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Measurement of semi-inclusive π+ electroproduction off the proton

Abstract : Semi-inclusive π+ electroproduction on protons has been measured with the CLAS detector at Jefferson Lab. The measurement was performed on a liquid-hydrogen target using a 5.75 GeV electron beam. The complete five-fold differential cross sections were measured over a wide kinematic range including the complete range of azimuthal angles between hadronic and leptonic planes, ϕ, enabling us to separate the ϕ-dependent terms. Our measurements of the ϕ-independent term of the cross section at low Bjorken x were found to be in fairly good agreement with pQCD calculations. Indeed, the conventional current fragmentation calculation can account for almost all of the observed cross section, even at small π+ momentum. The measured center-of-momentum spectra are in qualitative agreement with high-energy data, which suggests a surprising numerical similarity between the spectator diquark fragmentation in the present reaction and the antiquark fragmentation measured in e+e- collisions. We have observed that the two ϕ-dependent terms of the cross section are small. Within our precision the cos⁡2ϕ term is compatible with zero, except for the low-z region, and the measured cos⁡ϕ term is much smaller in magnitude than the sum of the Cahn and Berger effects.
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Submitted on : Tuesday, October 1, 2013 - 11:12:54 AM
Last modification on : Wednesday, September 16, 2020 - 4:08:30 PM

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M. Osipenko, S. Bouchigny, M. Guidal, C. Hadjidakis, H. S. Jo, et al.. Measurement of semi-inclusive π+ electroproduction off the proton. Physical Review D, American Physical Society, 2009, 80, pp.032004. ⟨10.1103/PhysRevD.80.032004⟩. ⟨in2p3-00868247⟩



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