Plasma-Wakefield Accelerator Group

Abstract:

A new determination of the QA-QB mixing angle and of the antisymmetric coupling for the vector-pseudoscalar decay of the axial vector mesons is presented. This uses information from the decay rates of the A1 and C mesons found in the study of baryon exchange processes in K^-p interactions at 4.2 GeV/c combined with the decay rate B → ωπ. The consistency between the results obtained from backward produced A1 and C and diffractively produced Q1 and Q2 is discussed. © 1979.

Abstract:

We have observed e⁺e^- hadrons at C.M. energies of 13 GeV and 17 GeV at PETRA using the TASSO detector. We find R(13 GeV) = 5.6 ± 0.7 and R(17 GeV) = 4.0 ± 0.7. The additional systematic uncertainty is 20%. Comparing inclusive charged hadron spectra we observe scaling between 5 GeV and 17 GeV for x = p/pbeam > 0.2; however the 13 GeV cross section is above the 17 GeV cross section for smaller x. This may be due to copious bb̄ production. The events become increasingly jet like at high energies as evidenced by a shrinking sphericity distribution with increasing energy. © 1979.

Abstract:

The total and differential cross sections of the reactions K^-p → π⁰Λ (1520), ηΛ(1520) and η′ Λ(1520) have been measured. Prominent forward peaks are onserved in all three reactions. The first reaction shows also a backward peak. The spin density matrix elements of the Λ(1520) in this reaction are determined. For forward production the results show a remarkable alignment of the Λ(1520) corresponding to an M2 transition in the model of Stodolsky-Sakurai for 3 2^- baryon production. © 1979.

Abstract:

A partial-wave analysis and an isospin analysis are presented of the (Kππ)^- systems produced in the reactions K^-p→K^-π^-π⁺ and K^-p→K⁰π^-π^-p u sing the high-statistics bubble-chamber data at 4.2 GeV/c. The energy dependence of J^P = 1⁺ waves is investigated in a comparison with results at higher energy. The dominant 1⁺0+ (K^*π) with its maximum in the Q2 (1.4 GeV) region is an almost pure I = 1 2 state. The energy dependence of 1⁺0+ (K^*π) at low masses is consistent with pomeron exchange while at higher masses (including the Q2 region) other natural exchanges are involved. The 1^*1+ (Kρ{variant}) has its maximum at about 1.3 GeV. The relative phase between these two 1⁺ states is consistent with Q1-Q2 contribution to the 1⁺ state. Properties of the Q resonances are obtained in a fit of a two-resonance model to the 1⁺ date. There is no clear evidence for the 0^- resonance seen at SLAC. © 1979.