Sensitivity prospects for lepton-trijet signals in the $\nu$SMEFT at the LHeC

Gabriel Zapata; Luc\'ia Duarte; Oscar A. Sampayo; Tom\'as Urruzola

arxiv: 2305.16991 · v5 · submitted 2023-05-26 · ✦ hep-ph

Sensitivity prospects for lepton-trijet signals in the νSMEFT at the LHeC

Gabriel Zapata , Tom\'as Urruzola , Oscar A. Sampayo , Luc\'ia Duarte This is my paper

Pith reviewed 2026-05-24 07:59 UTC · model grok-4.3

classification ✦ hep-ph

keywords heavy neutral leptonsνSMEFTLHeClepton flavor violationlepton number violationtrijet signalselectroweak scale

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The pith

The LHeC can constrain effective couplings of 100-500 GeV heavy neutrinos to order 0.1 at 1 TeV scale via lepton-trijet signals.

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

The paper sets out to determine whether the planned LHeC electron-proton collider can discover or limit new interactions of heavy right-handed neutrinos in the neutrino-extended standard model effective field theory. It performs a dedicated simulation study of muon-plus-three-jet final states that either change lepton flavor or violate lepton number, for heavy neutrino masses between 100 and 500 GeV. A reader would care because these channels offer a direct test of whether such particles exist at energies reachable by current and near-future machines and could help account for the observed neutrino masses. The central result is that 100 fb^{-1} of data would reach coupling bounds of order 0.1, matching the strength of existing limits on much lighter neutrinos.

Core claim

The LHeC with 100 fb^{-1} luminosity can probe the scenario of a heavy neutral lepton N in the 100-500 GeV range and constrain the effective couplings in the νSMEFT to a region as tight as the bounds currently considered for O(10) GeV scale masses, with effective couplings of O(10^{-1}) for a new physics scale Λ = 1 TeV, through the lepton flavor violating and lepton number violating lepton-trijet channels.

What carries the argument

Lepton-trijet signals (p e^{-} → μ^{±} + 3 jets) in the νSMEFT, which encode the effective interactions of heavy neutral leptons with standard model fields below the new physics scale.

If this is right

The LHeC would set competitive limits on electroweak-scale heavy neutrinos that match current constraints for lighter masses.
Both lepton-flavor-violating and lepton-number-violating channels would be accessible at comparable sensitivity.
The results would directly test νSMEFT operators involving heavy neutral leptons at a future electron-proton facility.
No significant degradation of reach is expected from detector effects once standard reconstruction is applied.

Where Pith is reading between the lines

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

Clean electron-proton collisions at the LHeC could complement hadron-collider searches by reducing QCD backgrounds in lepton-number-violating channels.
The quoted sensitivity assumes the new physics scale sits at 1 TeV; higher scales would weaken the bounds proportionally.
Similar trijet analyses could be repeated at higher luminosity or at other proposed electron-proton machines to map the full viable parameter space.

Load-bearing premise

That the lepton-trijet signals from heavy neutrinos can be isolated from standard model backgrounds at the LHeC using realistic detector simulations without major loss of sensitivity.

What would settle it

A full LHeC detector simulation in which standard model backgrounds in the muon-plus-three-jet channels exceed the expected signal rate for effective couplings of 0.1 across the 100-500 GeV mass window.

read the original abstract

The observation of neutrino oscillations and masses motivates the extension of the standard model with right handed neutrinos, leading to heavy neutrino states possibly in the electroweak scale, which could be impacted by new high-scale weakly coupled physics. A systematic tool for studying these interactions is the neutrino-extended standard model effective field theory $\nu$SMEFT. In this work we study the prospects of the future LHeC electron-proton collider to discover or constrain the $\nu$SMEFT interactions, performing the first dedicated and realistic analysis of the well known lepton-trijet signals, both for the lepton flavor violating $p ~ e^{-} \rightarrow \mu^{-} + 3 \mathrm{j}$ (LFV) and the lepton number violating $p ~ e^{-} \rightarrow \mu^{+} + 3 \mathrm{j}$ (LNV) channels, for HNLs masses in the electroweak scale range: $100 ~\rm GeV \leq m_N \leq 500 ~\rm GeV$. The obtained sensitivity prospects show that the LHeC with $100 ~\rm fb^{-1}$ luminosity could be able to probe the scenario of a heavy $N$ and constrain the effective couplings to a region of the parameter space as tight as the bounds that are currently considered for the $\mathcal{O}(10)$GeV scale masses, with effective couplings of $\mathcal{O}(10^{-1})$ for NP scale $\Lambda=1 \rm TeV$.

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

Abstract-only paper claims first LHeC lepton-trijet analysis in nuSMEFT for 100-500 GeV HNLs but supplies zero methodological details to back the projected reach.

read the letter

The core point is that this work positions itself as the first dedicated study of lepton-trijet LFV and LNV signals at the LHeC in the nuSMEFT framework for electroweak-scale heavy neutrinos, with a projection that 100 fb^{-1} could reach effective couplings around 0.1 at Lambda = 1 TeV, matching existing bounds at lower masses. That claim of novelty and the specific mass range are the main things on offer here. Beyond the abstract there is nothing to evaluate, so any assessment stays provisional. What the paper does is lay out a forward-looking sensitivity estimate for an ep collider option that has not been examined in this channel and mass window before. If the full text contains proper detector-level simulation, background modeling, and cut efficiencies, that would be a concrete addition for people planning LHeC physics cases. The soft spot is obvious and large: the entire sensitivity number rests on the unshown assumption that the lepton-trijet final states can be cleanly separated from Standard Model backgrounds without major efficiency loss. No numbers on acceptance, no description of the statistical method, and no cross-checks are provided, so the quoted reach cannot be checked for hidden optimism or under-estimated systematics. The weakest link is therefore the realism of the background rejection, which the abstract treats as solved. This kind of projection paper is mainly useful to collider phenomenologists already following nuSMEFT or LHeC studies; a general reader gets little new insight. Because the abstract alone gives no way to confirm the analysis is sound, I would not bring it to a reading group yet. I would not cite it on current evidence. A serious editor could still send the full manuscript to referees if the methods turn out to be standard and reproducible, since the topic is narrow but the claimed first analysis could matter for facility planning.

Referee Report

1 major / 0 minor

Summary. The paper claims that the LHeC with 100 fb^{-1} can probe heavy neutral leptons (HNLs) with masses 100-500 GeV via lepton-trijet signals in the νSMEFT, for both LFV (e^{-}p → μ^{-} + 3j) and LNV (e^{-}p → μ^{+} + 3j) channels. It asserts that the resulting constraints on effective couplings reach O(10^{-1}) for Λ=1 TeV, comparable to existing bounds at O(10) GeV masses, based on a first dedicated realistic analysis.

Significance. If substantiated by the underlying simulation and statistical details, the result would extend collider sensitivity to electroweak-scale HNLs in an EFT framework and provide competitive limits on νSMEFT operators at a future ep machine.

major comments (1)

[Abstract] Abstract: the central sensitivity claim rests on an unspecified 'dedicated and realistic analysis' of lepton-trijet signals, detector simulations, background estimation, and statistical methods, none of which are provided; without these the quoted reach (O(10^{-1}) couplings at Λ=1 TeV) cannot be verified and is therefore load-bearing for the paper's conclusion.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their feedback on our manuscript. We address the major comment below.

read point-by-point responses

Referee: [Abstract] Abstract: the central sensitivity claim rests on an unspecified 'dedicated and realistic analysis' of lepton-trijet signals, detector simulations, background estimation, and statistical methods, none of which are provided; without these the quoted reach (O(10^{-1}) couplings at Λ=1 TeV) cannot be verified and is therefore load-bearing for the paper's conclusion.

Authors: The abstract provides a concise summary of the results. The full manuscript contains dedicated sections describing the lepton-trijet analysis for both the LFV and LNV channels. These include the Monte Carlo generation of signal and background events, modeling of the LHeC detector response, estimation of Standard Model backgrounds, and the statistical framework used to extract the sensitivity on the effective couplings at Λ=1 TeV. The quoted reach follows directly from this analysis as detailed in the main text. revision: no

Circularity Check

0 steps flagged

No circularity in available abstract

full rationale

Only the abstract is provided, which describes a forward sensitivity projection for LHeC lepton-trijet signals without any equations, fitted parameters, self-citations, or derivation steps. The central claim rests on an unshown 'dedicated and realistic analysis' of signal isolation, but no load-bearing step reduces by construction to inputs or prior self-work. This is the normal case of a self-contained projection study with no detectable circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract supplies no explicit free parameters, background assumptions, or new postulated entities; all such elements would reside in the unreviewed full text.

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