arXiv subjects

D. Müller

Publications and source records attributed to D. Müller.

77 records · Page 5Linked to original sources

arXiv1995

Extraction of the pion distribution amplitude from polarized muon pair production

We consider the production of muon pairs from the scattering of pions on longitudinally polarized protons. We calculate the cross section and the single spin asymmetry for this process, taking into account pion bound state effects. We work in the kinematic region where the photon has a large longitudinal momentum fraction, which allows us to treat the bound state problem perturbatively. Our predictions are directly proportional to the pion distribution amplitude. A measurement of the polarized Drell-Yan cross section thus allows the determination of the shape of the pion distribution amplitude.

hep-ph↗

arXiv1994

Semi-Exclusive Pion Production in Deep-Inelastic Scattering

We calculate azimuthal asymmetries and the Callan-Gross $R$-ratio for semi-exclusive pion production in deep inelastic scattering taking into account higher twist effects. Our results are qualitatively different from the QCD-improved parton model predictions for semi-inclusive deep inelastic scattering.

hep-ph↗

arXiv1994

The Parton Distribution Functions in the Limit $x_{Bj}\to 1$

We review both the counting rule and the influence of the evolution in $Q^2$ for the large $x_{Bj}$ behaviour of the valance quark distribution functions. Based on a factorization procedure we present a more general perturbative treatment to compute this behaviour. A complete analysis is performed in the scalar $ϕ^3_{[6]}$-theory for the parton distribution function of the ``meson'', which shows that logarithmical corrections arise from the distribution amplitude and that the reference momentum square $Q_0^2$ is fixed by $x_{Bj}$.

hep-ph↗

arXiv1994

Light-Ray Operators and their Application in QCD

The nonperturbative parton distribution and wave functions are directly related to matrix elements of light-ray (nonlocal) operators. These operators are generalizations of the standard local operators known from the operator product expansion. The renormalization group equation for these operators leads to evolution equations for more general distribution amplitudes which include the Altarelli-Parisi and the Brodsky-Lepage equations as special cases. It is possible to derive the Altarelli-Parisi kernel as a limiting case of the extended Brodsky-Lepage kernel. As new application of the operator product expansion the virtual Compton scattering near forward direction is considered.

hep-ph↗

arXiv1994

Angular Distributions in the Drell-Yan Process: A Closer Look at Higher Twist Effects

We calculate the angular distribution of the lepton produced in the Drell-Yan reaction taking into account pion bound state effects. We work in the kinematic region where one of the pion constituents goes far off-shell, which allows us to treat the bound state problem perturbatively. We show that the angular distribution is very sensitive to the shape of the pion distribution amplitude. The model we discuss fits the data if we choose a two-humped pion distribution amplitude suggested by QCD sum rules.

hep-ph↗