Speaker
Description
Light quarks form diquark clusters in hadrons and hadronic matter. We construct a chiral effective theory of spin 0 (scalar-pseudo-scalar) and 1 (axial-vector and vector) diquarks. The masses of the diquarks contain chiral invariant and non-invariant terms. The latter is given in terms of chiral condensate and thus variant in finite temperature and/or density. The parameters of the effective theory can be determined by the lattice data for diquarks as well as the masses of the single-heavy baryons (such as $\Lambda_Q$, $\Sigma_Q$ and so on with $Q= c$ or $b$). We find the mass terms of the scalar-pseudo-scalar diquarks contain a special $U_A(1)$ anomaly term, which induces an inverse mass hierarchy for the pseudo-scalar diquarks. The heavy baryon is modeled by a bound state of a heavy quark $Q$ and a diquark. We find that the inverse mass hierarchy results in qualitative difference of the mass spectra of $\Lambda_Q$ and $\Xi_Q$. The dependences of the scalar and axial-vector diquarks on the chiral order parameter are largely different. As a result, reduced chiral condensate may result in the inversion of the scalar and axial-vector diquarks, which may be observed as a change of the heavy baryon spectrum in dense matter. We apply the same model to the heavy tetraquark $T_{QQ}$ and obtain its spectrum.
Reference
M. Harada, Y.R. liu, M. Oka and K. Suzuki, Phys. Rev. D $\bf 101$, 054038 (2020),
Y. Kim, Y.R. Liu, M. Oka, and K. Suzuki, Phys. Rev. D ${\bf 104}$, 054012 (2021),
Y. Kim, M. Oka, and K. Suzuki, arXiv: 2202.06520 (2022).
