The production cross sections for the Λ, Σ0, Ξ−, Σ0 (1385), Ξ0 (1530) and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays. Baryon rates in direct ϒ decays are enhanced by a factor of 2.5 or more compared to the continuum. Such a large baryon enhancement cannot be explained by standard fragmentation models. The strangeness suppression for baryons and mesons turns out to be the same. A strong suppression of spin 3/2 states is observed.
Hyperon rates per multihadronic event in direct UPSILON decays.
Hyperon rates per multihadronic event in the continuum.
LAMBDA spectrum (1/SIG(had))*D(SIG)/D(X) for UPSILON (1S) direct decays, with X = P/Pmax.
Observation of the semileptonic decay of the charmed baryon in the decay channel has been made using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The cross section times branching ratio was found to be .
No description provided.
No description provided.
Averaging the above two results.
A measurement of gamma–gamma production of the final states$K^+ K^- \pi^+ \pi ^-$,$K^+ K^- \pi^0 \pi ^0$,$
Cross sections for the partial waves from an analysis where the five (JP,LZ) states (0+,0), (2-,0), (2+,+-2), (2+,0) and (0-,0) are included.
Cross section obtained for the three partial waves obtained when the two with smallest amplitude in the previous table are set to zero.
Cross sections for the various final states from the 'five partial wave' analysis.
Using the ARGUS detector at the DORIS II storage ring, we have observed the charmed baryons Σ c ++ and Σ c 0 , through their decays to Λ c + π ± . We have measured the mean Σ c −Λ c + mass difference as 167.6±0.3±1.6 MeV/ c 2 . The isospin mass splitting between the Σ c ++ and the Σ c 0 was found to be 1.2±0.7±0.3 MeV/ c 2 . The rate of Λ c + production from Σ c decays was found to be (36±12±11)% of the total rate of Λ c + production. The Σ c χ p spectrum was observed to be similar to that of the Λ c + , with a Peterson function parameter ϵ of 0.29±0.06.
DATA FROM UPSI(4S) WAS EXCLUDED.
The reaction γγ→K + K − π + π − π 0 has been observed for the first time, using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The cross section shows an enhancement for W γγ close to 3 GeV/ c 2 . Searches for γγ→ωφ and for γγ→φφ leading to this final state, as well as for γγ→φφ→2K + 2K − , have been performed. The derived upper limits for ωφ and φφ production are compatible with q q q q model predictions.
TOPOLOGICAL CROSS SECTION.
95 PCT CL UPPER LIMITS.
We report the first direct observation of B meson decays into Λ c + baryons using the decay channel Λ c + → pK − π + . The product of branching ratios Br(B→Λ c + X)·Br(Λ c + →pK − π + = (0.30±0.12±0.06)% is derived from an observed signal of 208±89 events. Using previous measurements of inclusive baryon rates we find a branching ratio for Λ c + → pK − π + of (4.1±2.4)%. The measured Λ c + momentum spectrum indicates that the multi-particle final states dominate the decay B→Λ c + X.
ACCEPTANCE CORRECTED.
Using the ARGUS detector at DORIS, we observe the production of D ∗+ s mesons in e + e − annihilation through their subsequent decays to a D + s and a photon. Photons which convert in the beam pipe or drift chamber inner wall are used to obtain a high precision measurement of the D ∗+ s -D + s mass difference, while photons detected in the shower counters are used to determine the production cross section, and to provide an independent measurement of the D ∗+ s -D + s mass difference. The observed D ∗+ s - D + s mass difference is 142.5±0.8±1.5 MeV/ c 2 , and σ(e + e − →D ∗+ s X)·BR(D ∗+ s →D + s γ)(·BR(D + s →φπ + ) is 4.4±1.1±1.0 pb at 10.2 GeV. The width of the D ∗+ s is less than 4.5 MeV/ c 2 at 90% confidence level.
Cross sections uncorrected for branching ratios.
Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, we have observed production of the charmed-strange baryon Ξ c + and its neutral isospin partner, the Ξ c 0 . The Ξ c + was reconstructed in the final state Ξ − π + π + , while the Ξ c 0 was seen in decay to Ξ − π + and Ξ − π + π + π − . The average Ξ c fragmentation spectrum has been determined, as well as the production cross section times branching ratio for each decay mode. The charged and neutral masses were measured to be 2465.1 ± 3.6 ± 1.9 MeV/ c 2 and 2472.1 ± 2.7 ± 1.6 MeV/ c 2 respectively, corresponding to a mass-splitting, M ( Ξ c + ) − M ( Ξ c 0 ), of −7.0±4.5±2.2 MeV/ c 2 .
No description provided.
Data requested from authors.
We report the first observation of an orbitally excited baryon, the Λ(1520), in quark and gluon fragmentation. The production rate is found to be (1.15±0.21±0.16)×10 −2 and (0.80±0.17 −0.13 +0.10 )×10 −2 Λ (1520) hyperons per event in direct ϒ decays and in the continuum, respectively. In contrast to the observed situation for ground state baryons, the production of the Λ(1520) in direct ϒ decays shows little or no enhancement with respect to continuum production.
Full X range uses extrapolation from fit to dsig/dz distribution.
No description provided.
UPSI(1S) DECAYS.
The final states K S 0 K S 0 π + π − and K S 0 K ∓ π 0 π ± , produced in two-photon reactions, have been studied using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The reaction γγ→ K ∗+ K ∗− has been observed for the first time. Its cross section is about eight times larger than that for γγ→ K ∗0 K ∗0 , but it has a similar W γγ dependence.
No description provided.
Topological cross section.
Topological cross section.
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