Abstract
In this article a systematic quantitative analysis of the isoscalar bosonic states is performed in the framework of supersymmetric light front holographic QCD. It is shown that the spectroscopy of the $\eta$ and $h$ mesons can be well described if one additional mass parameter -- which corresponds to the hard breaking of chiral $U(1)$ symmetry in standard QCD -- is introduced. The mass difference of the $\eta$ and $\eta'$ isoscalar mesons is then determined by the strange quark mass content of the $\eta'$. The theory also predicts the existence of isoscalar tetraquarks which are bound states of diquarks and anti-diquarks. The candidates for these exotic isoscalar tetraquarks are identified. In particular, the $f_0(1500)$ is identified as isoscalar tetraquark; the predicted mass value 1.52 GeV agrees with the measured experimental value within the model uncertainties.
Highlights
lightfront holographic QCD (LFHQCD) is inspired by the Maldacena conjecture [13]: a weakly coupled classical five-dimensional gravitational theory with anti–de Sitter (AdS) metric is a holographical dual to a strongly coupled four-dimensional quantum gauge field theory defined at the spacetime boundary of AdS5
We will review the main theoretical results for the hadron spectroscopy predicted by supersymmetric LFHQCD; a more detailed treatment is given in Refs. [2,3,10,16]
Due to the maximal symmetry of the AdS5 action, the corresponding four-dimensional theory is invariant under the conformal group
Summary
In a series of recent papers [1,2,3,4,5,6,7] it was shown that lightfront holographic QCD (LFHQCD) [8,9,10], especially after implementation of superconformal algebra [1,2] (supersymmetric LFHQCD), explains many spectroscopic and dynamical features of the observed hadrons, providing nontrivial analytic connections between the spectroscopy of hadrons and the dynamics underlying observables such as their form factors and quark distributions [11,12]. The equations of motion, derived from the five-dimensional AdS modified action, are mapped to the wave equations of a system of two massless color-confined constituents in QCD quantized on the light front; the fifth coordinate in AdS5, the holographic variable z, is identified with the boostinvariant transverse LF separation ζ (see Appendix A) In this approach, the “dictionary” between the bound-state wave functions of the classical five-dimensional theory and the four-dimensional theory quantized on the light front is fixed: for example, the bound state consisting of a confined color-singlet quark and an antiquark with orbital and total angular momentum zero represents a pseudoscalar meson.
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