Next-to-leading order QCD corrections to fully charm tetraquark radiative decays

We present the first complete next-to-leading-order (NLO) QCD calculation of the fully charm tetraquark radiative decays $T_{4c}(0^{++},2^{++})\toγJ/ψ$ and $T_{4c}(1^{+-})\toγη_c$ at leading order in the relative velocity. The NLO widths are $2.3$–$3.1$ times the leading-order (LO) widths for the long-distance matrix element (LDME) inputs considered here, with $m_c=1.5$ GeV and $μ_R=2m_c$. In the scalar channel, the NLO corrections change the relative contributions of the two color-spin components and their interference. For the tensor channel, the longitudinal fraction $f_L$ of the daughter $J/ψ$ changes from $0.11$ at LO to $0.18$ at strictly expanded NLO, with sensitivity to higher-order corrections. These NLO results provide valuable theoretical input for searches for states predicted below their respective lowest dicharmonium thresholds and for probing the spin and short-distance structure of observed tetraquark candidates.