Abstract
A partial wave analysis of antiproton–proton annihilation data in flight at 900 mathrm {MeV/}c into {pi ^0pi ^0eta }, {pi ^0eta eta } and {K^+K^-pi ^0} is presented. The data were taken at LEAR by the Crystal Barrel experiment in 1996. The three channels have been coupled together with pi pi -scattering isospin I = 0 S- and D-wave as well as I = 1 P-wave data utilizing the K-matrix approach. Analyticity is treated using Chew–Mandelstam functions. In the fit all ingredients of the K-matrix, including resonance masses and widths, were treated as free parameters. In spite of the large number of parameters, the fit results are in the ballpark of the values published by the Particle Data Group. In the channel {pi ^0pi ^0eta } a significant contribution of the spin exotic I^G=1^-J^{PC}=1^{-+}pi _1-wave with a coupling to pi ^0 eta is observed. Furthermore the contributions of phi (1020) pi ^0 and K^*(892)^pm K^mp in the channel {K^+K^-pi ^0} have been studied in detail. The differential production cross section for the two reactions and the spin-density-matrix elements for the phi (1020) and K^*(892)^pm have been extracted. No spin-alignment is observed for both vector mesons. The spin density matrix elements have been also determined for the spin exotic wave.
Highlights
Two decades ago pp annihilation data in flight from the Crystal Barrel experiment have already been analyzed by combining different channels [1,2]
The fitted mass and decay angular distributions for the reactions pp → π 0π 0η, π 0ηη and K + K −π 0 are compared with the data in Figs. 7, 8 and 9, respectively
The corresponding masses and widths are treated as free parameters so that these properties including their statistical uncertainties can directly be obtained from the outcome of the fit
Summary
Two decades ago pp annihilation data in flight from the Crystal Barrel experiment have already been analyzed by combining different channels [1,2]. Such an approach provides good means to face the challenges related to the large number of possible initial pp states and of overlapping resonances with the same quantum numbers in the light meson sector. The fundamental requirements of unitarity and analyticity are realized by making use of Chew–Mandelstam functions proposed by [7,8] The advantage of this description is that the search for resonances and the determination of their properties is not limited to the real axis of the complex energy plane where the data are located. In particular similarities between the pp annihilation processes into the channels φ(1020)π 0, K ∗(892)± K ∓ and the channels J/ψπ 0, D∗ Dconsisting of charm quarks can be expected
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