Catalog · Charged lepton · L023

L023 $\nu_\mu N\to\nu_\mu N\mu^+\mu^-$

Muon-neutrino trident production

Status REVIEWED VERIFIED High Code: NO Priority Low

PDG / equivalent values

Observable	Value	Year	Experiment / source	Provenance
CCFR-based BSM exclusion contours in Altmannshofer et al. 2014 trident reinterpretation	95 percent confidence level	2014	Altmannshofer2014:L023:ccfr_exclusion_cl	source ↑
Belle-II center-of-mass energy for auxiliary $L_\mu$ - $L_\tau$ reach	10.58 GeV	2017	Kaneta2017:L023:belleii_sqrt_s	source ↑
Belle-II integrated-luminosity goal for auxiliary $L_\mu$ - $L_\tau$ reach	50 ab^-1	2017	Kaneta2017:L023:belleii_luminosity_goal	source ↑
DUNE near-detector trident abstract accuracy projection	25 percent accuracy	2019	DUNE2019:L023:abstract_accuracy_projection	source ↑
DUNE near-detector trident projected running time per beam mode	about 3 years per neutrino and antineutrino beam mode	2019	DUNE2019:L023:beam_mode_exposure_projection	source ↑
DUNE near-detector trident body baseline contour accuracy	40 percent accuracy	2019	DUNE2019:L023:body_baseline_accuracy	source ↑
DUNE near-detector trident improved contour accuracy	25 percent accuracy	2019	DUNE2019:L023:improved_contour_accuracy	source ↑

Why this constrains the RS scan

Trident production constrains second-generation lepton currents rather than the quark $\Delta F=2$ system. In an RS lepton extension, KK electroweak bosons, brane kinetic mixing, or a light $L_\mu-L_\tau$-like gauge state can shift the effective $(\bar\nu_\mu\gamma^\alpha P_L\nu_\mu)(\bar\mu\gamma_\alpha\mu)$ and axial analogues. The constraint is therefore a distinct muon contact/gauge constraint, complementary to dipole LFV such as $\mu\to e\gamma$.

What's changed since the original paper

Relative to the arXiv:0804.1954-era RS flavor baseline (CsakiFalkowskiWeiler2008Flavor), the important updates are reinterpretations and future-experiment studies. Altmannshofer--Gori-- Pospelov--Yavin made the CCFR measurement a standard $L_\mu-L_\tau$ constraint, using $0.82\pm0.28$ and presenting $95\%$ CL exclusion contours (Altmannshofer2014TridentProbe). Belle-II studies connected the same gauge-current parameter space to $e^+e^-\to\gamma+$ missing energy at $\sqrt{s}=10.58~\mathrm{GeV}$ with a $50~\mathrm{ab}^{-1}$ luminosity goal, which is auxiliary collider reach rather than a trident measurement (KanetaShimomura2017BelleIITrident). The DUNE study repeats the historical CHARM-II/CCFR/NuTeV ratios and projects a near-detector trident measurement: its abstract gives about $25\%$ accuracy after roughly three years in each beam mode, while the body uses a $40\%$ baseline and a $25\%$ improved contour (Altmannshofer2019DUNETridents).

Validity and model dependence

The experimental observable is cleanly electroweak, but the bound is not a single universal number: it depends on the target material, neutrino spectrum, selection cuts, nuclear form factors, and the assumed mediator mass relative to the momentum transfer. CCFR is robust as a measured rate ratio; translating it to a new RS mediator requires a dedicated trident cross-section calculation and cannot be borrowed from the meson-mixing or dipole backends.

Code coverage in this repo

NO. Greps over quarkConstraints/, qcd/, flavorConstraints/, neutrinos/, yukawa/, warpConfig/, solvers/, scanParams/, and tests/ found no trident, CCFR, NuTeV, CHARM-II, DUNE, or $L_\mu-L_\tau$ implementation. The only ``CHARM'' hits are QCD charm-mass threshold constants, not this process (L023.yaml:code\_coverage).

Implementation difficulty

HIGH. A production constraint would need a new lepton-current operator convention, mediator matching, nuclear/target treatment, neutrino-flux integration, and an experiment-specific rate or likelihood. This is a new mode calculation, not a parameter update to the existing $\Delta F=2$ or $\mu\to e\gamma$ paths (L023.yaml:implementation\_difficulty\_reason).

Reason: Missing implementation requires a new neutrino-trident mode calculation: lepton-current operator conventions, mediator matching, nuclear form factors/target handling, neutrino flux integration, and experiment-specific rate or likelihood treatment.

Key references

Process-local source keys before bibliography consolidation: CCFR1991TridentsWZ; CHARMII1990FirstObservation; NuTeV1998Trident; Altmannshofer2014TridentProbe; Altmannshofer2019DUNETridents; KanetaShimomura2017BelleIITrident; CsakiFalkowskiWeiler2008Flavor.

value 95

RESOLVED

Match snapshot line 20

L17:   differences in background treatment between the initial report and later
L18:   publication.
L19: - The captioned constraint plot states that CCFR excludes parameter space at
L20:   95% confidence level for the L_mu - L_tau style Z' interpretation.
L21: - The paper finds that a gauged-muon-force explanation of the muon g-2 anomaly
L22:   is disfavored for m_Z' greater than about 400 MeV.
L23:

value 10.58

RESOLVED

Match snapshot line 19

L16:   0.82 +/- 0.28 and states that CCFR gives the most stringent bound among the
L17:   reported CCFR and CHARM-II searches.
L18: - It states that Belle-II is an e+e- collider at center-of-mass energy
L19:   sqrt(s) = 10.58 GeV with a goal of 50 ab^-1 integrated luminosity.
L20: - It emphasizes complementarity: Belle-II photon plus missing-energy searches
L21:   probe kinetic-mixing-driven production, while neutrino-beam trident
L22:   production probes muon-neutrino/muon contact or gauge interactions and can

value 50

AMBIGUOUS

Match 1 of 2 snapshot line 5

L2: Access date: 2026-05-16
L3: Primary URL: https://arxiv.org/abs/1701.00156
L4: arXiv: 1701.00156
L5: DOI: 10.1093/ptep/ptx050
L6: Title: On the possibility of search for L_mu - L_tau gauge boson at Belle-II
L7:   and neutrino beam experiments
L8: Authors: Yuya Kaneta and Takashi Shimomura

Match 2 of 2 snapshot line 19

L16:   0.82 +/- 0.28 and states that CCFR gives the most stringent bound among the
L17:   reported CCFR and CHARM-II searches.
L18: - It states that Belle-II is an e+e- collider at center-of-mass energy
L19:   sqrt(s) = 10.58 GeV with a goal of 50 ab^-1 integrated luminosity.
L20: - It emphasizes complementarity: Belle-II photon plus missing-energy searches
L21:   probe kinetic-mixing-driven production, while neutrino-beam trident
L22:   production probes muon-neutrino/muon contact or gauge interactions and can

value 25

RESOLVED

Match snapshot line 19

L16: - The text says CHARM-II and CCFR found rates compatible with Standard Model
L17:   expectations, while no signal could be established at NuTeV.
L18: - The DUNE arXiv abstract says the near detector could measure
L19:   nu_mu -> nu_mu mu+ mu- with about 25% accuracy after about 3 years each in
L20:   neutrino and antineutrino modes.
L21: - The v2 TeX body/conclusion uses a 40% baseline accuracy and discusses a
L22:   25% contour as an improved scenario.

value about 3

RESOLVED

Match snapshot line 19

L16: - The text says CHARM-II and CCFR found rates compatible with Standard Model
L17:   expectations, while no signal could be established at NuTeV.
L18: - The DUNE arXiv abstract says the near detector could measure
L19:   nu_mu -> nu_mu mu+ mu- with about 25% accuracy after about 3 years each in
L20:   neutrino and antineutrino modes.
L21: - The v2 TeX body/conclusion uses a 40% baseline accuracy and discusses a
L22:   25% contour as an improved scenario.

value 40

RESOLVED

Match snapshot line 21

L18: - The DUNE arXiv abstract says the near detector could measure
L19:   nu_mu -> nu_mu mu+ mu- with about 25% accuracy after about 3 years each in
L20:   neutrino and antineutrino modes.
L21: - The v2 TeX body/conclusion uses a 40% baseline accuracy and discusses a
L22:   25% contour as an improved scenario.
L23: - The paper quotes roughly 240 nu_mu -> nu_mu mu+ mu- trident events per year
L24:   at the DUNE near detector before analysis cuts, and O(10) signal events/year

value 25

RESOLVED

Match snapshot line 22

L19:   nu_mu -> nu_mu mu+ mu- with about 25% accuracy after about 3 years each in
L20:   neutrino and antineutrino modes.
L21: - The v2 TeX body/conclusion uses a 40% baseline accuracy and discusses a
L22:   25% contour as an improved scenario.
L23: - The paper quotes roughly 240 nu_mu -> nu_mu mu+ mu- trident events per year
L24:   at the DUNE near detector before analysis cuts, and O(10) signal events/year
L25:   after the detailed selection.