The Nature of the X(2175)

Vector Mesons in Medium and Dileptons in Heavy-Ion Collisions

Theoretical approaches to assess modifications of vector mesons in the medium, as well as their experimental identification via electromagnetic probes, are discussed. Implications for the nature of chiral symmetry restoration in hot/dense matter are outlined and put into context with the axialvector channel.

利用引力波检验暗致密天体的本质

Testing the nature of dark compact objects with gravitational waves

本文综述了利用当前及未来引力波观测检验暗致密天体本质的各类方法，为探索超越广义相对论的新物理或标准模型外的奇异物质场提供研究方向。

QCD Tests of the Puzzling Scalar Mesons

Motivated by several recent data, we test the QCD spectral sum rules (QSSR) predictions based on different proposals (\bar qq, \bar q\bar q qq, and gluonium) for the nature of scalar mesons. In the I=1 and 1/2 channels, the unusual (wrong) splitting between the a_0(980) and κ(900) and the a_0(980) width can be understood from QSSR within a \bar qq assignement. However, none of the \bar qq and \bar q\bar q qq results can explain the large κwidth, which may suggest that it can result from a strong interference with non-resonant backgrounds. In the I=0 channel, QSSR and some low-energy theorems (…

Insights into the nature of the $X(3872)$ through B meson decays

We study the decays $B_{c,u,d}\to X(3872)P$ in the perturbative QCD (PQCD) approach, where the puzzling resonance $X(3872)$ is involved and $P$ represents a light pseudoscalar meson $K$ and $π$. Assuming the $X(3872)$ as a $1^{++}$ charmonium state, we find the following results: (a) The branching ratios for the decays $B^+_c\to X(3872)π^+$ and $B^+_c\to X(3872) K^+$ agree with the results predicted by the covariant light-front approach within errors, but are larger than those given by the generalized factorization approach; (b) The branching ratio for the decay $B^+\to X(3872)K^+$ is predicte…