Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userComparison of Lambda and Sigma(0) Threshold Production in Proton-Proton Collisions
64
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Threshold measurements of the associated strangeness production reactions pp --> p K(+) Lambda and pp --> p K(+) Sigma(0) are presented. Although slight differences in the shapes of the excitation functions are observed, the most remarkable feature of the data is that at the same excess energy the total cross section for the Sigma(0) production appears to be about a factor of 28 smaller than the one for the Lambda particle. It is concluded that strong Sigma(0)-p final state interactions, and in particular the Sigma-N --> Lambda-p conversion reaction, are the likely cause of the depletion for the yield in the Sigma signal. This hypothesis is in line with other experimental evidence in the literature.
rate research
Read More
This paper reports results on simultaneous measurements of the reaction channels pp -> pK+Lambda and pp -> pK+Sigma^0 at excess energies of 204, 239, and 284 MeV (Lambda) and 127, 162, and 207 MeV (Sigma^0). Total and differential cross sections are given for both reactions. It is concluded from the measured total cross sections that the high energy limit of the cross section ratio is almost reached at an excess energy of only about 200 MeV. From the differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution of interfering nucleon resonances to the Lambda production mechanism is concluded while resonant Sigma^0-production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel. The data also indicate that kaon exchange plays a minor role in the case of Lambda- but an important role for Sigma^0-production. Thus the peculiar energy dependence of the Lambda-to-Sigma^0 cross section ratio appears in a new light as its explanation requires more than mere differences between the pLambda and the pSigma^0 final state interaction. The data provide a benchmark for theoretical models already available or yet to come.
The production of $Sigma^{0}$ baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to $sqrt{s_{NN}}=3.18$ GeV) is studied with the detector set-up HADES at GSI, Darmstadt. $Sigma^{0}$s were identified via the decay $Sigma^{0} rightarrow Lambda gamma$ with subsequent decays $Lambda rightarrow p pi^{-}$ in coincidence with a $e^{+}e^{-}$ pair from either external ($gamma rightarrow e^{+} e^{-}$) or internal (Dalitz decay $gamma^{*}rightarrow e^{+} e^{-}$) gamma
The momentum spectra of K+ produced at small angles in proton-proton and proton-deuteron collisions have been measured at four beam energies, 1.826, 1.920, 2.020, and 2.650 GeV, using the ANKE spectrometer at COSY-Juelich. After making corrections for Fermi motion and shadowing, the data indicate that K+ production near threshold is stronger in pp- than in pn-induced reactions. However, most of this difference could be made up by the unobserved K0 production in the pn case.
Exclusive data on the reactions pp -> ppK+K- and pp -> pK+ Lambda/Sigma0 have been taken at the cooler synchrotron COSY close to threshold. At equal excess energies, an enhancement of the Lambda/Sigma0 ratio by one order of magnitude has been observed compared to data at higher excess energies. New results obtained at the COSY-11 facility explore the transition region between this low-energy Sigma0 suppression and excess energies of 60 MeV. A first total cross section for elementary antikaon production below the phi threshold has been determined, two orders of magnitude smaller compared to kaon production at the same excess energy.
The inclusive production of {Lambda} hyperons in proton-proton collisions at $sqrt{s}$ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {Sigma}(1385), {Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK$^+${Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {Lambda} production cross section in p+p collisions at $sqrt{s}$ = 3.18 GeV of {sigma}(pp $to$ {Lambda} + X) = 207.3 $pm$ 1.3 +6.0 -7.3 (stat.) $pm$ 8.4 (syst.) +0.4 -0.5 (model) {mu}b is found.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
