Observation of the Baryonic Flavor-Changing Neutral Current Decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi>Λ</mml:mi><mml:mi>b</mml:mi><mml:mn>0</mml:mn></mml:msubsup><mml:mo>→</mml:mo><mml:mi>Λ</mml:mi><mml:msup><mml:mi>μ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>μ</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math>
Bibliographic record
Abstract
We report the first observation of the baryonic flavor-changing neutral current decay ${\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses a $p\overline{p}$ collisions data sample corresponding to $6.8\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for ${\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ are measured. We find $\mathcal{B}({\ensuremath{\Lambda}}_{b}^{0}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})=[1.73\ifmmode\pm\else\textpm\fi{}0.42(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. We also report the first measurement of the differential branching ratio of ${B}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\phi}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, using 49 signal events. In addition, we report branching ratios for ${B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, ${B}^{0}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, and $B\ensuremath{\rightarrow}{K}^{*}(892){\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ decays.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.002 |
| Meta-epidemiology (narrow) | 0.003 | 0.005 |
| Meta-epidemiology (broad) | 0.002 | 0.007 |
| Bibliometrics | 0.001 | 0.004 |
| Science and technology studies | 0.005 | 0.006 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.007 | 0.007 |
| Research integrity | 0.003 | 0.005 |
| Insufficient payload (model declined to judge) | 0.042 | 0.006 |
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; both teacher heads agree on what is shown here.
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".