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arxiv: 2409.20231 · v2 · pith:3JNPFE3Snew · submitted 2024-09-30 · ✦ hep-ph · hep-ex

Prospects of measuring the atmospheric muon neutrino and anti-neutrino flux ratio with the ATLAS detector

Deep Ghosh , Satyanarayan Mukhopadhyay , Biswarup Mukhopadhyaya This is my paper

Pith reviewed 2026-05-25 08:14 UTC · model grok-4.3

classification ✦ hep-ph hep-ex
keywords atmospheric neutrinosmuon charge ratioATLAS detectordeep inelastic scatteringneutrino fluxcosmic ray backgroundHCAL
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The pith

ATLAS can measure the energy dependence of the atmospheric muon neutrino to anti-neutrino flux ratio up to 100 GeV.

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

The paper explores using the ATLAS detector to determine the ratio of atmospheric muon neutrinos to anti-neutrinos through the charge of the muons they produce in deep inelastic scattering. Current flux models disagree on this ratio especially at higher energies, so an experimental measurement would constrain those predictions. The authors calculate event rates in the 4-kiloton hadron calorimeter for two classes of events: contained-vertex muons created inside the detector and external upward-going muons created in the rock below. They show that suitable selection criteria can suppress cosmic-ray muon background, allowing the energy-dependent charge ratio to be extracted with 1000 live days of data taken while the LHC beams are off.

Core claim

With 1000 live days of exposure, ATLAS expects 60 negative and 30 positive contained-vertex muon events plus 599 negative and 292 positive external upward-going events; these statistics permit measurement of the energy dependence of the negative-to-positive muon ratio up to 100 GeV muon energy, yielding an all-energy average ratio R_μ-/μ+ = 2.05^{+0.15}_{-0.14} at 68% C.L. for the external class.

What carries the argument

Computation of contained-vertex and external upward-going charged-current event rates from atmospheric muon (anti-)neutrinos via deep inelastic scattering in the ATLAS HCAL, together with selection cuts that remove cosmic-ray muon background.

If this is right

  • The muon charge ratio from atmospheric neutrinos can be measured as a function of energy up to 100 GeV.
  • Contained-vertex events yield 60 μ− and 30 μ+ while external upward-going events yield 599 μ− and 292 μ+ after cuts.
  • The averaged external-event ratio is R_μ−/μ+ = 2.05 with +0.15/−0.14 uncertainties at 68% C.L.
  • Data taking is restricted to periods when LHC beams are off but the detector and magnetic field remain on.

Where Pith is reading between the lines

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

  • A measured ratio differing from current flux models would directly discriminate among those models at energies above a few tens of GeV.
  • Other large LHC detectors could be repurposed for similar atmospheric-neutrino measurements during beam-off periods.
  • The same technique could be tested at future colliders to extend the energy reach of such ratio measurements.

Load-bearing premise

The proposed event selection criteria remove cosmic-ray muon background sufficiently that the atmospheric neutrino signal remains visible at the quoted statistics.

What would settle it

A data sample after the same cuts that contains far fewer than the predicted ~900 external events or shows a charge ratio inconsistent with 2.05 would indicate that background rejection or signal modeling has failed.

read the original abstract

There is a significant uncertainty in the prediction of atmospheric muon neutrino and anti-neutrino flux ratio using different flux models, especially at higher energies. We study the prospects of experimentally measuring this flux ratio as a function of energy with the ATLAS detector at the LHC. To this end, we compute the contained-vertex and external upward going charged current event rates induced by atmospheric muon (anti-)neutrinos through deep inelastic scattering at the 4 kiloton hadron calorimeter (HCAL) component of ATLAS. We illustrate the event selection criteria necessary to eliminate the cosmic ray muon background for the above event classes. While the contained vertex events have a striking topology with a muon being created inside the HCAL and then travelling to the muon chamber possibly through the tracker, for muons with energy larger than 3 GeV, nearly 10 times more events are obtained for the external upward going muons created in the rock column below the detector. Our estimates show that the energy dependence of the ratio of negative and positively charged muons induced by atmospheric muon neutrino and anti-neutrino fluxes can be measured by ATLAS upto a muon energy of 100 GeV, with 1000-live days of neutrino physics exposure over a period of several years, considering only the period with the LHC beams not in circulation, but the detector and magnetic fields of ATLAS in operation. With this exposure, we expect to obtain 60 $\mu^-$ and 30 $\mu^+$ contained vertex events, and $599~\mu^-$ and $292~\mu^+$ external upward-going events, after imposing the necessary selection criteria. For the latter class of events, this corresponds to an expected ratio of negative to positive charged muon events averaged over all energies, $R_{\mu^-/ \mu^+}=2.05^{+0.15}_{-0.14}$, at $68\%$ C.L. (Abridged)

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.

Referee Report

2 major / 2 minor

Summary. The manuscript proposes using the ATLAS detector during LHC beam-off periods to measure the energy-dependent ratio of atmospheric muon neutrino to antineutrino fluxes via contained-vertex and external upward-going charged-current deep-inelastic-scattering events in the 4 kt HCAL. The authors compute expected rates from standard flux models and DIS cross sections, illustrate qualitative selection criteria to reject cosmic-ray muons, and report that with 1000 live days one obtains 60 μ− and 30 μ+ contained events plus 599 μ− and 292 μ+ external events, yielding an all-energy ratio R_μ−/μ+ = 2.05^{+0.15}_{-0.14} (68 % C.L.) measurable up to 100 GeV muon energy.

Significance. If the background-rejection assumptions can be placed on a quantitative footing, the result would show that a large collider detector can deliver an independent atmospheric-neutrino measurement during beam-off running, thereby constraining flux-model uncertainties that are known to be large above a few tens of GeV. The calculation rests on well-established DIS cross sections and published flux parametrizations, which is a methodological strength.

major comments (2)
  1. [Event selection / abstract] Event-selection section (and abstract): the central claim that the quoted event yields (60/30 contained, 599/292 external) remain observable after cuts requires that cosmic-ray muon background be reduced to negligible levels relative to signal. The manuscript illustrates the criteria qualitatively (contained topology; upward direction) but supplies no Monte Carlo evaluation of signal efficiency, background rejection power, or residual background rate. This assumption is load-bearing for both the sensitivity statement and the reported ratio with its uncertainty.
  2. [Results / abstract] Results section: the reported ratio uncertainty (+0.15/−0.14 at 68 % C.L.) is presented without an explicit propagation of statistical and systematic contributions or a description of how the energy-dependent ratio is extracted from the binned event counts. The absence of this information prevents assessment of whether the quoted precision is consistent with the stated event statistics.
minor comments (2)
  1. [Abstract] The abstract states that the exposure corresponds to “1000-live days of neutrino physics exposure over a period of several years”; a brief statement of the assumed live-time fraction or duty cycle would clarify the operational feasibility.
  2. [Abstract / results] Notation for the ratio R_μ−/μ+ is introduced without an explicit definition of the averaging procedure (energy-weighted or event-weighted) used to obtain the single number 2.05.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments. We address the two major comments point by point below. Revisions will be made to improve transparency on assumptions and statistical methods.

read point-by-point responses

  1. Referee: [Event selection / abstract] Event-selection section (and abstract): the central claim that the quoted event yields (60/30 contained, 599/292 external) remain observable after cuts requires that cosmic-ray muon background be reduced to negligible levels relative to signal. The manuscript illustrates the criteria qualitatively (contained topology; upward direction) but supplies no Monte Carlo evaluation of signal efficiency, background rejection power, or residual background rate. This assumption is load-bearing for both the sensitivity statement and the reported ratio with its uncertainty.

    Authors: We agree that the absence of a quantitative Monte Carlo study of cosmic-ray muon rejection is a limitation. The manuscript relies on qualitative topological and directional arguments that are standard in neutrino experiments. As this is a prospects paper, a full background simulation was not performed. We will revise the event-selection section to explicitly state the assumption that residual background is negligible after cuts and note that a dedicated simulation study would be required for a definitive background estimate. revision: yes

  2. Referee: [Results / abstract] Results section: the reported ratio uncertainty (+0.15/−0.14 at 68 % C.L.) is presented without an explicit propagation of statistical and systematic contributions or a description of how the energy-dependent ratio is extracted from the binned event counts. The absence of this information prevents assessment of whether the quoted precision is consistent with the stated event statistics.

    Authors: The quoted uncertainty is obtained solely from Poisson statistics on the total external-event counts via standard ratio error propagation, δR/R = √(1/N− + 1/N+), with no systematic uncertainties included. The manuscript presents the all-energy ratio as an illustrative example; energy-binned extraction is mentioned but not shown because per-bin statistics would be low. We will add a paragraph in the results section describing the statistical procedure and clarifying the relation between total counts and expected precision in energy bins. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation relies on external flux models

full rationale

The paper derives expected event yields (60/30 contained-vertex, 599/292 external) and the ratio R_μ-/μ+=2.05 from external atmospheric neutrino flux models applied to DIS cross sections at the ATLAS HCAL. These quantities are presented as inputs to the measurement-prospect claim rather than outputs of any internal fit. No equations reduce a claimed prediction to a fitted parameter by construction, no self-citation chain supports a uniqueness theorem, and no ansatz is smuggled via prior work. The background-rejection assumption is stated qualitatively but does not create a definitional loop in the reported numbers. The central results remain independent of the paper's own fitted values.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central estimates rest on standard particle-physics inputs and existing atmospheric flux models rather than new fitted parameters or invented entities; the 1000-day exposure is an assumed operational scenario.

free parameters (1)
  • 1000 live days exposure
    Chosen operational assumption used to scale the projected event counts and sensitivity.
axioms (2)
  • standard math Deep inelastic scattering cross sections for muon neutrino interactions are taken from standard literature parametrizations
    Used to convert atmospheric fluxes into expected event rates in the HCAL.
  • domain assumption Atmospheric muon neutrino and antineutrino flux models from prior literature accurately represent the true fluxes for rate estimation
    Input spectra whose ratio is the target of the proposed measurement.

pith-pipeline@v0.9.0 · 5894 in / 1573 out tokens · 52176 ms · 2026-05-25T08:14:44.554249+00:00 · methodology

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Reference graph

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