R. Blokzijl

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.

The reactions K−p → Λπ0, Λη,Λη′ at 4.2 GeV/c

In a high statistics CERN 2 m bubble chamber experiment the differential cross sections and polarizations of the Λ for the reactions K−p → Λπ0, Λη, Λη′ at 4.2 GeV/c have been measured. The reaction K−p → Λη exhibits a pronounced dip around −t ∼0.5 (GeV/c)2 and all three reactions show a significant backward peaking (−u < 1.0 (GeV/c)2). The Λ polarization in the reaction K−p → Λπ0 is measured to be significantly different from zero throughout most of the available t-range. Forward cross sections enable a determination of RT, the ratio of singlet/octet coupling η1KK∗∗η8KK∗∗. Backward cross sections are utilized to estimate the effective η-nucleon coupling constant gηNN2 over the −u range 0–1.5 (GeV/c)2.

Non-strange vector meson production in K−p interactions at 4.2 GeV/c

Abstract The vector meson production, hypercharge exchange reactions K − p → ( φ , ω , ϱ ) Λ and ( φ , ϱ ) Σ 0 are studied at 4.2 GeV/ c incident momentum. The data come from a high statistics bubble chamber experiment with a sensitivity of ∼ 120 events/μb. Total and differential cross sections are presented. The vector meson density matrix elements and hyperon polarization are investigated as functions of momentum transfer. Amplitude analyses are performed for all five reactions. The results are compared with duality and quark model predictions, as well as used to test current ideas in two-body phenomenology.

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.

REACTIONS K

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.

sup -

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.

p

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.

Yields

Abstract Properties of Σ ± (1385) inclusively produced in 4.2 GeV/ c K − p interactions are studied. Inclusive cross sections are presented together with differential cross sections as functions of x and p t 2 for both Σ + (1385) and Σ − (1385). The complete density matrix for Σ + (1385) production at small momentum transfer is studied as a function of t and of recoil mass MM 2 . Substantial agreement with the predictions of the additive quark model is found. The Σ + (1385) production in the target fragmentation region is studied in the framework of the triple-Regge model.

0

The characteristics of the neutral kaons produced in the reaction 4.2 GeV/c K− + p → Ko + anything are compared with data at other momenta. A survey is made of medium-energy inclusive cross sections obtained by postulating σT(K−p) = σ−(K−) + σ−(Ko) + σ−(Y). The inclusive cross sections σ−(K−) and σ−(Ko) are found to be constant as functions of the incoming kaon momentum. Moreover, a comparison with inclusive K+ production in the reaction K+ + p shows σ−(K−) ≈ σ+(K+) ≈ 11.7 mb.