Pushing the Heavy Quark Expansion for b→ clν to Higher Order in 1/m_b

2024/10/20 by Ilija S. Milutin, Milutin, Ilija S., Thomas Mannel +3
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions

paper · pdf · doi:10.48550/arxiv.2410.15324

openalex publication_date 2024/10/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

The Heavy Quark Expansion (HQE) is the major tool to perform calculations for inclusive semileptonic B→ X_clν and, consequently, for precision determinations of the CKM matrix element V_cb. To further improve precision, we pushed the expansion to 1/m_b⁵ to include even higher order terms in the HQE. Notably, at 1/m_b⁵, ``intrinsic charm'' (IC) contributions proportional to 1/(m<sub>b</sub><sup>3</sup>m<sub>c</sub><sup>2</sup>) occur, which are numerically expected to be sizeable. We will therefore firstly discuss the determination of a reduced set of HQE parameters at 1/m<sub>b</sub><sup>5</sup>, employing Reparametrisation Invariance (RPI) to this end. Consequently, we will show how the IC and ``genuine" 1/m_b⁵ contribute to the different kinematical moments of B→ X_clν, focusing in this work on the lepton energy E_l moments. Using the ``lowest-lying state saturation ansatz'' (LLSA), we estimate the size of these contributions and observe a partial cancellation between the IC and ``genuine'' 1/m_b⁵ contributions, leading to an overall small contribution.

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