Search

Inclusive production of vector and tensor mesons is studied in a K−p experiment at 32 GeV/c in the MIRABELLE bubble chamber. The K∗0(890), ϱ0 and ω cross sections are comparable, about 4 mb each. The K∗0(1420 and cross sections are also comparable, about 1 mb each. The K∗o+(890), Φ, K∗o−(1420) and f cross sections beam fragmentation; ϱ production is almost forward-backward symmetric in the c.m.s. The pT production slopes of K∗o−(890) and ϱ are similar, the Φ slope is shallower. Vector and tensor mesons alone are responsible for ≅50% (≅60%) of final-state pions

Lambda production is studied in K − p interactions at 32 GeV/ c . The total Λ cross section is 2.31±0.03 mb . Using the measured Λγ combinations we find that (31±4)% of all Λ's are produced via the Σ 0 → Λγ decay. About 60% of the Λ's are associated with either a N N or K K pair; about 40% of the Λ's are produced through the hypercharge annihiltion reaction K − p→ Λ + π 'a. The two-peak structure of the invariant x distribution can be related to fragmentation processes. The Λ is found to be unpolarized in the target fragmentation region, whereas a transverse polarization is observed for forward produced Λ's. As a function of p ⊥, a polarization effect is measured at medium p ⊥.

We present a systematic investigation of channel cross sections in K−p interactions at 32 GeV/c. The energy dependence of these cross sections is discussed. We also investigate a few non-diffractive two-body reactions. The total cross sections of the two reactions K−p→K∗−(890)p and K−p→K∗−(1420)p have a markedly different energy behaviour. There is clear evidence for the reaction K−p→K∗0(890) N0(1688); its differnttial cross section exhibits a sharp forward slope of 24 ± 3 GeV−2.

Recent data on the production ofη, ϱ0, ω and other mesons in hadron-hadron collisions at intermediate energies are studied. Their transverse spectra dσ/dpT2 are all found to be approximately exponential, with similar slopes, ∼3.4 (GeV/c)−2, up to about pT2 = 2(GeV/c)2. The inclusive yields of the mesons are broadly in agreement with quark model predictions. In the case of pions, a distimction is made between those directly produced and those produced indirectly via resonance decay. It is estimated that between 10% and 30% of pions are directly produced.

An enhancement in the (K−π+) mass distribution at 1871 ± 10 MeV with full width of 285 ± 40 MeV is observed in the charge-exchange reaction K−p → K−π+n at 10 and 16 GeV/c. The energy dependence of its cross section, the shape of the differential cross section dσ/dt and the decay angular distributions are consistent with a production mechanism by pion exchange. No significant enhancement at the same mass is seen in the non-charge exchange reaction K−p → (Kπ)−p. The experimental evidence is reviewed and it is suggested that there may be more than one K∗ enhancement in the 1700–1900 mass region.

Results are presented on the inclusive π± production in K−p interactions at 32.1 GeV/c. The invariant longitudinal distributions have been calculated both for π+ and π− in the backward c.m. hemisphere and extrapolated in the forward hemisphere under some physical assumptions. The inclusive cross sections for π+ and π− amount to 32.9 ± 1.5 mb and 35.0 ± 0.7 mb respectively. The energy dependence of the inclusive pion production has been analyzed in the framework of Mueller-Regge phenomenology both in the proton fragmentation and in the central region.