pith. sign in

arxiv: 2601.11383 · v2 · submitted 2026-01-16 · ✦ hep-ph

Projections of Htoττ cross-section at FCC-ee

Sofia Giappichini , Markus Klute , Matteo Presilla , Xunwu Zuo , Maria Cepeda This is my paper

Pith reviewed 2026-05-16 13:19 UTC · model grok-4.3

classification ✦ hep-ph
keywords Higgs bosontau leptonFCC-eecross-section projectionZH productionvector boson fusiontau reconstruction
0
0 comments X

The pith

FCC-ee projections indicate at least an order of magnitude better precision on the H to tau tau cross-section than current LHC results.

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

This paper calculates the expected measurement precision for the Higgs boson decaying into a pair of tau leptons at the future FCC-ee collider. It examines the ZH production process at center-of-mass energies of 240 GeV and 365 GeV as well as the vector boson fusion process at 365 GeV. The analysis also evaluates multiple methods for reconstructing tau decays in the clean electron-positron collision environment. These projections matter because they would deliver far sharper constraints on the Higgs coupling to tau leptons and open access to polarization observables that remain limited at the LHC.

Core claim

Simulations of signal and background processes at FCC-ee show that the relative uncertainty on the H→ττ cross-section reaches the few-percent level in the ZH channel at both energies and in vector boson fusion at 365 GeV when optimized tau reconstruction techniques are applied, delivering at least a factor-of-ten improvement over present LHC sensitivity.

What carries the argument

Event simulations combined with tau decay reconstruction algorithms that exploit the low-background environment of e+e- collisions to separate signal from backgrounds in ZH and VBF production modes.

If this is right

  • The higher precision enables direct extraction of the Higgs-tau coupling strength with percent-level accuracy.
  • Tau polarization measurements become feasible, providing sensitivity to possible CP-violating effects in the Higgs sector.
  • Independent results from ZH and vector boson fusion channels allow cross-checks that reduce overall systematic uncertainty.
  • Improved tau identification methods strengthen both Standard Model tests and searches for new physics involving tau leptons.

Where Pith is reading between the lines

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

  • These projections could be combined with other Higgs decay channels at FCC-ee to produce tighter global constraints on deviations from the Standard Model.
  • The tau reconstruction techniques may transfer to future lepton colliders with similar detector designs.
  • If realized, the precision would make small beyond-Standard-Model effects in the third-generation lepton sector detectable for the first time.

Load-bearing premise

The projections depend on the FCC-ee detector and tau reconstruction algorithms achieving the assumed efficiencies and resolutions that have not yet been built or verified experimentally.

What would settle it

Actual data collected at FCC-ee showing that the combined statistical and systematic uncertainty on the measured H→ττ cross-section is several times larger than the projected values would falsify the central claim.

Figures

Figures reproduced from arXiv: 2601.11383 by Maria Cepeda, Markus Klute, Matteo Presilla, Sofia Giappichini, Xunwu Zuo.

Figure 1
Figure 1. Figure 1: On the left: Feynman diagram for ZH events in [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Confusion matrix of truth level tau decay modes against [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Comparison of different methods of reconstructing the [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: On the left: BDT score distribution for Z [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
read the original abstract

The Future Circular Collider (FCC) stands at the forefront of the European Strategy for Particle Physics as the future flagship project at CERN. The H$\to\tau\tau$ decay, featuring a large branching ratio, clean identification in the FCC-ee environment, and the possibility to reconstruct polarization information, is an excellent channel to measure Higgs boson properties. This work shows the expected precision for the H$\to\tau\tau$ cross-section measurement at the FCC-ee in the ZH production mechanism at $\sqrt{s}=$240 GeV and $\sqrt{s}=$365 GeV, as well as via the vector boson fusion process at $\sqrt{s}=$365 GeV. Furthermore, we explore and evaluate a set of methods for reconstructing tau decays. These techniques are critical for unlocking the full physics potential of the FCC-ee and for improving the understanding of tau-related observables in both Standard Model measurements and New Physics searches. The results obtained significantly enhance the FCC-ee outlook in the H$\to\tau\tau$ channel, improving it by at least an order of magnitude compared to the current sensitivity of measurements' performance at the LHC.

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 presents projections for the expected precision on the H→ττ cross-section measurement at the FCC-ee, focusing on ZH production at √s=240 GeV and 365 GeV as well as vector boson fusion at 365 GeV. It evaluates several tau decay reconstruction techniques and asserts that the resulting sensitivities represent at least an order-of-magnitude improvement relative to current LHC performance in this channel.

Significance. If the assumed detector performance and reconstruction efficiencies are realized, the work would materially strengthen the FCC-ee physics case for precision Higgs measurements, particularly by enabling better extraction of tau polarization and coupling information. The explicit exploration of multiple tau reconstruction approaches is a constructive contribution to future detector optimization studies.

major comments (2)
  1. [Results and projections sections] The central claim of an order-of-magnitude improvement rests on specific assumptions for tau identification efficiency, energy resolution, and background rejection in both ZH and VBF channels; these assumptions are not accompanied by a quantitative sensitivity study showing how the projected uncertainties scale under realistic variations or degradation of the assumed performance parameters.
  2. [Abstract and summary of results] No explicit comparison table or numerical values are provided for the projected relative uncertainties (e.g., δσ/σ) at each energy and production mode versus the corresponding LHC Run-2 or projected HL-LHC figures; without these numbers the improvement statement cannot be verified.
minor comments (2)
  1. [Abstract] The abstract would benefit from stating the numerical projected precisions rather than only the qualitative improvement factor.
  2. [Methods] Notation for the different tau decay modes and reconstruction algorithms should be defined consistently in the first section where they appear.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments and positive assessment of the potential impact of this work. We address each major comment below and will revise the manuscript to strengthen the presentation of the results.

read point-by-point responses

  1. Referee: [Results and projections sections] The central claim of an order-of-magnitude improvement rests on specific assumptions for tau identification efficiency, energy resolution, and background rejection in both ZH and VBF channels; these assumptions are not accompanied by a quantitative sensitivity study showing how the projected uncertainties scale under realistic variations or degradation of the assumed performance parameters.

    Authors: We agree that a dedicated sensitivity study would make the robustness of the projections clearer. In the revised manuscript we will add a new subsection that varies the assumed tau identification efficiency, energy resolution, and background rejection within conservative ranges (e.g., ±5–10 %) and shows the resulting change in the extracted cross-section uncertainties for the ZH and VBF channels. This will quantify how the order-of-magnitude improvement holds under realistic degradations of the input parameters. revision: yes

  2. Referee: [Abstract and summary of results] No explicit comparison table or numerical values are provided for the projected relative uncertainties (e.g., δσ/σ) at each energy and production mode versus the corresponding LHC Run-2 or projected HL-LHC figures; without these numbers the improvement statement cannot be verified.

    Authors: We acknowledge that an explicit numerical comparison is required for verification. We will insert a new table in the summary-of-results section that reports the projected relative uncertainties δσ/σ for the ZH channel at 240 GeV, the ZH channel at 365 GeV, and the VBF channel at 365 GeV, together with the corresponding LHC Run-2 measured values and HL-LHC projections. The table will allow direct verification of the stated improvement. revision: yes

Circularity Check

0 steps flagged

No circularity: forward projections rest on external assumptions

full rationale

The paper computes expected precisions for H→ττ cross sections at FCC-ee via ZH and VBF channels by applying assumed detector resolutions, efficiencies, and tau-reconstruction algorithms to simulated event samples. No equation or result is obtained by fitting a parameter to a subset of the paper's own data and then relabeling that fit as a prediction. No self-citation supplies a uniqueness theorem or ansatz that the present work then treats as an external fact. The central numerical projections are therefore independent of any internal reduction; they are simply the output of the stated simulation assumptions. This is the normal, non-circular structure of a collider-projection study.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no information is available on free parameters, axioms, or invented entities used in the full analysis.

pith-pipeline@v0.9.0 · 5499 in / 1197 out tokens · 45077 ms · 2026-05-16T13:19:17.900837+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 1 Pith paper

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

  1. Probing the electron Yukawa coupling via resonant Higgs boson production at FCC-ee via $e^+e^- \to H \to WW^*$ in lepton-plus-jets final states

    hep-ph 2026-04 unverdicted novelty 3.0

    Simulation projects 2.0 sigma significance for resonant Higgs production at FCC-ee, yielding an upper limit of kappa_e less than or equal to 1.35 at 95% CL on the electron Yukawa coupling modifier with 10 ab inverse l...

Reference graph

Works this paper leans on

33 extracted references · 33 canonical work pages · cited by 1 Pith paper · 10 internal anchors

  1. [1]

    G. Aad, et al., Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS anal- ysis of the LHC pp collision data at √s= 7and 8 TeV, JHEP 08 (2016) 045.arXiv:1606.02266, doi:10.1007/JHEP08(2016)045

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1007/jhep08(2016)045 2016

  2. [2]

    A. M. Sirunyan, et al., Observation of the Higgs bo- son decay to a pair ofτleptons with the CMS detec- tor, Phys. Lett. B 779 (2018) 283–316.arXiv:1708. 00373,doi:10.1016/j.physletb.2018.02.004

    work page doi:10.1016/j.physletb.2018.02.004 2018

  3. [3]

    Abidi et al., ECFA Higgs, electroweak, and top Factory Study , vol

    J. Altmann, et al., ECFA Higgs, electroweak, and top Factory Study, Vol. 5/2025 of CERN Yellow Re- ports: Monographs, 2025.arXiv:2506.15390,doi: 10.23731/CYRM-2025-005

    work page doi:10.23731/cyrm-2025-005 2025

  4. [4]

    Arduini, F

    G. Arduini, F. Bordry, R. Brinkmann, P. Burrows, K. Desch, S. Farrington, F. Gianotti, K. Hanagaki, N. Holtkamp, J. Keintzel, B. Kilminster, T. Lesiak, L. Rivkin, F. Sabatié, M. Tuts, A. Zoccoli, Assess- ment of large-scale accelerator projects at CERN - Report of ESG WG2a, Tech. rep., Geneva (2025). URLhttps://cds.cern.ch/record/2947728

    work page arXiv 2025

  5. [5]

    de Blas et al.,Physics Briefing Book: Input for the 2026 update of the European Strategy for Particle Physics, vol

    J. de Blas, et al., Physics Briefing Book: Input for the 2026 update of the European Strategy for Par- ticle Physics (11 2025).arXiv:2511.03883,doi: 10.17181/CERN.35CH.2O2P

    work page doi:10.17181/cern.35ch.2o2p 2026

  6. [6]

    FCC-ee: The lepton collider: Future Circular Collider Conceptual Design Report, V olume 2

    A. Abada, et al., FCC-ee: The Lepton Collider: Fu- ture Circular Collider Conceptual Design Report Vol- ume 2, Eur. Phys. J. ST 228 (2) (2019) 261–623. doi:10.1140/epjst/e2019-900045-4

    work page doi:10.1140/epjst/e2019-900045-4 2019

  7. [7]

    Future Circular Collider Feasibility Study Report: Volume 1, Physics, Experiments, Detectors

    M. Benedikt, et al., Future Circular Collider Feasibil- ity Study Report: Volume 1, Physics, Experiments, Detectors (4 2025).arXiv:2505.00272

    work page internal anchor Pith review arXiv 2025

  8. [8]

    Abada, et al., FCC Physics Opportunities: Future Circular Collider Conceptual Design Report Volume 1, Eur

    A. Abada, et al., FCC Physics Opportunities: Future Circular Collider Conceptual Design Report Volume 1, Eur. Phys. J. C 79 (6) (2019) 474.doi:10.1140/ epjc/s10052-019-6904-3

    work page 2019

  9. [9]

    Benedikt, et al., Future Circular Collider Feasi- bility Study Report: Volume 2, Accelerators, Techni- cal Infrastructure and Safety (4 2025).arXiv:2505

    M. Benedikt, et al., Future Circular Collider Feasi- bility Study Report: Volume 2, Accelerators, Techni- cal Infrastructure and Safety (4 2025).arXiv:2505. 00274,doi:10.1140/epjs/s11734-025-01967-4

    work page doi:10.1140/epjs/s11734-025-01967-4 2025

  10. [10]

    Prospects in electroweak, Higgs and Top physics at FCC (3 2025).doi:10.17181/n78xk-qcv56

    work page doi:10.17181/n78xk-qcv56 2025

  11. [11]

    A. Tumasyan, et al., A portrait of the Higgs boson by the CMS experiment ten years after the discov- ery., Nature 607 (7917) (2022) 60–68, [Erratum: Na- ture 623, (2023)].arXiv:2207.00043,doi:10.1038/ s41586-022-04892-x

    work page arXiv 2022

  12. [12]

    G. Aad, et al., A detailed map of Higgs boson in- teractions by the ATLAS experiment ten years after the discovery, Nature 607 (7917) (2022) 52–59, [Erra- tum: Nature 612, E24 (2022)].arXiv:2207.00092, doi:10.1038/s41586-022-04893-w

    work page doi:10.1038/s41586-022-04893-w 2022

  13. [13]

    Cepeda, et al., Report from Working Group 2: Higgs Physics at the HL-LHC and HE-LHC, CERN Yellow Rep

    M. Cepeda, et al., Report from Working Group 2: Higgs Physics at the HL-LHC and HE-LHC, CERN Yellow Rep. Monogr. 7 (2019) 221–584.arXiv:1902. 00134,doi:10.23731/CYRM-2019-007.221

    work page doi:10.23731/cyrm-2019-007.221 2019

  14. [14]

    Projection ofH→τ τcross-section measurement re- sults to the HL-LHC, Tech. rep. (2022)

    work page 2022

  15. [15]

    LHC HXSWG interim recommendations to explore the coupling structure of a Higgs-like particle

    A. David, A. Denner, M. Duehrssen, M. Grazzini, C. Grojean, G. Passarino, M. Schumacher, M. Spira, G. Weiglein, M. Zanetti, LHC HXSWG interim rec- ommendations to explore the coupling structure of a Higgs-like particle (9 2012).arXiv:1209.0040

    work page internal anchor Pith review Pith/arXiv arXiv 2012

  16. [16]

    J. R. Andersen, et al., Handbook of LHC Higgs Cross Sections: 3. Higgs Properties (7 2013).arXiv:1307. 1347,doi:10.5170/CERN-2013-004. 5

    work page doi:10.5170/cern-2013-004 2013

  17. [17]

    Aad, et al., Highlights of the HL-LHC physics projections by ATLAS and CMS (4 2025).arXiv: 2504.00672

    G. Aad, et al., Highlights of the HL-LHC physics projections by ATLAS and CMS (4 2025).arXiv: 2504.00672

    work page arXiv 2025

  18. [18]

    Adachi, et al., Measurement of theτ-lepton mass with the Belle II experiment, Phys

    I. Adachi, et al., Measurement of theτ-lepton mass with the Belle II experiment, Phys. Rev. D 108 (3) (2023) 032006.arXiv:2305.19116,doi:10.1103/ PhysRevD.108.032006

    work page arXiv 2023

  19. [19]

    Lusiani, Tau physics prospects at fcc-ee

    A. Lusiani, Tau physics prospects at fcc-ee. (2024). doi:https://doi.org/10.17181/57pxj-6xd43

    work page doi:10.17181/57pxj-6xd43 2024

  20. [20]

    Wilkinson, S

    G. Wilkinson, S. Monteil, J. F. Kamenik, A. Lusiani, Prospects in flavour physics at the fcc (Mar. 2025). doi:10.17181/jnzpp-1fw39. URLhttps://doi.org/10.17181/jnzpp-1fw39

    work page doi:10.17181/jnzpp-1fw39 2025

  21. [21]

    WHIZARD: Simulating Multi-Particle Processes at LHC and ILC

    W. Kilian, T. Ohl, J. Reuter, WHIZARD: Simulat- ing Multi-Particle Processes at LHC and ILC, Eur. Phys. J. C 71 (2011) 1742.arXiv:0708.4233,doi: 10.1140/epjc/s10052-011-1742-y

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1140/epjc/s10052-011-1742-y 2011

  22. [22]

    O'Mega: An Optimizing Matrix Element Generator

    M. Moretti, T. Ohl, J. Reuter, O’Mega: An Op- timizing matrix element generator (2001) 1981– 2009arXiv:hep-ph/0102195

    work page internal anchor Pith review Pith/arXiv arXiv 2001

  23. [23]

    PYTHIA 6.4 Physics and Manual

    T. Sjostrand, S. Mrenna, P. Z. Skands, PYTHIA 6.4 Physics and Manual, JHEP 05 (2006) 026. arXiv:hep-ph/0603175,doi:10.1088/1126-6708/ 2006/05/026

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1088/1126-6708/ 2006

  24. [24]

    A comprehensive guide to the physics and usage of PYTHIA 8.3

    C. Bierlich, et al., A comprehensive guide to the physics and usage of PYTHIA 8.3, SciPost Phys. Codeb. 2022 (2022) 8.arXiv:2203.11601,doi: 10.21468/SciPostPhysCodeb.8

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.21468/scipostphyscodeb.8 2022

  25. [25]

    Abbrescia, et al., (2025)

    M. Abbrescia, et al., The IDEA detector concept for FCC-ee (2 2025).arXiv:2502.21223

    work page arXiv 2025

  26. [26]

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

    J. de Favereau, C. Delaere, P. Demin, A. Giammanco, V. Lemaître, A. Mertens, M. Selvaggi, DELPHES 3, A modular framework for fast simulation of a generic collider experiment, JHEP 02 (2014) 057.arXiv: 1307.6346,doi:10.1007/JHEP02(2014)057

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1007/jhep02(2014)057 2014

  27. [27]

    FASTJETuser manual

    M. Cacciari, G. P. Salam, G. Soyez, FastJet User Manual, Eur.Phys.J.C72(2012)1896.arXiv:1111. 6097,doi:10.1140/epjc/s10052-012-1896-2

    work page doi:10.1140/epjc/s10052-012-1896-2 2012

  28. [28]

    H. Qu, L. Gouskos, ParticleNet: Jet Tag- ging via Particle Clouds, Phys. Rev. D 101 (5) (2020) 056019.arXiv:1902.08570,doi:10.1103/ PhysRevD.101.056019

    work page arXiv 2020

  29. [29]

    Bedeschi, L

    F. Bedeschi, L. Gouskos, M. Selvaggi, Jet flavour tagging for future colliders with fast simulation, The European Physical Journal C 82 (7) (Jul. 2022). doi:10.1140/epjc/s10052-022-10609-1. URLhttp://dx.doi.org/10.1140/epjc/ s10052-022-10609-1

    work page doi:10.1140/epjc/s10052-022-10609-1 2022

  30. [30]

    Tau lepton reconstruction at collider experiments using impact parameters

    D. Jeans, Tau lepton reconstruction at collider ex- periments using impact parameters, Nucl. Instrum. Meth. A 810 (2016) 51–58.arXiv:1507.01700,doi: 10.1016/j.nima.2015.11.030

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1016/j.nima.2015.11.030 2016

  31. [31]

    Measurement of the $\tau$-lepton lifetime at Belle

    K. Belous, et al., Measurement of theτ-lepton life- time at Belle, Phys. Rev. Lett. 112 (3) (2014) 031801. arXiv:1310.8503,doi:10.1103/PhysRevLett.112. 031801

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1103/physrevlett.112 2014

  32. [32]

    Konar, A

    P. Konar, A. K. Swain, Reconstructing semi- invisible events in resonant tau pair production from higgs, Physics Letters B 757 (2016) 211–215. doi:10.1016/j.physletb.2016.03.070. URLhttps://www.sciencedirect.com/science/ article/pii/S0370269316300417

    work page doi:10.1016/j.physletb.2016.03.070 2016

  33. [33]

    Hayrapetyan et al., The CMS Statistical Analysis and Combination Tool: Combine, Comput

    A. Hayrapetyan, et al., The CMS Statistical Anal- ysis and Combination Tool: COMBINE, Submitted to Computing and Software for Big Science (4 2024). arXiv:2404.06614. 6

    work page arXiv 2024