Shapes and sizes of diquarks in lattice QCD
Bibliographic record
Abstract
The idea of diquarks as effective degrees of freedom in QCD has been a successful concept in explaining observed hadron spectra. Recently they have also played an important role in studying doubly heavy tetraquarks in phenomenology and on the lattice. The first member of this family of hadrons is the $T_{cc}$, newly discovered at LHCb. Despite their importance, the colored nature of diquarks has been an obstacle in lattice studies. We address this issue by studying diquarks on the lattice in the background of a heavy static quark, i.e. in a gauge-invariant formalism, with quark masses down to almost physical pion masses in full QCD. We determine mass differences between different diquark channels as well as diquark-quark mass differences. Of particular interest are diquarks with "good" scalar, $\bar{3}_F$, $\bar{3}_c$, $J^P=0^+$, quantum numbers. We find attractive quark-quark spatial correlations only in this channel and observe that the "good" diquark shape is spherical. From the spatial correlations in the "good" diquark channel we extract a diquark size of $\sim 0.6~\rm{fm}$. Our results provide quantitative support for modelling the low-lying baryon spectrum using good light diquark effective degrees of freedom.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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".