In order to determine the ηNN coupling constant we have measured the two reactions K − p→ Λη and K − p→ Λπ 0 with a magnetic wire chamber spectrometer which contained a gamma counter for the γγ decays of π 0 and η. The Λ polarization and the differential cross sections are given. The latter have quite different u dependences. Their ratio is interpreted, in terms of a nucleon-Regge exchange model, as the effect of a small ηNN coupling constant for which we obtain G η NN 2 = G π NN 2 · (0.26 ± 0.10) as allowed by SU(3). The large value given by Heisenberg's non-linear field theory, G η NN 2 = G π NN 2 · 0.9, is excluded by this measurement if the characteristic u dependence of the Λπ 0 channel is attributed to N α Regge exchange.
Axis error includes +- 10/10 contribution.
No description provided.
Axis error includes +- 10/10 contribution.
A study is presented of the inclusive production cross sections of K ∗± (892) vector mesons in pp interactions at 12 and 24 GeV/ c and in π + p interactions at 16 GeV/ c . The K ∗± inclusive cross section is ∼0.9 mb for both pp at 24 GeV/ c and π + p interactions at 16 GeV/ c . For pp interactions, σ( K ∗+ ) and σ( K ∗− ) are seen to rise with energy, showing a threshold behaviour. In both pp and π + p interactions, σ( K ∗+ ) largely exceeds σ( K ∗− ) at these energies and this excess is interpreted as K ∗+ production by beam and target fragmentations. The decays of K ∗±0 yield ∼30% of the K 0 observed in the final states. The p T 2 dependence of both K ∗+ and K ∗ − cross sections is described by an exponential with slope of ∼3.3 (GeV/ c ) −2 . The longitudinal momentum spectra for K ∗+ in 16 GeV/ c π + p and 24 GeV/ c pp interactions are similar in shape in the target hemisphere. The K ∗− spectra are similar over the whole kinematic region when viewed in the quark c.m.s. and point to a central production mechanism. Comparing K ∗+ and ρ 0 production, striking similarities are found.
No description provided.
ASSUMED SIG(KS)=SIG(KL).
No description provided.
In partial wave analyses of the ( π − π − π + ) system, substantial shape changes of the 1 + S ( ϱπ ) intensity as a function of t , and relative phase changes of ≈ 90°, provide compelling evidence for a resonant A 1 of mass ≈ 1280 MeV and width ≈ 300 MeV.
No description provided.
The J PC = 2 −+ partial wave intensities and their large phase changes prove the resonant nature of the A 3 meson (mass ≈ 1670 MeV, width ≈ 210 MeV). The decay modes are f 0 π , ϱ 0 π , and ϵ 0 π . Evidence is found for a further 2 − enhancement.
No description provided.
The A 2 meson is studied in the decay mode ϱ 0 π − using partial wave analyses of 600 000 events from the reaction π − p→ π − π − π + p at 63 and 94 GeV incident momentum. Common production mechanisms are indicated for this resonance and diffractive 1 + and 2 − components.
No description provided.
Results on e + e − annihilation into hadrons at c.m. energies between 22 and 31.6 GeV are presented. The data were accumulated with the PLUTO detector at PETRA. The events are dominantly of the two-jet type. The value of the relative hadronic cross section R =3.88 ± 0.22 along with the details of the sphericity and thrust distribution rule out an open (tt̄) channel (Q t = 2 3 ) below 30 GeV. The inclusive muon results support the above conclusion.
CROSS SECTIONS CORRECTED FOR BEAM-GAS SCATTERING BACKGROUND, INITIAL STATE RADIATION, TAU HEAVY LEPTON CONTRIBUTION AND TWO-PHOTON EVENTS.
We present evidence for a narrow Y ∗ with a mass of 3.17 GeV and a width ⩽ 20 MeV decaying to ΣKK̄ + pions, ΛKK̄ + pions and ΞK + pions. The data come from two high statistics K − p bubble chamber experiments with a sensitivity of ≈100 eV/ μb at 8.25 GeV/ c and ≈ 45 eV/ μb at 6.5 GeV/ c .
OBSERVATION OF R(3170) ONLY DECAYING INTO 5 OR 6 PARTICLES (CROSS SECTION NOT CORRECTED FOR DECAYS WITH MORE THAN ONE UNSEEN FINAL STATE PARTICLE).
A peak in the pK−π+ and p¯K+π− invariant-mass spectra at 2.285±0.006 GeV/c2 is observed, which is associated with the lowest-lying charmed baryon (Λc). A cross section times branching ratio of 0.037±0.012 nb at Ec.m.=5.2 GeV is measured with a substantial fraction of the events produced with an equal recoiling mass. New measurements of inclusive p and Λ cross sections are also presented, allowing an estimate of the branching ratio B(Λc→pK−π+)=0.022±0.010.
THE TOTAL INCLUSIVE CHARMED LAMBDA CROSS SECTION IS DERIVED FROM THE OBSERVED PRODUCTION RATE VIA THE <P K- PI+> CHANNEL USING THE STEP IN INCLUSIVE PROTON PRODUCTION AT THE CHARMED-BARYON THRESHOLD AND REASONABLE ASSUMPTIONS. THE BRANCHING RATIO (LAMBDA/C+ --> P K- PI+) IS THEN 2.2 +- 1.0 PCT.
ACTUALLY TWICE THE INCLUSIVE ANTI-PROTON CROSS SECTION (EACH BARYON PAIR IS COUNTED TWICE).
EACH BARYON PAIR PRODUCED IS OF COURSE COUNTED TWICE IN THIS CROSS SECTION.
None
CORRECTIONS HAVE BEEN APPLIED FOR CONTRIBUTIONS FROM BEAM-GAS SCATTERING, TWO PHOTON SCATTERING, TAU HEAVY LEPTON PAIR PRODUCTION, AND FOR RADIATIVE EFFECTS. THE 13 AND 17 GEV MEASUREMENTS WERE PREVIOUSLY REPORTED IN R. BRANDELIK ET AL., PL 83B, 261 (1979).
PRELIMINARY INCLUSIVE CHARGED PARTICLE DISTRIBUTIONS.
Measurements of the reactions e++e−→e++e−, μ++μ−, and τ++τ− at PETRA energies (s12=13,17,27.4,30 and 31.6 GeV) are reported. The results show that these reactions agree well with the predictions of quantum electrodynamics thus determining that all the known charged leptons are pointlike particles to a distance < × 10−16 cm.
No description provided.
No description provided.
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