Hadronic lepton-pair production beyond the leading order in perturbative QCD

Hadronic lepton-pair production in perturbative QCD is calculated to order $\text{g}{}^{\mathrm{<mtext>2</mtext>}}$ to be usable in combination with the existing calculation of the anomalous dimension of order $\text{g}{}^{\mathrm{<mtext>4</mtext>}}$. The structure function of the subprocess $\text{q}\text{+}\text{q}\text{→ γ +}$ anything in an arbitrary covariant gauge for gluons is found to have gauge-dependent contributions which are exactly cancelled by contributions from operator matrix elements to give the gauge-independent “coefficient function” for lepton-pair production in the minimal subtraction scheme. This provides a consistency check of the perturbative QCD recipe. A comparison is made with other existing calculations.     

Processes involving fragmentation functions beyond the leading order in QCD

We point out that the electron propagator, calculated from a truncated Johnson-Baker-Willey equation, suffers from the following defects: lack of renormalizability gauge dependence of the electron electromagnetic mass, as well as unacceptable analytic structure.     

Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results.     

Largep T double photon production in hadronic collisions-beyond leading logarithm QCD calculation

We calculateO(α _s ) corrections to largep _T double photon production in hadronic collisions. We find that these corrections to the basic \(q\bar q \to \gamma \gamma \) subprocess are important, preventing to describe double photon production on the basis of the leading logarithm approximation only. We give a phenomenological discussion of the results obtained at SPS, ISR and \(Sp\bar pS\) energies. In particular, we investigate how the effect of the intrinsic parton <K _T> may be disentangled from the perturbative contribution. We also calculate the aplanarity distribution characteristic of 3 jet events.     

Space- and time-like cut vertices in QCD beyond the leading order—The singlet sector

The analytic continuation relation found in the non-singlet structure of the processes e⁺h→e^?X and e^?e⁺→hX up to the next-to-the-leading-logarithm approximation, is shown to be true also for the singlet case. This relation is used to find the two-loop anomalous dimensions for the singlet time-like cut vertices from the anomalous dimension of the singlet space-like cut vertices. We give also the singlet time-like coefficient functions.     

Cross sections for semihard interactions in hardronic collisions beyond the leading order of perturbative QCD

An estimate of cross sections which correspond to semihard interactions such as gluon (mini) jet production is presented. It takes into account recent results concerning gluon distributions in the small x region beyond the leading log Q² approximation and rescattering corrections in the hadron-hadron channel. The estimated cross sections are at very high energies significantly smaller in their magnitude than a simple integration of the two-jet inclusive cross section might imply yet they are still expected to constitute a substantial part or σ_tot in the TeV energy regime.     

Remarks on beyond leading order

In recent years a two-scale expansion was established to study reactions of the type NN→NNπ within chiral perturbation theory. Then the diagrams of some subclasses that are invariant under the choice of the pion field no longer appear at the same chiral order. In this Letter we show that the proposed expansion still leads to well defined results. We also discuss the appropriate choice of the heavy baryon propagator.     

Inclusive dijet production at HERA: direct photon cross sections in next-to-leading order QCD

We have calculated inclusive two-jet cross sections in next-to-leading order QCD for direct photo-production in lowQ ² ep collisions at HERA. Infrared and collinear singularities in real and virtual contributions are cancelled with the phase space slicing method. Analytical formulas for the different contributions giving the dependence on the slicing parameter are presented. Various one and two-jet distributions have been computed demonstrating the flexibility of the method.     

Higher-order QCD corrections in prompt photon production

We exhibit a method for simultaneously treating recoil and threshold corrections in single-photon inclusive cross sections, working within the formalism of collinear factorization. This approach conserves both the energy and transverse momentum of resummed radiation. At moderate p(T), we find the potential for substantial enhancements from higher-order perturbative and power-law nonperturbative corrections.     

Lepton-hadron processes beyond leading order in quantum chromodynamics

We present a summary of QCD formulae describing the effects of scaling violation in leptonhadron processes, with the inclusion of recently derived higher order corrections. Deep inelastic leptoproduction, one-hadron inclusive distributions in leptoproduction and ine ⁺ e ^? annihilation and Drell-Yan processes are discussed in detail. Higher order corrections to parton densities, fragmentation functions and to lepton-parton cross-sections in the above processes are presented in a common factorization scheme, so that a comparative analysis of various processes as well as an independent analysis of each of them is possible. A discussion of the various scheme dependences at next-to-leading level is also included.