The reactions π−p→K0Λ,K0Σ0 are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to ∼90 events/μb. The differential cross sections and hyperon polarizations are presented and compared with existing data from earlier electronic experiments. The data in the forward hemisphere are used to perform an amplitude analysis of the 0−1/2+→0−1/2+ hypercharge exchange processes.
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The reactionsπ−p→K0∑0(1385) andπ−p→K+∑−(1385) are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to approximately 90 events/μb. The total and differential cross sections and the density matrix elements of the Σ(1385) are presented. The results are compared with those obtained for the related processesπpp→K+∑+(1385) and\(K^ -p \to \pi ^ \mp\sum ^ \pm(1385)\) in this energy range. Evidence is presented for the existence of production mechanisms with exotic exchanges in thet channel.
FROM THE CHANNEL PI- P --> LAMBDA K0 PI0 WHICH HAS A CROSS SECTION OF 72 +- 4 MUB.
FROM THE CHANNEL PI- P --> LAMBDA K+ PI- WHICH HAS A CROSS SECTION OF 79 +- 3 MUB.
FORWARD CROSS SECTION.
With use of the LENA detector at the DORIS e+e− storage ring, the hadronic cross section and the μ-pair decay branching ratio of the ϒ(9.46) resonance have been measured. Γee=1.23±0.10 (±0.14) keV, Bμμ=[3.5±1.4 (±0.4)]%, and Γtot=35−10+25 ({+9}{−7}) keV have been obtained. The first set of errors gives the statistical uncertainty. The numbers in parentheses represent systematic errors arising from the uncertainty in the total hadronic cross section.
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During an energy scan at the Cornell Electron Storage Ring, with use of the Columbia University-Stony Brook NaI detector, an enhancement in σ(e+e−→hadrons) is observed at center-of-mass energy ∼10.55 GeV. The mass and leptonic width of this state (ϒ′′′) suggest that it is the 4S13 bound state of the b quark and its antiquark. After applying to the data a cut in a (pseudo) thrust variable, the natural width is measured to be Γ=12.6±6.0 MeV, indicating that the ϒ′′′ is above the threshold for BB¯ production.
VISIBLE TOTAL HADRONIC CROSS SECTION FOR FIRST, THIRD AND FOURTH UPSILONS.
We present a study of the decay properties of charmed D mesons produced near the peak of the ψ′′(3770) resonance in e+e− annihilation. Branching fractions for nine Cabibbo-favored and three Cabibbo-suppressed decay modes are presented along with upper limits on one additional Cabibbo-favored and four additional Cabibbo-suppressed decay modes. A study of Kππ-decay-mode Dalitz plots reveals a large quasi-two-body pseudoscalar-vector component for the D0 decays and an apparent nonuniform population on the Dalitz plot for the D+ decay into K−π+π+. Using tagged events, we measure the charged-particle multiplicity and strange-particle content of D decays. A measurement of the D+ and D0 semileptonic decay fractions indicates that the D+ has a significantly longer lifetime than the D0.
INCLUSIVE CROSS SECTIONS UNCORRECTED FOR RADIATIVE EFFECTS.
As part of a study of large p T phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈 γ /all〉 = 0.074 ± 0.012 for 6 GeV/ c < p T 10 GeV/ c , and 〈 γ /all〉 = 0.26 ± 0.04 for p T > 10 GeV/ c , with an additional systematic uncertainty of ±0.05 for both values.
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A study of the reaction π − p → X − p based on 1.27 × 10 6 events, corresponding to a mean sensitivity of 200 events/μb, is presented. Properties of the exclusive channels π − p → π − π 0 p, π + π − π − p, π + π − π − π 0 p, π + π + π − π − π − p and π + π + π − π − π − π 0 p are discussed.
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The reactions K − p → Ξ 0 − (1320) K 0 + , Ξ − (1320) K + (890), Ξ 0 − (1530) K 0 − and Ξ 0 − (1530) K 0 + (890) are studied at 4.2 GeV/ c incident momentum. The data come from a high-statistics bubble chamber experiment with a sensitivity of ∼ 133 events/ μ b. Total anddifferential cross sections are presented. The results are compared to the SU(3)-related processes K + p → pK + and K + p → pK + (890) in the backward hemisphere. In the forward hemisphere “forbidden” peaks are observed and current ideas about them are discussed.
FULLY CORRECTED FOR ALL CUTS AND UNSEEN DECAY MODES.
TOTAL, FORWARD AND BACKWARD CROSS SECTIONS. FULLY CORRECTED FOR CUTS, K0 AND LAMBDA UNSEEN DECAY MODES AND OTHER K*(892) AND XI(1530P13) DECAYS. IN 3-BODY FINAL STATES, THETA REFERS TO THE PI-K SYSTEM.
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We present final results on the inclusive production of the\(\bar K^{*0} (890)\),K*−(890),K*0(890),K*−(890),K*−(1420), and\(\bar K^{*0} (1420)\) resonances inK−p interactions at 32 GeV/c. Total cross sections and invariantx-distributions are determined. Inclusive cross sections of\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) amount to ≃4 mb each, of\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (1420)\) to ≃1 mb and ofK*0(890) to ≃0.8 mb. These values are in agreement with additive quark model predictions. All strangenessS=−1 resonances are predominantly produced in the forward hemisphere, the tensor mesons being more peripherally produced than the vector ones. The\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) density matrix elements andt-distributions are obtained. The unnatural spin-parity exchange contribution to inclusive\(\bar K^{*\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{o} } (890)\) production amounts to ≳60% at |t|<0.4 GeV2 and decreases with increasing |t|. Whenever relevant, a comparison is also made with available data at other energies.
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We have analyzed 1113 events of the reaction e + e − → hadrons at CM energies of 12 and 30 GeV in order to make a detailed comparison with QCD. Perturbative effects can be well separated from effects depending on the quark and gluon fragmentation parameters to yield a reliable measurement of the coupling constant α S . At 30 GeV, the result is α S = 0.17 ± 0.02 (statistical) ± 0.03 (systematic). QCD model predictions, using the fragmentation parameters determined along with α S , agree with both gross properties of the final states and with detailed features of the three-jet states.
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