Precision Model-Independent Bounds from Global Analysis of $b\to c\ell \nu$ Form Factors

Abstract

We present a model-independent global analysis of hadronic form factors for the semileptonic decays $b\to c\ell \nu$ that exploits lattice-QCD data, dispersion relations, and heavy-quark symmetries. The analysis yields predictions for the relevant form factors, within quantifiable bounds. These form factors are used to compute the semileptonic ratios $R(H_c)$ and various decay-product polarizations. In particular, we find $R(D_s^{\ast })=0.20(3)$ and $R(J/\psi )=0.25(3)$, predictions that can be compared to results of upcoming LHCb measurements. In developing this treatment, we obtain leading-order NRQCD results for the nonzero-recoil relations between the $B_c^{+}\to \{J/\psi ,{\eta }_c\}$ form factors.

13 pages, 8 figures

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• FLAG Review 2021
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• FLAG Review 2024
• Semitauonic $b$-hadron decays: A lepton flavor universality laboratory
• Challenges in Semileptonic B Decays
• ${\Lambda }_c\to {\Lambda }^{\ast }(1520)$ form factors from lattice QCD and improved analysis of the ${\Lambda }_b\to {\Lambda }^{\ast }(1520)$ and ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595,2625)$ form factors
• Das ist der HAMMER: Consistent new physics interpretations of semileptonic decays
• $B\to D\ell {\nu }_{\ell }$ form factors beyond leading power and extraction of $|V_{cb}|$ and $R(D)$
• ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595,2625){\ell }^{-}\bar{\nu }$ form factors from lattice QCD
• Dispersive bounds for local form factors in ${\Lambda }_b\to \Lambda$ transitions
• Semileptonic $B_c\to {\eta }_c,J/\psi$ transitions
• Optimized Lepton Universality Tests in $B\to V\ell \bar{\nu }$ decays
• Implication of $b\to c\tau \nu$ flavor anomalies on $B_s\to D_s^{\ast }\tau \nu$ decay observables
• New physics footprints in the angular distribution of $B_s\to D_s^{\ast }(\to D_s\gamma ,D_s\pi )\tau \nu$ decays
• ${\bar{B}}_c\to {\eta }_c$, ${\bar{B}}_c\to J/\psi$ and $\bar{B}\to D^{(\ast )}$ semileptonic decays including new physics
• Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays
• Analyzing the semileptonic and nonleptonic $B_c\to J/\psi ,{\eta }_c$ decays
• Test of lepton flavor universality in semileptonic B${}_{\text{c}}^{+}$ meson decays in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Correlated study on some $B_c\to P$ and $B_c\to S$ wave channels in light of new inputs
• Measurement of the ratio of the B${}_{\mathrm{c}}^{+}$ $\to$ J/$\psi$${\tau }^{+}{\nu }_{\tau }$ and B${}_{\mathrm{c}}^{+}$ $\to$ J/$\psi$ ${\mu }^{+}{\nu }_{\mu }$ branching fractions using three-prong $\tau$ lepton decays