P. Amaudruz 13a M. Arneodo 14 A. Arvidson 15 B. Badelek I7~++ G. Baum ~ J. Beaufays 9b,** I.G. Bird 4c,* M. Botje 13 C. Broggini 8d w. Bruckner 4* A. Brüll 3*, W.J. Burger 13e J~Ciborowski 9~**, R. van Dantzig 9,**, H. Döbbeling 4g,*, J. Domingo 13h J~Drinkard 12 H. Engelien 3,*, M.I. Ferrero 14 L. Fluri 8 P. Grafstrom 15i D. von Harrach ~ M. van der Heijden 9,**, C. Heusch 12 Q~Ingram 13 K. Janson 15 M. de Jong 9,** E.M. Kabuss 41.*, R. Kaiser 3*, T.J. Ketel 9,**, F. Klein 6,* B. Korzen ‘~“~‘, U. Krüner 18,* S. Kullander ~ U. Landgraf 3*, F. Lettenström 12 T. Lindqvist ‘~ G.K. Mallot 6,* C. Mariotti 14 G. van Middelkoop 2,9,** A. Milsztajn ~, Y. Mizuno 4k,* J~Nassalski 16,9,-4-,** D. Nowotny 4.*, N. Pavel 18(,~ c~Peroni 14 H. Peschel 18m,* B. Povh ~,5,* R. Rieger 6,* K. Rith 4,*, K. Röhrich bn,* E. Rondio 17,++ L. Ropelewski 17.±+ A. Sandacz ~ C. Scholz ~,*, R. Schumacher 13o U. Sennhauser ~ F. Sever 1q,~ T.-A. Shibata 5,*, M. Siebler “i’, A. Simon 4,*, A. Staiano 14 G. Taylor br M. Treichel 4s,*, M. Virchaux ~ J.L. Vuilleumier 8 T. Walcher ~ R. Windmolders ~ and F. Zetsche ~,*

We present a measurement of the longitudinal spin cross section asymmetry for deep inelasticmuon-nucleon interactions with two high transverse momentum hadrons in the final state. Twomethods of event classification are used to increase the contribution of the Photon Gluon Fusionprocess to above 30%. The most effective one, based on a neural network approach, provides theasymmetries A

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+/-0.010 and A_d(lN->lhhX)=0.070+/-0.076+/-0.010. From these values we derive an averaged gluon polarization delta(G)/G=-0.20+/-0.28+/-0.10 at an average fraction of nucleon momentum carried by gluons eta=0.07.

A muon beam polarimeter was built for the SMC experiment at the CERN SPS, for beam energies of 100 and 190 GeV. The beam polarisation is determined from the asymmetry in the elastic scattering off the polarised electrons of a ferromagnetic target whose magnetisation is periodically reversed. At muon energies of 100 and 190 GeV the measured polarisation is Pμ=−0.80±0.03 (stat.)±0.02 (syst.) and Pμ=−0.797±0.011 (stat.)±0.012 (syst.), respectively. These results agree with measurements of the beam polarisation using a shape analysis of the decay positron energy spectrum.

Arrays of limited streamer tubes of the Iarocci type were deployed in our experiment at CERN as part of a forward muon detector system with provisions for the beam to pass through the center of each panel in the array. A total of 16 4 m×4 m panels were assembled with inductive readout strips on both sides of each panel. An active feedback system was deployed to regulate the high voltage to the streamer tubes to insure a constant efficiency for minimum ionizing particles. The arrays were operated in this environment for over five years of data taking. Streamer tube track-reconstruction efficiencies and tube replacement rates are reported.

The polarized target of the Spin Muon Collaboration at CERN was used for deep inelastic muon scattering experiments during 1993–1996 with a polarized muon beam to investigate the spin structure of the nucleon. Most of the experiments were carried out with longitudinal target polarization and 190 GeV muons, and some were done with transverse polarization and 100 GeV muons. Protons as well as deuterons were polarized by dynamic nuclear polarization (DNP) in three kinds of solid materials — butanol, ammonia, and deuterated butanol — with maximum degrees of polarization of 94%, 91% and 60%, respectively. Considerable attention was paid to the accuracies of the NMR polarization measurements and their analyses, the accuracies achieved were between 2.0% and 3.2%. The SMC target system with two cells of opposite polarizations, each cell 65 cm long and 5 cm in diameter, constitutes the largest polarized target system ever built and facilitates accurate spin asymmetry measurements. The design considerations, construction and performance of the target are reviewed.

We present the results of the spin asymmetries Al of the proton and the deuteron in the kinematic region extending down to x = 6 x 10(-5) and Q(2) = 0.01 GeV2. The data were taken with a dedicated low x trigger, which required hadron detection in addition

The 1996 data taking of the SMC experiment used polarized protons to measure the spin-dependent structure function g(1) of the proton. Three liters of solid granular ammonia were irradiated at the Bonn electron linac in order to create the paramagnetic radicals which are needed for polarizing the protons. Proton polarizations of +/- (90 +/- 2.5)% were routinely reached. An analysis based on a theoretical line shape for spin-1. systems with large quadrupolar broadening was developed which allowed the nitrogen polarization in the ammonia to be determined with a 10% relative error. The measured quadrupolar coupling constant of N-14 agrees well with earlier extrapolated values. The polarization of the nitrogen nuclei was measured as a function of the proton polarization in order to provide a test of the equal spin temperature (EST) hypothesis. It was found to be closely valid under the dynamic nuclear polarization conditions with which the protons are polarized. Large deviations from EST could be induced by cross relaxing the proton and nitrogen spin systems at low fields. Nitrogen polarizations up to 40% were reached by these means. (C) 1998 Elsevier Science B.V. All rights reserved.

We present the final results of the spin asymmetries A(1) and the spin structure functions g(1) of the proton and the deuteron in the kinematic range 0.0008 < x < 0.7 and 0.2 < Q(2) < 100 GeV2. For the determination of A(1), 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. [S0556-2821(98)07017-9].

Results are presented for F2d/F2p and Rd-Rp from simultaneous measurements of deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120, 200 and 280 GeV. The difference Rd-Rp, determined in the range 0.0020.1 the ratio decreases with Q^2.

We present a new measurement of the spin-dependent structure function g1d of the deuteron from deep inelastic scattering of 190 GeV polarized muons on polarized deuterons. The results are combined with our previous measurements of g1d. A perturbative QCD evolution in next-to-leading order is used to compute g1d(x) at a constant Q2. At Q2 = 10 GeV2, we obtain a first moment Γ1d=∫1dg1ddx=0.041±0.008, a flavour-singlet axial charge of the nucleon a0 = 0.30 ± 0.08, and an axial charge of the strange quark as = −0.09 ± 0.03. Using our earlier determination of Γ1p, we obtain Γ1p − Γ1m = 0.183 ± 0.035 at Q2 = 10GeV2. This result is in agreement with the Bjorken sum rule which predicts Γ1p − Γ1n = 0.186 ± 0.002 at the same Q2.

We have measured the spin-dependent structure function $g_1~p$ in inclusive deep-inelastic scattering of polarized muons off polarized protons, in the kinematic range $0.003 < x < 0.7$ and $1 GeV~2 < Q~2 < 60 GeV~2$. A next-to-leading order QCD analysis is used to evolve the measured $g_1~p(x,Q~2)$ to a fixed $Q~2_0$. The first moment of $g_1~p$ at $Q~2_0 = 10 GeV~2$ is $\Gamma~p = 0.136\pm 0.013(stat.) \pm 0.009(syst.)\pm 0.005(evol.)$. This result is below the prediction of the Ellis-Jaffe sum rule by more than two standard deviations. The singlet axial charge $a_0$ is found to be $0.28 \pm 0.16$. In the Adler-Bardeen factorization scheme, $\Delta g \simeq 2$ is required to bring $\Delta \Sigma$ in agreement with the Quark-Parton Model. A combined analysis of all available proton and deuteron data confirms the Bjorken sum rule.

An analytic model of the deuteron absorption function has been developed and is compared to experimental NMR signals of deuterated butanol obtained at the SMC experiment in order to determine the deuteron polarization. The absorption function model includes dipolar broadening and a frequency-dependent treatment of the intensity factors. The high-precision TE signal data available are used to adjust the model for Q-meter distortions and dispersion effects. Once the Q-meter adjustment is made, the enhanced polarizations determined by the asymmetry and TE-calibration methods compare well within the accuracy of each method. In analyzing the NMR signals, the quadrupolar coupling constants could be determined for both the CD and the OD bonds of deuterated butanol.

We have measured the spin-dependent structure function g p 1 in inclusive deep-inelastic scattering of polarized muons o polarized protons, in the kinematic range 0:003 < x < 0:7 and 1GeV < Q < 60GeV. A next-to-leading order QCD analysis is used to evolve the measured g p 1 (x;Q 2 ) to a xed Q0. The rst moment of g p 1 at Q 2 0 = 10GeV 2 is p 1 = 0:136 0:013 (stat.) 0:009 (syst.) 0:005 (evol.). This result is below the prediction of the Ellis{Ja e 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, g ' 2 is required to bring in agreement with the Quark-Parton Model. A combined analysis of all available proton and deuteron data con rms the Bjorken

Results are presented for F~/FP2 and R d-R p from simultaneous measurements of deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120, 200 and 280 GeV. The difference R d-R p, determined in the range 0.002 < x < 0.4 at an average Q2 of 5 GeV 2, is compatible with zero. The x and Q2 dependence of Fd/FP 2 was measured in the kinematic range 0.001 < x < 0.8 and 0.1 < Q2 < 145 GeV 2 with small statistical and systematic errors. For x > 0.1 the ratio decreases with Q2.