V. Chaloupka

Review of particle properties

Abstract This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 42 (1970) 87]. Data are evaluated, listed, averaged, and summarized in tables. A data booklet is also available.

Measurement of the total and partial p̄p cross section between 1901 and 1950 MeV

Abstract The presence of a structure in the pp total cross section at 1930–1940 MeV, with a narrow width of 9 MeV is confirmed. The interpretation of the effect as a single, non interfering, resonance is made difficult by the comparison of the elastic scattering with the charge exchange cross sections.

A study of π−π− scattering from π−p interactions at 3.93 GeV/c

Abstract A modified Chew-Low extrapolation procedure is applied to the reaction π − p→ Δ ++ π − π − to extract the I = 2 ππ elastic cross sections from threshold to 1260 MeV. The predictions of the one-pion-exchange model are used to estimate the contributions from background processes of the type π − p→ Δ 0 ϱ 0 . The moments of the π − π − angular distribution are also extrapolated to the pion pole and a phase shift analysis performed. The s-wave inelasticity is constrained using information on the inelastic cross section coming from six-body final states. The magnitude of the s-wave phase shift at the K 0 mass is found to be 7.2 0 ± 1.0 0 , increasing to 26.2 0 ± 2.5 0 at 1 GeV. d- and g-waves contribute above about 900 MeV, but the corresponding phase shifts are small compared with the s-wave. All three phase shifts have the same sign.

Production and decay properties of the δ (970) meson

Abstract Using an 880 events per microbarn sample of K − p interactions at 4.2 GeV/ c the production and decay properties of the δ (970) have been investigated in the following reactions: K − p → Σ + (1385) ηπ − and K − p ar Σ + (1385)K 0 K − .

Evidence for resonance behaviour of A1 and A3 mesons coherently produced on nuclei

Abstract An analysis of about 60 000 events produced in the reaction π − A → ( π + π − π − )A on nine different nuclear targets A at 8.9, 12.9, and 15.1 GeV/ c has been performed using the Illinois PWA program. In the A 1 region our “coherent” sample of events (which contains about 11% of incoherently produced events) is described by only four partial waves: the 1 + S and 1 + P amplitudes, which both show a peak, and the O − S and O − P waves, which are rather constant. We observed variations of both 1 + S and 1 + P phases relative to the O − P phase by about 90° across the A 1 peak. This observation suggests the presence of resonant 1 + waves in the A 1 mass region (∼1.1 GeV). In the A 3 region we observe that the 2 − state shows resonance behaviour and that fπ and ϱπ are two decays modes with amplitudes of opposite signs.

A partial-wave analysis of the 3π system in the reaction K−p → π+π−π0 Λ at 4.2 GeV/c

A partial-wave analysis of the (3π)0 system produced peripherally in the reaction K−p → π+π−π0 Λ at 4.2 GeV/c is presented. The observation of the weak Λ decay allows a determination of all the transversity production amplitudes except for two phases. The production of known resonances having decay modes other than 3π is used to test the isobar model ansatz. Significant ω(783), φ(1020) and A2(1310) production is observed. The spin parity of the ω∗(1675) is established as 3−. No evidence for production of other resonances, such as axial vector-mesons, is found.

Production and decay properties of the B meson

Abstract Results of a mass-independent spin-parity analysis of the μπ system from the reaction π − p → pμπ − at 3.9, 5 and 7.5 GeV/ c are presented. We obtain a unique JP = 1 + assignment for the B meson as well as results on its production density matrix and the D/S ratio of its decay.

Spin-parity structure of the (Kππ)0 system produced in the charge-exchange reaction K−p → (K0π+π−)n at 4.2 GeVc

Abstract A partial wave analysis of the K 0 π + π − system produced in the charge exchange reaction K − p → ( K 0 π + π − ) n at 4.2 GeV/ c has been performed both as a function of Kππ mass and of t ′. The 1 + S wave forms the largest contribution to the K ππ system and peaks at roughly the same mass as the Q in diffractive K ππ production. The polarization properties of the 1 + S ( K ∗ π) and 1 + S (Kϱ) waves differ fromt those of the diffractive 1 + wave. There is some evidence for a resonance contribution to 1 + S ( K ∗ π) . The strong 2 + wave the K ∗ (1420) and the K ϱ/ K ∗ ϱ decay branching ratio determined to be 0.36±0.10. An enhancement with spin-parity 1 − is observed under K ∗ (1420) .

Spin Parity Structure of the (anti-K pi pi)0 System Produced in the Charge Exchange Reaction K- p --> (anti-K0 pi+ pi-) n at 4.2-GeV/c

Abstract A partial wave analysis of the K 0 π + π − system produced in the charge exchange reaction K − p → ( K 0 π + π − ) n at 4.2 GeV/ c has been performed both as a function of Kππ mass and of t ′. The 1 + S wave forms the largest contribution to the K ππ system and peaks at roughly the same mass as the Q in diffractive K ππ production. The polarization properties of the 1 + S ( K ∗ π) and 1 + S (Kϱ) waves differ fromt those of the diffractive 1 + wave. There is some evidence for a resonance contribution to 1 + S ( K ∗ π) . The strong 2 + wave the K ∗ (1420) and the K ϱ/ K ∗ ϱ decay branching ratio determined to be 0.36±0.10. An enhancement with spin-parity 1 − is observed under K ∗ (1420) .

Axial vector meson production

Abstract Recently available differential cross section and density matrix information on π − p → B − p at 4 GeV/ c are successfully described in terms of t channel exchanges and s channel absorptive effects. The s channel helicity amplitude which is dominant at small | t | (zero net helicity flip ω exchange) is found to have a zero at − t = 0.2 GeV 2 . SU(3) and higher symmetries are used to predict cross sections for further axial vector meson production processes, in particular non-diffractive A 1 production. The importance of these processes with regard to Regge phenomenology and meson spectroscopy is emphasized.