Measurement of the Beam Asymmetry for the ETA and ETA Prime Mesons with the GlueX Experiment
Bibliographic record
Abstract
The GlueX Experiment in Hall D at Jefferson Lab ultimately aims to provide evidence of hybrid mesons, quark-antiquark pairs with gluonic excitations, which are predicted by quantum chromodynamics calculations on the lattice. GlueX features a linearly-polarized photon beam incident on a liquid hydrogen target and a nearly-four-pi hermetic detector capable of measuring positions and momenta of both charged and neutral final state particles generated in the target. The short-term physics goals of GlueX are to measure observables and properties of the known particles, especially those that are likely decay products of hybrids, such as the eta and eta-prime mesons. An overview of the detector subsystems and the long-term physics goals of GlueX are presented, along with analyses on the Sigma beam asymmetry of the eta and eta-prime mesons. The measurements of Sigma are presented versus the four-momentum transfer squared using a photon beam energy of 8.2-8.8 GeV in the three main decay channels of the eta (eta -> 2gamma, eta -> pi+pi-pi0, and eta -> 3pi0) and the largest branching fraction decay channel of the eta-prime (eta-prime -> pi+pi-eta, with eta -> 2gamma). These are the first results for the beam asymmetry of the eta-prime measured at this beam energy. The results, which are in agreement with past published measurements for the eta by GlueX and with modern theory predictions for the eta and eta-prime, indicate a dominance of natural parity exchange in the resonance production mechanism.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".