We have measured the cross section for γγ production with the TOPAZ detector in the energy region √ s =50.0–61.4 GeV. The observed cross section for γγ production integrated over |cos θ | ⩽ 0.77 is 50.2±0.8±2.2 pb at 〈√ s 〉=57.6 GeV and the ratio of this value to the QED prediction is 1.01±0.02±0.04. The angular distribution is in good agreement with the QED predictions, thereby setting limits on the compositeness scales, Λ L+R + =168 GeV, Λ L+R − =97 GeV, Λ L,R =141 GeV, Λ L,R − =81 GeV, and Λ L−R ± =68 GeV, at the 95% confidence level. The reaction e + e − → γγγ was also studied and was found consistent with the QED prediction.
No description provided.
No description provided.
No description provided.
We have measured the K + K - /π + π - ratio R from p annihilations in gaseous D 2 and H 2 at atmospheric pressure. The measurement was performed with the OBELIX spectrometer. From the measured value in gaseous D 2 (0.27±0.02) we infer a P wave contribution to p −p annihilation in D 2 of (18±7)%.
Two different triggers were used.
Inelastic scattering of 490 GeV μ + from deuterium and xenon nuclei has been studied for x Bj > s .001. The ratio of the xenon/deuterium cross section per nucleon is observed to vary with x Bj , with a depletion in the kinematic range 0.001 < x Bj < 0.025 which exhibits no significant Q 2 dependence. An electromagnetic calorimeter was used to verify the radiative corrections.
Xenon structure function parameterized as being equal to the DEUT structurefunction.
Xenon structure function parameterized by an x-dependent shadowing factor times the DEUT structure function.
Data collected in the experiment R704 at the CERN ISR are used to study the annihilation process p p → π 0 π 0 at several centre-of-mass energies between 2.97 and 3.56 GeV. A total sample of 7359 events has been identified, from which cross sections and angular distributions in the interval 0 < | cos θ ∗ | < 0.5 have been measured.
No description provided.
No description provided.
Multiplicity, inclusive, correlation and collective characteristics of multiparticle production processes inK+ Al,K+ Au, π+ Al and π+ Au interactions at 250 GeV/c are studied with the European Hybrid Spectrometer, providing high statistics and almost 4 π acceptance for final state charged particles. It is shown that the proton energy spectrum practically does not depend on the target atomic weight, but the proton angular distributions reveal a strongA-dependence. In a model independent way, the average number of intranuclear collisions is extracted, and it is shown that their dominant part (60% for Al and 80% for Au) is caused by interactions of the non-leading particles produced in the target fragmentation. The multiplication ratio of the produced particles for the Au nucleus changes fromR≃40 at the smallest rapidities in the target fragmentation region, down toR=0.37±0.06 at the largest rapidities in the beam fragmentation region. It is found that the average total longitudinal momentum of the charged products of the beam fragmentation depends weakly on the number of leading hadron (cluster) intranuclear collisions which are characterized by a low inelasticity coefficient 〈k〉=0.17±0.03.
No description provided.
No description provided.
Backward emitted protons with momentump>0.3 GeV/c in interactions of neutrino in the energy range 10–200 GeV with photoemulsion nuclei were investigated. Energy spectrum slope parameter of backward protons was measured to beT0=48.9±7.9 MeV. TheA-dependence power index of relative mean yield of backward protons was found to bea=0.68±0.12. A drop in the mean yield of backward protons at the four momentum squared over ∼15 (GeV/c)2 (the neutrino energy over ∼50 GeV) was observed.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
NUCLEUS IS AVERAGE NUCLEI OF NUCLEAR EMULSION, <A> ABOUT 80.
Using the CELLO detector, we have measured cross sections for the processγγ→π+π− in the mass range 0.75–1.9 GeV/c2. A partial wave fit to the data indicates the presence of a sizeableS-wave amplitude with signs of resonant behaviour. Values for the γγ width of thef2(1270) are given, showing the model-dependence of this quantity. At higher dipion masses, the model of Brodsky and Lepage is found to give an order of magnitude description of the data.
No description provided.
No description provided.
Meson production in proton, oxygen and sulphur interactions with uranium targets at 200 GeV/nucleon is studied. We measure the inclusive meson cross-section d σ/dPT2 and its evolution fromp+U to S+U. The cross-section fitted with an exponential gives an inverse slopePT0 of the order of 210 MeV/c. As a function of the neutral transverse energy,PT0 values show a slight rise followed by a plateau. The normalized difference (σ+−σ−)/σ− between positive and negative meson cross-sections is found to increase withET.
No description provided.
No description provided.
No description provided.
None
NUCLEUS IS P, C, AL, CU.
NUCLEUS IS P, C, AL, CU.
NUCLEUS IS P, C, AL, CU.
The electroproduction of π0 on the proton was measured from 0 to 2.5 MeV above threshold for virtual-photon 4-momenta of -0.05 and -0.1 (GeV/c)2. The sum of the lowest-order contributing multipoles, a0=‖E0+‖2-εL‖L0+‖2, was determined with a precision an order of magnitude better than previously possible. Our results for a0 are consistent with present calculations. Our extracted value for ‖L0+‖2 at the ‘‘photon point’’ is in agreement with recent predictions.
Joined statistics for two incident electron energy of 300 and 500 MeV.
Forum