Inclusive π 0 production has been measured at the CERN Intersecting Storage Rings in αα and α p collisions near 90°, for p T between 2 and 5 GeV/c. The differential cross sections show a slower exponential fall-off with p T than has been observed in pp collisions at the corresponding nucleon-nucleon centre-of-mass energies at large p T . The ratio of the π 0 production cross sections for αα collisions to those for pp collisions is observed to be larger than 16.
The inclusive production of π 0 at large values of p T in pp collisions at the ISR has been studied. In this experiment the two photons are resolved and separately measured for p T values of up to 6 GeV/ c , giving confidence that the desired signal has been separated from various backgrounds.
Data are presented on the reaction e+e− → γ + no other detected particle at centre-of-mass energies of 89.48, 91.26 and 93.08 GeV. The cross-section for this reaction is related directly to the number of light neutrino generations which couple to the Z° boson, and to several other possible phenomena such as the production of excited neutrinos, the production of any invisible ‘X’ particle, and the magnetic moment of the tau neutrino. Based on the observed number of single photon events, the number of light neutrinos that couple to the Z° is measured to be Nv = 2.89 ± 0.38. No evidence is found for anomalous production of energetic single photons, and upper limits at 95% confidence level are determined for excited neutrino production (BR < 4 − 8 × 10−6 depending on its mass), production of an invisible ‘X’ particle (σ, < 0.1 pb for masses below 60 GeV), and the magnetic moment of the tau neutrino (< 5.1 × 10-6 μB).
The production of the χ1 and χ2 states of charmonium has been observed in 300 GeV/c π±N and pN interactions. The fraction of the total inclusive J/ψ production due to radiative χ decay has been determined to be 0.40±0.04, 0.37±0.03, and 0.30±0.04 for the π+, π−, and proton data, respectively. Total cross sections have been obtained of 131±18±14 and 188±30±21 nb/nucleon in the 300 GeV/c π−N interactions for χ1 and χ2 production. By measuring the contributions to the J/ψ production due to both ψ’ and radiative χ decay, the cross sections for direct J/ψ production have been determined to be 97±14, 102±14, and 89±12 nb/nucleon for π+, π−, and protons, respectively.
Fractions of total J/PSI production due to radiative CHI1 and CHI2 decays.
Fractions of total J/PSI production due to radiative CHI1 and CHI2 decays.
Fractions of total J/PSI production due to radiative CHI1 and CHI2 decays.
We present a measurement and comparison of the χc1 and χc2 production cross sections determined from interactions of 300-GeV/c π± and p with a Li target. We find χc1χc2 production ratios of 0.52−0.27+0.57 and 0.08−0.15+0.25 from reactions induced by π± and p, respectively.
The cross section per nucleon. The differential cross section is fitted by the equation : D(SIG)/D(COS(THETA)) = CONST*(1+CONST*COS(THETA)**2), where THETA is the angle between the MU+ and beam momentum in the CHI/C rest frame.
Production of Sigma- and Lambda(1520) in hadronic Z decays has been measured using the DELPHI detector at LEP. The Sigma- is directly reconstructed as a charged track in the DELPHI microvertex detector and is identified by its Sigma -> n pi decay leading to a kink between the Sigma- and pi-track. The reconstruction of the Lambda(1520) resonance relies strongly on the particle identification capabilities of the barrel Ring Imaging Cherenkov detector and on the ionisation loss measurement of the TPC. Inclusive production spectra are measured for both particles. The production rates are measured to be <N_{Sigma-}/N_{Z}^{had}> = 0.081 +/- 0.002 +/- 0.010, <N_{Lambda(1520)}/N_{Z}^{had}> = 0.029 +/- 0.005 +/- 0.005. The production rate of the Lambda(1520) suggests that a large fraction of the stable baryons descend from orbitally excited baryonic states. It is shown that the baryon production rates in Z decays follow a universal phenomenological law related to isospin, strangeness and mass of the particles.
The measured differential cross section for SIGMA- production.
The total production rate of SIGMA-. The second systematic (DSYS) error is due to the extrapolation to the fullx-range.
The measured differential cross section for LAMBDA(1520) production. The first error is the fit error.
The inclusive production cross section of ω 0 and η′ were measured at transverse momenta of 3 to 7GeV/ c at 90° in the centre of mass. The ω 0 /π 0 and η′/π 0 production ratios were found to be 0.87 ± 0.17 and 0.9 ± 0.25, respectively, at 3.5 GeV and constant up to 7 GeV/ c . The large meson/ π 0 production ratio supports the hypothesis that high- p T mesons are the leading fragments of the basic constituent jet. The η ′/ η ratio exemplifies the SU(3) singlet nature of the η ′.
ETAPRIME DECAY TO GAMMA GAMMA IS DETECTED.
The inclusive η production cross section at the CERN ISR has been measured for p T values of up to 11 GeV/ c . We find that the η π 0 cross-section ratio has an average value of 0.55 ± 0.07 and varies little with p T .
No description provided.
Rates for gamma + 1 jet.
Rates for gamma + 2 jet.
Rates for gamma + 3 jet.
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