B. Povh

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 ...

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

A full set of nuclear shell orbitals for the Λ particle observed in 32ΛS and 40ΛCa

Abstract The strangeness exchange reaction (K − , π − ) on 32 S and 40 Ca has been studied. The strongest transitions are assigned to states having a configuration with the Λ particle in a 1s, 1p, 1d, 2s, and 1f orbit coupled to the nuclear core. These Λ shells are approximately equidistantly spaced, the energy spacings being about 9 MeV. In the first approximation the Λ particle behaves like a “spinless neutron” in a harmonic oscillator potential.

Spectroscopy of the hypernucleus Λ12C

Abstract Kaons were stopped in a 12 C target. The momenta of pions accompanying the kaon interactions were measured with a magnetic spectrometer. States in Λ 12 C with binding energies of the Λ particle of 11 ± 1 MeV and 0 ± 1 MeV have been observed.

The Q2 dependence of the structure function ratio F2Sn/F2C and the difference RSn - RC in deep inelastic muon scattering

The Q(2) dependence of the structure function ratio F-2(Sn)/F-2(C) for 0.01 < x < 0.75 and 1 < Q(2) < 140 GeV2 is reported. For x < 0.1 the size of shadowing decreases linearly with In Q(2) and the maximum rate is about 0.04 at x = 0.01. The rate decreases with x and is compatible with zero for x greater than or equal to 0.1. The difference R(Sn) - R(C), where R is the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, is also given. No dependence on x is seen and the average value is 0.040 +/- 0.021 (stat.) +/- 0.026 (syst.) at a mean Q(2) of 10 GeV2.

The A dependence of the nuclear structure function ratios

Results are presented for six nuclei from Be to Pb on the structure function ratios F-2(A)/F-2(C)(X) and their A dependence in deep inelastic muon scattering at 200 GeV incident: muon energy. The data cover the kinematic range 0.01 < x < 0.8 with Q(2) ranging from 2 to 70 GeV2. The A dependence of nuclear structure function ratios is parametrised and compared to various models.

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.

Ratio of J/Psi production cross sections in deep inelastic muon scattering from tin and carbon

We present results on J/ψ production in muon interactions with tin and carbon targets at incident muon energies of 200 and 280 GeV. The ratio of cross sections per nucleon for J/ψ production on tin and carbon, R(Sn/C), is studied as a function of pT2, z and x. We find an enhancement for coherent J/ψ production Rcoh(Sn/C) = 1.54 ± 0.07, a suppression for quasielastic production Rqe(Sn/C) = 0.79 ± 0.06 and for inelastic production Rin(Sn/C) = 1.13 ± 0.08. The inelastic cross section ratio can be interpreted within the Colour Singlet model as an enhancement of the gluon distribution in tin with respect to that in carbon. The dependence of the ratio on z and pT2 can explain the discrepancy between the results obtained in previous experiments.

Excited states of light hypernuclei

The γ spectra obtained with K− mesons stopped in 6Li and 7Li targets exhibited a γ line at 1.09 MeV (intensities 0.14 ± 0.02% and 0.37 ± 0.04%, respectively) which could be identified as a hypernuclear line, and a second one at 1.42 MeV (intensities 0.10 ± 0.02% and 0.04 ± 0.04%, respectively), the assignment of which is less certain. The 1.09 MeV line and the 1.42 MeV line (if this latter is, in fact, a hypernuclear one) must both be due to γ transitions in hypernuclei with mass number four. The excitation energy of 1.09 MeV, ascribed in turn to either 4ΛH∗ or 4ΛHe∗He∗, was used to recalculate the parameters of the phenomenological potentials proposed by Herndon and Tang for the Λ-N s-state interaction.