Eur. Phys. J. C (2008) 56: 63-73
https://doi.org/10.1140/epjc/s10052-008-0640-4

Regular Article - Theoretical Physics

Is X(3872) really a molecular state?

¹ Institute of High Energy Physics, P.O. Box 918-4, Beijing, 100049, P.R. China
² Department of Physics, Peking University, Beijing, 100871, P.R. China

^* e-mail: zhusl@phy.pku.edu.cn

Received: 4 April 2008
Revised: 13 May 2008
Published online: 7 June 2008

Abstract

After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the D⁰D̄^*0 system. The σ 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^*Dπ 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 DD̄^* system exist only with either a very large coupling constant (twice the experimental value) or a large cutoff (Λ ∼ 6 GeV or β ∼ 6 GeV²). In contrast, there probably exists a loosely bound S-wave BB̄^* molecular state. Once produced, such a molecular state would be rather stable, since its dominant decay mode is the radiative decay through B^*→Bγ. Experimental search of these states will be very interesting.