Measurements of the total reaction cross section for 12−16C, 14−17N, and 16−18O on carbon target at intermediate energies were performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. A larger enhancement of σR for 15C was observed than for its neighbors. Evidence for possible anomalous nuclear structure in 15C was revealed in the analysis of the total reaction cross section in terms of the difference factor d.
No description provided.
The p̄ 3 He annihilation cross section is measured for the first time in the momentum interval (50÷60) MeV/ c . About 9000 pictures collected by the Streamer Chamber Collaboration (PS179) at LEAR–CERN have been scanned. Six events are found, corresponding to σ ann =1850±700 mb. The result is compared to the set of measurements presently available in the region of low p̄ momentum.
The mean beam momentum at the center of the fiducial volume = 55 MeV.
The antineutron–proton total cross section has been measured in the low momentum range 50–400 MeV/ c (below 100 MeV/ c for the first time). The measurement was performed at LEAR (CERN) by the OBELIX experiment, thanks to its unique antineutron beam facility. A thick target transmission technique has been used. The measured total cross section shows an anomalous behaviour below 100 MeV/ c . A dominance of the isospin I =0 channel over the I =1 one at low energy is clearly deduced.
Measured values of the total cross section.
Neutral and charged two-pion production in p+d→ 3 He+2 π reactions has been studied at CELSIUS at a proton beam energy of 477 MeV. The total cross section for double pion production is 0.22±0.03 μ b. The ratio of the cross sections for the production of charged pion pairs with isospin T =1 and T =0 was determined to be σ ( π + π − ; T =1)/ σ ( π + π − ; T =0)=1.4±0.4.
(I=1, I=0) stands for isospin of PI+ PI- system.
The d( α , 6 Li ∗ 3.56 ) π 0 reaction has been studied at E c.m. =1.2 and 1.9 MeV above threshold with an alpha-particle beam incident on a deuterium cluster-jet target in CELSIUS. Complete differential cross sections were measured at both energies, integrated to σ =228±6+70 nb and 141±12+42 nb respectively. Observed large anisotropies are discussed in relation to the cluster structure of the 6 Li ∗ halo.
The excited LI6* level has E=3.56 mev (at the highest beam energy the second T=1 state in LI6 at 5.37 mev is possible to populate).
A search for double- Λ hypernuclei ( 12 ΛΛ Be) and H -dibaryons using the 12 C( K − , K + ) reaction was performed at the BNL-AGS using a high-intensity 1.8 GeV/ c K − beam. A missing-mass analysis below the end point of the quasi-free Ξ − production was used to investigate these S =−2 systems. The upper limit obtained for the forward-angle cross section of 12 ΛΛ Be production is 6 to 10 nb/sr. This is the first search for the direct production of double- Λ hypernuclei to reach the sensitivity required to observe the signal predicted by theoretical calculations. For the H -production cross section, we have obtained an upper limit in the range of a few nb/sr to 10 nb/sr for the H mass below 2100 MeV/ c 2 . This upper limit is the most sensitive H search result to date for a tightly bound H .
Upper limit is given.
The production of the H-dibaryon could occur via the (K-, K+) reaction on two protons in a nucleus: K- (PP) --> K+ H-dibaryon. Upper limit is given.
Total cross sections for the pp --> pp eta' reaction have been measured in the excess energy range from Q = 1.53 MeV to Q = 23.64 MeV. The experiment has been performed at the internal installation COSY-11 using a stochastically cooled proton beam of the COoler SYnchrotron COSY and a hydrogen cluster target. The determined energy dependence of the total cross section weakens the hypothesis of the S-wave repulsive interaction between the eta' meson and the proton. New data agree well with predictions based on the phase-space distribution modified by the proton-proton final-state-interaction (FSI) only.
Total cross sections w.r.t the excess energy in the CM system. Statistical errors only are given. As well as the 15 PCT overall systematic uncertainty there is an uncertainty on the energy of 0.44 MeV.
The p ̄ Ne annihilation cross section is measured for the first time in the momentum interval (53÷63) MeV/c. About 9000 pictures collected by the Streamer Chamber Collaboration (PS179) at LEAR-CERN have been scanned. Four events are found, corresponding to σ ann =2210±1105 mb. The result is compared to the set of measurements presently available in the region of low p̄ momentum.
No description provided.
The production of single photons has been studied in the reaction e+e- -> gamma + invisible particles at centre-of-mass energies of 183 GeV and 189 GeV. A previously published analysis of events with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data were collected with the DELPHI detector and correspond to integrated luminosities of about 51 pb^{-1} and 158 pb^{-1} at the two energies. The number of light neutrino families is measured to be 2.84 +/- 0.15(stat) +/- 0.14(syst). The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also determined.
No description provided.
Combined result.
Bhabha scattering data recorded at \sqrt{s}=189 GeV by the L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are alpha^-1(-2.1 GeV^2) - alpha^-1(-6.25 GeV^2) = 0.78 +/- 0.26 alpha^-1(-12.25 GeV^2) - alpha^-1(-3434 GeV^2) = 3.80 +/- 1.29, in agreement with theoretical predictions.
No description provided.
Results extracted from the small angle Bhabha scattering sample at Z peak. Results contained total experimental uncertainty.
Results extracted from the large angle Bhabha scattering sample at sqrt(s) = 189 GeV. Results contained total experimental and theoretical uncertainty.
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