Glueballs as rotating folded closed strings

Abstract

In previous papers [1,2] we argued that mesons and baryons can be described as rotating open strings in holographic backgrounds. Now we turn to closed strings, which should be the duals of glueballs. We look at the rotating folded closed string in both flat and curved backgrounds.A basic prediction of the closed string model is that the slope of Regge trajectories is half that of open strings. We propose that a simple method to identify glueballs is to look for resonances that belong to trajectories with a slope of approximately 0.45 GeV −2 , half the meson slope. We therefore look at the experimental spectra of flavorless light mesons to see if such a scheme, where some of the states are placed on open string trajectories and some on closed ones, can fit known experimental data. We look at the f 0 (J P C = 0 ++ ) and f 2 (2 ++ ) resonances. As there is no preference for a single scheme of sorting the different states into meson and glueball trajectories, we present several possibilities, each identifying a different state as the glueball. We supplement each scheme with predictions for the masses of excited glueballs.We show that the width of the decay into two mesons is different for glueballs and mesons thus providing a supplementary tool to distinguish between them. In addition, we look at some lattice QCD results for glueball spectra and check their compatibility with the closed string model.One of the main conclusions of this paper is that an extension of experimental data on the spectrum of flavorless hadrons is needed, in particular in the region between around 2.4 GeV and 3 GeV.

Excited mesons, baryons, glueballs and tetraquarks: predictions of the Holography Inspired Stringy Hadron model

“…The latter have a slope which is half that of the former. The slope of glueball trajectories can also be measured on the lattice as we did in [4] or as in [14,15]. In addition the low lying states of closed string should have only even angular momentum and even parity and charge conjugation.…”

“…The spectra of the baryons and their fits were worked out in [3]. Folded closed strings describe glueballs [4]. Exotic tetraquarks are formed of strings connecting baryonic vertices and anti-baryonic vertices [5].…”

“…The lore about the glueballs is that there is no way to separate them from flavorless mesons. As was discussed in [4] since mesons are open strings and glueballs are closed string, there should be a way to distinguish between them. The latter have a slope which is half that of the former.…”

“…We similarly discuss tensor glueballs and the spectrum of f 2 states. One supportive evidence for the existence of the glueball among these states is the fact that one cannot put all the flavorless states only on meson trajectories [4].…”

Factorization for radiative heavy quarkonium decays into scalar Glueball

“…its mass, e.g. Lattice QCD [1][2][3][4], QCD Sum Rules [5][6][7][8][9][10][11], Supergravity Dual [12], Top-down Holographic Dual [13][14][15], Rotating Closed Strings [16], MIT Bag Model [17]. In these approaches, the scalar Glueball is expected generally to populate the low enery region from 1 GeV to 2.2 GeV, which is also a region rich in qq states.…”