Johannes Blümlein

On the anomalous dimension of the transversity distribution \(h_1(x,Q^2)\)

Abstract. We calculate the leading order anomalous dimension of the transversity structure function directly using three different methods, the local light–cone expansion in the forward case, the non–forward case, and the short–distance expansion of the forward Compton amplitude. Our results agree with the original calculation by Artru and Mekhfi [Z. Phys. 45 (1990) 669], which has been doubted recently. We also comment on the next-to-leading order anomalous dimension.

\(\mathcal{O}(\alpha ^2 L^2 )\) radiative corrections to deep inelasticep scattering for different kinematical variables

AbstractThe QED radiative corrections are calculated in the leading log approximation up ton

ep

mathcal{O}(alpha ^2 )

THE QCD COUPLING AND PARTON DISTRIBUTIONS AT HIGH PRECISION

n for different definitions of the kinematical variables using jet measurement, the ‘mixed’ variables, the double angle method, and a measurement based onθe andyJB. Higher order contributions due to exponentiation of soft radiation are included.The QED radiative corrections are calculated in the leading log approximation up to O(� 2 ) for different definitions of the kinematical variables using jet measurement, the

Introduction to parton distribution functions

The pair production cross-section for scalar and vector leptoquarks at ep colliders is calculated for the case of photon-gluon fusion. In a model independent analysis we consider the most general C and P conserving couplings of gluons and photons to both scalar and vector leptoquarks described by an effective low-energy Lagrangian which obeys U(1)em × SU(3)c invariance. Numerical predictions are given for the kinematical regime at HERA and LEP ⊗ LHC.

Leptoquark pair production in hadronic interactions

The physics of the strong interactions always has been tightly connected to the study of nucleons at shorter and shorter distances. The measurement of the anomalous magnetic moments of the proton and neutron in 1933 and 1939 made clear that nucleons are no elementary particles. During the 1950ies the Hofstadter experiments revealed the charge distributions inside nucleons at scales Q ≃ 0.5 ·M N . Yet it was unknown how these distributions came about. In 1964 Murray Gell– Mann proposed the quark model, to catalog the plethora of observed baryons and mesons. Independently G. Zweig suggested aces as the building blocks of hadrons. A direct connection to the lepton-nucleon scattering data was not made at that time. Back in 1954 C.N. Yang and R Mills proposed novel bosonic field theories based on gauge invariance with respect to non-abelian groups. This development went unrelated to strong interactions for a long time. With the advent of the Stanford Linear Accelerator in 1968 the nucleon structure could be resolved at much shorter distances by the MIT-SLAC experiments beyond the resonant region W ≥ 2GeV for values Q up to 30 GeV. The remarkable finding by these experiments were that i) the structure function νW2(ν,Q ) which has been expected to depend on both kinematic variables ν and Q independently, turned out to take the same values for fixed values of x = Q/(2MNν) irrespectively of ν and Q 2 at high enough values. This phenomenon is called scaling. ii) The ratio of the longitudinal structure function WL and W2 turned out to be very small. Bjorken 13 had predictedA survey is given on the present status of the nucleon parton distributions and related precision calculations and precision measurements of the strong coupling constant

Working Group I: Parton distributions: Summary report for the HERA LHC Workshop Proceedings

alpha_s(M_Z^2)

On the Expectations for Leptoquarks in the Mass Range of O(200 GeV)

. We also discuss the impact of these quantities on precision observables at hadron colliders.