Heavy-quark limit of B-meson distribution amplitudes in light-front holography with longitudinal confinement

@misc{khosravi2026heavyquark,
  title = {{Heavy-quark limit of $B$-meson distribution amplitudes in light-front holography with longitudinal confinement}},
  author = {Reza Khosravi},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.01641},
  eprint = {2611.01641},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.01641},
}

TY  - UNPB
TI  - Heavy-quark limit of B-meson distribution amplitudes in light-front holography with longitudinal confinement
AU  - Reza Khosravi
PY  - 2026
DA  - 2026/11/01
PB  - arXiv
DO  - 10.48550/arxiv.2611.01641
UR  - https://arxiv.org/abs/2611.01641
AB  - The heavy-quark limit of light-front holographic wave functions for heavy--light mesons is investigated, with particular emphasis on the leading-twist B-meson light-cone distribution amplitude, ϕ_B^+(ω). Two prescriptions for incorporating finite quark masses are compared: the invariant mass ansatz (IMA) and the longitudinal confining framework based on the Li--Maris--Zhao--Vary (LMZV) potential. In the IMA, although the peak of the distribution amplitude remains at a soft spectator momentum, its characteristic width decreases as Δω∝ m_B^−1/2 in the heavy-quark limit, causing the longitudinal distribution to collapse asymptotically to δ(ω−m_q). Accordingly, the inverse moment approaches the finite limit λ_B,IMA → m_q = 𝒪(Λ_QCD). In contrast, the LMZV framework approaches a finite leading-power (LP) profile with a stable width of order 𝒪(Λ_QCD) and a stable inverse moment, λ_B,LMZV^LP = m_q + σ/2 = 𝒪(Λ_QCD), which is independent of the heavy-quark mass. The heavy-quark scaling of f_B is also examined using the local axial-vector current at zero transverse separation. While the LMZV longitudinal wave function has a non-singular heavy-quark limit, the bare light-front current does not reproduce the canonical heavy-quark effective theory scaling f_B ∝ m_B^−1/2: the decay constant scales as f_B ∝ m_B^−1 in the LMZV framework and as f_B ∝ m_B^−5/4 in the IMA. Thus, a non-singular heavy-quark limit of the longitudinal wave function is necessary but insufficient to ensure the correct heavy-quark scaling of local current matrix elements without systematic current matching.
ER  -