Pushing the Heavy Quark Expansion for $b\to cl\barν$ to Higher Order in $1/m_b$
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| Format: | Preprint |
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2024
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| _version_ | 1866910657929019392 |
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| author | Milutin, Ilija S. Mannel, Thomas Vos, K. Keri |
| author_facet | Milutin, Ilija S. Mannel, Thomas Vos, K. Keri |
| contents | The Heavy Quark Expansion (HQE) is the major tool to perform calculations for inclusive semileptonic $B\to X_cl\barν$ and, consequently, for precision determinations of the CKM matrix element $V_{cb}$. To further improve precision, we pushed the expansion to $1/m_b^5$ to include even higher order terms in the HQE. Notably, at $1/m_b^5$, ``intrinsic charm'' (IC) contributions proportional to $1/(m_b^3m_c^2)$ occur, which are numerically expected to be sizeable. We will therefore firstly discuss the determination of a reduced set of HQE parameters at $1/m_b^5$, employing Reparametrisation Invariance (RPI) to this end. Consequently, we will show how the IC and ``genuine" $1/m_b^5$ contribute to the different kinematical moments of $B\to X_cl\barν$, 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'' $1/m_b^5$ contributions, leading to an overall small contribution. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_15324 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Pushing the Heavy Quark Expansion for $b\to cl\barν$ to Higher Order in $1/m_b$ Milutin, Ilija S. Mannel, Thomas Vos, K. Keri High Energy Physics - Phenomenology The Heavy Quark Expansion (HQE) is the major tool to perform calculations for inclusive semileptonic $B\to X_cl\barν$ and, consequently, for precision determinations of the CKM matrix element $V_{cb}$. To further improve precision, we pushed the expansion to $1/m_b^5$ to include even higher order terms in the HQE. Notably, at $1/m_b^5$, ``intrinsic charm'' (IC) contributions proportional to $1/(m_b^3m_c^2)$ occur, which are numerically expected to be sizeable. We will therefore firstly discuss the determination of a reduced set of HQE parameters at $1/m_b^5$, employing Reparametrisation Invariance (RPI) to this end. Consequently, we will show how the IC and ``genuine" $1/m_b^5$ contribute to the different kinematical moments of $B\to X_cl\barν$, 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'' $1/m_b^5$ contributions, leading to an overall small contribution. |
| title | Pushing the Heavy Quark Expansion for $b\to cl\barν$ to Higher Order in $1/m_b$ |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2410.15324 |