The Strong Transitions Of Heavy Quarkonia And Interactions Between Heavy Mesons

In recent years,more and more new particles have been observed with the improve-ment of colliding energy and measuring precision at experiment.These include the poorly understood exotic states,like X,Y,Z,and a number of ordinary hadronic states but with masses close to the threshold.The decay patterns of these new states near threshold are very different with the low-lying ones.For example,the hadronic transitions of largely excited heavy quarkonium are more complicated,and thus the branching fractions and invariant mass spectra are anomalous.Although the QCD multipole expansion is very successful in describing the hadronic transitions of low-lying excited heavy quarkonium,but it turns to break down for above-threshold states.The uncomprehensible phenomena in traditional framework prompt us to use new mechanism to interpret the anomalous experimental data.In this work,we firstly studied the dipion transition of D-wave charmonium X(3823),i.e.,X(3823)?J/??+?-.We noticed the ?+?-mass spectrum predicted by QCD multipole expansion is inconsistent with the experimental data at low energy region.For the mass of X(3823)is very close to DD*threshold,we considered the coupled-channel effect for this process.Our results show that the contribution from the coupled channel is in the same order of magnitude with the direct channel.Furthermore,with the coupled-channel effect being involved,the ?+?-mass spectrum can be reproduced to fit the experimental data better.Next,we focused on the ? transition of ?(5S)to D-wave bottomonium ?(13DJ),viz,?(5S)??(13DJ)?.We firstly evaluated the branching fractions via QCD multipole expansion,the results are B[?(5S)??(13D1)?](?)4.7 x 10-6,B[?(5S)??(13D2)?](?)8.4 x 10-6,B[?(5S)??(13D3)?]= 0.But the hadronic loop mechanism predicts B[?(5S)?T(13D1)?](?)(0.5?5.1)× 10-3,B[?(5S)??(13D2)?](?)(0.7?7.5)×10-3,B[T(5S)?T(13D3)?]](?)(0.9?9.6)×10-4.This indicates that the contribution from hadronic loop mechanism is dominant,and the recent Belle experiment has confirmed our predictions.In addition,we studied the effective potentials of BB,BB*,and B*B*systems with chiral effective field theory up to one-loop level,and found the potentials in 0(1+)BB*and B*B*systems are attractive.After solving schrodinger equation,we obtained the binding energies are ?EBB*=-18-31.5+17.6 MeV and ?EB*B*=-99-87.9+73.2 MeV for BB*and B*B*systems,respectively.The study on B(*)B(*)interactions not only provides some useful information to explore exotic double-bottom molecular states for future experiments,but also is helpful for the extrapolations of Lattice QCD simulations.