Abstract
In this paper we further develop a string model of hadrons by computing their strong decay widths and comparing them to experiment. The main decay mechanism is that of a string splitting into two strings. The corresponding total decay width behaves as Γ=π2ATL where T and L are the tension and length of the string and A is a dimensionless universal constant. We show that this result holds for a bosonic string not only in the critical dimension. The partial width of a given decay mode is given by Γi/Γ=Φiexp(−2πCmsep2/T) where Φi is a phase space factor, msep is the mass of the “quark” and “antiquark” created at the splitting point, and C is a dimensionless coefficient close to unity. Based on the spectra of hadrons we observe that their (modified) Regge trajectories are characterized by a negative intercept. This implies a repulsive Casimir force that gives the string a “zero point length”.We fit the theoretical decay width to experimental data for mesons on the trajectories of ρ, ω, π, η, K⁎, ϕ, D, and Ds⁎, and of the baryons N, Δ, Λ, and Σ. We examine both the linearity in L and the exponential suppression factor. The linearity was found to agree with the data well for mesons but less for baryons. The extracted coefficient for mesons A=0.095±0.015 is indeed quite universal. The exponential suppression was applied to both strong and radiative decays. We discuss the relation with string fragmentation and jet formation. We extract the quark–diquark structure of baryons from their decays. A stringy mechanism for Zweig suppressed decays of quarkonia is proposed and is shown to reproduce the decay width of ϒ states. The dependence of the width on spin and flavor symmetry is discussed. We further apply this model to the decays of glueballs and exotic hadrons.
Highlights
The spectra of hadrons, both mesons and baryons, fit nicely a stringy description
In the holography inspired stringy hadron (HISH) model [6] we argue that the description of the spectra, decays and other properties of hadrons - mesons, baryons, glueballs and exotics - should be recast as a description in terms of holographic stringy configurations only, and not fields
That we have discussed the decay width associated with a breakup of a open string without or with massive endpoints in critical or non-critical dimensions, we would like to analyze the probability of such a process taking place for hadrons
Summary
The spectra of hadrons, both mesons and baryons, fit nicely a stringy description. This is an observation that has already been made in the early days of string theory [1] for hadrons made out of light quarks. The suppression factor for stringy holographic hadrons is described in 5.2 This includes the calculation of the probability to hit a flavor brane in flat spacetime in a discretised string bit model, and a continuous string. We end up this section with holographic stringy decays via breaking of the vertical segments of the stringy hadron, and section 6.6, where we determine certain constraints on possible decay modes bases on the fact that the decaying states are on Regge trajectories This is done for the linear trajectories to those with first order massive corrections and for heavy quarks. First in subsection 8.1 we define the fitting model This includes the relation of the string length to the phenomenological intercept, and the introduction of phase space and time dilation factors to the decay width. In appendix A we have listed the different hadrons used in the fits of section 8 and their calculated masses and widths in the HISH model
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