Semi-Inclusive Charged-Pion Electroproduction off Protons and Deuterons: Cross Sections, Ratios and Access to the Quark-Parton Model at Low Energies
Creators: name: Asaturyan, R.
name: Ent, R.
name: Mkrtchyan, H.
name: Navasardyan, T.
name: Tadevosyan, V.
name: Adams, G. S.
name: Ahmidouch, A.
name: Angelescu, T.
name: Arrington, J.
name: Asaturyan, A.
name: Baker, O. K.
name: Benmouna, N.
name: Bertoncini, C.
name: Blok, H. P.
name: Boeglin, W. U.
name: Bosted, P. E.
name: Breuer, H.
name: Christy, M. E.
name: Connell, S. H.
name: Cui, Y.
name: Dalton, M. M.
name: Danagoulian, S.
name: Day, D.
name: Dunne, J. A.
name: Dutta, D.
name: Khayari, N. El
name: Fenker, H. C.
name: Frolov, V. V.
name: Gan, L.
name: Gaskell, D.
name: Hafidi, K.
name: Hinton, W.
name: Holt, R. J.
name: Horn, T.
name: Huber, G. M.
name: Hungerford, E.
name: Jiang, X.
name: Jones, M.
name: Joo, K.
name: Kalantarians, N.
name: Kelly, J. J.
name: Keppel, C. E.
name: Kubarovsky, V.
name: Li, Y.
name: Liang, Y.
name: Mack, D.
name: Malace, S. P.
name: Markowitz, P.
name: McGrath, E.
name: McKee, P.
name: Meekins, D. G.
name: Mkrtchyan, A.
name: Moziak, B.
name: Niculescu, G.
name: Niculescu, I.
name: Opper, A. K.
name: Ostapenko, T.
name: Reimer, P. E.
name: Reinhold, J.
name: Roche, J.
name: Rock, S. E.
name: Schulte, E.
name: Segbefia, E.
name: Smith, C.
name: Smith, G. R.
name: Stoler, P.
name: Tang, L.
name: Ungaro, M.
name: Uzzle, A.
name: Vidakovic, S.
name: Villano, A.
name: Vulcan, W. F.
name: Wang, M.
name: Warren, G.
name: Wesselmann, F. R.
name: Wojtsekhowski, B.
name: Wood, S. A.
name: Xu, C.
name: Yuan, L.
name: Zheng, X.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: A large set of cross sections for semi-inclusive electroproduction of charged pions ($π^\pm$) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared $W^2$ &gt; 4 GeV$^2$ and range in four-momentum transfer squared $2 &lt; Q^2 &lt; 4$ (GeV/c)$^2$, and cover a range in the Bjorken scaling variable 0.2 &lt; x &lt; 0.6. The fractional energy of the pions spans a range 0.3 &lt; z &lt; 1, with small transverse momenta with respect to the virtual-photon direction, $P_t^2 &lt; 0.2$ (GeV/c)$^2$. The invariant mass that goes undetected, $M_x$ or W', is in the nucleon resonance region, W' &lt; 2 GeV. The new data conclusively show the onset of quark-hadron duality in this process, and the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark --&gt; pion production mechanisms. The x, z and $P_t^2$ dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for $π^+$ and $π^-$) have been studied. The ratios are found to be in good agreement with expectations based upon a high-energy quark-parton model description. We find the azimuthal dependences to be small, as compared to exclusive pion electroproduction, and consistent with theoretical expectations based on tree-level factorization in terms of transverse-momentum-dependent parton distribution and fragmentation functions. In the context of a simple model, the initial transverse momenta of $d$ quarks are found to be slightly smaller than for $u$ quarks, while the transverse momentum width of the favored fragmentation function is about the same as for the unfavored one, and both fragmentation widths are larger than the quark widths.