[论文解读] Inclusive and exclusive semileptonic decays of heavy mesons on the lattice

Zhi Hu, Alessandro Barone+5 more|arXiv (Cornell University)|Jan 14, 2026

Quantum Chromodynamics and Particle Interactions被引用 0

一句话总结

该论文展示如何直接从格点量子色动力学四点相关函数中提取包含和排他性半尺螺子重介子衰变的可观测量，讨论包含情形中核近似的系统误差控制，并给出基于HQET与BCL的排他性形状因子分析。

ABSTRACT

We report the recent progress from our group in extracting observables of both inclusive and exclusive semileptonic heavy-meson decays directly from lattice QCD four-point correlators. On the inclusive side, we illustrate how to estimate the systematic uncertainties from omitted higher-order terms and non-zero smearing of the kernel approximation, building on two important features of the Chebyshev expansion. On the exclusive side, we perform BCL parameterizations of the pseudoscalar to pseudoscalar form factors and compare the fitted coefficients with those from earlier results by HPQCD. We also perform a HQET-based parameterization of the P-wave form factors to shed new light on the 1/2-vs-3/2 puzzle. This work constitutes a step toward a unified lattice treatment of inclusive and exclusive semileptonic decays, relevant for the Vcb puzzle. In this study, we use lattice ensembles from the RBC/UKQCD collaboration for numerical investigations. Future developments from our group will focus on the control of other systematic effects for inclusive decays and investigations of other techniques with reduced statistical errors to extract exclusive contributions from lattice four-point correlators.

研究动机与目标

• Motivate a unified lattice approach to semileptonic B decays to address the Abs(V_cb) puzzle.
• Show how inclusive observables can be reconstructed from four-point correlators using spectral representations.
• Extract exclusive form factors for B_s decays and compare with HPQCD results.
• Investigate 1/2-vs-3/2 puzzle through HQET-based parameterizations of P-wave form factors.

提出的方法

• Compute lattice four-point correlators with B_s meson interpolators and V-A current insertions.
• Approximate the energy kernel with a Chebyshev expansion and relate to lattice correlators via C_{J_mu J_nu}(q^2,t).
• Use Chebyshev coefficients a_{sigma,k}^{mu nu} and estimate systematic uncertainty from truncation beyond N_cut.
• Apply a modified Bourrely-Caprini-Lellouch (BCL) parameterization to f_+^s and f_0^s for B_s -> D_s, and fit to lattice data.
• Implement HQET-based parameterization for P-wave form factors to study 1/2-vs-3/2 contributions.
• Discuss ground-state subtraction and multi-exponential fits to isolate exclusive channels.

实验结果

研究问题

• RQ1 Can inclusive semileptonic observables for heavy-meson decays be reconstructed directly from lattice four-point correlators?
• RQ2 What are the systematic effects from kernel approximations in the inclusive reconstruction and how can they be controlled?
• RQ3 Do lattice-extracted form factors for B_s -> D_s (and P-wave channels) align with or inform HPQCD results and HQET expectations?
• RQ4 What light the lattice results provide for the 1/2-vs-3/2 puzzle in heavy-meson decays?
• RQ5 Can a unified lattice framework reduce the Abs(V_cb) tension between inclusive and exclusive determinations?

主要发现

• Inclusive observable reconstruction converges with Chebyshev-based kernel approximations as sigma -> 0 and N -> infinity.
• Ground-state contributions can be separated and treated separately from excited states in the kernel expansion.
• B_s -> D_s form factors f_+^s and f_0^s are described by a 3-parameter (two form factors) modified BCL fit with consistency in certain coefficients compared to HPQCD.
• P-wave HQET-inspired parameterization yields tau_1/2^(0) and tau_3/2^(0) values with large uncertainties, offering insight but consistent with zero within errors.
• HQET-based analysis suggests non-negligible radial excited-state contributions to Uraltsev sum rules and potential implications for 1/2-vs-3/2 puzzle.
• The study advances a step toward a unified lattice treatment of inclusive and exclusive semileptonic decays relevant for the Abs(V_cb) puzzle.
• Results are demonstrated on RBC/UKQCD ensembles with B_s decays to X_cs (X_cs includes D_s, D_s0*, D_s1, D_s2).