Constrained second-order power corrections in HQET: $R(D^{(\ast )})$, $|V_{cb}|$, and new physics

Abstract

We postulate a supplemental power counting within the heavy quark effective theory, that results in a small, highly-constrained set of second-order power corrections, compared to the standard approach. We determine all $\bar{B}\to D^{(\ast )}$ form factors, both within and beyond the standard model to $\mathcal{O}({\alpha }_s/m_{c,b},1/m_{c,b}^2)$, under truncation by this power counting. We show that the second-order power corrections to the zero-recoil normalization of the $\bar{B}\to D^{(\ast )}l\nu$ matrix elements ($l=e$, $\mu$, $\tau$) are fully determined by hadron mass parameters, and are in good agreement with lattice QCD (LQCD) predictions. We develop a parametrization of these form factors under the postulated truncation, that achieves excellent fits to the available LQCD predictions and experimental data, and we provide precise updated predictions for the $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ decay rates, lepton flavor universality violation ratios $R(D^{(\ast )})$, and the CKM matrix element $|V_{cb}|$. We point out some apparent errors in prior literature concerning the $\mathcal{O}(1/m_c{m}_b)$ corrections, and note a tension between commonly-used simplified dispersive bounds and current data.

85 pages, 11 figures, 19 tables; published version; minor typos corrected

References in corpus (7)

• $R(D^{\ast })$, $|V_{cb}|$, and the Heavy Quark Symmetry relations between form factors
• Extraction of $|V_{cb}|$ from $B\to D^{(\ast )}\ell {\nu }_{\ell }$ and the Standard Model predictions of $R(D^{(\ast )})$
• The $V_{cb}$ puzzle: an update
• Semitauonic $b$-hadron decays: A lepton flavor universality laboratory
• Precise predictions for ${\Lambda }_b\to {\Lambda }_c$ semileptonic decays
• Lepton-flavour non-universality of $\bar{B}\to D^{\ast }\ell \bar{\nu }$ angular distributions in and beyond the Standard Model
• Precise predictions for B -> Xc tau nu decay distributions

Cited by in corpus (15)

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• Global fit to $b\to c\tau \nu$ anomalies as of Spring 2024
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• Determination of $|V_{cb}|$ using ${\overline{B}}^0\to D^{\ast +}{\ell }^{-}{\bar{\nu }}_{\ell }$ decays with Belle II
• Coup de grace to the charged Higgs solution of $P_5^{\prime }$ and $R_{D^{(\ast )}}$ discrepancies
• First Measurement of $R(X_{\tau /\ell })$ as an Inclusive Test of the $b\to c\tau \nu$ Anomaly
• Implications for the $\Delta A_{FB}$ anomaly in ${\bar{B}}^0\to D^{\ast +}{\ell }^{-}\bar{\nu }$ using a new Monte Carlo Event Generator
• Tests of light-lepton universality in angular asymmetries of $B^0\to D^{\ast -}\ell \nu$ decays
• Test of lepton flavor universality with measurements of $R(D^{+})$ and $R(D^{\ast +})$ using semileptonic $B$ tagging at the Belle II experiment
• Electric Dipole Moments as Probes of $B$ Anomaly
• Exploring the $\tau$ polarization in $B\to X\tau \bar{\nu }$ along different axes
• Measurement of inclusive $B\to X_u\ell \nu$ partial branching fractions and $|V_{ub}|$ at Belle II
• Lepton universality tests and searches for new physics in charged current decays at Belle II
• On magnitudes of some CKM matrix elements
• Joint LHCb--Belle II Prospects to Constrain New Physics in $B\to D^{(\ast )}\tau \nu$