226 research outputs found

    Improved Calculations of Quark Distributions in Hadrons: the case of pion

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    The earlier introduced method of calculation of quark distributions in hadrons, based on QCD sum rules, is improved. The imaginary part of the virtual photon forward scattering amplitude on some hadronic current is considered in the case, when initial and final virtualities of the current p12p^2_1, and p22p^2_2 are different, p12p22p^2_1\not= p^2_2. The operator product expansion (OPE) in p12p^2_1, p22p^2_2 is performed. The sum rule for quark distribution is obtained using double dispersion representation of the amplitude on one side in terms of calculated in QCD OPE and on the other side in terms of physical states contributions. Double Borel transformation in p12p^2_1, p22p^2_2 is applied to the sum rule, killing background non-diagonal transition terms, which deteriorated the accuracy in previous calculations. The case of valence quark distribution in pion is considered, which was impossible to treat by the previous method. OPE up to dimension 6 operators is performed and leading order perturbative corrections are accounted. Valence uu-quark distribution in π+\pi^+ was found at intermediate xx, 0.15<x<0.70.15 < x < 0.7 and normalization point Q2=2GeV2Q^2=2 GeV^2. These results may be used as input for evolution equations.Comment: 29 pages, LaTeX 2e, 13 eps figures include

    Intrinsic transverse parton momenta in deeply inelastic reactions

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    Intrinsic transverse parton momenta pT play an important role in the understanding of azimuthal/spin asymmetries in semi-inclusive deep-inelastic scattering (SIDIS) and the Drell-Yan process (DY). We review and update what is presently known about pT from these processes. In particular, we address the question to which extent data support the popular Gauss model for the pT-distributions. We find that the Gauss model works very well, and observe that the intrinsic transverse momenta in SIDIS and DY are compatible, which is a support for the factorization approach. As a byproduct we recover a simple but practical way of taking into account the energy dependence of pT-distributions.Comment: 19 pages, 11 figure
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