pith. sign in

arxiv: 2411.00096 · v3 · submitted 2024-10-31 · ✦ hep-ph · hep-ex

Why detect forward muons at a muon collider

Pith reviewed 2026-05-23 17:51 UTC · model grok-4.3

classification ✦ hep-ph hep-ex
keywords muon colliderforward muonsHiggs propertiesinvisible decaysHiggs portalvector boson scatteringCP properties
0
0 comments X

The pith

Detecting forward muons enables Higgs property measurements and invisible new-particle searches at a muon collider.

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

The paper examines how detecting forward muons that accompany neutral vector bosons at a muon collider can advance particle physics measurements. In lower energy regimes these muons help measure the total Higgs production cross section and its branching ratio to invisible states. At higher energies the same detection becomes crucial for identifying new heavy particles that interact through the Higgs portal but decay invisibly. The angular distribution of the muons also carries information about interference between different helicity states, allowing probes of the CP properties of the Higgs coupling to the Z boson.

Core claim

Detection of forward muons accompanying neutral effective vector bosons at a muon collider is essential for studying Higgs boson properties such as inclusive production cross section and invisible branching ratios, and for searching for invisible new heavy particles produced via Higgs portal interactions; additionally, their angular correlations can be used to characterize vector boson scattering and fusion processes including the CP nature of the Higgs-Z coupling.

What carries the argument

The forward muon detector that records muons at small angles relative to the beam line, tagging the production of effective neutral vector bosons in muon collisions.

If this is right

  • Measurement of the inclusive Higgs production cross section is enabled by the extended angular coverage.
  • The branching ratio of the Higgs to invisible final states can be determined.
  • Searches for new heavy invisible particles become feasible when they are produced through the Higgs portal.
  • Angular correlations of forward muons provide sensitivity to quantum interference in vector boson processes, such as the CP properties of the Higgs-Z coupling.

Where Pith is reading between the lines

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

  • The design of muon collider experiments should prioritize dedicated forward muon detection systems to realize these physics opportunities.
  • Similar forward detection strategies could be relevant for other high-energy collider proposals involving muon or electron beams.
  • If the rates are as expected, this approach could provide complementary information to central detectors in vector boson fusion analyses.

Load-bearing premise

Sufficient production rates of neutral effective vector bosons accompanied by detectable forward muons exist in the kinematic regimes relevant for Higgs and new physics studies.

What would settle it

A measurement showing that the number of forward muons in vector boson production events falls significantly below theoretical predictions, rendering the proposed measurements statistically unfeasible.

Figures

Figures reproduced from arXiv: 2411.00096 by Andrea Wulzer, Ennio Salvioni, Maximilian Ruhdorfer.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Distributions of [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p011_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p012_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Normalised distributions of the [PITH_FULL_IMAGE:figures/full_fig_p017_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. Normalised distributions of ∆ [PITH_FULL_IMAGE:figures/full_fig_p018_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. Projected constraints on the coefficients parametris [PITH_FULL_IMAGE:figures/full_fig_p019_9.png] view at source ↗
read the original abstract

We survey the opportunities offered by the detection of the forward muons that accompany the creation of neutral effective vector bosons at a muon collider, in different kinematic regimes. Vectors with relatively low energy produce the Higgs boson and the extended muon angular coverage enables studies of the Higgs properties, such as the measurement of the inclusive production cross section and of the branching ratio to invisible final states. New heavy particles could be produced by vectors of higher energy, through Higgs portal interactions. If the new particles are invisible, the detection of the forward muons is essential in order to search for this scenario. The angular correlations of the forward muons are sensitive to the quantum interference between the vector boson helicity amplitudes and can be exploited for the characterisation of vector boson scattering and fusion processes. This is illustrated by analysing the CP properties of the Higgs coupling to the Z boson. Our findings provide a physics case and a set of benchmarks for the design of a dedicated forward muon detector.

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

0 major / 2 minor

Summary. The manuscript is a survey of physics opportunities enabled by detecting forward muons that accompany neutral effective vector bosons at a muon collider. It covers three main regimes: low-energy vectors for Higgs production and property measurements (including inclusive cross section and invisible branching ratios), higher-energy vectors for producing new heavy particles via Higgs-portal interactions (with forward muons essential for tagging invisible final states), and angular correlations among forward muons to probe helicity amplitudes and CP properties in vector boson scattering/fusion, illustrated with the Higgs-Z coupling. The paper supplies a physics case and benchmarks for designing a dedicated forward muon detector.

Significance. If the standard effective-vector-boson kinematics and production rates hold, the work supplies a clear, literature-grounded motivation for forward muon coverage that could meaningfully extend the Higgs and new-physics reach of a muon collider. The emphasis on invisible-particle searches and helicity-sensitive observables is a concrete strength for detector-design discussions.

minor comments (2)
  1. [Abstract] Abstract: the phrase 'our findings provide ... a set of benchmarks' is slightly ambiguous for a survey paper; it would help to state explicitly which quantitative benchmarks are newly derived versus drawn from the cited literature on VBF/VBS processes.
  2. The manuscript relies on qualitative arguments from standard collider phenomenology; adding a short table or paragraph that lists the relevant kinematic cuts, expected rates, or efficiency requirements (even if referenced) would make the detector-design case more actionable.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the careful reading and positive assessment of our manuscript, including the clear summary of the physics opportunities and the recommendation for minor revision. No specific major comments were listed in the report, so we have no point-by-point revisions to address at this time.

Circularity Check

0 steps flagged

No significant circularity

full rationale

This is a survey paper outlining physics motivations and benchmarks for forward muon detection in VBF/VBS regimes at a muon collider. The abstract and structure present no derivation chain, no fitted parameters renamed as predictions, and no load-bearing self-citations or ansatze. Claims rest on standard effective-vector-boson kinematics already established in the literature, with the central argument (forward muons essential for tagging invisible new-particle production) being a conceptual motivation rather than a self-referential reduction. The paper is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claims rest on standard assumptions of effective vector boson approximation and Standard Model processes at high-energy colliders; no free parameters, new axioms, or invented entities are introduced in the abstract.

axioms (1)
  • domain assumption Effective vector boson approximation holds for neutral vector boson production at muon colliders
    Invoked implicitly when discussing kinematic regimes for Higgs production and new particle searches.

pith-pipeline@v0.9.0 · 5692 in / 1207 out tokens · 34874 ms · 2026-05-23T17:51:05.507122+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Heavy Vector Triplets at a Muon Collider

    hep-ph 2026-05 unverdicted novelty 5.0

    Muon colliders can probe heavy vector triplets up to 12 TeV, competitive with HE-LHC but below FCC-hh projections, including indirect electroweak precision limits.

  2. New Physics Reach through Precision at Future Colliders: a Multi-Pronged Approach

    hep-ph 2026-04 unverdicted novelty 5.0

    Future e+e- colliders can constrain new physics through precision Higgs and electroweak measurements in Higgs-coupling, EFT, and SMEFT frameworks, with updated SMEFiT code released.

Reference graph

Works this paper leans on

90 extracted references · 90 canonical work pages · cited by 2 Pith papers · 28 internal anchors

  1. [1]

    Using Eq

    = dρZ1 h1,h′ 1 dρZ2 h2,h′ 2 dρH h1,h2,h′ 1,h′ 2 , (27) thus features a characteristic dependence on the ϕ± (and p⊥) variables—dictated by the dependence of the Z1,2 density matrices—that makes it potentially observable. Using Eq. (26), we find dσ(h1,h2)⊗(h′ 1,h′

  2. [2]

    resurrect

    ∝e−i∆h1ϕ+ ei∆h2ϕ− dρH h1,h2,h′ 1,h′ 2 , (28) where ∆h1,2 = h1,2 − h′ 1,2. The terms with h1 = h′ 1 and h2 = h′ 2 correspond to di- agonal entries of the hard density matrix (23). They are proportional to the modulus square of the individual he- licity amplitudes and so in turn to the polarisedZZ → X scattering cross sections. The terms with h1 ̸= h′ 1 and...

  3. [3]

    signed ∆ϕjj

    to label the different contributions to the cross section. Equation (28) becomes dσh⊗h′ ∝e−i∆h ∆ϕdρH h,h′ , (33) where ∆ϕ = ϕ+ − ϕ− and ∆h = h − h′. The helicity difference ∆ h can assume the values 0, ±1 and ±2. Therefore, owing to Eq. (33) the distribu- tion of ∆ϕ is the sum of a ∆ ϕ-independent contribution, plus two ∆ϕ-dependent terms composed by trig...

  4. [4]

    J. P. Delahaye, M. Diemoz, K. Long, B. Mansouli´ e, N. Pastrone, L. Rivkin, D. Schulte, A. Skrinsky, and A. Wulzer, arXiv:1901.06150 [physics.acc-ph]

  5. [5]

    Accettura et al., Eur

    C. Accettura et al., Eur. Phys. J. C 83, 864 (2023), [Er- ratum: Eur. Phys. J. C 84, 36 (2024)], arXiv:2303.08533 [physics.acc-ph]

  6. [6]

    Mounet et al., CERN Yellow Rep

    N. Mounet et al., CERN Yellow Rep. Monogr.1, 1 (2022), arXiv:2201.07895 [physics.acc-ph]

  7. [7]

    Narain et al., arXiv:2211.11084 [hep-ex]

    M. Narain et al., arXiv:2211.11084 [hep-ex]

  8. [8]

    Asai et al., arXiv:2407.19176 [hep-ex]

    S. Asai et al., arXiv:2407.19176 [hep-ex]

  9. [9]

    Al Ali et al., Rept

    H. Al Ali et al. , Rept. Prog. Phys. 85, 084201 (2022), arXiv:2103.14043 [hep-ph]

  10. [10]

    K. M. Black et al. , JINST 19, T02015 (2024), arXiv:2209.01318 [hep-ex]

  11. [11]

    Forward tracking at the next e+ e- collider part I: the physics case

    J. Fuster, S. Heinemeyer, C. Lacasta, C. Mari˜ nas, A. Ruiz Jimeno, and M. Vos, JINST 4, P08002 (2009), arXiv:0905.2038 [hep-ex]

  12. [12]

    Forward tracking at the next \boldmath{$e^+e^-$} collider Part II: experimental challenges and detector design

    S. Aplin, M. Boronat, D. Dannheim, J. Duarte, F. Gaede, A. Ruiz-Jimeno, A. Sailer, M. Valentan, I. Vila, and M. Vos, JINST 8, T06001 (2013), arXiv:1303.3187 [physics.ins-det]

  13. [13]

    International Muon Collider Collaboration, CERN Yel- low Rep. Monogr. 2, 1 (2024), arXiv:2407.12450 [physics.acc-ph]

  14. [14]

    Muon collider detector DELPHES card,

    “Muon collider detector DELPHES card,” https: //github.com/delphes/delphes/blob/master/cards/ delphes_card_MuonColliderDet.tcl

  15. [15]

    Ruhdorfer, E

    M. Ruhdorfer, E. Salvioni, and A. Weiler, SciPost Phys. 8, 027 (2020), arXiv:1910.04170 [hep-ph]

  16. [16]

    Ruhdorfer, E

    M. Ruhdorfer, E. Salvioni, and A. Wulzer, Phys. Rev. D 107, 095038 (2023), arXiv:2303.14202 [hep-ph]

  17. [17]

    P. Li, Z. Liu, and K.-F. Lyu, Phys. Rev. D 109, 073009 (2024), arXiv:2401.08756 [hep-ph]

  18. [18]

    Forslund and P

    M. Forslund and P. Meade, JHEP 08, 185 (2022), arXiv:2203.09425 [hep-ph]

  19. [19]

    Forslund and P

    M. Forslund and P. Meade, JHEP 01, 182 (2024), arXiv:2308.02633 [hep-ph]

  20. [20]

    Bandyopadhyay, S

    P. Bandyopadhyay, S. Parashar, C. Sen, and J. Song, JHEP 07, 253 (2024), arXiv:2401.02697 [hep-ph]

  21. [21]

    Barducci and A

    D. Barducci and A. Dondarini, JHEP 10, 165 (2024), arXiv:2404.09609 [hep-ph]

  22. [22]

    Frigerio and N

    M. Frigerio and N. Vignaroli, arXiv:2409.02721 [hep-ph]

  23. [23]

    Bandyopadhyay and S

    P. Bandyopadhyay and S. Parashar, Phys. Rev. D 110, 115032 (2024), arXiv:2410.06298 [hep-ph]

  24. [24]

    Costantini, F

    A. Costantini, F. De Lillo, F. Maltoni, L. Mantani, O. Mattelaer, R. Ruiz, and X. Zhao, JHEP 09, 080 (2020), arXiv:2005.10289 [hep-ph]

  25. [25]

    T. Han, D. Liu, I. Low, and X. Wang, Phys. Rev. D 103, 013002 (2021), arXiv:2008.12204 [hep-ph]

  26. [26]

    Buttazzo, R

    D. Buttazzo, R. Franceschini, and A. Wulzer, JHEP 05, 219 (2021), arXiv:2012.11555 [hep-ph]

  27. [27]

    Fusing Vectors into Scalars at High Energy Lepton Colliders

    D. Buttazzo, D. Redigolo, F. Sala, and A. Tesi, JHEP 11, 144 (2018), arXiv:1807.04743 [hep-ph]

  28. [28]

    Liu and K.-P

    W. Liu and K.-P. Xie, JHEP 04, 015 (2021), arXiv:2101.10469 [hep-ph]

  29. [29]

    Argyropoulos, O

    S. Argyropoulos, O. Brandt, and U. Haisch, Symmetry 13, 2406 (2021), arXiv:2109.13597 [hep-ph]

  30. [30]

    The Higgs Portal Above Threshold

    N. Craig, H. K. Lou, M. McCullough, and A. Thalapillil, JHEP 02, 127 (2016), arXiv:1412.0258 [hep-ph]

  31. [31]

    Testing Electroweak Baryogenesis with Future Colliders

    D. Curtin, P. Meade, and C.-T. Yu, JHEP 11, 127 (2014), arXiv:1409.0005 [hep-ph]

  32. [32]

    ATLAS Collaboration, JHEP 08, 027 (2022), arXiv:2202.00487 [hep-ex]

  33. [34]

    Anomalous Higgs boson couplings in vector boson fusion at the CERN LHC

    V. Hankele, G. Kl¨ amke, D. Zeppenfeld, and T. Figy, Phys. Rev. D 74, 095001 (2006), arXiv:hep-ph/0609075

  34. [35]

    Panico, F

    G. Panico, F. Riva, and A. Wulzer, Phys. Lett. B 776, 473 (2018), arXiv:1708.07823 [hep-ph]

  35. [36]

    Calzolari and F

    D. Calzolari and F. Meloni, private communication

  36. [37]
  37. [38]

    Moretti, T

    M. Moretti, T. Ohl, and J. Reuter, arXiv:hep- ph/0102195

  38. [39]

    WHIZARD: Simulating Multi-Particle Processes at LHC and ILC

    W. Kilian, T. Ohl, and J. Reuter, Eur. Phys. J. C 71, 1742 (2011), arXiv:0708.4233 [hep-ph]

  39. [40]

    A comprehensive guide to the physics and usage of PYTHIA 8.3

    C. Bierlich et al. , SciPost Phys. Codebases 8 (2022), arXiv:2203.11601 [hep-ph]

  40. [41]

    Frixione, O

    S. Frixione, O. Mattelaer, M. Zaro, and X. Zhao, arXiv:2108.10261 [hep-ph]

  41. [42]

    Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations

    P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietk- erk, JHEP 03, 015 (2013), arXiv:1212.3460 [hep-ph]

  42. [43]

    de Blas et al., JHEP 01, 139 (2020), arXiv:1905.03764 [hep-ph]

    J. de Blas et al., JHEP 01, 139 (2020), arXiv:1905.03764 [hep-ph]

  43. [44]

    Silveira and A

    V. Silveira and A. Zee, Phys. Lett. B 161, 136 (1985)

  44. [45]

    McDonald, Phys

    J. McDonald, Phys. Rev. D 50, 3637 (1994), arXiv:hep- ph/0702143

  45. [46]

    C. P. Burgess, M. Pospelov, and T. ter Veldhuis, Nucl. Phys. B 619, 709 (2001), arXiv:hep-ph/0011335

  46. [47]

    LZ Collaboration, Phys. Rev. Lett. 131, 041002 (2023), arXiv:2207.03764 [hep-ex]

  47. [48]

    Higgs portal dark matter in non-thermal cosmologies

    E. Hardy, JHEP 06, 043 (2018), arXiv:1804.06783 [hep- ph]

  48. [49]

    Cohen, N

    T. Cohen, N. Craig, G. F. Giudice, and M. McCullough, JHEP 05, 091 (2018), arXiv:1803.03647 [hep-ph]

  49. [50]

    Singlet Scalar Top Partners from Accidental Supersymmetry

    H.-C. Cheng, L. Li, E. Salvioni, and C. B. Verhaaren, JHEP 05, 057 (2018), arXiv:1803.03651 [hep-ph]

  50. [51]

    Composite Scalar Dark Matter

    M. Frigerio, A. Pomarol, F. Riva, and A. Urbano, JHEP 07, 015 (2012), arXiv:1204.2808 [hep-ph]

  51. [52]

    Dark matter shifts away from direct detection

    R. Balkin, M. Ruhdorfer, E. Salvioni, and A. Weiler, JCAP 11, 050 (2018), arXiv:1809.09106 [hep-ph]

  52. [53]

    Fermi-LAT and DES Collaborations, Astrophys. J. 834, 110 (2017), arXiv:1611.03184 [astro-ph.HE]

  53. [54]

    ForwardMuonMuC repository,

    “ForwardMuonMuC repository,” https://github.com/ maxruhdorfer/ForwardMuonMuC

  54. [55]

    Englert and J

    C. Englert and J. Jaeckel, Phys. Rev. D 100, 095017 (2019), arXiv:1908.10615 [hep-ph]

  55. [56]

    A New Probe of Naturalness

    N. Craig, C. Englert, and M. McCullough, Phys. Rev. Lett. 111, 121803 (2013), arXiv:1305.5251 [hep-ph]

  56. [57]

    Haisch and G

    U. Haisch and G. Koole, JHEP 04, 166 (2022), 23 arXiv:2201.09711 [hep-ph]

  57. [58]

    CTA Collaboration, JCAP 01, 057 (2021), arXiv:2007.16129 [astro-ph.HE]

  58. [59]

    Fermi, Nuovo Cim

    E. Fermi, Nuovo Cim. 2, 143 (1925), arXiv:hep- th/0205086

  59. [60]

    C. F. von Weizsacker, Z. Phys. 88, 612 (1934)

  60. [61]

    Dawson, Nucl

    S. Dawson, Nucl. Phys. B 249, 42 (1985)

  61. [62]

    G. L. Kane, W. W. Repko, and W. B. Rolnick, Phys. Lett. B 148, 367 (1984)

  62. [63]

    Probing the Scattering of Equivalent Electroweak Bosons

    P. Borel, R. Franceschini, R. Rattazzi, and A. Wulzer, JHEP 06, 122 (2012), arXiv:1202.1904 [hep-ph]

  63. [64]

    Nardi, L

    F. Nardi, L. Ricci, and A. Wulzer, (2024), arXiv:2405.08220 [hep-ph]

  64. [65]

    M. J. Duncan, G. L. Kane, and W. W. Repko, Phys. Rev. Lett. 55, 773 (1985)

  65. [66]

    Hagiwara, R

    K. Hagiwara, R. D. Peccei, D. Zeppenfeld, and K. Hikasa, Nucl. Phys. B 282, 253 (1987)

  66. [67]

    Precision diboson measurements at hadron colliders

    A. Azatov, D. Barducci, and E. Venturini, JHEP 04, 075 (2019), arXiv:1901.04821 [hep-ph]

  67. [68]

    Hwang, U

    H. Hwang, U. Min, J. Park, M. Son, and J. H. Yoo, JHEP 08, 069 (2023), arXiv:2301.13663 [hep-ph]

  68. [69]

    El Faham, G

    H. El Faham, G. Pelliccioli, and E. Vryonidou, JHEP 08, 087 (2024), arXiv:2405.19083 [hep-ph]

  69. [70]

    Aoude, E

    R. Aoude, E. Madge, F. Maltoni, and L. Mantani, JHEP 12, 017 (2023), arXiv:2307.09675 [hep-ph]

  70. [71]

    CMS Collaboration, Phys. Rev. D 105, 052003 (2022), arXiv:2111.13948 [hep-ex]

  71. [72]

    ATLAS Collaboration, Eur. Phys. J. C 79, 535 (2019), arXiv:1902.05759 [hep-ex]

  72. [73]

    ATLAS Collaboration, Phys. Lett. B 843, 137895 (2023), arXiv:2211.09435 [hep-ex]

  73. [74]

    ATLAS Collaboration, ATLAS-CONF-2022-053

  74. [75]

    Kauer et al., arXiv:2203.02418 [hep-ph]

    N. Kauer et al., arXiv:2203.02418 [hep-ph]

  75. [76]

    CMS Collaboration, Eur. Phys. J. C 84, 779 (2024), arXiv:2403.00657 [hep-ex]

  76. [77]

    ATLAS Collaboration, JHEP 05, 105 (2024), arXiv:2304.09612 [hep-ex]

  77. [78]

    FeynRules 2.0 - A complete toolbox for tree-level phenomenology

    A. Alloul, N. D. Christensen, C. Degrande, C. Duhr, and B. Fuks, Comput. Phys. Commun.185, 2250 (2014), arXiv:1310.1921 [hep-ph]

  78. [79]

    BSM Characterisation FeynRules model,

    “BSM Characterisation FeynRules model,” https://feynrules.irmp.ucl.ac.be/wiki/ BSMCharacterisation

  79. [80]

    LHC Higgs Cross Section Working Group, CERN Yellow Rep. Monogr. 2, 1 (2017), arXiv:1610.07922 [hep-ph]

  80. [81]

    DELPHES 3, A modular framework for fast simulation of a generic collider experiment

    J. de Favereau, C. Delaere, P. Demin, A. Giammanco, V. Lemaˆ ıtre, A. Mertens, and M. Selvaggi ( DELPHES Collaboration), JHEP 02, 057 (2014), arXiv:1307.6346 [hep-ex]

Showing first 80 references.