Diquark Study in Quark Model

To find the diquark correlation in baryons, the baryon spectra with different light-heavy quark combinations are calculated with the help of Gaussian expansion method in naive quark model and chiral quark model. By calculating the diquark energies and separations between any two quarks in baryons, we analyze the diquark effect in the ud-q/Q, us-Q, ss-q/Q, QQ-q/Q(q=u,d, or s; Q=c,b) systems. The results shown that there are diquark correlations in baryons, especially for qq-Q and QQ-q systems, the same diquark has almost the same energy and size in different baryons. For the orbital ground states of baryons, compared to the vector-isovector diquark, the scalar-isoscalar diquarks have lower energy and smaller size, making them good diquarks. For QQ-q systems, the larger the mass of Q, the smaller the diquark separation, and the more pronounced the diquark effect. For qq-Q systems, the separation between two light quarks is still larger than the separation between light and heavy quarks, so structure of these diquarks must be considered. By comparing the naive quark model and the chiral quark model, the introducing of meson exchange increases the size of diquark a little in most systems.