Subleading contributions to the decay width of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>T</mml:mi><mml:mrow><mml:mi>c</mml:mi><mml:mi>c</mml:mi></mml:mrow><mml:mo>+</mml:mo></mml:msubsup></mml:math> tetraquark

Abstract

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 ${D}^{+}{D}^{0}{\ensuremath{\pi}}^{0}$, ${D}^{0}{D}^{0}{\ensuremath{\pi}}^{+}$, and ${D}^{+}{D}^{0}\ensuremath{\gamma}$. 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 (${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{pole}}=48\ifmmode\pm\else\textpm\fi{}{2}_{\ensuremath{-}12}^{+0}\text{ }\text{ }\mathrm{keV}$) 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 ${\mathrm{\ensuremath{\Gamma}}}^{\mathrm{LO}}=49\ifmmode\pm\else\textpm\fi{}16\text{ }\text{ }\mathrm{keV}$ and ${\mathrm{\ensuremath{\Gamma}}}^{\mathrm{NLO}}=5{8}_{\ensuremath{-}6}^{+7}\text{ }\text{ }\mathrm{keV}$, 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 ${T}_{cc}^{+}$.

Topics & Concepts