The production of two high-p_T jets in the interactions of quasi-real photons in e+e- collisions at sqrt{s_ee} from 189 GeV to 209 GeV is studied with data corresponding to an integrated e+e- luminosity of 550 pb^{-1}. The jets reconstructed by the k_T cluster algorithm are defined within the pseudo-rapidity range -1 < eta < 1 and with jet transverse momentum, p_T, above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum ptmean of the jets and is compared to perturbative QCD calculations.
Total cross section for dijet production. Errors are combined statistics and systematics.
Measured dijet production cross section as a function of the mean jet transverse momentum. Errors include both statistics and systematics.
Measured dijet production cross section as a function of jet pseudorapiditydifference. Errors include both statistics and systematics.
We have studied inclusive KS0, Λ, and Λ¯ production and strange-resonance production in the reactions pp→(KS0, Λ, or Λ¯)+π±+anything at 405 GeV/c. The observed cross sections are 7.43 ± 0.45 mb for KS0, 4.01 ± 0.35 mb for Λ, and 0.63 ± 0.12 mb for Λ¯. From the analyses of the effective-mass distributions for the (KS0π±), (Λπ±), and (Λ¯π±) systems, the resonance production cross sections are determined as 4.1 ± 1.0 mb for K*+(890), 3.6 ± 1.0 mb for K*−(890), 3.4 ± 1.7 mb for K*±(1420), 0.67 ± 0.12 mb for Σ+(1385), 0.45 ± 0.09 mb for Σ−(1385), and 0.25 ± 0.08 mb for Σ¯±(1385). The inclusive total and differential cross sections are discussed in comparison with data at lower energies. The direct production cross sections for pseudoscalar, vector, and tensor K mesons are estimated to be 2.3 ± 1.2, 3.4 ± 1.0, and 1.7 ± 0.8 mb, respectively. Direct pseudoscalar-K-meson production accounts for less than one-third of the total inclusive kaon production. Evidence of vector-meson dominance in inclusive meson production at high energy is indicated.
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Cross sections are presented for the inclusive production of Λ hyperons in electron-positron annihilations at s=29 GeV based on the full 291-pb−1 sample of data taken in the High Resolution Spectrometer experiment at the SLAC e+e− storage ring PEP. These results, and the associated correlation analyses, are consistent with the Lund model predictions with the strange diquark suppression ratio δ fixed at 0.59±0.10±0.18, as compared to the standard Lund value of 0.32. The Λ multiplicity has been found to be 0.182±0.020 per event. The opposite-strangeness multiplicity 〈nΛΛ¯〉 has been measured to be 0.046±0.020, whereas the like-strangeness multiplicity 〈nΛΛ+Λ¯Λ¯〉 is 0.009±0.028. A strong correlation is found between Λ's and Λ¯'s; when one is found in an event, the other is found in the same event with a probability that exceeds 50%.
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Extrapolate to full z interval using Lund fit.
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The inclusive production ofK*±(890), ρρ(770), ω0(780) andf0(1,270) mesons is studied in\(\bar pp\) experiment at 32GeV/c in the MIRABELLE bubble chamber by the analysis of (K0π±) and (π+π−) invariant mass distributions. The inclusive cross sections are σ(K*±)=2.45±0.30 mb, σ(ρ0)=8.8 ±0.9 mb, σ(ω+)≃6.2 mb, and σ(f0)=2.2±0.7 mb. The C.M. longitudinal distribution of theK*±(890) is slightly shifted to the primary particles fragmentation regions; the ρ0 is produced more centrally. The studied mesons alone are responsible for 40% of final state poins. The production features of various resonances are compared with quark models predictions.
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New data are presented on the charged multiplicity distribution for non single-diffractive events produced in pp̄ interactions at a CM energy s = 540 GeV . The distribution in the full pseudorapidity range is compared with data from the ISR. Using the scaling variable z = n 〈n〉 a change of shape is observed. The effect is manifested as an increase from 2% to 6% in the proportion of high multiplicity ( z > 2) events. For the central pseudorapidity range, | η | ⪅ 1.5, scaling is approximately valid up to s = 540 GeV .
MOMENTS OF THE CHARGED MULTIPLICITY DISTRIBUTIONS. DISPERSION IS MEAN(N-MEAN(N)**2). CQ IS MEAN(N**Q)/MEAN(N)**Q.
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Backward Multiplicity.
Forward Multiplicity.
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The inclusive production of Ξ − and Ξ ∗0 (1530) is investigated in K − p interactions at 10 and 16 GeV/ c . The inclusive production cross sections are 172 ± 20 μ b and 135 ± 15 μ b for the Ξ − , and 43 ± 7 μ b and 32 ± 5 μ b for the Ξ ∗0 (1530) at 10 and 16 GeV /c , respectively. In the beam momentum range up to 16 GeV/ c , the energy dependence of the cross section for Ξ − production in K − p interactions is similar to Σ − production in π − p interactions. It is, instead, different from the energy behaviour of Σ − production cross sections observed in π − p interactions. The Ξ − and Ξ ∗0 (1530) are both produced more in the forward ( x > 0) than in the backward hemisphere, indicating the presence of hyperon-exchange processes.
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The inclusive cross section and the average multiplicity are evaluated for most of the charged ( π ± , p, K ± ) and neutral (γ, π 0 , K 0 , K 0 , Λ, Λ , n ) particles produced in 32 GeV/ c K − p interactions; corresponding results are obtained for each charged topology separately. New results are given for the total charged multiplicity cross sections. The average longitudinal momentum of neutrals is found to be roughly equal to that of charged particles. The π + and π − multiplicity distributions are reconstructed and compared to the π 0 and to the total charged multiplicity distributions.
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Axis error includes +- 30/30 contribution (SYSTEMATIC ERROR FOR K0 MULTIPLICITY, WHICH IS EVALUATED FROM 2 ASSUMPTIONS: ALL K0'S COME FROM THE FINAL STATES (N K 2AK PIONS) OR (LAMBDA/SIGMA K AK PIONS) AND CHARGE DISTRIBUTION IN THESE FINAL STATES OBEYS A STATISTICAL ISOSPIN MODEL OF F.CERULUS,NC 19, 528. ALSO ASSUMED THAT SIG(K+)=SIG(KO). VALUES OF SIG(XI-) AND RATIOS SIG(SIGMA+)/SIG(LAMBDA), SIG(SIGMA-)/SIG(LAMBDA) ARE TAKEN FROM 14.3 GEV EXPERIMENT LOUEDEC 76,NC 41A, 166, STATISTICAL ERRORS BEING DOUBLED. FOR ALL ANTIBARYONS ASSUMED THAT SIG(ANTIBARYON)/SIG(BARYON)=SIG(ANTILAMBDA)/SIG(LAMBDA) =0.046+-0.020. SLOW PROTONS WITH PLAB < 1.2 GEV/C ARE IDENTIFIED, AN ESTIMATE FOR FAST PROTON PRODUCTION IS TAKEN FROM FACCINI 77,NP B127, 109).
Axis error includes +- 30/30 contribution (SYSTEMATIC ERROR FOR K0 MULTIPLICITY, WHICH IS EVALUATED FROM 2 ASSUMPTIONS: ALL K0'S COME FROM THE FINAL STATES (N K 2AK PIONS) OR (LAMBDA/SIGMA K AK PIONS) AND CHARGE DISTRIBUTION IN THESE FINAL STATES OBEYS A STATISTICAL ISOSPIN MODEL OF F.CERULUS,NC 19, 528. ALSO ASSUMED THAT SIG(K+)=SIG(KO). VALUES OF SIG(XI-) AND RATIOS SIG(SIGMA+)/SIG(LAMBDA), SIG(SIGMA-)/SIG(LAMBDA) ARE TAKEN FROM 14.3 GEV EXPERIMENT LOUEDEC 76,NC 41A, 166, STATISTICAL ERRORS BEING DOUBLED. FOR ALL ANTIBARYONS ASSUMED THAT SIG(ANTIBARYON)/SIG(BARYON)=SIG(ANTILAMBDA)/SIG(LAMBDA) =0.046+-0.020. SLOW PROTONS WITH PLAB < 1.2 GEV/C ARE IDENTIFIED, AN ESTIMATE FOR FAST PROTON PRODUCTION IS TAKEN FROM FACCINI 77,NP B127, 109).
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