Search for narrow low-mass resonances in the four-muon final state with the ATLAS detector at the LHC
Bibliographic record
Abstract
A search for new low-mass resonances in the four-muon final state in the four-muon invariant mass range from $10-50$~GeV is performed using $pp$ collision data recorded with the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 20.3~fb$^{-1}$ at a centre-of-mass energy ($\\sqrt{s}$) of 8~TeV collected in 2012, and 51.5~fb$^{-1}$ and 58.5~fb$^{-1}$ collected at $\\sqrt{s}=13$~TeV in 2015--2017 and 2018, respectively. An excess at 18~GeV in the invariant mass spectrum of the four-muon system of the selected $\\Upsilon(1\\mathrm{S})+\\mu^+\\mu^-\\to\\mu^+\\mu^-\\,\\mu^+\\mu^-$ final state is observed in the 8~TeV data. Although not blinded, typical selection criteria are used and variations studied to explore the stability of the excess, resulting in local significances of the excess of between be $3.6\\,\\sigma$ and $6.3\\,\\sigma$ corresponding to global significances of $1.9\\,\\sigma$ to $5.4\\,\\sigma$. A baseline choice of selection cuts defined for the analysis at 8~TeV was defined in the 8~TeV data to be further probed at Run 2. Subsequent analysis of 13~TeV data finds a smaller excess at the same four-muon invariant mass with a significance of $1.9\\,\\sigma$ in early 13~TeV data runs, while data collected with more restrictive trigger selections in the 2018 dataset finds no evidence of a signal. LHCb and CMS have observed no excess at this mass. Signal MC and di-$\\Upsilon(1\\mathrm{S})$ production studies in data are used to quantify performance across the three data-taking periods, finding reductions in expected sensitivity in the 13~TeV dataset compared to that at 8~TeV. The lack of observation of a signal in the 13~TeV is assessed to be in tension with the structure observed at an invariant mass of 18~GeV in the 8 TeV dataset, up to a maximum of $2.7\\sigma$. We subsequently set and report limits on the total production cross section times branching fraction to a four-muon final state for a new state at a mass of 18~GeV for a variety of models.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".