Is X(3872) really a molecular state?

Abstract

After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the D-0(D) over bar*(0) system. The s meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental D*D pi coupling constant g = 0.59 and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the D-0(D) over bar* system exist only with either a very large coupling constant (twice the experimental value) or a large cutoff (Lambda similar to 6GeV or beta similar to 6GeV(2)). In contrast, there probably exists a loosely bound S-wave B (B) over bar* molecular state. Once produced, such a molecular state would be rather stable, since its dominant decay mode is the radiative decay through B* -> B gamma. Experimental search of these states will be very interesting.