Search

Using the CUSB detector at CESR, we have observed hadronic cascade decays ϒ ″ → ( ϒ or ϒ ′) + ( π + π − or π 0 π 0 ), where ϒ ( ϒ ′) → ( e + e − or μ + μ − ). We derive branching fractions of ϒ ″ → ϒ ′ π + π − . The dipion mass spectrum from ϒ ″ → ϒπ + π − shows no preference for high masses, in strong contrast to the decays ϒ ″ → ϒππ and ψ″ → J ψππ .

The π + π − partial waves are studied up to the F-wave in the mass region from 580 to 1780 MeV/ c 2 at low four-momentum transfer. The study is based on a previous hydrogen target experiment and a more recent polarized target experiment. Using the results of both experiments for 0.01 ⩽ | t | ⩽ 0.20 GeV 2 / c 2 , a partial-wave analysis is performed in each mass bin ( Δm = 40 MeV/ c 2 ) independently. For the first time a model-independent analysis has been possible, which enables us to check the assumptions made in previous studies. In general we find a unique solution determining the exact intensity of each partial wave. The uniqueness of our solution is related to the Barrelet zeros being real in the mass region where their imaginary part were supposed to produce ambiguities. We observe a non-π exchange contribution even in the helicity m = 0 amplitudes.

We report on inclusive K0 production in the region of the upsilon resonances (9.4–10.6 GeV). The K0 yield for the resonances and continuum below the BB threshold is found to be constant at 0.82 ± 0.10 K0 per observed hadronic event. At the ϒ(4S), however, the K0 yield is significantly higher, 1.58 ± 0.35. This increase in K0 production and the differential cross section dσ/dp of kaons are consistent with BB decay of the ϒ(4S) resonance with the bottom quarks subsequently decaying primarily into charmed quarks.

The reaction pi /sup -/p/sub pol./ to pi /sup -/ pi /sup +/ pi /sup - /p has been measured at 17 GeV/c using a polarized target. The data sample contains about 60000 interactions on polarized protons. The nucleon polarization as a function of momentum transfer is very similar to elastic pi /sup -/p scattering and is nearly independent of the 3 pi mass, except for a possible structure around 1.2 GeV. Using the isobar model, the authors have performed a partial-wave analysis and extracted the 3 pi amplitudes. The generalized 3 pi density matrix elements agree with earlier determinations. Relative phases obtained from density matrix elements agree well with the ones obtained from transversity amplitudes. This proves the validity of the coherence assumption made in the interpretation of unpolarized target results. The results confirm the existence of an A/sub 1/ resonance in the region 1.2-1.3 GeV. (20 refs).

The A 2 meson is studied in the decay mode ϱ 0 π − using partial wave analyses of 600 000 events from the reaction π − p→ π − π − π + p at 63 and 94 GeV incident momentum. Common production mechanisms are indicated for this resonance and diffractive 1 + and 2 − components.

The reaction π − p→K + K − n has been studied on a hydrogen target (27 000 events) at 18.4 GeV/ c and on a polarized target (54 000 events) at 17.2 GeV/ c . A combination of results of both experiments allows a partial-wave analysis of the K + K − system between 1.1 and 1.74 GeV mass without any model assumptions. In general our fits yield unique solutions. Using results of our previous analysis of π + π − final states and assuming the dominance of the positive G -parity states in the K + K − system, the branching ratios BR ( K K /ππ) of partial waves into K K and ππ are determined. The S-wave appears to be mainly a broad e (1300) with BR ( K K /ππ) = 0.068 −0.021 +0.017 . The weak P-wave can be described by a tail of the ϱ(770) with BR ( K K /ππ) = 0.081 −0.025 +0.029 . The D-wave is interpreted in terms of a superposition of f(1270) + A 2 (1310) + f′(1515) resonances. The fit yields BR ( K K /ππ) = 0.069 −0.031 +0.023 for the f(1270) and BR( ππ /all) = 0.027 −0.013 +0.071 for the f′(1515). The F-wave shows the g(1690) meson with BR ( K K /ππ) = 0.191 −0.037 +0.040 . All the above values refer to the t bin between 0.01 and 0.20 (GeV/ c ) 2 . Some results are also given for the high- t region.

D ∗± , D ± , D 0 , and D 0 production has been observed in π −Be interactions at 120, 175, and 200 GeV. The dependence of the D cross section on transverse and longitudinal momentum is presented. The ratio of D∗ to D and charged to neutral D production is determined. Leading particle effects in D production are investigated. Relative branching ratios for several D decay modes are evaluated. A limit on D 0 − D 0 mixing is given.

In order to determine the ηNN coupling constant we have measured the two reactions K−p→Λη and K−p→Λπ0 with a magnetic wire chamber spectrometer which contained a gamma counter for the γγ decays of π0 and η. The Λ polarization and the differential cross sections are given. The latter have quite different u dependences. Their ratio is interpreted, in terms of a nucleon-Regge exchange model, as the effect of a small ηNN coupling constant for which we obtain GηNN2 = GπNN2 · (0.26 ± 0.10) as allowed by SU(3). The large value given by Heisenberg's non-linear field theory, GηNN2 = GπNN2 · 0.9, is excluded by this measurement if the characteristic u dependence of the Λπ0 channel is attributed to Nα Regge exchange.

We describe the construction and performance of a position sensitive sandwich counter consisting of 27 strip-shaped elements which form a cylinder around a liquid hydrogen target. The lead-scintillator strips are equipped with photomultipliers at both ends; the position of the shower is determined from the time difference of the two photomultiplier signals. Over the sensitive range of the strips (122 cm) the spatial resolution is better than 4.5 cm (fwhm) for electron energies above 250 MeV. The thickness of the counter is 4 radiation lengths of lead, which yields an efficiency above 94% for photon energies above 150 MeV. This detector surrounded a liquid hydrogen target and was used in an experiment with a magnetic spectrometer to detect fast forward particles. From the analysis of this experiment we deduce the probability of detecting a given number of photons in the channel K−p→Λ (forward) π0. The results are found to be in agreement with Monte Carlo predictions.

The reaction π − p→ π + π − n has been measured in a high-statistics experiment on a transversely polarized proton target at 17.2 GeV, and unexpectedly large nucleon polarization effects have been observed. Combining the results of this experiment with a measurement on a hydrogen target allows a model-independent partial-wave analysis in terms of the “nucleon transversity” amplitudes. Unique or at most twofold ambiguous solutions are obtained. In particular we find a high lower limit ( ⪆30% ) of the spin non-flip unnatural exchange amplitudes at low | t |. These amplitudes, interpreted as being due to the exchange of an object with the quantum numbers of the A 1 , have been assumed to be absent in previous analyses. In checking the consequences of this finding on the old results, we test the validity of the rank-two assumotions for the density matrix. We find a small but significant deviation, which shows the need for a new phase-shift analysis including the A 1 exchange contribution.

The ϒ′ state has been observed as a narrow resonance at M ( ϒ ′) = 10.02 ± 0.02 GeV in e + e − annihilations, using a NaI and lead-glass detector in the DORIS storage ring at DESY. The ratio Г ee Г had /Г tot of electronic, hadronic, and total widths has been measured to be 0.32 ± 0.13 keV. The parameters of the Г particle have also been determined to be/ M (Г)

The reaction π-p → K+K-n has been studied on hydrogen (27 000 events) at 18.4 GeV/c and on a transversely polarized butanol target (54 000 events) at 17.2 GeV/c. A combination of results of both experiments allows to obtain unique solutions for a partial wave analysis of the K+K-system without any model assumptions. This analysis was performed at low four-momentum transfer 0.01 < |t| < 0.2 (GeV/c)2 and in the mass range between 1.10 and 1.74 GeV. Using results of our previous analysis of π+π- final states and assuming the dominance of the positive G-parity states in the K+K- system, the branching ratios BR(KK/ππ) of partial waves S,P,D and F into KK and ππ are determined.

Partial wave analysis is performed on a combined sample of 1,500,000 events with an average polarization of 68%. (AIP)