Bibliographic record
Abstract
Rare 𝐵-meson decays provide a sensitive window into potential physics beyond the Standard Model (SM), as they occur only through loop-level processes and are heavily suppressed by the Glashow-Iliopoulos-Maiani (GIM) mechanism. These suppressed transitions, such as the 𝑏 → 𝑠 processes, are particularly useful in the investigation of new particles that may contribute through virtual effects. One compelling possibility is the existence of vector-like quarks (VLQs), which can mix with Standard Model quarks and modify flavor-changing neutral current (FCNC) processes. VLQs, being singlets under the electroweak symmetry and not requiring symmetry breaking for mass generation, can be much heavier than SM quarks. Although difficult to detect directly at colliders, their effects may be observed indirectly through precise measurements in rare decays. In this work, we explore the influence of down-type iso-singlet VLQs on rare 𝐵 decays, focusing on decay 𝐵⁺ → 𝐾⁺𝑣𝑣̄, which is both theoretically clean and sensitive to new physics. Recent results from the Belle-II collaboration report a branching ratio of [2.3 ± 0.5 (stat)] × 10⁻⁵ [43], which provides evidence at the 2.7σ level and lies significantly above the Standard Model prediction of [0.45±0.7]×10⁻⁵ [72]. This discrepancy motivates the study of VLQ contributions to this process. To constrain the new physics parameter 𝑈ₛᵦ, we also examine related decays such as 𝐵ₛ → μ⁺μ⁻ and 𝐵 → 𝑋ₛμ⁺μ⁻. Using these constraints, we compute modified Wilson coefficients (C₇, C₉, C₁₀ and CL) within an effective field theory framework, incorporating VLQ contributions. These coefficients are then used to calculate the branching ratios for 𝐵 → 𝑋ₛ𝑣𝑣̄ and 𝐵 → 𝐾𝑣𝑣̄. Our analysis shows that the inclusion of VLQs can significantly enhance these branching ratios. The resulting parameter space, illustrated by ᵪ² contour plots, highlights VLQs as a viable and testable candidate to explain anomalies in rare 𝐵-meson decays.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".