varepsilon = 510 \pm 50 eV,&\quad\rm \Gamma = 290 \pm 140 eV,\quad \%Y = .53 \pm .04\cr{rcub}{dollar}{dollar}(TABLE/EQUATION ENDS)where {dollar}\varepsilon{dollar} = E{dollar}\sb{lcub}\rm meds{rcub}{dollar} {dollar}-{dollar} E{dollar}\sb{lcub}\rm calc{rcub}{dollar}, {dollar}\Gamma{dollar} is the Lorentzian FWHM, and %Y is the ratio (measured yield)/(yield calculated with no strong interaction).;Optical model calculations with a = (0.928 + i0.022) fm are able to reproduce all observed effects in the {dollar}\Sigma\sp-{dollar}-W spectra. Such calculations with a = (0.247 + i0.039) fm reproduce the observed shift and width of the (10{dollar}\to{dollar}9) transition in {dollar}\Sigma\sp-{dollar}-Pb, but fail to reproduce the observed yield reduction. It is doubtful if the current status of the theory of {dollar}\Sigma\sp-{dollar}-N interactions can explain this discrepancy.
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1988
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8822126.pdf
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Physics
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https://dx.doi.org/doi:10.21220/s2-w5vk-pa03