scholarly journals Methods for the nonperturbative approximation of form factors and scattering amplitudes

2000 ◽  
Author(s):  
John R. Hiller
Keyword(s):  
Scattering Amplitudes ◽  
Form Factors ◽  
Nonperturbative Approximation

scholarly journals Applications of AdS/CFT Duality to QCD

2006 ◽  
Vol 21 (04) ◽  
pp. 762-768 ◽  
Author(s):  
Stanley J. Brodsky ◽  
Guy F. de Téramond
Keyword(s):  
Scattering Amplitudes ◽  
Quantum Chromodynamics ◽  
Power Law ◽  
Mass Parameter ◽  
Light Quark ◽  
Form Factors ◽  
Light Front ◽  
Baryon Spectrum ◽  
Conformal Theory ◽  
Counting Rules

Even though quantum chromodynamics is a broken conformal theory, the AdS/CFT correspondence has led to important insights into the properties of QCD. For example, as shown by Polchinski and Strassler, dimensional counting rules for the power-law falloff of hadron scattering amplitudes follow from dual holographic models with conformal behavior at short distances and confinement at large distances. We find that one also obtains a remarkable representation of the entire light-quark meson and baryon spectrum, including all orbital excitations, based on only one mass parameter. We also show how hadron light-front wavefunctions and hadron form factors in both the space-like and time-like regions can be predicted.

scholarly journals Scalar isoscalar form factors for energies above 1 GeV

2019 ◽  
Vol 202 ◽  
pp. 06002
Author(s):  
Stefan Ropertz ◽  
Christoph Hanhart ◽  
Bastian Kubis
Keyword(s):  
Experimental Data ◽  
Scattering Amplitudes ◽  
Form Factors ◽  
Padé Approximants ◽  
High Accuracy ◽  
Data Description ◽  
Pade Approximants ◽  
Low Energies

We present a new parametrization for scattering amplitudes and form factors, which is consistent with high-accuracy dispersive representations at low energies but at the same time allows for a data description of higher mass resonances such as the f0(1500) and f0(2020). The formalism is general and thus can be applied to many decay processes. As an example we discuss the decay of $ \bar {B}_s^0 $ → J/ψππ(KK). From the amplitude fixed in a fit to the experimental data pole positions and residues are extracted via Padé approximants.

scholarly journals Light-by-light forward scattering amplitudes in Lattice QCD

2018 ◽  
Vol 175 ◽  
pp. 06030
Author(s):  
Antoine Gérardin ◽  
Jeremy Green ◽  
Oleksii Gryniuk ◽  
Georg von Hippel ◽  
Harvey B. Meyer ◽  
...  
Keyword(s):  
Scattering Amplitudes ◽  
Lattice Qcd ◽  
Cross Sections ◽  
Correlation Functions ◽  
Sum Rules ◽  
Form Factors ◽  
Forward Scattering ◽  
Meson Pole ◽  
Point Correlation ◽  
Dispersive Approach

We present our preliminary results on the calculation of hadronic light-by-light forward scattering amplitudes using vector four-point correlation functions computed on the lattice. Using a dispersive approach, forward scattering amplitudes can be described by γ*γ* → hadrons fusion cross sections and then compared with phenomenology. We show that only a few states are needed to reproduce our data. In particular, the sum rules considered in this study imply relations between meson–γγ couplings and provide valuable information about individual form factors which are often used to estimate the meson-pole contributions to the hadronic light-by-light contribution to the (g – 2) of the muon.

Asymptotic form factors and scattering amplitudes

1968 ◽  
Vol 27 (10) ◽  
pp. 647-649 ◽  
Author(s):  
R. Brout ◽  
F. Englert
Keyword(s):  
Scattering Amplitudes ◽  
Asymptotic Form ◽  
Form Factors

scholarly journals Gluing operation and form factors of local operators in N = 4 Super Yang-Mills theory

2018 ◽  
Vol 177 ◽  
pp. 09004
Author(s):  
A.E. Bolshov
Keyword(s):  
Scattering Amplitudes ◽  
Stress Tensor ◽  
Form Factors ◽  
Tensor Operator ◽  
Yang Mills ◽  
Local Operators ◽  
Non Local ◽  
Super Yang Mills Theory

The gluing operation is an effective way to get form factors of both local and non-local operators starting from different representations of on-shell scattering amplitudes. In this paper it is shown how it works on the example of form factors of operators from stress-tensor operator supermultiplet in Grassmannian and spinor helicity representations.

scholarly journals Scattering amplitudes for all masses and spins

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Nima Arkani-Hamed ◽  
Tzu-Chen Huang ◽  
Yu-tin Huang
Keyword(s):  
Scattering Amplitudes ◽  
Beta Function ◽  
Form Factors ◽  
Group Index ◽  
Massless Particles ◽  
Helicity Formalism ◽  
Massive Particles ◽  
Helicity Amplitudes ◽  
General Mass ◽  
Rank 2

Abstract We introduce a formalism for describing four-dimensional scattering amplitudes for particles of any mass and spin. This naturally extends the familiar spinor-helicity formalism for massless particles to one where these variables carry an extra SU(2) little group index for massive particles, with the amplitudes for spin S particles transforming as symmetric rank 2S tensors. We systematically characterise all possible three particle amplitudes compatible with Poincare symmetry. Unitarity, in the form of consistent factorization, imposes algebraic conditions that can be used to construct all possible four-particle tree amplitudes. This also gives us a convenient basis in which to expand all possible four-particle amplitudes in terms of what can be called “spinning polynomials”. Many general results of quantum field theory follow the analysis of four-particle scattering, ranging from the set of all possible consistent theories for massless particles, to spin-statistics, and the Weinberg-Witten theorem. We also find a transparent understanding for why massive particles of sufficiently high spin cannot be “elementary”. The Higgs and Super-Higgs mechanisms are naturally discovered as an infrared unification of many disparate helicity amplitudes into a smaller number of massive amplitudes, with a simple understanding for why this can’t be extended to Higgsing for gravitons. We illustrate a number of applications of the formalism at one-loop, giving few-line computations of the electron (g − 2) as well as the beta function and rational terms in QCD. “Off-shell” observables like correlation functions and form-factors can be thought of as scattering amplitudes with external “probe” particles of general mass and spin, so all these objects — amplitudes, form factors and correlators, can be studied from a common on-shell perspective.

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