B. Jongejans

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 − .

Backward production of a spin parity 1+ϱπ enhancement at 1.04 GeV

Abstract A spin-parity 1 + ϱπ enhancement is observed for the 3π mass spectrum in the reaction K − p → Σ − π + π + π − where events with a small (K − → Σ − ) momentum transfer are selected. The mass (1040 MeV) and width (230 MeV) of this enhancement are reminiscent of the A 1 → ϱπ bump which has mainly been observed in the diffractive-like processes. The cross section for this enhancement at 4.15 GeV/ c incident K − momentum is (3.6 ± 0.5) μ b.

Study of the reaction

Abstract Results are presented on effective-mass distributions, differentisl cross sections and longitudinal c.m. momentum distributions for the channels K − p → K − p π o , K o p π − and K − π + n , obtained from a sample of approximately 28 000 inelastic two-pronged interactions at 4.2 GeV/ c incident momentum. The results are in satisfactory agreement with the prediction of a generalized Veneziano-model corrected for (non-dual) π -and pomeron exchange. For the channel K − pπ o pomeron exchange contributes about 20% of the cross section. In the channel K − π + n the dual, pion and pomeron contributions are responsible for resp. 15%, 65% and 20% of the total cross section. We also present results on total and differential cross sections and spin-density matrix elements for the quasi two-body reactions K − p → K ∗− (890) p and K ∗o (890) n . These results are compared with single Regge-pole exchange model predictions. The reaction mechanism of K ∗− (890) production is dominated by the ω(θ) trajectory exchange with some admixture of π -exchange. The mechanism for K ∗o (890) production is dominated by π -exchange with some admixture of (A 2 ) trajectory exchange.

The reactions K−p → O−12+ at an incoming momentum of 4.25 GeV/c☆

A bubble-chamber study is presented of a 10 events/μb experiment using K− mesons of 4.25 GeV/c incident momentum. Differential and total cross sections are determined for 7 different reactions: K−p → K0n (la), → π0Λ (lb), → ηΛ (lc), → η′Λ (ld), → π−Σ (le), → π+Σ− (lf), K+ Ξ− (lg). The experimental characteristics in dσ/dt of each reaction are described: (la) shows a levelling off at t = 0 (GeV/c)2, a break at t = −0.6 (GeV/c)2 and no backward events, (lb) dσ/dt has a smooth behaviour and a measurable backward component with an indication of a dip at u = −0.2 (GeV/c)2, (1c) dσ/dt shows a dip in the region between t ≈ −0.2 and −0.4 (GeV/c)2, (ld) dσ/dt has a smooth behaviour; neither this reaction nor the preceding one shows a clear evidence for backward events, (le) dσ/dt has a break at t = −0.5 (GeV/c)2; there is a significant cross section in the backward region; (lf) and (lg) show mainly backward production. The polarization of the hyperon is measured in the reactions (lb), (lc), (ld) and (le) in the forward production peak. The statistics do not allow the detection of a definite structure in the polarization but the sign and magnitude are determined. An interpretation of the results is given in terms of a dual Regge model, including the effects of absorption as elaborated recently by several authors.

Production and decay properties of f′(1514) in K−p interactions at 4.2 GeV/c

Abstract Results are presented for the hypercharge exchange reaction K−p→f′(1514)Λ at a beam momentum of 4.15 GeV/c. Total and differential cross sections have been determined. The Λ polarization and the tensor meson density matrix elements are given as a function of t′.

A study of the hypercharge exchange reactions K−p → 1−12+ at an incoming momentum of 4.25 GeV/c

Abstract Results are reported of a study of the hypercharge reactions K−p → ωΛ (la), K−p → φΛ (lb), K−p → φ∑o (lc), K−p → ϱoΛ (ld), K−p → ϱo∑o (le), K−p → ϱ−∑+ (lf) in a 12 events/ub bubble chamber experiment using K−mesons of 4.25 GeV/c momentum. Total and differential cross sections are presented as well as the density matrix elements of the peripherally produced vector meson and (except for reaction (1f)) the hyperon polarization. For reactions (1a) and (1b) an amplitude analysis is performed. The mass and the width of the ϱ−, φ− and f-meson have been determined.

Lambda production in the fragmentation processes p→K− and K− →p Λ at 4.25 GeV/c

Abstract In the reaction K − +p→ Λ +X at 4.25 GeV/ c both the target fragmentation of the proton into lambda and the beam fragmentation of kaon into lambda have been studied. The sample consists of 21 000 Λ events with t >−1.0 (GeV/ c ) 2 and 9000 Λ events with u > −1.0 (GeV/ c ) 2 . Abundant π 0 and meson resonance production for residual masses M x c 2 is observed. In the t -channel of am effective exchange trajectory is deduced. which lies between the K and K(890) trajectories. In the u -channel the effective exchange trajectory is in good agreement with a nucleon trajectory. The extrapolated average pion multiplicities of the residual mass system in the t -channel are in very good agreement with the values measured in antiproton-proton annihilations at rest.

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) .

Study of the I = 32 K−π− elastic scaterring from the reaction K−p→K−π−pπ+ at 4.25 GeV/c incident K− momentum☆

Abstract Results on the elastic K−π− scattering have been obtained from a study of the K−π− system in 15 000 events of the type K−p→K−π−pπ+ at a K− beam momentum of 4.25 GeV/c. The on-mass-shell values of the spherical harmonic moments of the K−π− scattering angular distribution and the K−π− elastic cross section have been obtained by extrapolation to the pion pole. From these values we determined the s- and p-wave phase shifts δ03 and δ13 as a function of the effective mass of the K−π− system between threshold and 1.25 GeV/c2. The value of |δ03| is smaller than 17° for all mass values and the existence of a p-wave cannot be neglected. At mK−π− = 1.18 GeV/c2 there are two solutions for the phase shifts. On the average, the cross section of the K−π− elastic scattering over the region of the effective mass considered amounts to approximately 2.5 mb.