Time-of-flight measurement with the ALPHA-g Barrel Scintillator detector for gravitational studies of anti-matter
Bibliographic record
Abstract
Abstract The ALPHA-g experiment recently made headlines for the first direct measurement of the gravitational free-fall of anti-hydrogen. Crucial to this milestone is a detector system capable of accurately recording the vertical position of annihilating anti-atoms, with two critical requirements: precise localization of anti-hydrogen annihilations into the “up” or “down” regions, and effective discrimination against the cosmic ray background. To accomplish this, charged pions produced in the annihilation are tracked using a radial time projection chamber detector, and fitted to a common vertex. These pions are also detected by the “Barrel Scintillator” detector, composed of 2.6-meter plastic scintillator bars with silicon photomultipliers at both ends. The arrival time of photons at the silicon photomultipliers is used to determine the time of the pion hitting the bar. This timing information is then used as part of a multivariate analysis to reject externally incident cosmic rays. This poster showcases the time calibration procedure used to obtain time-of-flight measurement of cosmic rays in the Barrel Scintillator, and the background rejection algorithm that will be used for forthcoming ALPHA-g measurements of the gravitational behaviour of anti-hydrogen.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".