0000000000178749
AUTHOR
E. Klempt
PROTONIUM: The Mainz Cascade Model
Recent experiments at LEAR have studied extensively the properties of antiprotonic hydrogen, often also called protonium.
New states as observed by the Crystal Barrel experiment
Abstract The Crystal Barrel Detector has been in operation since October 1989. Results on the analysis of the annihilation of protonium at rest into three pseudoscalars is presented. The π 0 π 0 π 0 final state confirms the existence of ƒ 2 (1520)→π 0 π 0 . In the ηη system of the π 0 ηη final state an isoscalar J PC = 0 ++ resonance with a mass of 1560 MeV/c 2 and a width of 245 MeV/c 2 is observed. The identification with ƒ 0 (1590) is doubtful since the ηη' decay is not observed with the corresponding strength. Our analysis yields an upper limit for the relative branching ratio BR(ƒ 0 (1560)→ηη') BR(ƒ 0 (1560)→ηη) .
The muon magnetic moment
Muon mass and muon magnetic moment are not calculabIe within the theory of Quantum Eiectrodynamics; they rather define the reference acaie in which masses and energies should be determined when muons are used to test QED or to search for anomalous muon coupiings which couid provide the "raison d'@tre" for the muon. Oniy the anomaious part of the muon magnetic moment experimentaily determined with remarkable precision I), can be oaIculated 2~" Theory and experiment agree preciseiy once corrections being appiied for hadronic and weak processes which poiiute the immaculated fieid of QED at high momentum transfers. Muon mass and muon magnetic moment are, in particular, needed for the interpreta…
Antiproton-proton annihilation at rest into KKπ0π0
Abstract The annihilation channel p p →K + K − π 0 in liquid hydrogen at rest has been studied with the Crystal Barrel detector at LEAR. The measured branching ratio is: BR ( p p → K + K − π 0 )=(2.37±0.15)×10 −3 . A partial wave analysis shows that this reaction is dominated by the π (K K ) S , K K ∗ (892) and π φ (1020) intermediate states. Weak signals are observed for π a 2 (1320), π f 2 (1270), π f 2 ′(1525) and K(Kπ) S . A satisfactory description of the Dalitz plot requires the introduction of π (K K ) P intermediate states with at least one pole.
The πd scattering length from Kα X-rays
Abstract X-rays from the K α transition (2P → 1S) of the π − d mesic atom have been observed. Their energy, 2592.8 −2.0 +1.6 , has been measured by the critical absorber technique, using the M V absorption edge in bismuth. The strong interaction shift in the 1S state is −4.8 eV, corresponding to a scattering length a ( π d) = −(0.052 −0.017 +0.022 ) m π −1 , in agreement with recent calculations. The intensity ratio K α /K total = 0.548 ± 0.015.
P̅P annihilation at rest: annihilation dynamics and meson spectroscopy
Proton-antiproton annihilations provide an excellent tool to study the dynamics of quarks and gluons in the confinement region. Annihilations at rest into two mesons show selection rules which can be related to symmetries between SU(3) invariant amplitudes. In the annihilation process not only conventional (q\(\bar{\text{q}}\)) mesons are produced but also states which do not fit into the meson nonets. It is shown how knowledge of the atomic state of the pp system at annihilation can be used to restrict the possible quantum numbers of meson resonances.
Partial wave analysis inK-matrix formalism
A description is given of the K-matrix formalism. The formalism, which is normally applied to two-body scattering processes, is generalized to production of two-body channels with finalstate interactions. A multi-channel treatment of production of resonances has been worked out in the P-vector approach of Aitchison. An alternative approach, derived from the P-vector, gives the production amplitude as a product of the T-matrix for a two-body system and a vector Q specifying its production. This formulation, called Q-vector approach here, has also been worked out. Examples of practical importance are given.
Final states with strangeness from Crystal Barrel and Asterix
Abstract We discuss φ production in p p annihilation at rest from the Asterix and Crystal Barrel experiments and compare the branching ratios to similar final states without strangeness. The ωπ 0 φπ 0 production ratio is unexpectedly low. In the search for new states, the φπ0 mass spectrum shows no evidence for a resonance in the 1450 MeV/c2 mass range but the K☆K0π0 Dalitz plot shows interesting structure.