Holographic QCD Models Predict Heavy Meson Masses and Decay Rates.

Holographic modelling of quantum chromodynamics (QCD) successfully predicts properties of heavy vector mesons, including constituent quark mass and decay widths. Calculations, utilising the Segre formula, extend to radially excited states, demonstrating agreement with experimental data and offering a novel approach to meson spectroscopy within the AdS/QCD framework.

Understanding the fundamental building blocks of matter necessitates probing the strong force, one of the four fundamental forces of nature, which binds quarks together to form hadrons such as protons and neutrons. Recent research utilises a theoretical framework known as AdS/QCD – a duality relating quantum field theories to gravity in anti-de Sitter space – to model the behaviour of heavy vector mesons, composite particles containing heavy quarks. This approach allows physicists to calculate key properties of these mesons, including their masses and decay rates. A collaborative study, detailed in a new publication by Saulo Diles (Universidade Federal do Pará and Universidade Federal de Campina Grande), Miguel Angel Martin Contreras (University of South China), and Alfredo Vega (Universidad de Valparaíso), presents novel calculations of quark masses and decay widths using this holographic methodology. Their work, entitled ‘Holographic quark masses and radiative decays of heavy vector mesons’, offers a fresh perspective on meson spectroscopy and provides results for both ground and radially excited states, benchmarked against existing experimental data.

Probing Quarkonium with Holographic Models and Constituent Quark Approaches

Heavy quarkonium spectroscopy – the investigation of particles composed of heavy quarks and their antiquarks – benefits from a dual approach utilising holographic models of Quantum Chromodynamics (QCD) and the constituent heavy quark model. This combined methodology offers a robust framework for analysing these complex hadronic systems.

Researchers employ the Segre formula – a mathematical relationship used to determine the mass of a particle based on the masses of its constituents – within holographic calculations. This allows extraction of key observables relevant to quarkonia, including the constituent quark mass (the effective mass of a quark within the hadron), the three-photon decay width (a measure of how quickly a particle decays into three photons), and an effective fine structure constant. This constant parameterises the strength of the strong interaction within the quarkonium system.

Holographic models of QCD calculate the spectrum of heavy vector meson masses – composite particles made of a quark and antiquark with a specific spin – and electromagnetic decay constants by analysing the behaviour of the current-current correlation function in the ‘bulk’ – a higher-dimensional space representing the underlying physics. The constituent heavy quark model, conversely, focuses on the observed phenomenology of these mesons, utilising a non-relativistic approximation – a simplification assuming the quarks move at speeds much slower than the speed of light.

Calculations are extending to encompass radially excited quarkonia states, where the constituent quarks orbit each other at higher energy levels. These excited states provide additional tests of the theoretical models and offer insights into the particles’ internal dynamics.

Comparison of theoretical predictions with experimental data, gathered from facilities such as CLEO (Cornell Electron Storage Ring) and BESIII (Beijing Spectrometer III), validates the holographic model and assesses its accuracy in describing quarkonium behaviour. This validation is crucial for establishing a new approach to understanding meson spectroscopy within the Anti-de Sitter/Quantum Chromodynamics (AdS/QCD) framework. This theoretical tool uses gravity in a higher-dimensional space to model the strong force. This framework provides new methods for extracting fundamental properties and testing theoretical predictions.

Bridging the gap between holographic QCD and the established constituent quark model offers a complementary perspective on meson spectroscopy. This combined approach provides a viable method for studying the internal structure and dynamics of these particles, potentially revealing new insights into the strong force, one of the four fundamental forces of nature.