The cross section asymmetry Sigma has been measured for the photoproduction of pi0-mesons off protons, using polarized photons in the energy range Eg = 0.5 - 1.1 GeV. The CM angular coverage is Theta = 85 - 125 deg with energy and angle steps of 25 MeV and 5 deg, respectively. The obtained Sigma data, which cover the second and third resonance regions, are compared with existing experimental data and recent phenomenological analyses. The influence of these measurements on such analyses is also considered.
Axis error includes +- 3/3 contribution (Due to accuracy of the linear polarization calculations).
Axis error includes +- 3/3 contribution (Due to accuracy of the linear polarization calculations).
Axis error includes +- 3/3 contribution (Due to accuracy of the linear polarization calculations).
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A study of the reactions p Xe → K + K + X , p Xe → K + H(H → Σ − p)X and p Xe → K + K + H(H → Σ − p)X was performed using the 700-litre xenon bubble chamber DIANA, exposed to the 1 GeV/ c antiproton beam of ITEP (Moscow). From a sample of 7.8 · 10 5 antiproton annihilations at low energy in xenon nuclei 4 events were observed for the reaction p Xe | → K + K + X at rest ( P p ≤ 400 MeV /c ) and 8 for the same reaction in flight ( 400 ≤ P p ≤ 900 MeV /c ). The corresponding probabilities turned out to be 3.1 · 10 −5 and 3.4 · 10 −5 , respectively. No H -event was found in the two semi-inclusive reactions p Xe → K + HX and p Xe → K + K + HX . This lead to the upper limits 6 · 10 −6 and 8 · 10 −6 (90% C.L.), respectively. The corresponding upper limit for the fully inclusive reaction p Xe → HX turned out to be 1.2 · 10 −5 (90% C.L.), which is about one order of magnitude lower than the actual value reported in the literature.
No description provided.
Data from BEBC experiments are combined to provide large statistics for neutrino interactions. ChargedD* mesons are produced in (1.22±0.25)% of neutrino and (1.01±0.31)% of antineutrino charged current interactions. The mean fraction of the hadronic laboratory energy taken by theD*+ in these events is 0.59±0.03±0.08. Less than 18% of all chargedD* mesons from (anti)neutrino interactions are found to be daughters ofD**0 (at the 90% confidence level).
Mean fractional hadronic energy carried by the D*+- in the laboratory system.
Mean value of the Bjorken scaling variable X.
Rate of charged D* meson production per charged current neutrino interaction.
The measurement of different reactions of p d annihilation at rest in a gaseous target has been performed using the OBELIX spectrometer at LEAR (CERN). A strong deviation from the OZI-rule prediction was found from the measurement of the ratio R = φπ ωπ in two regions of proton momenta, P < 200 MeV/ c and P > 400 MeV/ c : R( φπ − ωπ − ) = (133 ± 26) × 10 −3 and (113 ± 30) × 10 −3 , respectively. These values are about 30 times greater than the theoretical prediction. For the first time the excitation of the †-resonance was observed among the final-state products of p d annihilation. The existence of a broad enhancement in the 4π invariant mass at m ≈ 1480 MeV, seen in previous experiments, was confirmed. A ≈ 100 MeV downward shift of the bump position, when the proton momentum increased up to P > 400 MeV/ c , was also observed, while the positions of ω, ϱ and f 2 (1270) did not change with the proton momentum. The following branching ratios were measured: BR( p d → π − φ p ) = (6.62 ± 0.49) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − φ p ) = (0.95 ± 0.22) × 10 −4 , for P > 400 MeV/ c ; BR( p d → π − ω p ) = (49.7 ± 8.9) × 10 −4 , for P < 200 MeV/ c ; BR( p d → π − ω p ) = (8.38 ± 1.09) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 2π − π + p ) = (150 ± 6) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 2π − π + p ) = (16.6 ± 0.9) × 10 −4 , for P > 400 MeV/ c ; BR( p d → 3π − 2π + p ) = (326 ± 12) × 10 −4 , for P < 200 MeV/ c ; BR( p d → 3π − 2π + p ) = (44 ± 7) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − ) = (0.96 ± 0.19) × 10 −4 , for P > 400 MeV/ c ; BR( p d → Λ K + π − π 0 ) = (3.5 ± 0.8) × 10 −4 , for P > 400 MeV/ c ; BR( p p → 2π − 2π + ) = (540 ± 20) × 10 −4 ; BR( p p → 3π − 3π + ) = (251 ± 21) × 10 −4 .
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In this letter the distribution of slow target associated particles emitted in Au + Emulsion interactions at 11.6 A GeV/ c is studied. The three models RQMD, FRITIOF and VENUS are used for comparisons and especially their treatment of rescattering is investigated.
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PROJECTILE ASSOCIATED HE-FRAGMENTS.
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Annihilation cross-sections σann for antineutrons on some nuclei (C, Al, Cu, Sn and Pb) at three antineutron momenta (180, 240 and 280 MeV/c) were measured at LEAR (CERN) with the OBELIX spectrometer. A behaviour σann=σ0Aν has been found withν≈2/3. The data are discussed following some models for antineutron-nucleus interaction.
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Neutrino interactions in BEBC produce theDS** (2536) charmed strange meson. The mass of this state is 2534.2±1.2 MeV. The production rate is 0.011±0.005 per neutrino charged current interaction at a mean neutrino energy of 61 GeV. An earlier claim for another\(c\bar s\) bound state near 2565 MeV, produced in neutrino interactions, is not supported.
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The double strangeness production has been observed in two final states of annihilation of antiprotons at momentum less than 0.9 GeV/ c on Xe nuclei: K + K + X (8 events) and K + K 0 ΛX (6 events). The probabilities of the reaction p Xe → K + K + X vary from 2 · 10 −5 (at rest) up to 7 · 10 −5 (in flight). The reaction p Xe → K + K 0 ΛX is observed only in flight with probability 3 · 10 −4 . The properties of the observed reactions are similar to those resulting from the cascade process with production of Ξ hyperon: p N → K ∗ −K ∗ , K ∗ → Kπ, −K ∗ N → ΞK, ΞN → ΛΛ . The new upper limit on the production probability of the stable H ( S = −2) dibaryon in the reaction Xe → K + K + H(H → Σ − p)X was obtained to be < 2 · 10 − (90% C . L .).
No description provided.
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