The x and Q 2 dependence of the single photon exchange cross section d 2 σ /d Q 2 d x and the proton structure functions F 2 ( x , Q 2 ) and R ( x , Q 2 ) have been measured in deep inelastic muon proton scattering in the region 0.02 < x < 0.8 and 3 < Q 2 < 190 GeV 2 . By comparing data at different incident muon energies R was found to have little kinematic dependence and an average value of −0.010 ± 0.037 (stat.) ± 0.102 (stat.). The observed deviations from scaling gave the value of Λ MS , the QCD mass scale parameter, to be 105 −45 +55 (stat.) −45 +85 (syst.) MeV. The fraction of the momentum of the nucleon carried by gluons was found to be ∼56% at Q 2 ∼22.5 GeV 2 . It is shown that to obtain a description of the data for F 2 ( x , Q 2 ) together with that measured in deep inelastic electron-proton scattering at lower Q 2 it is necessary to include additional higher twist contributions. The value of Λ MS remains unchanged with the inclusion of these contributions which were found to have an x -dependence of the form x 3 /(1 − x ).
No description provided.
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We have measured the deuteron magnetic form factor B(q2) for values of the momentum transfer squared between 7 and 28 fm−2. The data are compared with relativistic and nonrelativistic predictions including meson-exchange-current contributions. Significant disagreement is found for large momentum transfers.
No description provided.
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We have studied 419 τ pair events produced in the reactione+e−→τ+ τ− at a c.m. energy of 34.6 GeV. We measure the cross section and angular distribution, as well as the decay branching ratios. The production characteristics are consistent with the Standard Electroweak Model predictions of γ andZ0 interference. The branching ratios are generally consistent with the τ decaying according to standard weak interaction principles, but we observe somewhat more decays resulting in single charged hadrons plus neutrals than are predicted by present theory.
Corrected for radiative effects.
Measured cross section relative to Standard Model Prediction.
Asymmetry based on fits to angular distribution.
We report the observation of 21 dimuon events at the CERN p p Collider with the UA1 detector. The events range in invariant dimuon mass from 2 to 22 GeV / c 2 . The properties of these events are given. The bulk of the events are consistent with heavy-flavour production (mainly b b ) with a few candidates for Drell-Yan production. There remain a few events which are difficult to interpret in terms of these processes, in particular two events with isolated, like-sign muons.
No description provided.
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The reactions p¯p→π+π− and K+K− have been studied at 390, 490, 590, 690, and 780 MeV/c. An enhancement of about 150 μb has been observed in the cross sections of both reactions at the same beam momentum of 490 MeV/c. If this structure is interpreted as a meson resonance, it has a mass of 1940 ± 20 MeV and a width of less than 40 MeV.
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Hadronic production of charmed particles in association with muons from their semileptonic decay has been observed in a high-resolution streamer-chamber experiment performed at Fermilab. A miss-distance analysis of the pictures gives a signal of 17.3±4.7 events. Depending on the production model this corresponds to a range of neutron-nucleon cross sections from 8 to 50 μb, assuming an A23 dependence.
NEUTRON BEAM : 280 GEV - AVERAGE ENERGY, PEAKED AT 320 GEV WITH FWHW OF 130 GEV.
NEUTRON BEAM : 280 GEV - AVERAGE ENERGY, PEAKED AT 320 GEV WITH FWHW OF 130 GEV.
Large-angle cross sections for γd→π0d are systematically measured in the photon energy range between 500 and 1000 MeV. A good fit is obtained by use of a Glauber-model calculation which includes the dibaryon resonances F33(2.26) and G41(2.51), but the fit has an unusual nature in the role of resonance and nonresonance contributions.
Liquid hydrogen target for final calibration.
LIQUID DEUTERIUM TARGET.
The antineutron angular distribution in the reaction p¯C→n¯X was measured at 590 MeV/c. The shape of the distribution is found to be similar to that of the elementary process p¯p→n¯n, which indicates that the quasi-free process is the dominant mechanism for p¯C→n¯X. The antineutron production cross section per bound proton in the carbon nucleus is 0.14 times that for a free proton.
No description provided.
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We have measured the coherent nuclear production of π+ω systems at 202.5 GeV. This final state is dominated by the B+(1235) meson with a measured mass and full width of 1.271 ± 0.011 GeV and 0.232 ± 0.029 GeV, respectively. A radiative width of 230 ± 60 keV was extracted for the process B+(1235)→π+γ.
DATA REQUESTED FROM THE AUTHORS.