Structure of the Scalars

Understand

The PDG Tables list more scalar mesons than can fit into one quark model nonet: indeed, even more than can belong to two multiplets.

• Consequently, some of these must be states beyond the quark model.
• So which of these is ${\bar q}q$ or ${\bar{qq}}qq$ or multi-meson molecule or largely glue? How experiment can help us distinguish between these possibilities is discussed.