A structure has been observed at 2220 MeV in the mass spectrum of ηη ′ systems produced by 38GeV/ c and 100 GeV/ c ′ negative pions on protons. The angular distribution of the decay products shows that this structure is presumably a spin J ⩾ 2 meson.
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A coupled channel analysis has been carried out using a new amplitude analysis of the K 0 s K 0 s system produced in the reaction π − p→K 0 s K 0 s n at 22 GeV/ c , which contained about 40 000 new events in the low- t region (| t − t min |<0.1 GeV 2 ). Here only the I G =0 + , J PC =2 ++ amplitude from this analysis is considered, together with available data from other experiments in channels with the same quantum numbers in order to determine which 2 ++ isoscalar mesons have significant pseudoscalar-pseudoscalar couplings. It is found that four poles, f(1270), f'(1525), θ(1690), and f r (1810), are needed, plus a smooth background in order to fit these data; the need for the θ(1690) depends on the J/ψ radiative decay alone, and the f r (1810) is seen only in hadronic production.
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Inclusive production of π+ on four nuclear targets has been studied using a 40 GeV/c π- beam at the Serpukhov accelerator. No noticeable A-dependence has been found.
'CM' MEAN PION NUCLEON REST SYSTEM.
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Results are reported concerning the charged-particle multiplicity distribution obtained in an exposure of the high-resolution hydrogen bubble chamber LEBC to a beam of 800 GeV protons at the Fermilab MPS. This is the first time that such data have been available at this energy. The distribution of the number n ch of charged particles produced in inelastic interactions obeys KNO-scaling. The average multiplicity is 〈 n ch 〉 = 10.26±0.15. For n ch ⩾8 the data can be well fitted to a negative binomial. The difference between the overall experimental multiplicity distribution and that resulting from the latter fit is in agreement with the contribution expected from diffractive processes.
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TheA-dependence of the polarization ofΛ0,s produced inclusively in neutron-nucleus interactions at a mean neutron momentum of about 40 GeV/c has been measured in an experiment performed using the BIS-2 spectrometer at the Serpukhov accelerator. Carbon, Aluminium and Copper targets were used. TheΛ0,s were produced in the kinematical region of 0.6<pT<1.3 GeV/c and 0.2<xF<0.9. Describing the polarization of theΛ0,s by ℘=a·A a value of (−0.15+0.07/−0.60) was obtained by a fit to our data.
POLARIZATION IS DESCRIBED BY A POWER LOW: POL = C*A**B, WHERE C = -1.1, +0.4, -0.3 , A- ATOMIC NUMBER AND B = -0.15, +0.07, -0.6.
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We report a measurement of the inclusive D/D̄ production cross section in 800 GeV/ c proton-proton interactions. The experiment used the high resolution bubble chamber LEBC exposed to an 800 GeV/ c proton beam at the Fermilab MPS. We obtain σ( D/ D ̄ )=59 −15 +22 μ b (statistical errors), having analysed 25% of the total data sample. Comparison with 400 GeV/ c pp dat a obtained with LEBC at CERN shows a D/D̄ cross section increase by a factor of 1.7 −0.5 +0.7 . This is in good agreement with fusion model calculations.
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A narrow meson which decays into ηη is observed in 38 GeV/ c π − p collisions at large momentum transfer. The experiment has been performed at the Serpukhov accelerator with the GAMS-2000 spectrometer. The mass of this new meson is (1755 ± 8) MeV, its width is less than 50 MeV. Its spin-parity is J PC =0 ++ or less probably 2 ++ .
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The hadronic production of charmed states was studied in a two-arm spectrometer using a 205-GeV/c negative-pion beam incident upon a beryllium target. One arm, filled with dense absorber, triggered the detectors upon the passage of a muon with a moderate transverse momentum and a total momentum of at least 4 GeV/c. The other arm was an open-geometry magnetic spectrometer which had both neutral- and charged-particle identification capabilities. The apparatus, the data, and an invariant-mass-plot search for evidence of charmed-meson production through several charged-particle decay modes are described. The Kπ, Kππ, and Kπππ mass plots fail to reveal significant D-meson signals. Based upon the Kπ mass plots, the 95%-confidence upper limit on the DD¯ production cross section is found to be less than 51 μb per nucleon for the production models tested. A search for evidence of charged-D* production yields 30±16 combinations above background in association with the expected trigger muon charge. Interpreted as a D* signal, this excess corresponds to a model-dependent inclusive DD¯ production cross section of 34±18−9+14 μb per nucleon. Model-dependent upper limits on the ratio of the F to D cross sections are also presented.
Uncorrelated model for charmed mesons production.
'Correlated' model for pair of charmed mesons production.
Uncorrelated model for D/S+- mesons production.
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