Associated strangeness production at threshold

P. Kowina; M. Wolke; H.-H. Adam; A. Budzanowski; R. Czyzykiewicz; D. Grzonka; M. Janusz; L. Jarczyk; B. Kamys; A. Khoukaz; K. Kilian; T. Lister; P. Moskal; W. Oelert; T. Rozek; R. Santo; G. Schepers; T. Sefzick; M. Siemaszko; J. Smyrski; S. Steltenkamp; A. Strzalkowski; P. Winter; P. Wüstner; W. Zipper

doi:10.1140/epja/i2002-10234-2

EPJ

Associated strangeness production at threshold

P. Kowina¹^,2^*, M. Wolke¹, H.-H. Adam³, A. Budzanowski⁵, R. Czyzykiewicz⁴, D. Grzonka¹, M. Janusz⁴, L. Jarczyk⁴, B. Kamys⁴, A. Khoukaz³, K. Kilian¹, T. Lister³, P. Moskal¹^,4, W. Oelert¹, T. Rozek¹^,2, R. Santo³, G. Schepers¹, T. Sefzick¹, M. Siemaszko², J. Smyrski⁴, S. Steltenkamp³, A. Strzalkowski⁴, P. Winter¹, P. Wüstner⁶ and W. Zipper²

¹ IKP, Forschungszentrum Jülich, D-52425, Jülich, Germany
² Institute of Physics, University of Silesia, PL-40-007, Katowice, Poland
³ IKP, D-48149, Münster, Germany
⁴ Institute of Physics, Jagellonian University, PL-30-059, Kraków, Poland
⁵ Institute of Nuclear Physics, PL-31-342, Kraków, Poland
⁶ ZEL, Forschungszentrum Jülich, D-52425, Jülich, Germany

Abstract

The associated strangeness dissociation at threshold has been studied at the COSY-11 facility measuring the hyperon and the K ⁺ K ^- meson pair production. Measurements of the near-threshold $\Lambda$ and $\Sigma^0$ production via the $pp \rightarrow p K^ + \Lambda/\Sigma^0$ reaction (S. Sewerinet al., Phys. Rev. Lett. 83, 682 (1999)) at COSY-11 have shown that the $\Lambda/\Sigma^0$ cross-section ratio exceeds the value at high excess energies ( $Q\ge 300$ MeV (A. Baldiniet al., Total Cross-Sections for Reactions of High-Energy Particles, Landolt-Börnstein, New Series, Vol. I/12 (Springer, Berlin, 1988))) by an order of magnitude. For a better understanding additional data have been taken between 13 MeV and 60 MeV excess energy. The near-threshold production of the charged kaon-antikaon pair is related to the discussion about the nature of the scalar states in the 1 GeV/c ² mass range, i.e. the f ₀(980) and a ₀(980) (O. Krehl, R. Rapp, J. Speth, Phys. Lett. B 390, 23 (1997)). The interpretation as a $K \overline{K}$ molecule is strongly dependent on the K- $\overline{K}$ interaction which can be studied via the production channel. A first total cross-section value on the reaction $pp \rightarrow pp K^ + K^-$ at an excess energy of 17 MeV (C. Quentmeieret al., Phys. Lett. B 515, 276 (2001)), i.e. below the $\phi$ production threshold, was measured.

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EPJ

Associated strangeness production at threshold

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