G. Baum

Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigmaL/sigmaT.

The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q(2) < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F-2(p) and F-2(d) are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R = sigma(L)/sigma(T), for 0.002 < x < 0.12. The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002<x<0.60 and 0.5<Q2<75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002<x<0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.

Proton and deuteron F2 structure functions in deep inelastic muon scattering

The structure functions F2p and F2d measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006 less-tha ...

Measurement of the proton and the deuteron structure functions, F2p and F2d

The proton and deuteron structure functions F2p and F2d were measured in the kinematic range 0.006<x<0.6 and 0.5<Q^2<75 GeV^2, by inclusive deep inelastic muon scattering at 90, 120, 200 and 280 GeV. The measurements are in good agreement with earlier high precision results. The present and earlier results together have been parametrised to give descriptions of the proton and deuteron structure functions F2 and their uncertainties over the range 0.006<x<0.9.The proton and deuteron structure funtions F2p and F2d were measured in the kinematic range 0.006 < x < 0.6 and 0.5 < Q2 < 75 GeV2, by inclusive deep inelastic muon scattering at 90, 120, 200 and 280 GeV. The measurements are in good agreement with earlier high precision results. The present and earlier results together have been parametrised to give descriptions of the proton and deuteron structure functions F2 and their uncertainties over the range 0.006 < x < 0.9.

Exclusive ϱ0 and φ muoproduction at large Q2

Abstract Exclusive ϱ0 and φ muoproduction on deuterium, carbon and calcium has been studied in the kinematic range 2

The ratio F2n/F2p in deep inelastic muon scattering

Results are presented on the ratio of neutron and proton structure functions, F2n/F2p, deduced from deep inelastic scattering of muon from hydrogen and deuterium. The data, which were obtained at the CERN muon beam at 90 and 280 GeV incident energy, cover the kinematic range x = 0.002−0.80 and Q2 = 0.1−190 GeV2. The measured structure function ratios have small statistical and systematic errors, particularly at small and intermediate x. The observed Q2 dependence in the range x = 0.1−0.4 is stronger than predicted by perturbative QCD. From the present data together with results from other experiments it is suggested that the twist-four coefficient for the proton is smaller than that for the neutron for x larger than 0.2.

Quark and gluon distributions and αs from nucleon structure functions at low x

Abstract The Q2 dependence of the structure functions F2p and F2d recently measured by the NMC is compared with the predictions of perturbative QCD at next-to-leading order. Good agreement is observed, leading to accurate determinations of the quark and gluon distributions in the range 0.008 ⩽ × ⩽ 0.5. The strong coupling constant is measured from the low x data; the result agrees with previous determinations.

Precision measurement of the structure function ratiosF 2 He /F 2 D ,F 2 C /F 2 D andF 2 Ca /F 2 D

We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035<x<0.65 and 0.5<Q2<90 GeV2 is covered. At lowx the three ratios are significantly smaller than unity and the size of the depletion grows with decreasingx and increasing mass numberA. At intermediatex the ratios show an enhancement of about 2% above unity for C/D and Ca/D, possibly less for He/D. There are indications of someQ2 dependence in the Ca/D data. The integrals of the structure function differencesF2A−F2D are discussed.

Measurements of Rd-Rp and RCa-Rc in deep inelastic muon scattering

Results are presented on the difference in R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by c ...

Quasielastic J/ψ muoproduction from hydrogen, deuterium, carbon and tin

Abstract Quasielastic production of J / ψ mesons has been measured in muon interactions with hydrogen, deuterium, carbon and tin targets at incident muon energies of 200 and 280 GeV. The hydrogen and deuterium data were used to study the transverse momentum distribution of the J / ψ s. These data have been analysed together with previously published ϱ 0 data in the framework of the vector meson dominance model. The radii of the Jψ and the ϱ 0 as well as the total J / ψ - N and ϱ 0 - N cross sections were deduced. From the tin and carbon data the ratio of the quasielastic J / ψ production cross sections, R qe (Sn/C), has been extracted and found to be less than unity. In the Glauber approach this suppression can be related to the J / ψ absorption probability in nuclei. The suppression is also compared to those predicted by various colour transparency models.

Transverse momentum distributions for exclusiveρ0 muoproduction

We have studied transverse momentum distributions for exclusiveρ0 muoproduction on protons and heavier nuclei at 2<Q2<25 GeV2. TheQ2 dependence of the slopes of thept2 andt′ distributions is discussed. The influence of the non-exclusive background is investigated. Thept2-slope for exclusive events is 4.3±0.6±0.7 GeV−2 at largeQ2. Thept2 spectra are much softer than inclusivept2 spectra of leading hadrons produced in deep inelastic scattering.