Measurement of the inclusive electron spectrum from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> meson decays and determination of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo stretchy="false">|</mml:mo><mml:msub><mml:mi>V</mml:mi><mml:mrow><mml:mi>u</mml:mi><mml:mi>b</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">|</mml:mo></mml:math>
Bibliographic record
Abstract
Based on the full BABAR data sample of 466.5 million $B\overline{B}$ pairs, we present measurements of the electron spectrum from semileptonic $B$ meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ decays from the CKM-favored $B\ensuremath{\rightarrow}{X}_{c}e\ensuremath{\nu}$ decays, and from various other backgrounds, and determine the total semileptonic branching fraction $\mathcal{B}(B\ensuremath{\rightarrow}Xe\ensuremath{\nu})=(10.34\ifmmode\pm\else\textpm\fi{}{0.04}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.2{6}_{\mathrm{syst}})%$, averaged over ${B}^{\ifmmode\pm\else\textpm\fi{}}$ and ${B}^{0}$ mesons. We determine the spectrum and branching fraction for charmless $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ decays and extract the CKM element $|{V}_{ub}|$, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above $2.1\text{ }\text{ }\mathrm{GeV}/c$ is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element $|{V}_{ub}|$ are presented, with the lower limit on the electron momentum varied from $0.8\text{ }\text{ }\mathrm{GeV}/c$ to the kinematic endpoint. We determine $|{V}_{ub}|$ using each of these different calculations and find, $|{V}_{ub}|=(3.794\ifmmode\pm\else\textpm\fi{}{0.107}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.219\text{ }\mathrm{SF}}^{+0.292}{\text{ }}_{\ensuremath{-}0.068\text{ }\text{theory}}^{+0.078})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (De Fazio and Neubert), $(4.563\ifmmode\pm\else\textpm\fi{}{0.126}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.208\text{ }\mathrm{SF}}^{+0.230}{\text{ }}_{\ensuremath{-}0.163\text{ }\text{theory}}^{+0.162})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Bosch, Lange, Neubert, and Paz), $(3.959\ifmmode\pm\else\textpm\fi{}{0.104}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.154\text{ }\mathrm{SF}}^{+0.164}{\text{ }}_{\ensuremath{-}0.079\text{ }\text{theory}}^{+0.042})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Gambino, Giordano, Ossola, and Uraltsev), $(3.848\ifmmode\pm\else\textpm\fi{}{0.108}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.070\text{ }\text{theory}}^{+0.084})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".