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Showing 1 to 20 of 24 for “"Perturbative QCD"”.
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Perturbative QCD in exclusive processes
… to operational status. The sensitivity of perturbative QCD predictions for the nucleon form factors, ψ → pp̅, and 𝛾𝛾 → pp̅, to the theoretical uncertainties of the nucleon wave function and the form of the running coupling constant is investigated. A new prediction for the cross-section for …
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HIGH ENERGY RESUMMATION IN PERTURBATIVE QCD
… which is present at any fixed order in the perturbative expansion starting at NNLO.
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Collinear divergences and factorization in perturbative QCD
The issue of choosing a factorization scale in perturbative QCD is examined in detail. First a previously defined factorization scheme called the collinear scheme is implemented on Higgs production by bottom quark fusion, and then extended to Higgs production by gluon fusion. After this the issue …
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Collinear singularities and the factorization scale in perturbative QCD
… and the choice of the factorization scale in perturbative QCD calculations. First, we argue in favor of the use of a bottom-quark distribution function, which sums collinear logarithms, in the calculation of the cross section for Higgs-boson production in association with bottom quarks. As a …
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Quark and Gluon Form Factors at Three Loops in Perturbative QCD
… at up to three-loop order within massless perturbative Quantum Chromodynamics by studying the photon-quark-anti-quark vertex and the effective vertex of a Higgs boson and two gluons. We use Feynman diagram methods to derive expressions for the form-factors in terms of tensor loop integrals …
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Light Quark Masses from QCD Finite Energy Sum Rules
Due to quark-gluon confinement in QCD, the quark masses entering the QCD Lagrangian cannot be measured with the same techniques one would use to determine the mass of non-confined particles. They must be determined either numerically from Lattice QCD, or analytically using QCD sum rules. The latter …
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Two-loop corrections to the rho-propagator in the Kroll-Lee-Zumino theory
… (which is valid for low-energy interactions) and perturbative QCD (which is valid at high energies). In this thesis we perform a two-loop calculation of the rho-propagator. This quantity is closely related to the pion’s electromagnetic form factor, and will allow its calculation at this order.
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Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production in polarized proton collisions at [the square root of sigma] = 200 GeV.
… Finally, the measured ALL is compared to perturbative QCD predictions and from this comparison constraints are placed on [delta] [sigma].
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Measurement of the D*+- cross-section at HERMES
… energies and does agree with the expectation of perturbative QCD. With the upgrade of the HERMES detector and the large amount of additional data taken in 1998-2000, a first determination of the polarised gluon distribution from open charm production thus seems to be feasible.
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Measurement of longitudinal double spin asymmetries of [pi]+/- production in p[over-arrow] + p[over-arrow] collisions at [sqrt]s = 200 GeV at RHIC
… are compared to predictions based on perturbative QCD calculations and from this comparison model-dependent constraints are placed on the integral gluon polarization [Delta]G.
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Gluon propagator in classical color field of colliding hadrons and its implications for hadronic cross sections
… accepted gluon distribution function and perturbative QCD rises too rapidly when compared with the data and fails to satisfy Froissart bound. To tame the rise, we have developed a new formalism for the interaction between QCD gluon and the classical color field of the colliding nucleons, …
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Virtual Compton Scattering Processes in Quantum Chromodynamics
<p>Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual Parton distributions for the case when long-distance information is accumulated in nonforward matrix elements [special characters omitted] …
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Transverse spin asymmetries in neutral strange particle production
… These asymmetries are of interest because of perturbative QCD predictions that such asymmetries should be small. Measurements of such asymmetries may yield further insights into the transverse spin structure of the proton. The Relativistic Heavy Ion Collider (RHIC) is the world's first …
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Energy and centrality dependence of mid-rapidity charged particle multiplicity in relativistic heavy-ion collisions
The properties of quantum chromodynamics (QCD), the modern theory of the strong interaction, can be investigated through the study of relativistic nucleus-nucleus collisions. Recently, the Relativistic Heavy-Ion Collider (RHIC) was completed and started taking data at ten times higher …
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Measurement of the Drell--Yan differential cross section with the CMS detector at the LHC
… measurements are compared to predictions of perturbative QCD at the next-to-next-to-leading order computed with various sets of PDFs. The measured differential cross section and double ratio in bins of absolute rapidity are sufficiently precise to constrain the proton parton distribution …
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The readout system of the HERA-B Inner Tracker and prospects of HERA-B in the field of Drell-Yan physics
… significant deviations from the predictions of perturbative QCD were observed. Starting from an analysis of the di-muon triggered data of the run period 2000, the expected number of high-mass muon pairs produced by the Drell-Yan process is extrapolated. With a conservative estimate of the …
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Three-Point Correlator and Pion Form Factor in Quantum Chromodynamics: Methods of Calculation for Two-Loop Spectral Density
… form factor analysis within the framework of QCD sum rules and local quark-hadron duality approach. The nature of various types of contributions is established which are related to particular regions of momentum integrations inside Feynman integrals. The trace factors accompanying all six …
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Nonperturbative dynamics of strong interactions from gauge/gravity duality
… It is known that Quantum Chromodynamics (QCD) is a theory which describes strong interactions. For large energies, one can apply perturbative techniques to solve some of the QCD problems. However, for low energies QCD enters into the nonperturbative regime, where different analytical or …
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The SLD vertex detector upgrade (VXD3) and a study of bbg events
… direction were examined and were compared with perturbative QCD predictions. If was found that the QCD Parton Shower prediction was needed to describe the data well. These distributions are potentially sensitive to an anomalous b chromomagnetic moment к. к was measured to be -0.031±0.038 …
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Heavy quark interaction in Hot QCD matter: open charm and bottom production in relativistic Heavy-Ion Collisions
The Quantum Cromodynamics(QCD) is the non-abelian gauge field theory which describes the strong interaction within the Standard Model. The basic constituents of QCD are quarks and gluons that are confined in hadronic matter: at high temperatures and/or densities quark deconfinement occurs and …
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