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Quasi-elastic (z >0.95) photo-production of psi' mesons has been observed at HERA for photon-proton centre-of-mass energies in the range 40 to 160 GeV. The psi' mesons were identified through their decays to l+l- and to J/psi pi+ pi-, where the J/psi subsequently decays to l+l-, the lepton l being either a muon or an electron. The cross-section for quasi-elastic photoproduction was measured to be [18.0 +- 2.8 (stat) +- 3.0(syst)] nb at a photon-proton centre-of-mass energy of 80 GeV. The ratio of the psi' to J/psi quasi-elastic cross-sections is 0.150 +- 0.027 (stat) +- 0.022 (syst).
Overall value for photoproduction cross section combining the different decay modes and data sample.. 1994 and 1995 data.. The second systematic error is from the branching ratio uncertainties.
Combined cross section from PSI(3685) --> J/PSI(1S) < E+ E- > PI+ PI- and PSI(3685) --> J/PSI(1S) < MU+ MU- > PI+ PI- modes using both the 1994 and 1995 data.. The second systematic error is from the branching ratio uncertainties.
Cross section from PSI(3685) --> J/PSI(1S) < E+ E- > PI+ PI- mode.
Cross section from PSI(3685) --> J/PSI(1S) < MU+ MU- > PI+ PI- mode.
Cross section from PSI(3685) --> E+ E- + MU+ MU- mode.
Cross section from PSI(3685) --> J/PSI(1S) < E+ E- > PI+ PI- mode.
Cross section from PSI(3685) --> J/PSI(1S) < MU+ MU- > PI+ PI- mode.
Cross section from PSI(3685) --> E+ E- + MU+ MU- mode.
Second systematic error is due to uncertainties in the PSI(2S) partial widths. J/PSI cross section 119.5+-11.2+-12.0 nb is from NP B472, 3. Extrapolation to Q2=0.
The x and Q 2 dependence of the single photon exchange cross section d 2 σ /d Q 2 d x and the proton structure functions F 2 ( x , Q 2 ) and R ( x , Q 2 ) have been measured in deep inelastic muon proton scattering in the region 0.02 < x < 0.8 and 3 < Q 2 < 190 GeV 2 . By comparing data at different incident muon energies R was found to have little kinematic dependence and an average value of −0.010 ± 0.037 (stat.) ± 0.102 (stat.). The observed deviations from scaling gave the value of Λ MS , the QCD mass scale parameter, to be 105 −45 +55 (stat.) −45 +85 (syst.) MeV. The fraction of the momentum of the nucleon carried by gluons was found to be ∼56% at Q 2 ∼22.5 GeV 2 . It is shown that to obtain a description of the data for F 2 ( x , Q 2 ) together with that measured in deep inelastic electron-proton scattering at lower Q 2 it is necessary to include additional higher twist contributions. The value of Λ MS remains unchanged with the inclusion of these contributions which were found to have an x -dependence of the form x 3 /(1 − x ).
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VALUES OF Q**2 CORRESPONDING TO THE ENTRIES IN THIS TABLE ARE 15., 20., 27., 36., 48. RESPECTIVELY.
VALUES OF Q**2 CORRESPONDING TO THE ENTRIES IN THIS TABLE ARE 11.5, 15., 20., 27., 36., RESPECTIVELY.
VALUES OF Q**2 CORRESPONDING TO THE ENTRIES IN THIS TABLE ARE 27., 36., 48., 65. RESPECTIVELY.
VALUES OF Q**2 CORRESPONDING TO THE ENTRIES IN THIS TABLE ARE 15., 20., 27., 36., 48.,65., 90. RESPECTIVELY.
VALUES OF Q**2 CORRESPONDING TO THE ENTRIES IN THIS TABLE ARE 11.5, 15., 20., 27., 36., 48.,65.RESPECTIVELY.
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