2011/03/31 by R. Asaturyan, R. Ent, H. Mkrtchyan +96
Physics and Astronomy · #Deuterium #High-Energy Particle Collisions Research #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Parton #Physics #Pion #Quantum Chromodynamics and Particle Interactions #Quark #nucl-ex
paper · pdf · doi:10.1103/physrevc.85.015202
arxiv created 2011/12/15 · openalex publication_date 2012/01/11 · arxiv updated 2015/05/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A large set of cross sections for semi-inclusive electroproduction of charged pions (\ensuremathπ^\ifmmode±\else\textpm\fi) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared W2>4 GeV2 (up to \ensuremath≈7 GeV2) and range in four-momentum transfer squared 2<Q2<4 (GeV/c)2, and cover a range in the Bjorken scaling variable 0.2<x<0.6. The fractional energy of the pions spans a range 0.3<z<1, with small transverse momenta with respect to the virtual-photon direction, Pt2<0.2 (GeV/c)2. The invariant mass that goes undetected, Mx or W^\ensuremath', is in the nucleon resonance region, W^\ensuremath'<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\ensuremath→pion production mechanisms. The x, z, and Pt2 dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for \ensuremathπ+ and \ensuremathπ^\ensuremath-) 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.