Results on the reaction γγ → π + π − π 0 π 0 are presented. There is clear evidence for correlated ϱ + ϱ − production. The cross section is much lower than for γγ → ϱ 0 ϱ 0 .
Results using 3 parameter fit (rho+ rho-, rho+- pi+- pi0, and non-resonant 4pi) to data.
Results using 2 parameter fit (rho+ rho-, and non-resonant 4pi) to data.
In the reaction γγ→KS0KS0 resonance production of thef2− is observed. For the radiative with\(\Gamma _{\gamma \gamma } .B(f'_2\to K\bar K) = 0.11_{ - 0.02}^{ + 0.03}\pm 0.02keV\) is found. The small number of events in thef2,a2 mass region is consistent with the assumption of destructivef2−a2 interference. From the mass distribution we determine the relative phases between the tensor mesons. Upper limits on the radiative widths of the glueball candidatesf2(1720) andX (2220) are derived.
Only bins containing events are included, all others are zero.. Untagged plus single events.. Data read from graph.
Only bins containing events are included, all others are zero.. Untagged events.. Data read from graph.
Corrected for the angular distribution, which is assumed to be sin(theta)**4. Additional systematic error decreasing from 20% in the lowest mass bins to 15% for W > 1.5 GeV.. Data read from graph.
Two-photon production of the exclusive final statesp\(\bar p\)+nπ (n=0, 1, 2, and 3) has been investigated using the ARGUS detector at thee+e− storage ring DORIS II at DESY. The reactionsγγ→p\(\bar p\)π andγγ→p\(\bar p\)π+π−π0 have been observed for the first time, as have theΔ++ and\(\overline {\Delta ^{ ++ } } \) baryons in the final statep\(\bar p\)π+π−. No evidence was found forΔ++\(\overline {\Delta ^{ ++ } } \) production. Topological cross sections for two-photon production ofp\(\bar p\),p\(\bar p\)π0,p\(\bar p\)π+π− andp\(\bar p\)π+π−π0, as well as the crosssection forγγ→Δ++\(\bar p\)π+π−+c.c., have been measured. Upper limits are given for the cross section forγγ→Δ0\(\overline {\Delta ^0 } \),γγ→Δ++\(\overline {\Delta ^{ ++ } } \) andγγ→Λ\(\bar \Lambda \).
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
Data read from graph.. Additional overall systematic error 13% not included.
Measurements of inclusive transverse-momentum spectra for KS0 mesons produced in proton-antiproton collisions at s of 630 and 1800 GeV are presented and compared with data taken at lower energies. The ratio, as a function of pT, of the cross section for KS0 to that for charged hadrons is very similar to what is observed at lower energies. At 1800 GeV, we calculate the strangeness-suppression factor λ=0.40±0.05.
Estimated effective cross sections for events which pass the trigger and selection criteria. The uncertainties in these represent the principal source of error in the overall normalisation of the results.
Statistical errors only.
Statistical errors only.
The contradiction of the σ term of pion-nucleon scattering as deduced from the Karlsruhe-Helsinki phase shifts with the smaller value calculated by the chiral perturbation theory of QCD is well known. In an effort to clarify the discrepancy we have determined the real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering at a pion energy Tπ=54.3 MeV by measurement of the elastic scattering of positive and negative pions on protons in the Coulomb-nuclear interference region. The deduced value is in agreement with the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. The resulting large value of the σ term may be interpreted as being due to the influence of s¯s sea pairs even at large distances (small Q2) as previously suggested by the European Muon Collaboration measurement of deep-inelastic scattering of polarized muons on polarized protons.
No description provided.
The inclusive cross section for charged-D* production by 205-GeV/c π− mesons incident on a beryllium target was measured with a two-arm spectrometer triggered by prompt muons. Using the mass-difference technique often employed in D* studies, a signal of 31±11 charged D*’s was isolated; it includes contributions from both the D*+ and D*− charged modes in correlation with triggering muons of the proper charge. This corresponds to an inclusive charged-D* production cross section of 220±77−57+77 μb per Be nucleus or 24±9−6+9 μb per nucleon when the cross section is scaled linearly with atomic mass number. The first error is statistical and the second is systematic.
No description provided.
We have used the Fermilab 30-in. bubble-chamber hybrid spectrometer to study multiparticle production in the interactions of 200-GeV/c protons and π+ and K+ mesons with nuclei of gold, silver, and magnesium. We find that the multiplicities of produced particles and negative particles increase linearly with the number of projectile collisions, with no beam or target dependence. The number of secondary collisions in the nucleus increases significantly less rapidly with the number of projectile collisions than has been reported by a streamer chamber experiment. The properties of secondary collisions suggest that they arise from rescattering of recoil nucleons rather than intranuclear cascade of produced particles. Dispersions of multiplicity distributions at fixed impact parameter are in better agreement with a model of independent sources than with Koba-Nielsen-Olesen scaling.
No description provided.
PION means all charged secondaries except identified protons.
No description provided.
We present evidence for the non-Abelian nature of QCD from a study of multijet events produced in e+e− annihilations from √s =50 to 57 GeV in the AMY detector at the KEK storage ring TRISTAN. A comparison of the three-jet event fraction at TRISTAN to the fraction of the DESY storage ring PETRA shows that the QCD coupling strength αs decreases with increasing Q2. In addition, measurements of the angular distributions of four-jet events show evidence for the triple-gluon vertex.
No description provided.
No description provided.
Central collisions of 800-GeV protons with the heavy components of nuclear emulsion, Ag107 and Br80, have been investigated to determine the characteristics of small-impact-parameter collisions and, by comparison with the analysis of inclusive proton-emulsion inelastic interactions and inelastic proton-nucleon collisions, to study the dependence of the interaction process on the mean number of intranuclear collisions 〈ν〉. The data are also compared with the results obtained in proton-emulsion collisions, both central and inclusive, at 200 GeV. The variations in the secondary-particle multiplicities and the normalized pseudorapidity density correlate with 〈ν〉 and demonstrate that proton-nucleus interactions, both central and inclusive, can be described adequately by the incoherent superposition of proton-nucleon collisions.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
Scaled factorial moments, corrected for the shape of the single-particle pseudorapidity distribution, are analyzed in pseudorapidity and in two-dimensional (pseudorapidity and azimuth angle) space. An intermittent, power-law growth of the moments with decreasing bin size is found, with two-dimensional analysis revealing a much stronger effect than for one-dimensional for nucleus-nucleus data. The intermittent patterns are more evident for proton-nucleus than for nucleus-nucleus collisions, with the heaviest nucleus, S32, showing the weakest effect.
SEMICENTRAL EVENTS.
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