A study of the strangeness production process pp~AA at threshold and intermediate energies has been performed doing a full coupled-channel (pp, AA) calculation. The elastic part of the pp and AA interactions has been derived from a one-boson-exchange version of the Bonn NN potential and a corresponding extension to the hyperon-nucleon case whereas the annihilation part is taken into account by introducing suitable optical potentials. The transition interaction between pp and AA is based on Kand K*-meson exchange. A reasonably good description of empirical cross sections as well as polarization data is achieved. It is demonstrated that the results are quite sensitive even to short-range modifications of the channel interactions. We also compare our model with other approaches and suggest a new experiment which would be able to check the very different predictions of the meson-exchange and constituent quark model, respectively.PACS number(s): 25.43.+t, 13.75.Cs, 21.30. +j
The annihilation of the nucleon-antinucleon (NN ) system into two mesons including , ii, g', p, co, 5, a&, a~, f2 as well as K and K is studied in a distorted-wave Born-approximation approach, in the conventional framework based on nucleon, delta-isobar, and hyperon (A, X, Y ) exchange. Results for branching ratios are in fair agreement with the data; they show a strong sensitivity to the kind of initial-state interaction used. For polarizations and backward differential cross-section data of pp -+~+m. , E K, there are characteristic discrepancies between experiment and model predictions;possible reasons are discussed.
The range of the NN interaction is re-examined. We find that differences in the Nb7 models do have an influence on the region where annihilation predominantly takes place. A NN model derived consistently within meson theory leads to an annihilation range around 1 fm in spite of the small Compton wavelength of the exchanged baryons usually advocated in range arguments. PACS: 13.75; 21.30 One motivation for the study of the NN system is the occurrence of annihilation effects since here one could hope to learn something about the internal structure of the nucleons. It was argued that from the range of this annihilation one can deduce informations on that domain in which the description of nucleonic forces in terms of meson exchange is losing its validity and where one has to pass over to a theory relying essentially on quark degrees of freedom [-lJ. In this context rather different ranges are usually attributed to the mechanisms themselves leading to annihilation. Within a meson-theoretical approach [-2, 3] annihilation proceeds via the exchange of baryons, the range of which is commonly related to their Compton wavelength of less than 0.2 fm. Alternatively, if we think nucleons and antinucleons being constituted out of quarks then annihilation is accomplished by a rearrangement of these quarks into mesons and/or quark-antiquark fusion I-4, 5J. Such processes can occur as soon as the confinement regions of the quarks overlap, so that the annihilation range is more or less given by twice the bag radius, i.e. between 0.5 and 1.1 fro, depending on the particular model.Recently Shibata [-6] presented an investigation on the N~7 system where he analyzed the range of the interaction in the annihilation channel by means of a simple, phenomenological potential which was fitted to a set of low-energy antiproton data newly obtained at LEAR [7J. The major conclusion drawn from this analysis was that annihilation predominantly takes place at distances of nucleons and antinucleons around 1 fro. On the first glance (and in accordance with widespread belief), this result, being by a factor of five larger than the nucleon Compton wavelength, seems to rule out any meson-theoretical description of annihilation processes and appears to clearly establish the decisive role of explicit quarkgluon dynamics in NN annihilation.The aim of the present paper is to show, however, that this conclusion (which, if true, would have farreaching consequences) is unjustified. We will demonstrate that the annihilation 'range' obtained from such an analysis depends in fact on the particular model applied. Furthermore and most importantly, we will present a baryon-exchange annihilation model which can indeed provide (almost) sufficient annihilation and moreover, in spite of the small nucleon Compton wavelength, leads to an annihilation 'range' comparable to Shibata's model. Our ModelsStarting point for our calculation is the recent Bonn NN potential [8] ; it includes not only traditional oneboson-exchange diagrams but also explicit 2~z-and 7zp-excha...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.