φandωmeson production inppreactions atp

F. Balestra¹,

Y. Bedfer²,

R. Bertini³

et al.

Abstract

The exclusive production cross sections for and mesons have been measured in proton-proton reactions at p lab ϭ3.67 GeV/c. The observed / cross section ratio is (3.8Ϯ0.2 Ϫ0.9 ϩ1.2 )ϫ10 Ϫ3 . After phase space corrections, this ratio is enhanced by about an order of magnitude relative to naive predictions based upon the Okubo-Zweig-Iizuka ͑OZI͒ rule, in comparison to an enhancement by a factor ϳ3 previously observed at higher beam momenta. The modest increase of this enhancement near the production threshold is compared to the much larger increase of the / ratio observed in specific channels of p p annihilation experiments. Furthermore, differential cross section results are also presented which indicate that although the meson is predominantly produced from a 3 P 1 proton-proton entrance channel, other partial waves contribute significantly to the production mechanism at this beam momentum.

Dielectron production in Ar + KCl collisions at 1.76AGeV

“…− E thr ) notoriously exceeds predictions based on the φ-ω mixing angle and is sometimes related to a possible ss admixture in the nucleon ground-state wave function. Figure 8 shows R φ/ω obtained in this work and the THERMUS value from a fit to HADES data together with results from elementary p + p [42,43] and π + N [44] reactions, all plotted as function of the excess energy in the NN → NNφ and πN → Nφ reactions, respectively. This is different from the common definition in literature where the φ and ω yields are both taken at the same excess energy, corresponding hence to different bombarding energies, whereas we take the ratio of yields measured at a common beam energy.…”

Associated strangeness production in thepp→pK+K−pandXie1, Wilkin2 2010Phys. Rev. C

“…The results of the present calculation are compared with experimental data from Refs. [29] (closed circles), [42] (open square), [43] (closed squares), and [44] (open circle).…”

The legacy of the experimental hadron physics programme at COSY

“…The total cross sections measured at COSY for the non-φ contribution to the pp → ppK + K − reaction are shown in Fig. 73 along with one point measured earlier by the DISTO collaboration [168]. These show a steady rise with excess energy Q but the four-body phase space normalized in the 100 MeV region seriously underestimates the low energy data 6 .…”

“…In some experiments only the two final protons were measured [165,166] but in more refined approaches the π + and π − from the three-pion decay of the ω were detected in coincidence [167,168,169,170,171]. However, in all cases one is still faced with the problem of separating the ω signal from the background.…”

“…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.…”