We report on a study of inclusive particle production in pp-interactions at 400 GeV/c. The data are based on 472 K reconstructed events recorded in the NA 27 experiment using the LEBC-EHS facility at CERN. The production cross sections are determined of pseudo scalar (π±,0, η andK±), scalar (f0(975)), vector (ρ±,0(770), ω(783), ϕ(1020),K*0(892), and\(\bar K^{ * 0} \)(892)), and tensorf0 mesons, of protons and antiprotons, and theΔ++,+,0(1232), and Λ(1520) baryon resonances in the forward hemisphere of the center of mass system, as well as longitudinal and transverse momentum distributions. The results are compared with predictions of the FRITIOF model and with other experimental data.
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The energy dependence of the relative production rate of three-jet events is studied in hadronic e + e − annihilation events at center of mass energies between 22 and 46.7 GeV. Three-jet events are defined by a jet finding algorithm which is closely related to the definition of resolvable jets used in O( α s 2 ) perturbative QCD calculations, where the relative production rate of three-jet events is roughly proportional to the size of the strong coupling strength. The production rates of three-jet events in the data decrease significantly with increasing centre of mass energy. The experimental rates, which are independent of fragmentation model calculations, can be directly compared to theoretically calculated jet production rates and are in good agreement with the QCD expectations of a running coupling strength. The hypothesis of an energy independent coupling constant can be excluded with a significance of four standard derivations.
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Results of fitting the differential distributions in x F and p T 2 of D mesons produced in 400 GeV/ c p-p interactions to the form d 2 σ d x F d p T 2 ∝(1−x F ) n exp [−(p T 2 /〈p T 2 〉)] are discussed. The D + distribution is found to be relatively hard [ n =3.1±0.8〈 P t 2 〉=1.32±0.27 (GeV/ c ) 2 ] and the D̄ 0 distribution relatively soft [ n =8.1±1.9,〈 p T 2 〉=0.62±0.14 (GeV/ c ) 2 ] compared to the average for all D's [ n =4.9±0.5,〈 p T 2 〉=0.99±0.10 (GeV/ c ) 2 ]. It is suggested that these distributions could reflect contribution of leading di-quarks in pp collisions. Comparison is made with evidence for leading quarks in charm production in 360 GeV/ cπ − p interactions.
The invariant (C=INV) and non-invariant (C=NON-INV) distributions are fitted to (1-XL)**POWER. Pt distribution is fitted to EXP(-PT**2/SLOPE).
We present the measurements of the Λ c production cross section in proton-proton interactions at s =27.4 GeV and give new limits on the exclusive branching ratio Λ c →pK + π − .
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We have measured the inclusive production properties of D and D messons produced from pp interactions at s =27.4 GeV . The differential production cross section is well represented by the empirical form d 2 σ d x F d P 2 T = 1 2 [σ ( D / D )(n+1)b](1−|x F |) n exp (−bp 2 T ) with n=4.9 ± 0.5, b=(1.0±0.1)( GeV /c) −2 , and the inclusive D / D cross section σ ( D / D ) is (30.2±3.3) ωb. The QCD fusion model predicts D / D production which is in good agreement with our data except for the magnitude of the cross section which depends sensitively on the assumed mass of the charm quark.
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The production of photons ine+e−→γ+hadrons is investigated at three centre of mass energies around 14, 22 and 34 GeV. On average, photons carry 25% of the total available energy, with a multiplicity similar to the charged multiplicity. The inclusive photon spectra are found to scale with the centre of mass energy as a function of the Feynman variablex. π0 and η mesons are reconstructed from their decay photons. The slopes of the spectra are similar to that for charged pions and approximate scaling is observed for π0 production. The mean π0 and η multiplicities are given. The observed photon yield can be fully accounted for by hadron decays and initial state radiation. However, up to one extra photon per event from other sources cannot be excluded.
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MEAN CHARGED MULTIPLICITY.
MEAN CHARGED MULTIPLICITY AFTER SUBTRACTING SECONDARIES FROM KS AND LAMBDA DECAY, PLUS LEPTONS FROM HEAVY QUARK WEAK DECAYS ARE FROM DALITZ DECAYS. I.E. NUMBER OF CHARGED HADRONS HAVING LIFETIME > 10**-9 SEC.
INVERSE RELATIVE DISPERSION.
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