Evidence for X(3872) from DD* scattering on the lattice

TL;DR

This lattice QCD study provides evidence for the X(3872) state as a bound D D* system with specific scattering parameters, confirming its I=0 nature and distinguishing it from I=1 states.

Contribution

First lattice simulation to identify X(3872) as a candidate state near the D D* threshold in dynamical QCD with explicit scattering analysis.

Findings

X(3872) found 11 +/- 7 MeV below D D* threshold

Large negative scattering length a_0=-1.7 +/- 0.4 fm

No X(3872) candidate in I=1 channel

Abstract

A candidate for the charmonium(like) state X(3872) is found 11 +/- 7 MeV below the DD* threshold using dynamical Nf=2 lattice simulation with J^PC=1^++ and I=0. This is the first lattice simulation that establishes a candidate for X(3872) in addition to the nearby scattering states D D* and J/psi omega, which inevitably have to be present in dynamical QCD. We extract large and negative DD* scattering length a_0=-1.7 +/- 0.4 fm and the effective range r_0=0.5 +/- 0.1 fm, but their reliable determination will have to wait for a simulation on a larger volume. In I=1 channel, only the D D* and J/psi rho scattering states are found and no candidate for X(3872). This is in agreement with the interpretation that X(3872) is dominantly I=0, while its small I=1 component arises solely from the isospin breaking and is therefore absent in our simulation with m_u=m_d.