M. Aguilar-Benitez

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.

Charm D-meson production in 360 GeV/cπ−p interactions; Evidence for leading quarks

Abstract Charm D-meson production in 360 GeV π−p interactions has been studied using the high-resolution hydrogen bubble chamber LEBC and the European Hybrid Spectrometer. The data show evidence for leading quark effects both in the number of D-meson types and in the Feynman x distributions. The production cross section is of the form d 2 δ d x d p T 2 ∞(1-x) n exp (-ap T 2 ) with n = 2.8±0.8 and a = 1.1±0.3 (GeV/c)−2. The x distribution is, however, compatible with the presence of both central (n = 6) and leading (n = 1) D / D production. The fraction of D-messons in the leading component is estimated to be ≈30%. The rapidity gap between members of reconstructed charm pairs is small compared to the available rapidity range. The inclusive cross section for single D-messons in the forward direction is: δ(D/ D )=(40 8 +15 )μ b ( for x>0) .

Structure in the KK decay mode of the A2 meson

Abstract Evidence from the K K decay mode for the splitting of the A 2 meson is presented.

The reactions K−p→π∓Σ±(1385) at 4.2 GeV/c

Abstract The reactions K−p→π−Σ+(1385) and K−p→π+Σ−(1385) are studied at 4.2 GeVc incident momentum using data from a high statistics bubble chamber experiment corresponding to ∼80 events/μb. The total and differential cross sections are presented. Amplitude analyses are performed and the complete Σ±(1385) helicity spin density matrices are extracted. The results are compared with the predictions of the additive quark model and exchange degeneracy. A substantial cross section is observed for the reaction K−p→π+Σ−(1385) in the forward direction, which implies exotic meson quantum numbers in the t-channel. One possible interpretation of this process provides an explanation for the small but significant violations of the additive quark model predictions observed in the reaction K−p→π−Σ+(1385) at low four-momentum transfer. In the backward direction unnatural parity exchange is shown to give a larger contribution to K−p→Σ−(1385)π+ than natural parity exchange.

Study of hypercharge exchange reactions of the type K−p → 1−32± at 4.2 GeV/c

Abstract Results are presented for the quasi two-body hypercharge exchange reactions of the type using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions.

An analysis of the reaction pp → KOKOπ+π− at 0.7 GeV/c and the spin-parity of the F1 meson

Abstract Experimental results are presented on the reactions p p → K 1 O K 1 O π + π − and p p → K 1 O K 2 O π + π − at 0.7 GeV /c . The production of K∗, S∗, fO, ϕ, ϱ is observed, as well as the recently proposed F1 meson: its spin-parity quantum numbers are discussed.

AN ANALYSIS OF THE REACTION anti pp

Abstract Experimental results are presented on the reactions p p → K 1 O K 1 O π + π − and p p → K 1 O K 2 O π + π − at 0.7 GeV /c . The production of K∗, S∗, fO, ϕ, ϱ is observed, as well as the recently proposed F1 meson: its spin-parity quantum numbers are discussed.

Yields

Abstract In an experiment with 360 GeV/ c π − beam at the CERN SPS using the high resolution hydrogen bubble chamber LEBC and the European Hybrid Spectrometer, an event has been observed of the type π − p → D 0 D 0 + 8 prongs. The fully reconstructed decay modes are D 0 → K − π + π 0 π 0 and D 0 → K + π + π − π − , with all six charged tracks being detected in the spectrometer and all four photons from the π 0 decays detected in the lead glass gamma detection system. The D 0 has momentum 119.0 ± 0.6 GeV/ c , x F = 0.31, length 4.1 ± 0.1 mm and proper lifetime (2.1 ± 0.1) × 10 −13 s. The D 0 has momentum 78.5 ± 0.3 GeV/ c , x F = 0.19, length 7.5 ± 0.1 mm and proper lifetime (5.9 ± 0.1) × 10 −13 s.

K

AbstractResults are presented for the quasi two-body hypercharge exchange reactions of the type 0−1/2+→2+1/2+: