Search Results (7 total)

We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural network approach, provides the asymmetries A_p^lN→lhhX=0.030±0.057(stat)±0.010(syst) and A_d^lN→lhhX=0.070±0.076(stat)±0.010(syst). From these values we derive an averaged gluon polarization ΔG/G=-0.20±0.28(stat)±0.10(syst) at an average fraction of nucleon momentum carried by gluons 〈η〉=0.07.

We present the results of the spin asymmetries A₁ of the proton and the deuteron in the kinematic region extending down to x=6×10^-5 and Q²=0.01 GeV². The data were taken with a dedicated low x trigger, which required hadron detection in addition to the scattered muon, so as to reduce the background at low x. The results complement our previous measurements and the two sets are consistent in the overlap region. No significant spin effects are found in the newly explored region.

We present the final results of the spin asymmetries A₁ and the spin structure functions g₁ of the proton and the deuteron in the kinematic range 0.0008<x<0.7 and 0.2<Q²<100 GeV². For the determination of A₁, in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new method which minimizes the radiative background by selecting events with at least one hadron as well as a muon in the final state. We find that this hadron method gives smaller errors for x<0.02, so it is combined with the usual method to provide the optimal set of results.

We have measured the spin-dependent structure function g₁^p in inclusive deep-inelastic scattering of polarized muons off polarized protons, in the kinematic range 0.003<x<0.7 and 1 GeV²<Q²<60 GeV². A next-to-leading order QCD analysis is used to evolve the measured g₁^p(x,Q²) to a fixed Q₀². The first moment of g₁^p at Q₀²=10 GeV² is Γ₁^p=0.136±0.013 (stat) ±0.009 (syst) ±0.005 (evol). This result is below the prediction of the Ellis-Jaffe sum rule by more than two standard deviations. The singlet axial charge a₀ is found to be 0.28±0.16. In the Adler-Bardeen factorization scheme, Δg≃2 is required to bring ΔΣ in agreement with the quark-parton model. A combined analysis of all available proton, deuteron, and ³He data confirms the Bjorken sum rule.

We present a new determination of the nonsinglet structure function F₂^p - F₂ⁿ at Q²=4 GeV² using recently measured values of F₂^d and F₂ⁿ/F₂^p. A new evaluation of the Gottfried sum is given, which remains below the simple quark-parton model value of 1/3.

Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F₂ⁿ/F₂^p in the kinematic range 0.004<x<0.8 and 0.4<Q²<190 GeV², together with the structure function F₂^d determined from a fit to published data, are used to derive the difference F₂^p(x)-F₂ⁿ(x). The value of the Gottfried sum F(F₂^p-F₂ⁿ)dx/x=0.240±0.016 is below the quark-parton-model expectation of 1/3.