WHY X(3915) IS SO NARROW AS A χc0(2P) STATE?

Abstract

New resonance X(3915) was identified as the charmonium χc0(2P) by BaBar Collaboration, but there still seems an open question of this assignment: why its full width is so narrow? To answer this question, we calculate the Okubo–Zweig–Iizuka (OZI)-allowed strong decays [Formula: see text], where X(3915) is assigned as a χc0(2P) state, and estimate its full width in the cooperating framework of 3P0 model and the Bethe–Salpeter (BS) method using the Mandelstam formalism, during which nonperturbative quantum chromodynamics (QCD) effects of the hadronic matrix elements are well-considered by overlapping integral over the relativistic Salpeter wave functions of the initial and final states. We find the node structure of χc0(2P) wave function resulting in the narrow width of X(3915) and show the dependence of the decay width on the variation of the initial mass of X(3915). We point out that the rate of [Formula: see text] is crucial to confirm whether X(3915) is the χc0(2P) state or not.