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  • 1.
    Allasia, D
    et al.
    Università di Torino, INFN, Turin, Italy.
    Lettenström, Frans
    University of California, Santa Cruz CA, United States.
    Windmolders, R
    Université de l'Etat Mons, Mons, Belgium.
    Inelastic J ψ production in deep inelastic scattering from hydrogen and deuterium and the gluon distribution of free nucleons1991Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 258, nr 3-4, s. 493-498Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present results on inelastic J/PSI-production from muon interactions with hydrogen and deuterium at an incident muon energy of 280 GeV. The measured cross section ratio per nucleon for muon-induced J/PSI-production in deuterium and hydrogen was found to be R(D2/H2) = 1.01 +/- 0.15. The colour singlet model is shown to provide a good description of the observed differential cross section apart from a normalisation factor. The comparison between the observed cross section and the colour singlet model prediction allows the extraction of the gluon structure function G(chi) of the nucleon. The momentum fraction-chi of the nucleon carried by the gluon is measured in the range of chi = [0.02, 0.30]. The normalised gluon distribution of free nucleons thus found can be parametrised as chi-G(chi) = 1/2 (eta + 1)(1 - chi)eta, with eta = 5.1 +/- 0.9 (stat).

  • 2.
    Allasia, D
    et al.
    Università di Torino, INFN, Turin, Italy.
    Lettenström, Frans
    University of Uppsala, Uppsala, Sweden.
    Windmolders, R
    Université de l'Etat Mons, Mons, Belgium.
    Measurement of the neutron and the proton F2 structure function ratio1990Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 249, nr 2, s. 366-372Artikkel i tidsskrift (Fagfellevurdert)
  • 3.
    Amaudruz, P
    et al.
    Paul Scherrer Institut, Villigen, Switzerland.
    Lettenström, Frans
    University of California, Santa Cruz, United States.
    Zetsche, F
    Max-Planck Institut für Kernphysik, Heidelberg, Germany.
    A re-evaluation of the nuclear structure function ratios for D, He, 6Li, C and Ca1995Inngår i: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 441, nr 1-2, s. 3-11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a re-evaluation of the structure function ratios F-2(He)/F-2(D), F-2(C)/F-2(D) and F-2(Ca)/F-2(D) measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. We also present the ratios F-2(C)/F-2(Li), F-2(Ca)/F-2(Li) and F-2(Ca)/F-2(C) measured at 90 GeV. The results are based on data already published by NMC; the main difference in the analysis is a correction for the masses of the deuterium targets and an improvement in the radiative corrections. The kinematic range covered is 0.0035 < x < 0.65, 0.5 < Q(2) < 90 GeV2 for the He/D, C/D and Ca/D data and 0.0085 < x < 0.6, 0.84 < Q(2) < 17 GeV2 for the Li/C/Ca ones.

  • 4. Amaudruz, P
    et al.
    Lettenström, Frans
    University of California, Santa Cruz CA, United States.
    Zetsche, F
    Gottfried sum from the ratio F2n/F2p1991Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 66, nr 21, s. 2712-2715Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004 < x < 0.8 and 0.4 < Q2 < 190 GeV2, together with the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x) - F2n(x). The value of the Gottfried sum integral (F2p - F2n) dx/x = 0.240 +/- 0.016 is below the quark-parton-model expectation of 1/3.

  • 5.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villigen, Switzerland.
    Lettenström, Frans
    Institute for Particle Physics, University of California, Santa Cruz CA, United States.
    Zetsche, F
    Max Planck Institut für Kernphysik, Heidelberg, Germany.
    Measurements of Rd-Rp and RCa-Rc in deep inelastic muon scattering1992Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 294, nr 1, s. 120-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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 comparing the ratio of cross sections for the deep inelastic scattering of muons from deuterium and hydrogen targets at 90 and 280 GeV incident energy. The results cover the range x = 0.01 -0.30, at an average Q2 of 9 GeV2. The measured difference R(d)-R(p) shows no significant x dependence and is compatible with zero, as well as with expectations from perturbative QCD. We use the same method to obtain the difference R(Ca)-R(C) from cross section ratios measured on carbon and calcium targets at 90 and 200 GeV incident energy.

  • 6.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villingen, Switzerland.
    Lettenström, Frans
    University of California, Santa Cruz CA, United States.
    Zetsche, F
    MPI Heidelberg, Heidelberg, Germany.
    Precision measurement of structure function ratios for 6Li, 12C and 40Ca1992Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 53, nr 1, s. 73-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure function ratios F2C/F2Li, F2Ca/F2Li and F2Ca/F2C were measured in deep inelastic muon-nucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085 < x < 0.6 and 0.8 < Q2 < 17 GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.

  • 7.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villingen, Switzerland.
    Lettenström, Frans
    University of California, Santa Cruz CA, United States.
    Zetsche, F
    MPI Heidelberg, Heidelberg, Germany.
    Precision measurement of the structure function ratios F2He/F2D, F2C/F2D and F2Ca/F2D1991Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 51, nr 3, s. 387-393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the structure function ratios F2He/F2D, F2C/F2D and F2Ca/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 low x the three ratios are significantly smaller than unity and the size of the depletion grows with decreasing x and increasing mass number A. At intermediate x 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 some Q2 dependence in the Ca/D data. The integrals of the structure function differences F2A-F2D are discussed.

  • 8.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villigen, Switzerland.
    Lettenström, Frans
    Physics Department, Freiburg University, Freiburg, Germany.
    Zetsche, F
    Max Planck Institut für Kernphysik, Heidelberg, Germany.
    Proton and deuteron F2 structure functions in deep inelastic muon scattering1992Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 295, nr 1-2, s. 159-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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-than-or-equal-to x less-than-or-equal-to 0.6 and 0.5 less-than-or-equal-to Q2 less-than-or-equal-to 55 GeV2, and include the first precise data at small x, where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results.

  • 9.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villigen, Switzerland.
    Lettenström, Frans
    University of California, Institute for Particle Physics, Santa Cruz CA, United States.
    Zetsche, F
    Max-Planck Institut für Kernphysik, Heidelberg, Germany.
    The ratio F2 n/F2 p in deep inelastic muon scattering1992Inngår i: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 371, nr 1-2, s. 3-31Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results are presented on the ratio of neutron and proton structure functions, F2n/F2p, deduced from deep inelastic scattering of muons 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.

  • 10.
    Amaudruz, P
    et al.
    Paul Scherrer Institute, Villigen, Switzerland.
    Lettenström, Frans
    University of California, Santa Cruz CA, United States.
    Zetsche, F
    MPI für Kernphysik, Heidelberg, Germany.
    Transverse momentum distributions for exclusive ρ0 muoproduction1992Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 54, nr 2, s. 239-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied transverse momentum distributions for exclusive rho(0) muoproduction on protons and heavier nuclei at 2 < Q2 < 25 GeV2. The Q2 dependence of the slopes of the p(t)2 and t' distributions is discussed. The influence of the non-exclusive background is investigated. The p(t)2-slope for exclusive events is 4.3 +/- 0.6 +/- 0.7 GeV-2 at large Q2. The p(t)2 spectra are much softer than inclusive p(t)2 spectra of leading hadrons produced in deep inelastic scattering.

  • 11.
    Arvidson, A
    et al.
    Department of Information Technology (DOIT), The Royal Library, National Library of Sweden, Stockholm, Sweden.
    Lettenström, Frans
    Department for National Co‐operation and Development (BIBSAM), The Royal Library, National Library of Sweden, Stockholm, Sweden.
    The Kulturarw Project - the Swedish Royal Web Archive (vol 16, pg 105, 1998)1998Inngår i: Electronic library, ISSN 0264-0473, E-ISSN 1758-616X, Vol. 16, nr 3, s. 220-220Artikkel i tidsskrift (Fagfellevurdert)
  • 12.
    Arvidson, Allan
    et al.
    Department of Information Technology (DOIT), The Royal Library, National Library of Sweden, Stockholm, Sweden.
    Lettenström, Frans
    Department for National Co‐operation and Development (BIBSAM), The Royal Library, National Library of Sweden, Stockholm, Sweden.
    The Kulturarw(3) Project: The Swedish Royal Web Archive1998Inngår i: Electronic library, ISSN 0264-0473, E-ISSN 1758-616X, Vol. 16, nr 2, s. 105-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    KB (Kungliga biblioteket, The Royal Library), The National Library of Sweden, was founded in the 1500s. Since 1661, when the first Legal Deposit Law was introduced, it has functioned as the kingdom's national memory. Today KB receives everything printed that is distributed to the public in the form of books, journals, posters, maps, advertisements, catalogues and so on. Since 1994, following the latest version of the Legal Deposit Law, KB has also stored electronic publications ‘in fixed form’, i.e. published on CD-ROM, tape or diskette. The total growth at KB is about 1.5 shelf-kilometres per year. At that rate, KB's underground storage will be completely full by the year 2050.

  • 13.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom; Faculté des Sciences, Université de L'Etat à Mons, Mons, Belgium.
    Lettenström, Frans
    Istituto di Fisica, Università di Torino, Turin, Italy; Faculté des Sciences, Université de L'Etat à Mons, Mons, Belgium.
    Womersley, W J
    Department of Physics, University of Lancaster, Lancaster, United Kingdom; Faculté des Sciences, Université de L'Etat à Mons, Mons, Belgium.
    Measurement of the ratios of deep inelastic muon-nucleus cross sections on various nuclei compared to deuterium1988Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 202, nr 4, s. 603-610Artikkel i tidsskrift (Fagfellevurdert)
  • 14.
    Ashman, J
    et al.
    Department of Physics, University, Sheffield, United Kingdom.
    Lettenström, Frans
    Gustav Werners Institut, University, Uppsala, Sweden.
    Womersley, WJ
    Nuclear Physics Laboratory, University, Oxford, United Kingdom.
    Exclusive ρ0 and Φ production in deep inelastic muon scattering1988Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 39, nr 2, s. 169-175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data are presented on exclusive ρ0 and φ{symbol} production in deep inelastic muon scattering from a target consisting mainly of nitrogen. The ratio of the total cross sections for ρ0 and φ{symbol} production is found to be 9:(1.6±0.4) at 〈Q2〉=7.5 GeV2, consistent with the SU(3) prediction of 9:2. The t dependence for exclusive ρ0 production is found to become shallover as Q2 increases and, for large Q2, the t dependence is typical of that for a hard scattering process. Furthermore, the ratio of the cross sections for coherent: incoherent production from nitrogen is found to decrease rapidly with Q2. Such behaviour indicates that even for exclusive vector meson production the virtual photon behaves predominantly as an electromagnetic probe.

  • 15.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom.
    Lettenström, Frans
    Department of Radiation Science, University of Uppsala, Uppsala, Sweden.
    Ziemons, K
    III Physikalisches Institut A, Physikzentrum, RWTH, Aachen, Germany.
    A measurement of the ratio of the nucleon structure function in copper and deuterium1993Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 57, nr 2, s. 211-218Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function, F2, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.

  • 16.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom.
    Lettenström, Frans
    Istituto di Fisica, Università di Torino, Turin, Italy.
    Ziemons, K
    Fachbereich Physik, Universität Wuppertal, Wuppertal, Germany.
    A measurement of the spin asymmetry and determination of the structure function g1 in deep inelastic muon-proton scattering1988Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 206, nr 2, s. 364-370Artikkel i tidsskrift (Fagfellevurdert)
  • 17.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom.
    Lettenström, Frans
    Department of Radiation Science, University of Uppsala, Uppsala, Sweden.
    Ziemons, K
    III. Physikalisches Institut A, Physikzentrum, RWTH, Aachen, FRG.
    An investigation of the spin structure of the proton in deep inelastic scattering of polarised muons on polarised protons1989Inngår i: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 328, nr 1, s. 1-35Artikkel i tidsskrift (Fagfellevurdert)
  • 18.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom.
    Lettenström, Frans
    Department of Radiation Science, University of Uppsala, Uppsala, Sweden.
    Ziemons, K
    III Physikalisches Institut A, Physikzentrum, RWTH, Aachen, Germany.
    Forward produced hadrons in μp and μd scattering and investigation of the charge structure of the nucleon1991Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 52, nr 3, s. 361-387Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Final data measured with the EMC forward spectrometer are presented on the production of forward charged hadrons in mu-p and mu-d scattering at incident beam energies between 100 and 280 GeV. The large statistic of 373000 events allows a study of the semi-inclusive hadron production as a function of z, p(T)2 and <p(T)2> in small Q2, x(Bj) and W bins. Charge multiplicity ratios and differences as a function of z and x(Bj) are given for p, d and n-targets. From the differences of charge multiplicities the ratio of the valence quark distributions of the proton d-upsilon(x)/u-upsilon(x) is determined for the first time in charged lepton scattering. The Gronau et al. sum rule is tested, the measured sum being 0.31 +/- 0.06 stat. +/- 0.05 syst., compared with the theoretical expectation of 2/7 almost-equal-to 0.286. The measured sum corresponds to an absolute value of the ratio of the d and u quark charge of 0.44 +/- 0.10 stat. +/- 0.08 syst.

  • 19.
    Ashman, J
    et al.
    Department of Physics, University of Sheffield, Sheffield, United Kingdom.
    Lettenström, Frans
    Department of Radiation Science, University of Uppsala, Uppsala, Sweden.
    Ziemons, K
    III Physikalisches Institut A, Physikzentrum, RWTH, Aachen, Germany.
    Muoproduction of J/ψ and the gluon distribution of the nucleon1992Inngår i: Zeitschrift für Physik C Particles and Fields, ISSN 0170-9739, E-ISSN 1431-5858, Vol. 56, nr 1, s. 21-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurements are presented of the inclusive distributions of the J/psi meson produced by muons of energy 200 GeV from an ammonia target. The gluon distribution of the nucleon has been derived from the data in the range 0.04 < x < 0.36 using a technique based on the colour singlet model. An arbitrary normalisation factor is required to obtain a reasonable integral of the gluon distribution. Some comments are made on the use of J/psi production by virtual photons to extract the gluon distribution at HERA.

  • 20.
    Lettenström, Frans
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Uppsala, Sweden.
    A study of nuclear effects in deep inelastic muon scattering1988Doktoravhandling, monografi (Annet vitenskapelig)
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