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Close to threshold Λ production at COSY-11 with a polarized proton beam
| Content Provider | Semantic Scholar |
|---|---|
| Author | Grzonka, Dieter |
| Abstract | At present little is known about the strength of the hyperon– nucleon interaction at low energies (parameterized by the scattering length) and even less about its spin dependence. Most of the data are available for the Λ-p system but also here the experimentally extracted low energy parameters of s-wave scattering, the scattering length a and the effective range r, have large uncertainties. Furthermore, a clear separation of the spin singlet and triplet channels is not possible as long as no polarized target/beam system is used. A detailed analysis of the world data set for elastic Λp scattering gave as =−1.8+2.3 −4.2 fm and at =−1.6 +1.1 −0.8 fm [1] for the spin singlet and spin triplet scattering lengths, respectively, where the errors are strongly correlated. The reaction pp → K+pΛ at low excess energies has been investigated by the COSY-11 collaboration [2] to determine the low energy parameters of the ΛN interaction. An average value of −2± 0.2 fm for the ΛN scattering length was extracted in an analysis that utilizes the effective range expansion which, however, is only applicable for systems where the scattering length is significantly larger than the effective range. In addition, using this procedure one encounters strong correlations between the effective range parameters a and r that can only be disentangled by including other data, e.g. ΛN elastic cross sections, into the analysis [2]. A new method to determine the Λp scattering lengths was proposed in Ref. [3]. It allows the extraction of the Y N scattering lengths from the production data directly with a theoretical uncertainty of at most 0.3 fm. In Ref. [3] it was also shown that already a measurement of a single spin asymmetry in ~pp → Y NK allows to isolate the spin triplet contribution from the final Y N state, since the Pauli Principle strongly limits the number of structures possible for the initial state. It was especially shown that the asymmetry : d2σ(↑) dm′ 2dt − d2σ(↓) dm′ 2dt |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://ikpe1101.ikp.kfa-juelich.de/cosy-11/pub/annual_report_06/pkl.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
