I. Introduction： In contrast to the vector and tensor mesons, the identification of the scalar mesons is a long-standing puzzle. Scalar resonances are difficult to resolve because some of them have large decay widths...I. Introduction： In contrast to the vector and tensor mesons, the identification of the scalar mesons is a long-standing puzzle. Scalar resonances are difficult to resolve because some of them have large decay widths which cause a strong overlap between resonances and background. In addition, several decay channels sometimes open up within a short mass interval （e.g. at the KK and ηη thresholds）, producing cusps in the line shapes of the near-by resonances. Furthermore, one expects non-qq scalar objects, such as glueballs and multiquark states in the mass range below 2 GeV （for reviews see, e.g., Refs. [1-5] and the mini-review on non-qq states in this Review of Particle Physics （RPP））.展开更多
文摘I. Introduction： In contrast to the vector and tensor mesons, the identification of the scalar mesons is a long-standing puzzle. Scalar resonances are difficult to resolve because some of them have large decay widths which cause a strong overlap between resonances and background. In addition, several decay channels sometimes open up within a short mass interval （e.g. at the KK and ηη thresholds）, producing cusps in the line shapes of the near-by resonances. Furthermore, one expects non-qq scalar objects, such as glueballs and multiquark states in the mass range below 2 GeV （for reviews see, e.g., Refs. [1-5] and the mini-review on non-qq states in this Review of Particle Physics （RPP））.
