Subleading contributions to the decay width of the Tcc+ tetraquark

Recently, the LHCb Collaboration announced the discovery of the T-cc(+) tetraquark. Being merely a few hundred keV below the D*+D-0 threshold, the T-cc(+) is expected to have a molecular component, for which there is a good separation of scales that can be exploited to make reasonably accurate theoretical predictions about this tetraquark. Independently of its nature, the most important decay channels will be D+D-0 pi(0), (DD0)-D-0 pi(+), and D+D-0 gamma. Its closeness to threshold suggests that the mass and particularly the width of the T-cc(+) tetraquark depend on the resonance profile. While the standard Breit-Wigner parametrization generates a T-cc(+) that is too broad for current theoretical calculations to reproduce, a three-body unitarized Breit-Wigner shape reveals instead a decay width (Gamma(pole) = 48 +/- 2(-12)(+0) keV) consistent with theoretical expectations. Here, we consider subleading-order contributions to the decay amplitude, which, though having at most a moderate impact in the width, still indicate potentially significant differences with the experimental width that can be exploited to disentangle the nature of the T-cc(+). Concrete calculations yield Gamma(LO) = 49 +/- 16 keV and Gamma NLO = 58(-6)(+7) keV, though we expect further corrections to the next-to-leading-order (NLO) decay widths from asymptotic normalization effects. We find that a detailed comparison of the NLO total and partial decay widths with experiment suggests the existence of a small (but distinguishable from zero) nonmolecular component of the T-cc(+).

Automated summary

The LHCb Collaboration has recently announced the discovery of the T-cc(+) tetraquark, which is only a few hundred keV below the D*+D-0 threshold. It is expected to have a molecular component, and theoretical predictions can be made accurately due to the separation of scales. The important decay channels include D+D-0 pi(0), (DD0)-D-0 pi(+), and D+D-0 gamma. The mass and width of the T-cc(+) tetraquark depend on the resonance profile due to its closeness to threshold.