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>c</mml:mi> <mml:mi>b</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">|</mml:mo> </mml:math> using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>B</mml:mi> <mml:mo stretchy="false">→</mml:mo> <mml:mi>D</mml:mi> <mml:mo>ℓ</mml:mo> <mml:msub> <mml:mi>ν</mml:mi> <mml:mi>l</mml:mi> </mml:msub> </mml:math> decays at Belle II
Bibliographic record
Abstract
We present a determination of the Cabibbo-Kobayashi-Maskawa matrix element | V c b | from the decay B → D ℓ ν ℓ using a 365 fb − 1 e + e − → ϒ ( 4 S ) → B B ¯ data sample recorded by the Belle II experiment at the SuperKEKB collider. The semileptonic decay of one B meson is reconstructed in the modes B 0 → D − ( → K + π − π − ) ℓ + ν ℓ and B + → D ¯ 0 ( → K + π − ) ℓ + ν ℓ , where ℓ denotes either an electron or a muon. Charge conjugation is implied. The second B meson in the ϒ ( 4 S ) event is not reconstructed explicitly. Using an inclusive reconstruction of the unobserved neutrino momentum, we determine the recoil variable w = v B · v D , where v B and v D are the four-velocities of the B and D mesons. We measure the total decay branching fractions to be B ( B 0 → D − ℓ + ν ℓ ) = ( 2.06
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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 | 0.004 | 0.005 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.005 | 0.003 |
| Science and technology studies | 0.003 | 0.000 |
| Scholarly communication | 0.004 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.004 |
| Insufficient payload (model declined to judge) | 0.046 | 0.026 |
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".