- th / 0 11 00 69 v 1 2 6 O ct 2 00 1 Analysis of the data on a + 0 - meson production from ANKE experiment

Recent results on the reaction pp → K + ¯ K 0 d (1) at T p = 2.645 GeV/c, obtained in the current experiment at ANKE spectrometer [1], are analysed phenomenologically. The purpose of the analysis is to answer the question whether these data give evidence for production of scalar a + 0 meson in the K ¯ K channel. The experimental K + ¯ K 0-mass spectrum from the reaction (1) is shown in Fig.1 (histogram). There are some arguments for resonance solution of this problem: i) The number of events observed in ANKE experiment [1] is in correspondence to what follows from theoretical estimations. Those theoretical predictions were based on the estimation of the production rate for a + 0 meson in a simple meson exchange model, see, ref. [2] for more details. ii) Theoretical estimations for nonresonance background [2] are expected to be strongly suppressed in comparison with what is seen at ANKE experiment. iii) The observed K + ¯ K 0-effective mass spectrum looks like a resonance or a rather sharp bump. Note that arguments i) and ii) are model dependent. The modern effective meson-nucleon theories of strong interactions are not able to predict cross sections for production of heavy mesons (m a ∼ 1 GeV) with high accuracy. What about argument iii), the allowed K ¯ K-mass interval is rather narrow (991.4 < M K ¯ K < 1037.3 MeV). That is why the phase volume limitations should already reproduce a resonance-like bump in the K ¯ K-mass spectrum. The complicating point of the situation is in the following: the expected width of a 0 meson (Γ a ∼ 80 MeV) is larger that the allowed K ¯ K-mass interval ∆m ∼ 40 MeV. That is why great efforts are to be performed to make distinction between resonance and nonresonance solutions. Let us consider first the case, when the reaction amplitude is considered to be constant. Then the shape of the K ¯ K-spectrum is given by phase space factor, i.e. dσ dm = N k q. (2) Here m is the mass of the K + ¯ K 0 system, k is the deuteron reaction c.m. momentum, q is the relative momentum of kaons in the K ¯ K system, and N is normalization constant. The distribution (2) is shown in Figure 1 by dotted curve. As it is seen from Figure, this …