| 1. |
- Bakker, B.L.G., et al.
(author)
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Light-front quantum chromodynamics. A framework for the analysis of hadron physics
- 2014
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In: Nuclear Physics B - Proceedings Supplements. - : Elsevier BV. - 0920-5632. ; 251-252, s. 165-174
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Journal article (peer-reviewed)abstract
- An outstanding goal of physics is to find solutions that describe hadrons in the theory of strong interactions, Quantum Chromodynamics (QCD). For this goal, the light-front Hamiltonian formulation of QCD (LFQCD) is a complementary approach to the well-established lattice gauge method. LFQCD offers access to the hadrons' nonperturbative quark and gluon amplitudes, which are directly testable in experiments at existing and future facilities. We present an overview of the promises and challenges of LFQCD in the context of unsolved issues in QCD that require broadened and accelerated investigation. We identify specific goals of this approach and address its quantifiable uncertainties. © 2014 Elsevier B.V.
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| 2. |
- Ma, H. -H, et al.
(author)
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Setting the renormalization scale in perturbative QCD : Comparisons of the principle of maximum conformality with the sequential extended Brodsky-Lepage-Mackenzie approach
- 2015
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In: Physical Review D. - : American Physical Society. - 1550-7998 .- 1550-2368 .- 2470-0010. ; 91:9
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Journal article (peer-reviewed)abstract
- A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach to all orders. In this paper we discuss two distinct methods. One is based on the "Principle of Maximum Conformality" (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the "sequential extended BLM" (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0-expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. We then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio Re+e- at four-loop order in pQCD.
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| 3. |
- Vary, James P., et al.
(author)
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Applications of basis light-front quantization to QED
- 2014
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In: Nuclear Physics B - Proceedings Supplements. - : Elsevier BV. - 0920-5632. ; 251-252, s. 10-15
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Journal article (peer-reviewed)abstract
- Hamiltonian light-front quantum field theory provides a framework for calculating both static and dynamic properties of strongly interacting relativistic systems. Invariant masses, correlated parton amplitudes and time-dependent scattering amplitudes, possibly with strong external time-dependent fields, represent a few of the important applications. By choosing the light-front gauge and adopting an orthonormal basis function representation, we obtain a large, sparse, Hamiltonian matrix eigenvalue problem for mass eigenstates that we solve by adapting ab initio no-core methods of nuclear many-body theory. In the continuum limit, the infinite matrix limit, we recover full covariance. Guided by the symmetries of light-front quantized theory, we adopt a two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall anti-de Sitter/quantum chromodynamics (AdS/QCD) model obtained from light-front holography. We outline our approach and present results for non-linear Compton scattering, evaluated non-perturbatively, where a strong and time-dependent laser field accelerates the electron and produces states of higher invariant mass i.e. final states with photon emission. © 2014.
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| 4. |
- Vary, J. P., et al.
(author)
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Basis light-front quantization : a new approach to non-perturbative scattering and time-dependent production processes
- 2013
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In: Acta Physica Polonica B, Proceedings Supplement. - 1899-2358 .- 2082-7865. ; 6:1, s. 257-262
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Journal article (peer-reviewed)abstract
- Hamiltonian light-front quantum field theory constitutes a framework for deriving invariant masses, correlated parton amplitudes of self-bound systems and time-dependent scattering amplitudes. By choosing the lightfront gauge and adopting an orthonormal basis function representation, we obtain a large, sparse, Hamiltonian matrix for mass eigenstates that is solvable by adapting ab initio no-core methods of nuclear many-body theory. In the continuum limit, the infinite matrix limit, we recover full covariance. There is considerable freedom in the choice of the orthonormal and complete set of basis functions with key considerations being convenience and convergence properties. We adopt a two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall anti-de Sitter/quantum chromodynamics (AdS/QCD) model obtained from light-front holography. We outline our approach and present preliminary results for non-linear Compton scattering, evaluated non-perturbatively, where a strong (possibly time-dependent) laser field excites an electron that emits a photon.
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