Abstract:We apply the picture proposed in a previous Letter, which relates the hyperon polarization in unpolarized hadron-hadron collisions to the left-right asymmetry in singly polarized reactions, to the production of different hyperons in reactions using different projectiles and/or targets. We discuss the different ingredients of the proposed picture in detail and present the results for hyperon polarization in the reactions such as pp, K − p, π ± p, and Σ − p collisions. We compare the results with the available d… Show more
“…Various models are proposed, assigned either to the quark-exchange [52,53,54,55,56,57] or to the meson-exchange picture [58,59,60,61,62]. But, there is still no theoretical description which is able to explain the experimental observations consistently [49].…”
Abstract. Results on Λ hyperon production are reported for collisions of p (3.5 GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about 90 MeV at a rapidity of y = 1.0, i.e. slightly below the center-of-mass rapidity for nucleonnucleon collisions, ycm = 1.12. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The Λ phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of the present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. Presumably, this finding results from an insufficient modelling in the transport models of the elementary processes being relevant for Λ production, rescattering and absorption. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing Λ polarization in the weak decay Λ → pπ − . Finite negative values of the polarization in the order of 5 − 20 % are observed over the entire phase space studied. The absolute value of the polarization increases almost linearly with increasing transverse momentum for pt > 300 MeV/c and increases with decreasing rapidity for y < 0.8.
PACS.25.75.Dw, 25.75.Gz
“…Various models are proposed, assigned either to the quark-exchange [52,53,54,55,56,57] or to the meson-exchange picture [58,59,60,61,62]. But, there is still no theoretical description which is able to explain the experimental observations consistently [49].…”
Abstract. Results on Λ hyperon production are reported for collisions of p (3.5 GeV) + Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI Helmholtzzentrum for Heavy-Ion Research, Darmstadt. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about 90 MeV at a rapidity of y = 1.0, i.e. slightly below the center-of-mass rapidity for nucleonnucleon collisions, ycm = 1.12. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The Λ phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of the present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. Presumably, this finding results from an insufficient modelling in the transport models of the elementary processes being relevant for Λ production, rescattering and absorption. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing Λ polarization in the weak decay Λ → pπ − . Finite negative values of the polarization in the order of 5 − 20 % are observed over the entire phase space studied. The absolute value of the polarization increases almost linearly with increasing transverse momentum for pt > 300 MeV/c and increases with decreasing rapidity for y < 0.8.
PACS.25.75.Dw, 25.75.Gz
“…The existing phenomenological approaches are, in more or less extent, fragmentary in reproducing the data (see, e.g., Refs. [24,25,26,27,28,29,30,31,32,33,34,35] and the references therein).…”
Transverse polarization of Λ 0 hyperons in inclusive photoproduction at xF > 0 is tackled within the framework of the quark recombination model, which has been successfully applied to the polarization of different hyperons in a variety of unpolarized hadron-hadron reactions. The results are compared with recent experimental data of HERMES.
“…Certainly, there have been proposed many models attempting to account for the results, e.g. [4,5,6,7,8,9,10,11,12,13,14,15,16], however neither of them is able to describe the complete set of the available measurements.…”
Section: Introductionmentioning
confidence: 99%
“…[4,5,6,7,8,9,10,11,12,13,14,15,16], however neither of them is able to describe the complete set of the available measurements.…”
Abstract. It is shown that the recent HERMES data on the transverse Λ 0 polarization in the inclusive quasi-real photoproduction at xF > 0 can be accommodated by the strange quark scattering model. Relations with the quark recombination approach are discussed.
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.