Subthreshold Production of Low MomentumK+inp+Cat 1.2 GeV

Abstract

The double differential cross section of low momentum kaons (# 0.3 GeV͞c) from p 1 C collisions at subthreshold bombarding energies has been for the first time measured by the use of the CLAMSUD magnetic spectrometer installed at the CELSIUS storage ring. Invariant cross sections extracted from the data show a source rapidity shifted below the nucleon-nucleon rapidity, in agreement with the existence of multistep processes in the K 1 production cross section. The total cross section of the inclusive reaction 12 C͑p, K 1 ͒ at 1.2 GeV was extracted and compared with recent data systematics as a function of the proton bombarding energy. [S0031-9007 (98)06266-8] PACS numbers: 25.40.Ve, 25.40.QaWhile the production of pions at subthreshold energies, i.e., at energies lower than the threshold for free nucleonnucleon (NN) collisions, has been extensively studied both in proton-nucleus [1] and in nucleus-nucleus [2] collisions, only recently have the first data on the production of K 1 from proton-nucleus collisions in the subthreshold regime been published [3].

Phenomenological analysis ofK+-meson production in proton-nucleus collisions

“…Our analysis of the target-mass dependence of K + -meson production in pA collisions at T p ≤2.9 GeV show that, based on the existing data [1,2,3,5,6] • [4]. The line shows a fit to the data by Eq.7 with parameters listed in Table II.…”

“…• [4]. Again, the data can be well fitted by an exponential function with parameters given in Table II.…”

“…The data from Refs. [4,7] are not taken into account here, since only a single target material was used for these measurements. A similar analysis of the A dependence for meson production at high energies can be found in in Refs.…”

“…However, one cannot apply the commonly adopted x F analysis of the K + -data at energies below the free N N threshold, since a pN CMS with the nucleon at rest is kinematically not allowed. One may select an overall pA CMS [4], however then the joint analysis of subthreshold kaon production and the data available above the N N threshold becomes rather questionable.…”

“…Total K + -production cross sections have been measured at the PNPI synchrocyclotron for targets between Be and Pb and projectile energies T p between 0.8 and 1.0 GeV [1], i.e., at beam energies far below the free nucleon-nucleon threshold. Inclusive differential cross sections have been studied at BEVALAC [2], SATURNE [3] and CELSIUS [4]. Partial momentum spectra have been obtained at different laboratory emission angles in the range 10…”