Search results for "Dispersion theory"

showing 3 items of 3 documents

The hadronic light-by-light contribution to the muon's anomalous magnetic moment

2019

In view of the current 3 - 4 $\sigma$ deviation between theoretical and experimental values for the muon's anomalous magnetic moment, we review the ongoing efforts in constraining the hadronic light-by-light contribution to $a_\mu$ by using dispersive techniques combined with a dedicated experimental program to obtain the required hadronic input.

PhysicsNuclear and High Energy PhysicsMuonAnomalous magnetic dipole moment010308 nuclear & particles physicsDispersion theoryHadronFOS: Physical sciences01 natural sciencesHigh Energy Physics - ExperimentNuclear physicsHigh Energy Physics - PhenomenologyHigh Energy Physics - Experiment (hep-ex)High Energy Physics - Phenomenology (hep-ph)0103 physical sciencesDispersion (optics)High Energy Physics::ExperimentCurrent (fluid)010306 general physics
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Compton scattering by the proton through θcms = 75° and 90° in the Δ-resonance region

1997

Abstract Differential cross sections for Compton scattering by the proton have been measured in the energy interval between 200 and 500 MeV at scattering angles of θcms = 75° and θcms = 90° using the CATS, the CATS/TRAJAN, and the COPP setups with the Glasgow Tagger at MAMI (Mainz). The data are compared with predictions from dispersion theory using photo-meson amplitudes from the recent VPI solution SM95. The experiment and the theoretical procedure are described in detail. It is found that the experiment and predictions are in agreement as far as the energy dependence of the differential cross sections in the Δ-range is concerned. However, there is evidence that a scaling down of the reso…

PhysicsNuclear and High Energy PhysicsProton010308 nuclear & particles physicsScatteringDispersion theoryCompton scattering01 natural sciencesResonance (particle physics)Nuclear physicsAmplitude0103 physical sciencesEnergy intervalAtomic physics010306 general physicsScalingNuclear Physics A
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The role of charged exotic states in e+e− → ψ(2S) π+π−

2019

Abstract In this work, we use the dispersion theory to provide a physical description of recent BESIII data on the reaction e + e − → ψ ( 2 S ) π + π − . Taking into account explicitly the effects of charged exotic intermediate states in the t- and u-channels as well as the two-pion final state interaction, we describe the invariant mass distribution for four different e + e − center-of-mass energies. The effects of the ππ rescattering are accounted for in a single channel Omnes approach which is found to explain the ππ-invariant mass distributions at all e + e − center-of-mass energies. For q = 4.226 GeV and q = 4.258 GeV the already established charged exotic state Z c ( 3900 ) is conside…

PhysicsNuclear and High Energy PhysicsWork (thermodynamics)010308 nuclear & particles physicsDispersion theoryState (functional analysis)01 natural scienceslcsh:QC1-999Nuclear physicsPionDistribution (mathematics)0103 physical sciencesIntermediate stateInvariant mass010306 general physicsDispersion (chemistry)Nuclear Experimentlcsh:PhysicsPhysics Letters B
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