J.V. Major

Charged Σ hyperon production by K− meson interactions at rest

Abstract Bubble chamber pictures have been scanned for the interactions of stopping K− mesons in hydrogen. New determinations of the ratios γ= K − p →Σ − π + K − p →Σ + π − , R c = K − → charged particles K − p → all final states for K− meson interactions at rest, are presented, as well as the branching ratio B= Σ + → n π + Σ + → n + +, p π 0 . The values found for Rc, 0.664±0.011, and for B, 0.488±0.008, are in agreement with previous results. On the other hand, two values, resulting from different methods of analysis, have been found for γ, namely 2.38±0.04 and 2.35±0.07. They agree with one of the two previous precise measurements but are inconsistent with the other.

Kaon scattering and charged Sigma hyperon production in K-p interactions below 300 MeV/c

In an experiment on K--proton interactions in a hydrogen bubble chamber, the cross sections and angular distributions have been studied for elastic and charge-exchange scattering, and charged sigma hyperon production in the momentum range 90-300 MeV/c. Good agreement is found with previous cross sections except for the charge-exchange channel where the new values are 60% larger. The production distributions of the charged sigma hyperons and the polarisation of the Sigma + hyperon clearly indicate that P waves are present down to about 150 MeV/c, much lower than previously reported.

Charge-exchange scattering in K-p interactions below 300 MeV/c

Cross sections for K-p charge exchange, based on new data equal in statistics to the sum of those of all previous determinations below 300 MeV/c, are presented. The results confirm an earlier observation by this collaboration that the previous measurements of these cross sections at low momentum were significantly underestimated. Evidence for the presence of P wave scattering is presented.

A02 production by charge exchange in π+n interactions at 4 GeV/c

Abstract A partial wave analysis of the reaction π + n → π + π − π 0 p yields an A 0 2 production cross section of 225 ± 30μb for momentum transfer squared c ) 2 ; the differential cross-section and density matrix are presented and compared with ω 0 production in the light of theoretical models.

A search for spectator isobars in deuteron collisions

Abstract A search has been made for spectator delta resonances from the breakup of deuterons by a 4 GeV/c incident π+ beam. It is shown that the narrow pπ enhancement produced backwards in the laboratory system is mostly not Δ, and an upper limit of 0.8% is estimated for the Δ Δ component of the deuteron.

A study of ϱ0 and f0 production in 4 GEV/c π+d interactions

Abstract The production of ϱ 0 and f 0 mesons has been studied using a sample of 15485 fits to the reaction π + d → p s p π + π − at 4 GeV/ c . Results are presented on the spin structure and production mechanisms of these resonances. An Estabrooks and Martin analysis has been carried out in the ϱ 0 region, giving results similar to those obtained in their analysis of 17.2 GeV/ c data. Natural parity exchange is less important at our momentum, however. In the case of f 0 production, we find evidence for the presence of s-, p- and d-waves in the π π system. Averaging all events in the f 0 peak, the s- and d-waves are found to be close in phase. The f 0 production mechanism has been investigated using a positivity analysis of the complete J = 0, 1, 2 density matrix, and the same general features are observed as are seen in ϱ 0 production. However, the unnatural parity exchange component is found to be even more dominant in f 0 production than in ϱ 0 production. Our results are compared with the predictions of various models.

Backward production of meson resonances in 4 GeV/c π+ d interactions

Abstract We have studied the backward production of ϱ 0 , f 0 and ω 0 mesons at 4 GeV/ c . Results are presented on total and differential cross-sections, and on the spin density matrix elements. Our results suggest (i) that the three reactions studied are mediated by similar exchanges; (ii) that they resemble backward photoproduction data rather than backward elastic scattering data; and (iii) that substantial s-wave contributions could be present in the ϱ 0 and f 0 regions.

Branching ratios of the f0 meson

Branching ratios have been determined for the f0 meson produced in 4 GeV/c π+d interactions. The decay rates to 2π+2π− and KK are 2.4 ± 0.6% and 2.5 ± 1.5% respectively, both relative to the ππ mode. Upper limits are given for the decays to ηπ+π−, ηη and K±π±K0.

A partial wave analysis of the (3π)0 system from the charge exchange reaction π+n→π+π−πop AT 4 GeV/c

Abstract From a partial wave analysis of the (3 π ) o state in the charge exchange reaction π + n→ π + π − π o p, we observe strong unnatural parity as well as natural parity production. The observed strong unnatural parity states are identified with well-established resonances. The unnatural parity production is consistent with Reggeized Deck model predictions, with the exception of the I = 1, JP = 1 + state. Here there is no evidence for A 1 production at ∼1.1 GeV, but the data could support resonance production at higher masses.

Test of the vector dominance model by forward and backward ϱo and ωo production

We compare new data on π+n → ϱop and π+n → ωop at 4 GeV/c with single-pion photoproduction data. Good agreement is obtained with the predictions of the vector dominance model from unpolarized photoproduction data. However, in the forward direction, the proportion of natural parity exchange observed in vector meson production is much smaller than that predicted by the VDM from polarized photoproduction data.