A new method to access heavy meson lightcone distribution amplitudes from first-principle

We present a method to compute lightcone distribution amplitudes (LCDAs) of heavy meson within heavy quark effective theory (HQET). Our method utilizes quasi distribution amplitudes (quasi-DAs) with a large momentum component P^z. We point out that by sequentially integrating out P^z and m_H, one can disentangle different dynamical scales. Integrating out P^z allows to connect quasi-DAs to QCD LCDAs, and then integrating out m_H enables to relate QCD LCDAs to HQET LCDAs. To verify this proposal, we make use of lattice QCD simulation on a lattice ensemble with spacing a = 0.05187 fm. The preliminary findings for HQET LCDAs qualitatively align with phenomenological models. Using a recent model for HQET LCDAs, we also fit the first inverse moment λ_B^-1 and the result is consistent with the experimentally constrain from B →γℓν_ℓ. This agreement demonstrates the promise of our method in providing first-principle predictions for heavy meson LCDAs.