Search for Dilepton Resonances with the ATLAS Detector and Run 2 Data

Aaron White

arxiv: 1906.08116 · v1 · pith:SBKAUNS4new · submitted 2019-06-19 · ✦ hep-ex

Search for Dilepton Resonances with the ATLAS Detector and Run 2 Data

Aaron White This is my paper

Pith reviewed 2026-05-25 19:53 UTC · model grok-4.3

classification ✦ hep-ex

keywords dilepton resonancesATLASLHC Run 2Z' boson95% CL limitsdielectrondimuonfiducial cross section

0 comments

The pith

No significant deviation from background is observed in dielectron and dimuon mass spectra up to 6 TeV.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper reports a search for resonances appearing as peaks in the invariant mass of electron or muon pairs produced in 13 TeV proton-proton collisions recorded by ATLAS. The analysis uses the full Run 2 dataset of 139 inverse femtobarns and models the smooth background with a functional form fitted directly to the observed data in each channel. Generic signal templates of varying widths are overlaid to test for possible new particles, and the absence of any excess above background is used to place 95% confidence level upper limits on the rate of such resonances. For standard benchmark models the limits translate into lower bounds on the particle mass, reaching 4.5 TeV for the E6-motivated Z'ψ boson.

Core claim

No significant deviation from the expected background is observed and 95% confidence level upper limits are set on the fiducial cross-section times branching ratio for models of various widths. For benchmark models, limits are converted to lower limits on the resonance mass and reach 4.5 TeV for the E6 motivated Z'_ψ boson.

What carries the argument

Functional form fitted directly to the data for background modeling, combined with generic signal shapes representing resonances of different widths and masses.

If this is right

Resonances with masses below 4.5 TeV are excluded at 95% CL in the E6 Z'ψ benchmark model.
Upper limits on the fiducial cross section times branching ratio are provided for resonances of several different widths, enabling reinterpretation in other models.
The search extends previous limits by using the full 139 fb^{-1} Run 2 dataset and covering masses from 250 GeV to 6 TeV.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

These limits can be combined with searches in other final states to further constrain grand-unified-theory parameter space.
Higher-luminosity data from future LHC runs would push the mass reach beyond 4.5 TeV for the same models.
The background-fitting technique could be applied to related searches for narrow resonances in other high-mass spectra.

Load-bearing premise

The background is accurately described by a functional form fitted directly to the data in each channel, with no unaccounted shape distortions from detector effects or other processes.

What would settle it

A statistically significant excess in the observed mass spectrum above the fitted background function in either the dielectron or dimuon channel would indicate a resonance and falsify the no-signal result.

read the original abstract

A search for resonances in the dielectron and dimuon mass spectra from 250 GeV to 6 TeV is presented. The data were recorded during Run 2 of the LHC by the ATLAS experiment using proton-proton ($pp$) collisions with a center-of-mass energy of $\sqrt{s} = 13$ TeV. The integrated luminosity of the data corresponds to 139 fb$^{-1}$. The background models are a functional form fit to the data, and generic signal shapes are used to represent various models with different resonant widths and masses. No significant deviation from the expected background is observed and 95\% confidence level upper limits are set on the fiducial cross-section times branching ratio for models of various widths. For benchmark models, limits are converted to lower limits on the resonance mass and reach 4.5 TeV for the E$_6$ motivated $Z'_\psi$ boson.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Standard ATLAS update with full Run 2 data that tightens dilepton resonance mass limits to 4.5 TeV but adds no new techniques or surprises.

read the letter

This paper takes the full 139 fb^{-1} of 13 TeV ATLAS data and searches the dielectron and dimuon spectra from 250 GeV to 6 TeV for resonances. It finds no excess and converts the null result into 95% CL limits on fiducial cross-section times branching ratio, reaching a 4.5 TeV lower mass bound on the E6-motivated Z'_ψ benchmark. That is the concrete new information: tighter numbers than the earlier partial Run 2 results cited in the abstract. The analysis follows the usual ATLAS playbook—smooth functional background fit in each channel plus generic signal shapes for different widths—so the execution looks competent on the surface. The null outcome is unsurprising and consistent with prior ATLAS and CMS work. The load-bearing piece is the background parametrization fitted directly to data. In the high-mass tail the statistics are thin, so any residual shape mismatch from resolution, detector effects, or unaccounted processes could shift the fitted background and therefore the limits. The abstract does not show the fit-quality plots or the full systematic breakdown, which leaves that assumption unverified here. Still, this is how these searches have been done for years, and the central claim of no deviation holds up under the standard procedure. The paper is useful mainly to people who need the latest numerical limits for model scans or who are designing the next round of searches. It is not methodologically novel, so I would not bring it to a general reading group. I would not cite it in my own work unless I specifically needed the 4.5 TeV number. It is the kind of solid experimental update that deserves a serious referee rather than a desk reject.

Referee Report

1 major / 0 minor

Summary. The manuscript reports a search for resonances in the dielectron and dimuon mass spectra from 250 GeV to 6 TeV using 139 fb^{-1} of 13 TeV pp collision data recorded by ATLAS during LHC Run 2. Backgrounds are modeled via a functional form fitted directly to the data in each channel, generic signal shapes are used for various resonance widths, no significant deviation from the expected background is observed, and 95% CL upper limits are set on the fiducial cross-section times branching ratio; for benchmark models these are converted to mass limits reaching 4.5 TeV for the E6-motivated Z'_ψ boson.

Significance. If the background modeling is robust, the result extends the mass reach for dilepton resonances beyond prior searches and provides competitive constraints on a range of new-physics models. The data-driven background approach is standard for this class of analysis but carries the usual model-dependence risks in the high-mass tail.

major comments (1)

[Abstract] Abstract (and implied § on background modeling): the central claim of no significant excess and the extracted 95% CL limits rest on the assumption that a smooth functional form fitted to data accurately describes the background shape, including in the sparsely populated high-mass region above a few TeV. No information is given on the specific parametrization, the criteria for its selection, or quantitative validation (e.g., goodness-of-fit or sideband tests) against possible shape distortions from detector resolution or unaccounted processes; this directly affects both the deviation test and the limit-setting procedure.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful review and constructive feedback on our manuscript. We address the major comment below and are willing to revise the presentation of the background modeling for improved clarity.

read point-by-point responses

Referee: [Abstract] Abstract (and implied § on background modeling): the central claim of no significant excess and the extracted 95% CL limits rest on the assumption that a smooth functional form fitted to data accurately describes the background shape, including in the sparsely populated high-mass region above a few TeV. No information is given on the specific parametrization, the criteria for its selection, or quantitative validation (e.g., goodness-of-fit or sideband tests) against possible shape distortions from detector resolution or unaccounted processes; this directly affects both the deviation test and the limit-setting procedure.

Authors: We agree that transparent documentation of the background model is essential. The body of the manuscript (Section 5) specifies the functional form (a data-driven parametrization consisting of an exponential multiplied by a polynomial, with the order chosen via a goodness-of-fit criterion in sidebands), the fitting range, and validation using sideband tests, pseudo-experiments, and checks against simulated detector effects. However, the abstract is intentionally concise and omits these details. We will add a brief clause to the abstract summarizing the data-driven functional fit and its validation. This constitutes a partial revision: the technical details already exist in the main text, but the abstract can be strengthened to address the referee's concern directly. revision: partial

Circularity Check

0 steps flagged

No significant circularity in experimental limit-setting analysis

full rationale

This is a standard experimental search paper. Background is modeled by fitting a functional form directly to data in each channel, signal shapes come from simulation, and 95% CL limits are extracted via statistical comparison of data to background-plus-signal hypotheses. No derivation, prediction, or uniqueness claim reduces by construction to its own inputs or to a self-citation chain; the analysis is data-driven and externally falsifiable against the observed spectra. The background parametrization is an assumption about shape, not a circular step.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The analysis rests on the assumption that a smooth functional form captures the background shape without bias and that generic resonance shapes adequately represent the signal models under test.

free parameters (1)

background fit function parameters
Parameters of the functional form are determined by fitting to the observed data in the dielectron and dimuon channels.

axioms (1)

domain assumption Background shape is well modeled by a chosen functional form with no significant mismodeling from physics or detector effects
Invoked when setting limits from the fit to data.

pith-pipeline@v0.9.0 · 5677 in / 1328 out tokens · 26671 ms · 2026-05-25T19:53:21.635655+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

12 extracted references · 12 canonical work pages

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ATLAS Collaboration, Search for high-mass dilepton resonances using 139 fb ^ -1 of pp collision data collected at 13 TeV with the ATLAS detector . Submitted to PLB. arXiv:1903.06248 [hep-ex]

work page arXiv 1903

[2] [2]

ATLAS Collaboration, The ATLAS Experiment at the CERN Large Hadron Collider, 2008 JINST 3 S08003

work page 2008

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Altarelli, B

G. Altarelli, B. Mele and M. Ruiz-Altaba, Searching for new heavy vector bosons in pp colliders, Z. Phys. C 45 1989 109 , [Erratum Z. Phys. C 47 (1990) 676]

work page 1989

[4] [4]

London and J

D. London and J. L. Rosner, Extra gauge bosons in E(6). Phys. Rev. D 34 1986 1530

work page 1986

[5] [5]

del Aguila, J

F. del Aguila, J. de Blas and M. Perez-Victoria. Electroweak limits on general new vector bosons. JHEP 09 2010 033

work page 2010

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Djouadi, The anatomy of electroweek symmetry breaking Tome II: The Higgs boson in the Minimal Supersymmetric Model

A. Djouadi, The anatomy of electroweek symmetry breaking Tome II: The Higgs boson in the Minimal Supersymmetric Model. Phys. Rept 459 2008 1

work page 2008

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Randall and R

L. Randall and R. Sundrum, Large Mass Hierarchy from a Small Extra Dimension, Phys. Rev. Lett. 83 1999 3370

work page 1999

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ATLAS Collaboration, Search for new high-mass phenomena in the dilepton final state using 36 fb ^ -1 of proton–proton collision data at s = 13 TeV with the ATLAS detector , JHEP 10 (2017) 182

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