scholarly journals Pseudo-scalar meson form factors with maximally twisted Wilson fermions at Nf=2

2008 ◽  
Author(s):  
Silvano Simula
Keyword(s):  
Scalar Meson ◽  
Form Factors ◽  
Pseudo Scalar ◽  
Wilson Fermions

scholarly journals SU(3) breaking and the pseudo-scalar spectrum in multi-taste QCD

2018 ◽  
Vol 175 ◽  
pp. 04001
Author(s):  
Michael Creutz
Keyword(s):  
Sigma Model ◽  
Physical Spectrum ◽  
Pseudo Scalar ◽  
Wilson Fermions

Using the Sigma model to explore the lowest order pseudo-scalar spectrum with SU(3) breaking, this talk considers an additional exact “taste” symmetry to mimic species doubling. Rooting replicas of a valid approach such as Wilson fermions reproduces the desired physical spectrum. In contrast, extra symmetries of the rooted staggered approach leave spurious states and a flavor dependent taste multiplicity.

scholarly journals ω AND η (η') MESONS FROM NN AND ND COLLISIONS AT INTERMEDIATE ENERGIES

2010 ◽  
Vol 19 (05n06) ◽  
pp. 894-902 ◽  
Author(s):  
L. P. KAPTARI ◽  
B. KÄMPFER
Keyword(s):  
Cross Sections ◽  
Good Description ◽  
Meson Production ◽  
Form Factors ◽  
Angular Distributions ◽  
Transition Form ◽  
Vector Meson Production ◽  
Intermediate Energies ◽  
Electron Production ◽  
Pseudo Scalar

The production of pseudo scalar, η, η′, and vector, ω, ρ, ϕ, mesons in NN collisions at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. It is shown that a good description of cross sections and angular distributions, for vector meson production, can be accomplished by considering meson and nucleon currents only, while for pseudo scalar production an inclusion of nucleon resonances is needed. The di-electron production from subsequent Dalitz decay of the produced mesons, η′ → γγ* → γe+e- and ω → πγ* → πe+e- is also considered and numerical results are presented for intermediate energies and kinematics of possible experiments with HADES, CLAS and KEK-PS. We argue that the transition form factor ω → γ*π as well as η′ → γ*γ can be defined in a fairly model independent way and the feasibility of an experimental access to transition form factors is discussed.

scholarly journals Meson form-factors and wave-functions with Wilson fermions

1993 ◽  
Vol 30 ◽  
pp. 419-422 ◽  
Author(s):  
Rajan Gupta ◽  
David Daniel ◽  
Jeffrey Grandy
Keyword(s):  
Form Factors ◽  
Wave Functions ◽  
Wilson Fermions

N* PHYSICS AT MAMI — RESULTS AND PERSPECTIVES

2014 ◽  
Vol 26 ◽  
pp. 1460051
Author(s):  
MICHAEL OSTRICK
Keyword(s):  
Partial Wave ◽  
Scalar Meson ◽  
Crystal Ball ◽  
Preliminary Results ◽  
Model Independent ◽  
Pseudo Scalar ◽  
Photo Production

New measurements of transverse target and beam-target asymmetries in pion photo-production were performed using the Crystal Ball at the Mainz Microtron MAMI. Preliminary results are discussed in the context of model-independent partial wave analyses for pseudo-scalar meson photo-production below Ecm = 2 GeV.

scholarly journals QUARK MODEL ESTIMATES OF THE STRUCTURE OF THE MESON-N-N*(1/2-) TRANSITION VERTICES

2007 ◽  
Vol 16 (01) ◽  
pp. 81-95
Author(s):  
M. DILLIG ◽  
S. S. ROCHA ◽  
G. F. MARRANGHELLO ◽  
E. F. LÜTZ ◽  
C. A. Z. VASCONCELLOS
Keyword(s):  
Form Factors ◽  
Baryon Resonance ◽  
Explicit Representation ◽  
Coupling Constants ◽  
Meson Exchange ◽  
Diquark Model ◽  
Actual Problem ◽  
Exchange Processes ◽  
Starting Point ◽  
Pseudo Scalar

We address an actual problem of baryon-resonance dominated meson-exchange processes in the low GeV regime, i.e. the phase and the structure of meson-NN* transition vertices. Our starting point is a quark-diquark model for the baryons (obeying approximate covariance; the mesons are kept as elementary objects), together with the relative phases for the NN vertices, as determined from low energy NN scattering. From the explicit representation of the N and N* baryons, we exemplify the derivation of phases, coupling constants and form factors of the NN* (J = 1/2-) transition vertices for pseudo-scalar, scalar and vector mesons.

Interactions between Neutron and Proton

1950 ◽  
Vol 3 (4) ◽  
pp. 519
Author(s):  
P Swan
Keyword(s):  
Short Range ◽  
Scalar Meson ◽  
High Energy ◽  
Low Energy ◽  
Scattering Data ◽  
Energy Data ◽  
Central Potential ◽  
Proton Interaction ◽  
Short Range Repulsion ◽  
Pseudo Scalar

An attempt has been made to find an interaction between neutron and proton which will account for not only the binding energy and quadripole moment of the deuteron and the low energy scattering data, but also the results of the experiments on the scattering of 90 MeV. neutrons by protons. Three types of modification of the triplet neutron-proton interaction have been used which embody the following features : (1) A non-central potential of spherical well form, whose radius of interaction is varied. (2) A non-central potential whose form is closer to that of the pseudo-scalar meson potential than the usual Rarita-Schwinger form, but which does not possess the objectionable singularities of the former. (3) The inclusion of a large short-range repulsion. In each case exchange forces of the usual types have been used. The results obtained, like those of other workers in this field using different forms of interaction, fail to agree with the high energy data.

scholarly journals Nucleon form factors and couplings with $N_{\mathrm f}=2+1$ Wilson fermions

2017 ◽  
Author(s):  
Tim Harris ◽  
Dalibor Djukanovic ◽  
Georg von Hippel ◽  
Parikshit Junnarkar ◽  
Harvey B. Meyer ◽  
...  
Keyword(s):  
Form Factors ◽  
Nucleon Form Factors ◽  
Wilson Fermions

scholarly journals Two-photon exchange in leptophilic dark matter scenarios

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Raghuveer Garani ◽  
Federico Gasparotto ◽  
Pierpaolo Mastrolia ◽  
Henrik J. Munch ◽  
Sergio Palomares-Ruiz ◽  
...  
Keyword(s):  
Dark Matter ◽  
Momentum Transfer ◽  
Direct Detection ◽  
Form Factors ◽  
Scalar Particle ◽  
Analytical Form ◽  
Photon Exchange ◽  
Two Photon ◽  
Zero Momentum ◽  
Pseudo Scalar

Abstract In leptophilic scenarios, dark matter interactions with nuclei, relevant for direct detection experiments and for the capture by celestial objects, could only occur via loop-induced processes. If the mediator is a scalar or pseudo-scalar particle, which only couples to leptons, the dominant contribution to dark matter-nucleus scattering would take place via two-photon exchange with a lepton triangle loop. The corresponding diagrams have been estimated in the literature under different approximations. Here, we present new analytical calculations for one-body two-loop and two-body one-loop interactions. The two-loop form factors are presented in closed analytical form in terms of generalized polylogarithms up to weight four. In both cases, we consider the exact dependence on all the involved scales, and study the dependence on the momentum transfer. We show that some previous approximations fail to correctly predict the scattering cross section by several orders of magnitude. Moreover, we quantitatively show that form factors in the range of momentum transfer relevant for local galactic dark matter, can be significantly smaller than their value at zero momentum transfer, which is the approach usually considered.

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