scholarly journals Infrared Singularities of Scattering Amplitudes in Perturbative QCD

2009 ◽  
Vol 102 (16) ◽  
Author(s):  
Thomas Becher ◽  
Matthias Neubert
Keyword(s):  
Scattering Amplitudes ◽  
Perturbative Qcd ◽  
Infrared Singularities

Hadrons, partons and QCD

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Perturbative Qcd ◽  
Cross Section ◽  
Parton Distribution ◽  
Scale Invariance ◽  
Distribution Functions ◽  
Annihilation Cross Section ◽  
Quantum Corrections ◽  
Parton Distribution Functions ◽  
Hadron Masses ◽  
Infrared Singularities

This chapter first discusses the breaking of scale invariance of QCD with massless quarks by quantum corrections and explains that this effect is responsible for the bulk of hadron masses. Then the parton picture is introduced, where one replaces a hadron which is probed in a hard process by free quarks and gluons. Perturbative QCD describes via the DGLAP equations the evolution of parton distribution functions f(x,Q2) as functions of Q2, requires however as as input f(x,Q20) from measurements at a fixed scale Q0 »QCD. The total annihilation cross section e+e →hadrons is calculated and it is shown that infrared singularities due to massless gluons and quarks cancel.

scholarly journals The Regge Limit and infrared singularities of QCD scattering amplitudes to all orders

2018 ◽  
Author(s):  
Leonardo Vernazza ◽  
Simon Caron-Huot ◽  
Einan Gardi ◽  
Joscha Reichel
Keyword(s):  
Scattering Amplitudes ◽  
Regge Limit ◽  
Infrared Singularities

scholarly journals Infrared singularities of QCD scattering amplitudes in the Regge limit to all orders

2018 ◽  
Vol 2018 (3) ◽  
Author(s):  
Simon Caron-Huot ◽  
Einan Gardi ◽  
Joscha Reichel ◽  
Leonardo Vernazza
Keyword(s):  
Scattering Amplitudes ◽  
Regge Limit ◽  
Infrared Singularities

scholarly journals A Stroll through the Loop-Tree Duality

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1029
Author(s):  
José de Jesús Aguilera-Verdugo ◽  
Félix Driencourt-Mangin ◽  
Roger José Hernández-Pinto ◽  
Judith Plenter ◽  
Renato Maria Prisco ◽  
...  
Keyword(s):  
Scattering Amplitudes ◽  
Euclidean Space ◽  
Feynman Integrals ◽  
Innovative Technique ◽  
Causal Representation ◽  
Definition Of ◽  
Infrared Singularities

The Loop-Tree Duality (LTD) theorem is an innovative technique to deal with multi-loop scattering amplitudes, leading to integrand-level representations over a Euclidean space. In this article, we review the last developments concerning this framework, focusing on the manifestly causal representation of multi-loop Feynman integrals and scattering amplitudes, and the definition of dual local counter-terms to cancel infrared singularities.

scholarly journals Isospin-1/2 Dπ scattering and the lightest $$ {D}_0^{\ast } $$ resonance from lattice QCD

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Luke Gayer ◽  
Nicolas Lang ◽  
Sinéad M. Ryan ◽  
David Tims ◽  
Christopher E. Thomas ◽  
...  
Keyword(s):  
Scattering Amplitudes ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Light Quark ◽  
Energy Levels ◽  
Experimental Result ◽  
Infinite Volume ◽  
Resonance Pole ◽  
Strongly Coupled ◽  
Light Quark Mass

Abstract Isospin-1/2 Dπ scattering amplitudes are computed using lattice QCD, working in a single volume of approximately (3.6 fm)3 and with a light quark mass corresponding to mπ ≈ 239 MeV. The spectrum of the elastic Dπ energy region is computed yielding 20 energy levels. Using the Lüscher finite-volume quantisation condition, these energies are translated into constraints on the infinite-volume scattering amplitudes and hence enable us to map out the energy dependence of elastic Dπ scattering. By analytically continuing a range of scattering amplitudes, a $$ {D}_0^{\ast } $$ D 0 ∗ resonance pole is consistently found strongly coupled to the S-wave Dπ channel, with a mass m ≈ 2200 MeV and a width Γ ≈ 400 MeV. Combined with earlier work investigating the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , and $$ {D}_0^{\ast } $$ D 0 ∗ with heavier light quarks, similar couplings between each of these scalar states and their relevant meson-meson scattering channels are determined. The mass of the $$ {D}_0^{\ast } $$ D 0 ∗ is consistently found well below that of the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , in contrast to the currently reported experimental result.

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