C. J. Batty

Strong interaction physics from hadronic atoms

Strong interaction effects in kaonic, sigma and antiprotonic atoms are analyzed with density dependent (DD) t eff in a teff ρ approach to the optical potential. Different radial sensitivities are observed and the importance of realistic nuclear density distributions is demonstrated. For kaonic atoms the phenomenological DD potential can be related to the propagation of the Λ (1405) in the nuclear medium. For Σ − atoms the potentials can be related to a relativistic mean field (RMF) approach which places constraints on various meson-Σ hyperon coupling constant ratios. For \(\bar{p}\) atoms DD potentials enable reasonable p-wave terms to be accommodated. In all cases the low density limit can be respected with the DD potentials.

Density dependent K- nuclear optical potentials from kaonic atoms

Abstract The density depedence of the K − optical potential V opt ( r ) at zero kinetic energy is studied by fitting it to a comprehensive set of atomic data across the periodic table. Two families of solutions offering improved fits over that for a t eff ϱ ( r ) parameterization are identified, one containing solutions for V opt with r.m.s. radii larger than those of the matter density ϱ, as expected from finite-range folding corrections. The other gives rise to Re V opt of a size smaller than that of ϱ. The latter family offers substantially improved fits to the data, with particularly strong attraction inside the nucleus (200 ± 20 MeV). For a subfamily of solutions, V opt becomes repulsive at large distances, and solutions satisfying the low-density limit V opt → t K N ϱ can be found. Comments are made on the relevance of Λ(1405) nuclear dynamics to these findings.

High-statistics study of f0(1500) decay into π0π0

Abstract A partial-wave analysis of the reaction p p →π 0 π 0 π 0 has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f0(975) and f0(1300), the scalar resonance with mass m = (1500 ± 15) MeV and width Γ = (120 ± 25) MeV is necessary to describe the data.

Coupled channel analysis of pp annihilation into π0π0π0, π0ηη and π0π0η

We confirm the existence of the two IG(JPC) = 0+(0++) resonances f0(1370) and f0(1500) reported by us in earlier analyses. The analysis presented here couples the final states π0π0π0, π0π0η and π0ηη of pp annihilation at rest. It is based on a 3 × 3 K-matrix. We find masses and widths of M = (1390±30) MeV, Γ = (380±80) MeV; and M = (1500±10) MeV, Γ = (154 ± 30) MeV, respectively. The product branching ratios for the production and decay into π0π0 and ηη of the f0(1500) are (1.27 ± 0.33) · 10−3 and (0.60 ± 0.17) · 10−3, respectively.

Observation of a 2+ + resonance at 1515 MeV in proton-antiproton annihilations into 3π0

Abstract Antiproton-proton annihilations at rest into 3 π 0 are analyzed in terms of π 0 π 0 final state interactions. A J PC = 2 + + resonance at a mass of 1515 ± 10 MeV with a width of 120 ± 10 MeV is required to explain the data. This result is supported by previous observations made on the ππ system in p p and p n annihilations which show that the resonance has I = 0. This resonance is practically degenerate in mass with the f′ 2 (1525) but the two resonances have very different production and decay characteristics.

The pseudoscalar mixing angle ΘPS from ν and ν′ production in p annihiltion at rest

Abstract We have determined ratios of branching ratios for p p annihilations at rest into π 0 η and π 0 η ′, into ηη and ηη ′, and into ωη and ωη ′. All reactins are observed in two different all-neutral final states. The ratios permit a determination of the pseudoscalar mixing angle. We find Θ PS = −(17.3±1.8)°.

Density dependence of the Σ nucleus optical potential derived from Σ− atom data

Abstract We study phenomenologically the density dependence of the Σ nucleus optical potential V opt ( r ) at zero kinetic energy by fitting it to a comprehensive set of atomic data across the periodic table. The best fit solutions for V opt depart considerably from a standard t eff ϱ ( r ) form in that Re V opt tends to flip sign from attraction outside the nucleus to repulsion in the surface region. However, the quality of the atomic data is too poor to determine unambiguously V opt inside the nucleus. For such density dependent potentials, well defined single-particle hypernuclear states are unlikely to exist.

Proton-antiproton annihilation into ηηπ-observation of a scalar resonance decaying into ηη

Abstract The results of a measurement of pp annihilation at rest into ηηπ 0 are presented. Assuming a resonance dominated model for the annihilation process an isoscalar J PC =0 ++ resonance decaying into ηη is observed with a mass of 1560±25 MeV/ c 2 and a width of 245±50 MeV/ c 2 .

Observation of kaonic hydrogen atom X-rays

Abstract A special liquid-hydrogen target has been used with a stopping kaon beam in order to search for the X-rays from kaonic hydrogen atoms. A peak at 6.52 ± 0.06 keV, consistent with the unshifted energy of 2p-1s X-rays from K − −p atoms, has been observed with a yield of about 0.1%. The energy shift would imply rather small values for the real K − −p scattering length at threshold.

Measurement of kaonic and pionic X-rays from liquid helium

Abstract The strong interaction widths, shifts and relative intensities have been measured for the last observed X-ray transitions in kaonic and pionic helium. The effect of the strong interaction on the 2p level in kaonic helium was much larger than anticipated from optical-model calculations. The energy shift of the 2p level was determined to be −35±12eV and the natural line width 30±30eV, whereas optical-model calculations predicted a shift and width of approximately 0.1 eV and 2.0 eV, respectively.