Evidence that absorption in the π+ π− π− system in nuclear matter is stronger in the JP = 0− than in the JP = 1+ state

In the reaction π^? + A → π⁺π^?π^? + A at 15.1 GeV/c the coherently produced 3π mass spectrum has a broad peak around 1.1 GeV which consists mainly of a J^P = 1⁺ state and of a smaller fraction of 0^-. Comparing the observed dependence of the production of these diffractive states on the atomic weight A of the target nuclei with the optical model, we have studied the absorption of the produced states in nuclear matter. We have found the following values of the absorption cross-sections: σ₂(0^-) = 49_?7⁺⁹ mb and σ₂(1⁺) = 15.8_?1.3^+1.5 mb.     

Measurement of the fragmentation of hadronic systems of different flavour and colour selected by lepton pairs

A lepton-pair trigger was used to select a hadronic system in different flavour and colour states: properties of the transformation of this system into hadrons were measured in terms of charge flow, multiplicity distribution, and fragmentation function. It is observed that, while the effects of flavour are clearly seen, the colour degrees of freedom are not observed in the region of low p_T.     

A study of ππ → KK using an experiment on π−p → KS0KS0n at 8.9 GeV/c

We present an analysis of the K_S⁰K_S⁰ system, based on 6380 events, produced in the reactions π^?p → K_S⁰K_S⁰n. Using a one-pion exchange model with absorption we determine the S- and D-wave amplitudes of ππ → $\text{K}\text{K}$. Several A₂ production amplitudes were also included in the fits and we conclude that an unnatural parity exchange amplitudes which does not interfere with pion exchange, seems to present. A branching ratio $\text{Γ(}\text{f}\text{→}\text{K}\text{K}\text{/ Γ(}\text{f}\text{→ ππ) = 0.029 ± 0.006}$ is determined. With this and other new values of branching ratios we have fitted the 2⁺ → 0^?0^? decay rates of the SU(3) relations resulting in (36.2 ± 1)° for the tensor nonet mixing angle.     

Measurement of the polarization in the forward peak of π−p→K0λ at 5 GeV/c

The π^?p→K⁰λ polarization has been measured at 5 GeV/c in the range 0<?t<1.4 (GeV/c)². The polarization is small for ?t?0.4 (GeV/c)², becoming negative at the higher values of ?t.     

Polarization measurement of the pp → nn charge exchange at 8 Gev/c

The $\text{p}\text{p}\text{→}\text{n}\text{n}$ polarization has been measured at 8 GeV/c and for ?t values ranging from 0 up to 0.8 (GeV/c)². A small and negative polarization has been found.     

Measurement of the polarization in K−p→K0n charge exchange at 8 GeV/c

The K^?p → $\text{K}$⁰n polarization has been measured at 8 GeV/c and for ?t values ranging from 0 up tp 1.2 (GeV/c)². A negative polarization has been found.     

Measurement of hadronic production of the χ1++(3507) and the χ2++(3553) through their radiative decay to Jϕ

The _χ1⁺⁺(3507) and the _χ2⁺⁺(3553) states have been observed in the Goliath spectrometer at the CERN SPS in 185 GeV/cπ^?-Be collisions. Their radiative decays contribute 27.7% (for the χ₁⁺⁺) and 12.8% (for the χ₂⁺⁺) to $\text{J}\text{?}$ production. At this energy, their cross sections are 65±19 nb and 96±29 nb, respectively     

Measurement of the differential cross section and the spin-correlation parameters P,A and R in the backward peak of π−p→K0Λ at 5 GeV/c

We present measurements for the baryon-exchange reaction π^?p→ΛK⁰ at 5 GeV/c over the range ?u<2(GeV/c)². The differential cross section is obtained from events produced on a liquid hydrogen target. These data are combined with events produced on a butanol polarized target and the parameters P, A, and R are then determined from an analysis of the decay angular distribution of the forward-going Λ. From our data it is possible to determine the magnitudes and the relative phase of the two invariant amplitudes A′ and B. The consequences for the ratio B/A′ are discussed in detail.     

Evidence for resonance behaviour of A1 and A3 mesons coherently produced on nuclei

An analysis of about 60 000 events produced in the reaction π^?A → (π⁺π^?π^?)A on nine different nuclear targets A at 8.9, 12.9, and 15.1 GeV/c has been performed using the Illinois PWA program.In the A₁ region our “coherent” sample of events (which contains about 11% of incoherently produced events) is described by only four partial waves: the 1⁺S and 1⁺P amplitudes, which both show a peak, and the O^?S and O^?P waves, which are rather constant. We observed variations of both 1⁺S and 1⁺P phases relative to the O^?P phase by about 90° across the A₁ peak. This observation suggests the presence of resonant 1⁺ waves in the A₁ mass region (～1.1 GeV).In the A₃ region we observe that the 2^? state shows resonance behaviour and that fπ and ?π are two decays modes with amplitudes of opposite signs.     

The charge exchange pp → nn at 5.0 and 7.76 GeV/c near the forward direction

The differential cross section for the charge exchange $\text{p}\text{p}\text{→}\text{n}\text{n}$ has been measured with high statistics at 7.76 GeV/c and at 5.0 GeV/c. The 7.76 GeV/c data show a very narrow [Δt ? 0.01 (GeV/c)²] forward peak superposed on a slow exponential fall-off.