Scalar-isovector K¯ production close to threshold

Abstract

The reaction pp→dK +K 0 has been investigated at excess energies Q= 47.4 and 104.7 MeV above the K +K 0 threshold at COSY-Jülich. Coincident dK + pairs were detected with the ANKE spectrometer, and subsequently ∼ 2000 events with a missingK 0 invariant-mass were identified, which fully populate the Dalitz plot. The joint analysis of invariant-mass and angular distributions reveals s-wave dominance between the two kaons, in conjunction with a p-wave between the deuteron and the kaon pair, i.e. KK production via the a + 0 (980) channel. Integration of the differential distributions yields total cross sections of σ(pp→dK +K 0 )=(38±2stat±14syst) nb and (190±4stat±39syst) nb for the low and high Q value, respectively. PACS. 25.10.+s Nuclear reactions involving few-nucleon systems -13.75.-n Hadron-induced low-and intermediate-energy reactions and scattering (energy ≤ 10 GeV)

Strangeness production in hadron reactions

“…They are from Refs. [2][3][4][5][6][7][8][9][10][11][12][13]. On a first view the cross sections seem to follow an universal curve except for the dd → K + K − α reaction, which is completely off the other data.…”

The legacy of the experimental hadron physics programme at COSY

“…3) An interpolation of the pn results to energies where pp → dK +K 0 was measured [270,271] gives isospin ratios of σ 0 /σ 1 = 0.9±0.9 at Q = 47 MeV and 0.5±0.5 at 105 MeV, Fig. 77.…”

“…The background for the a 0 (980) could be smaller in the K +K 0 charged channel and searches were undertaken at ANKE for scalar meson production in the pp → K +K 0 d reaction at proton beam energies of 2.65 GeV [270] and 2.83 GeV [271]. Selection rules play a very important role here because the combination of the Pauli principle and angular momentum and parity conservation do not allow all three final particles to be in relative s-waves.…”

“…The resulting total cross sections are shown in Fig. 77 along with those for pp → dK +K 0 [270,271].…”

“…Total cross section for non-φ KK production in nucleon-nucleon collisions near threshold. The closed circles denote pn → dK + K − data [273] and the open triangles pp → dK +K 0 [270,271], whereas the open circles show the results for pp → ppK + K − up to 2008 [256,257,258,261,168]. The dotted curve is the best fit to the pp → dK +K 0 data within a simple final state interaction model [103], whereas the solid curve includes also the isospin-zero contribution needed to describe the energy dependence of the pn → dK + K − total cross section.…”