Asymptotic freedom in strong magnetic fields.

Perturbative gluon exchange interaction between quark and antiquark, or in a 3q system, is enhanced in a magnetic field and may cause vanishing of the total qq[over ¯] or 3q mass, and even unlimited decrease of it-recently called the magnetic collapse of QCD. The analysis of the one-loop correction below shows a considerable softening of this phenomenon due to qq[over ¯] loop contribution, similar to the Coulomb case of QED, leading to approximately logarithmic damping of gluon exchange interaction (≈O(1/ln|eB|)) at large magnetic field.

Dynamical origin and the pole structure of X(3872).

The dynamical mechanism of channel coupling with the decay channels is applied to the case of coupled charmonium--DD* states with JPC=1++. A pole analysis is done and the DD* production cross section is calculated in qualitative agreement with experiment. The sharp peak at the D0D0* threshold and flat background are shown to be due to Breit-Wigner resonance, shifted by channel coupling from the original position of 3954 MeV for the 23P1, QQ state.