Glueballs, Hybrids, Multiquarks. Experimental facts versus QCD inspired concepts

Since the discovery of the first charmed meson in 1976, many open-charm and open-bottom hadrons were observed. In 2003 two narrow charm-strange states $D_{s0}^*(2317)$ and $D_{s1}(2460)$ were discovered by the BaBar and CLEO Collaborations, respectively. After that, more excited heavy hadrons were reported. In this work, we review the experimental and theoretical progress in this field.

A review of the open charm and open bottom systems

Since the discovery of the first charmed meson in 1976, many open-charm and open-bottom hadrons were observed. In 2003 two narrow charm-strange states [Formula: see text] and D s1(2460) were discovered by the BaBar and CLEO Collaborations, respectively. After that, more excited heavy hadrons were reported. In this work, we review the experimental and theoretical progress in this field.

Light-cone distribution amplitudes of axial-vector mesons

We report measurements of the properties of the D(+)(sJ)(2317) and D(+)(sJ)(2457) resonances produced in continuum e(+)e(-) annihilation near sqrt[s]=10.6 GeV. The analysis is based on an 86.9 fb(-1) data sample collected with the Belle detector at KEKB. We determine the masses to be M(D(+)(sJ)(2317))=2317.2+/-0.5(stat)+/-0.9(syst) MeV/c(2) and M(D(+)(sJ)(2457))=2456.5+/-1.3(stat)+/-1.3(syst) MeV/c(2). We observe the radiative decay mode D(+)(sJ)(2457)-->D(+)(s)gamma and the dipion decay mode D(+)(sJ)(2457)-->D(+)(s)pi(+)pi(-) and determine their branching fractions. No corresponding decays are observed for the D(sJ)(2317) state. These results are consistent with the spin-parity assignments of 0(+) for the D(sJ)(2317) and 1(+) for the D(sJ)(2457).

Measurements of the $D_{sJ}$ resonance properties

Under the assumption that both light and heavy quarkonia populate approximately linear Regge trajectories with the requirements of additivity of intercepts and inverse slopes, the masses of different meson multiplets are estimated. The predictions derived from the quasi-linear Regge trajectories are in reasonable agreement with those given by many other references.

Meson spectrum in Regge phenomenology

In the $f_2(1270)-f^\prime_2(1525)$ mixing framework, the isoscalar singlet-octet mixing angle for 1$^3P_2$ tensor nonet is determined to be the value of $27.5^\circ$ and the decays of the two states are investigated. Comparing the predicted results of the decays of the two states with the available experimental data, we find that the predicted results are in good agreement with the experimental data, which shows that the $f_2(1270)$ and $f^\prime_2(1525)$ wave functions don't need other components such as glueballs or the 2 $^3P_2$,3 $^3P_2$,...$q\bar{q}$.

Properties of the tensor mesons $f_2(1270)$ and $f^\prime_2(1525)$

The implications of the f1(1285)-f1(1420) mixing for the K1(3P1)- K1(1P1) mixing angle are investigated. Based on the f1(1285)-f1(1420) mixing angle ∼ 50° suggested from the analysis for a substantial body of data concerning the f1(1420) and f1(1285), the masses of the K1(3P1) and K1(1P1) are determined to be ∼ 1307.35±0.63 MeV and 1370.03±9.69 MeV, respectively, which therefore suggests that the K1(3P1)- K1(1P1) mixing angle is about ±(59.55±2.81)°. Also, it is found that the mass of the h′1(1P1) (mostly of s¯) state is about 1495.18±8.82 MeV. Comparison of the predicted results and the available experimental information of the h1(1380) shows that without further confirmation on the h1(1380), the assignment of the h1(1380) as the s¯ member of the 1P1 meson nonet may be premature.

Regarding the axial-vector mesons

Based on the main assumption that a0(980) and D * sJ(2317) belong to the 13P0 q¯ multiplet, in the framework of Regge phenomenology and meson-meson mixing, it is suggested that a0(980), K * 0(1052), f0(1099) and f0(530) constitute the ground scalar meson nonet, and that the f0(1099) is composed mostly of s¯, while the f0(530) is mainly a u¯ + d¯ system. It is supposed that these states would likely correspond to the observed scalar states a0(980), κ(900), f0(980) and f0(600)/σ, respectively. The agreement between the present findings and those given by other different approaches is satisfactory.

A possible assignment for the ground scalar meson nonet

In the three-state mixing framework, considering the possible glueball components of $\eta$
 and $\eta^\prime$
 , we investigate the hadronic decays of $f_0(1370)$
 , $f_0(1500)$
 and $f_0(1710)$
 into two pseudoscalar mesons. The quarkonia–glueball content of the three states is determined from a fit to the new data presented by the WA102 Collaboration. We find that these data are insensitive to the possible glueball components of $\eta$
 and $\eta^\prime$
 . Furthermore, we discuss some properties of the mass matrix describing the mixing of the isoscalar scalar mesons.

De-Min Li

Papers

Meson spectrum in Regge phenomenology

Properties of the tensor mesons $f_2(1270)$ and $f^\prime_2(1525)$

Regarding the axial-vector mesons

A possible assignment for the ground scalar meson nonet

Properties of the scalar mesons \(f_0(1370), f_0(1500)\) and \(f_0(1710)\)