The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the dimuon massM and transverse momentumPT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at highET)/(ψ/Continuum at lowET), from which theJ/ψ relative suppression can be extracted. This suppression is enhanced at lowPT.
Ratio of number of J/PSI's to number of continuum events in given mass interval.
In the analysis of the reactione+e−→e+e−KS0Ks0 clear evidence for exclusive γγ→f2′ resonance production is observed. The productΓγγ ·B(f2′→K\(\bar K\)) is measured to be 0.10−0.03−0.02+0.04+0.03 keV independent of ana priori assumption on the helicity structure. Our data are consistent with a pure helicity 2 contribution and we derive an upper limit for the ratioΓγγ(0)/Γγγ. The absence of events in the mass region around 1.3 GeV clearly proves destructivef2−a2 interference and allows to measure the relative phases betweenf2,a2 andf2′. Upper limits on the production of the glueball candidate statesf2(1720) andX(2230) as well as theKS0KS0-continuum are given.
Data read from graph.
This paper presents experimental results on π + π − production threshold from the collision of quasi-real photons. The data, obtained at the e + e − collider DCI, are a combination of the results from the DM1 and DM2 experiments. Using the e + e − and π + π − production for normalization and cross-checks, we observe a pion pair yield at low invariant mass ( W < 500 MeV/ c 2 ) which is approximately twice the one expected from Born terms.
Data read from graph.
Data read from graph.
Results are presented of an untagged e + e − → e + e − + π + π − experiment performed at PEP with the DELCO detector. In the invariant-mass range 0.7 ⩽ W ππ < 2.0 GeV/ c 2 , the QED e + e − background is identified and eliminated, and both the π + π − predictions and the μ + μ − and K + K − background substractions are normalized to the measurement of the e e + e − events. The results agree with a simple model of superposition and interference of the f 0 (1270) resonance, produced with helicity 2, with a Born-term continuum. From a fit of the model to the data, the radiative width of the f 0 is determined to be Γ f 0 → γγ = 2.70 ± 0.21 keV.
Data read from graph.
Using the ARGUS detector at DORIS we have obtained evidence for a resonance which decays into an F meson and a photon. The observed mass is 2109 ± 9 ± 7 MeV, which is 144 ± 9 ± 7 MeV greater than the F meson mass. Its properties are consistent with those of the F ∗ meson with J P = 1 − .
No description provided.
We have observed exclusive production of K + K − and K S O K S O pairs and the excitation of the f′(1515) tensor meson in photon-photon collisions. Assuming the f′ to be production in a helicity 2 state, we determine Λ( f ′ → γγ) B( f ′ → K K ) = 0.11 ± 0.02 ± 0.04 keV . The non-strange quark of the f′ is found to be less than 3% (95% CL). For the θ(1640) we derive an upper limit for the product Λ(θ rarr; γγ K K ) < 0.03 keV (95% CL ) .
Data read from graph.. Errors are the square roots of the number of events.
Data read from graph.. Errors are the square roots of the number of events.
The high mass μ + μ − pairs produced by 280 GeV μ + on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons ( π , K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σ γ ·(γ→μ + μ − )<13·10 −39 cm 2 /nucleon.
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We investigate the four-photon final state produced in γγ colissions. In the π 0 π 0 channel we observe f(1270) production with predominantly helicity 2 and measure a partial width Γ γγ 2.9 +0.6 −0.4 ± keV (independent of assumptions on the helicity). We observe A 2 (1310) production in the π 0 η channel and find a partial width Γ γγ = 0.77 ± 0.18 ± 0.27 KeV (assuming helicity 2). We give an upper limit for f ≈ ηη .
Data read from graph. Systematic error on M is of order of 2% or less.
Data read from graph.
No description provided.
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