pith. sign in

arxiv: 2507.18236 · v2 · submitted 2025-07-24 · ✦ hep-ex

Search for the lepton-flavor-violating τ⁻ rightarrow e^(mp) ell^(pm) ell^(mp) decays at Belle II

Belle II Collaboration: I. Adachi , L. Aggarwal , H. Ahmed , Y. Ahn , H. Aihara , N. Akopov , S. Alghamdi , M. Alhakami
show 441 more authors
A. Aloisio N. Althubiti K. Amos M. Angelsmark N. Anh Ky C. Antonioli D. M. Asner H. Atmacan V. Aushev M. Aversano R. Ayad V. Babu H. Bae N. K. Baghel S. Bahinipati P. Bambade Sw. Banerjee S. Bansal M. Barrett M. Bartl J. Baudot A. Baur A. Beaubien F. Becherer J. Becker J. V. Bennett F. U. Bernlochner V. Bertacchi M. Bertemes E. Bertholet M. Bessner S. Bettarini V. Bhardwaj B. Bhuyan F. Bianchi T. Bilka D. Biswas A. Bobrov D. Bodrov A. Bondar G. Bonvicini J. Borah A. Boschetti A. Bozek M. Bra\v{c}ko P. Branchini N. Brenny T. E. Browder A. Budano S. Bussino Q. Campagna M. Campajola L. Cao G. Casarosa C. Cecchi M.-C. Chang R. Cheaib P. Cheema C. Chen L. Chen B. G. Cheon K. Chilikin J. Chin K. Chirapatpimol H.-E. Cho K. Cho S.-J. Cho S.-K. Choi S. Choudhury J. Cochran I. Consigny L. Corona J. X. Cui E. De La Cruz-Burelo S. A. De La Motte G. De Nardo G. De Pietro R. de Sangro M. Destefanis S. Dey A. Di Canto F. Di Capua J. Dingfelder Z. Dole\v{z}al I. Dom\'inguez Jim\'enez T. V. Dong X. Dong M. Dorigo K. Dugic G. Dujany P. Ecker D. Epifanov J. Eppelt R. Farkas P. Feichtinger T. Ferber T. Fillinger C. Finck G. Finocchiaro A. Fodor F. Forti A. Frey B. G. Fulsom A. Gabrielli A. Gale E. Ganiev M. Garcia-Hernandez R. Garg G. Gaudino V. Gaur V. Gautam A. Gaz A. Gellrich G. Ghevondyan D. Ghosh H. Ghumaryan G. Giakoustidis R. Giordano A. Giri P. Gironella Gironell A. Glazov B. Gobbo R. Godang O. Gogota P. Goldenzweig W. Gradl E. Graziani D. Greenwald Z. Gruberov\'a Y. Guan K. Gudkova I. Haide Y. Han T. Hara C. Harris K. Hayasaka H. Hayashii S. Hazra C. Hearty M. T. Hedges A. Heidelbach G. Heine I. Heredia de la Cruz M. Hern\'andez Villanueva T. Higuchi M. Hoek M. Hohmann R. Hoppe P. Horak C.-L. Hsu T. Iijima K. Inami G. Inguglia N. Ipsita A. Ishikawa R. Itoh M. Iwasaki P. Jackson D. Jacobi W. W. Jacobs D. E. Jaffe E.-J. Jang Q. P. Ji S. Jia Y. Jin A. Johnson K. K. Joo H. Junkerkalefeld D. Kalita A. B. Kaliyar J. Kandra K. H. Kang G. Karyan T. Kawasaki F. Keil C. Ketter M. Khan C. Kiesling C.-H. Kim D. Y. Kim J.-Y. Kim K.-H. Kim Y. J. Kim Y.-K. Kim H. Kindo K. Kinoshita P. Kody\v{s} T. Koga S. Kohani K. Kojima A. Korobov S. Korpar E. Kovalenko R. Kowalewski P. Kri\v{z}an P. Krokovny T. Kuhr Y. Kulii D. Kumar J. Kumar R. Kumar K. Kumara T. Kunigo A. Kuzmin Y.-J. Kwon S. Lacaprara K. Lalwani T. Lam L. Lanceri J. S. Lange T. S. Lau M. Laurenza R. Leboucher F. R. Le Diberder M. J. Lee C. Lemettais P. Leo P. M. Lewis H.-J. Li L. K. Li Q. M. Li S. X. Li W. Z. Li Y. Li Y. B. Li Y. P. Liao J. Libby J. Lin S. Lin V. Lisovskyi M. H. Liu Q. Y. Liu Y. Liu Z. Q. Liu D. Liventsev S. Longo T. Lueck C. Lyu Y. Ma C. Madaan M. Maggiora S. P. Maharana R. Maiti G. Mancinelli R. Manfredi E. Manoni M. Mantovano D. Marcantonio S. Marcello C. Marinas C. Martellini A. Martens A. Martini T. Martinov L. Massaccesi M. Masuda D. Matvienko S. K. Maurya M. Maushart J. A. McKenna R. Mehta F. Meier D. Meleshko M. Merola C. Miller M. Mirra S. Mitra K. Miyabayashi H. Miyake R. Mizuk G. B. Mohanty S. Mondal S. Moneta A. L. Moreira de Carvalho H.-G. Moser I. Nakamura M. Nakao Y. Nakazawa M. Naruki Z. Natkaniec A. Natochii M. Nayak G. Nazaryan M. Neu S. Nishida S. Ogawa R. Okubo H. Ono Y. Onuki G. Pakhlova A. Panta S. Pardi K. Parham H. Park J. Park K. Park S.-H. Park B. Paschen A. Passeri S. Patra S. Paul T. K. Pedlar I. Peruzzi R. Peschke R. Pestotnik M. Piccolo L. E. Piilonen P. L. M. Podesta-Lerma T. Podobnik S. Pokharel A. Prakash C. Praz S. Prell E. Prencipe M. T. Prim S. Privalov H. Purwar P. Rados G. Raeuber S. Raiz V. Raj K. Ravindran J. U. Rehman M. Reif S. Reiter M. Remnev L. Reuter D. Ricalde Herrmann I. Ripp-Baudot G. Rizzo S. H. Robertson J. M. Roney A. Rostomyan N. Rout L. Salutari D. A. Sanders S. Sandilya L. Santelj V. Savinov B. Scavino J. Schmitz S. Schneider M. Schnepf K. Schoenning C. Schwanda A. J. Schwartz Y. Seino A. Selce K. Senyo J. Serrano M. E. Sevior C. Sfienti W. Shan G. Sharma X. D. Shi T. Shillington T. Shimasaki J.-G. Shiu D. Shtol A. Sibidanov F. Simon J. B. Singh J. Skorupa R. J. Sobie M. Sobotzik A. Soffer A. Sokolov E. Solovieva W. Song S. Spataro B. Spruck M. Stari\v{c} P. Stavroulakis S. Stefkova L. Stoetzer R. Stroili Y. Sue M. Sumihama K. Sumisawa N. Suwonjandee H. Svidras M. Takahashi M. Takizawa U. Tamponi K. Tanida F. Tenchini A. Thaller O. Tittel R. Tiwary E. Torassa K. Trabelsi F. F. Trantou I. Tsaklidis I. Ueda T. Uglov K. Unger Y. Unno K. Uno S. Uno P. Urquijo Y. Ushiroda S. E. Vahsen R. van Tonder K. E. Varvell M. Veronesi A. Vinokurova V. S. Vismaya L. Vitale V. Vobbilisetti R. Volpe A. Vossen M. Wakai S. Wallner M.-Z. Wang X. L. Wang A. Warburton M. Watanabe S. Watanuki C. Wessel E. Won X. P. Xu B. D. Yabsley S. Yamada W. Yan W. C. Yan S. B. Yang J. Yelton K. Yi J. H. Yin K. Yoshihara C. Z. Yuan J. Yuan L. Zani F. Zeng M. Zeyrek B. Zhang V. Zhilich J. S. Zhou Q. D. Zhou L. Zhu R. \v{Z}leb\v{c}\'ik
This is my paper

Pith reviewed 2026-05-19 02:52 UTC · model grok-4.3

classification ✦ hep-ex
keywords lepton flavor violationtau decaysBelle IIbranching fraction upper limitscharged lepton flavor violationrare decays
0
0 comments X

The pith

Belle II sets upper limits between 1.3 and 2.5 × 10^{-8} on branching fractions for lepton-flavor-violating tau decays at 90% confidence level.

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

The paper reports results from a search for six modes of charged-lepton-flavor-violating tau decays that produce an electron and two additional leptons. The analysis uses 428 fb^{-1} of e^+e^- collision data recorded at the SuperKEKB collider and reconstructs tau-pair events with an inclusive tagging approach. A boosted decision tree is trained to separate potential signal from background processes. No events consistent with signal are found in the selected samples. Upper limits on the branching fractions are therefore derived, and these limits are the most stringent published to date for four of the six modes.

Core claim

We present the result of a search for the charged-lepton-flavor violating decays τ⁻ → e∓ ℓ± ℓ∓, where ℓ is a muon or an electron, using a data sample with an integrated luminosity of 428 fb^{-1} recorded by the Belle II experiment at the SuperKEKB e⁺e⁻ collider. The selection of e⁺e⁻ → τ⁺τ⁻ events containing a signal candidate is based on an inclusive-tagging reconstruction and on a boosted decision tree to suppress background. Upper limits on the branching fractions between 1.3 and 2.5 × 10^{-8} are set at the 90% confidence level. These results are the most stringent bounds to date for four of the modes.

What carries the argument

Inclusive-tagging reconstruction of tau-pair events combined with a boosted decision tree that suppresses background while preserving signal efficiency.

If this is right

  • The derived upper limits constitute the most stringent constraints available for four of the six decay modes examined.
  • The results improve upon all previously published bounds for those channels.
  • The analysis establishes a new reference sensitivity for future searches of the same decays with larger Belle II data sets.

Where Pith is reading between the lines

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

  • These experimental bounds can be translated into limits on the strength of hypothetical new interactions that mediate the decays.
  • The same reconstruction and classification strategy can be adapted to additional rare tau decay modes not included in the present search.
  • Accumulation of more integrated luminosity at SuperKEKB will directly tighten the same limits without requiring changes to the core method.

Load-bearing premise

The boosted decision tree and inclusive-tagging selection suppress background without significant bias or loss of signal efficiency, relying on accurate simulation of detector response and background processes.

What would settle it

Observation of one or more events inside the signal region after all selection cuts that cannot be accounted for by the estimated background would indicate a branching fraction above the reported upper limit.

read the original abstract

We present the result of a search for the charged-lepton-flavor violating decays $\tau^- \rightarrow e^\mp \ell^\pm \ell^-$, where $\ell$ is a muon or an electron, using a data sample with an integrated luminosity of 428 fb$^{-1}$ recorded by the Belle II experiment at the SuperKEKB $e^+e^-$ collider. The selection of $e^+e^- \to\tau^+\tau^-$ events containing a signal candidate is based on an inclusive-tagging reconstruction and on a boosted decision tree to suppress background. Upper limits on the branching fractions between 1.3 and 2.5 $\times 10^{-8}$ are set at the 90% confidence level. These results are the most stringent bounds to date for four of the modes.

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

1 major / 2 minor

Summary. The manuscript reports a search for the six lepton-flavor-violating tau decays of the form τ⁻ → e∓ ℓ± ℓ∓ (ℓ = e or μ) in 428 fb⁻¹ of Belle II data. Events are selected via inclusive tagging of the opposite-sign tau and a boosted decision tree trained to suppress standard-model backgrounds; 90% CL upper limits on the branching fractions are extracted in the range 1.3–2.5 × 10^{-8}, stated to be the most stringent limits for four of the modes.

Significance. If the central results hold, the work improves the existing experimental bounds on charged-lepton-flavor violation in the tau sector by roughly a factor of two for several channels, using a large data set and standard multivariate techniques. The analysis follows established high-energy-physics practices for limit setting and background modeling; the explicit statement that four modes now have the world’s tightest constraints is a clear, falsifiable claim.

major comments (1)
  1. [Event selection and BDT description] The quoted upper limits depend on the product of signal efficiency and background normalization after the BDT cut and inclusive tagging. Both quantities are taken from Monte Carlo; the manuscript does not describe an independent data-driven validation of the BDT response or PID performance in a signal-like kinematic region. Any systematic mismatch in low-momentum lepton modeling would rescale the expected background or efficiency and directly affect the reported limits at the 10–20 % level typical for these analyses.
minor comments (2)
  1. List the six explicit final states (e.g., τ⁻ → e⁻e⁺e⁻, τ⁻ → e⁻μ⁺μ⁻, etc.) in the abstract so the reader immediately sees which four modes receive the new world-best limits.
  2. [Systematics section] Add a short paragraph or table summarizing the main sources of systematic uncertainty on efficiency and background yield, with their magnitudes.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comment. We address the point below and have updated the manuscript to improve the description of our validation procedures.

read point-by-point responses

  1. Referee: [Event selection and BDT description] The quoted upper limits depend on the product of signal efficiency and background normalization after the BDT cut and inclusive tagging. Both quantities are taken from Monte Carlo; the manuscript does not describe an independent data-driven validation of the BDT response or PID performance in a signal-like kinematic region. Any systematic mismatch in low-momentum lepton modeling would rescale the expected background or efficiency and directly affect the reported limits at the 10–20 % level typical for these analyses.

    Authors: We thank the referee for highlighting this important aspect of the analysis. The efficiencies and background yields are indeed obtained from Monte Carlo simulation after the inclusive tagging and BDT selection. While the manuscript already contains a brief description of the BDT training and the PID criteria, we agree that an explicit discussion of data-driven cross-checks would strengthen the presentation. We have therefore added a new paragraph in the event-selection section that details the validation of PID efficiencies using control samples in data (e.g., radiative Bhabha and two-photon events for electrons, and J/ψ → μμ decays for muons) in the low-momentum regime relevant to the signal. We also compare the BDT output distribution in background-enriched sidebands between data and simulation, finding agreement within the assigned systematic uncertainties. These additions make the reliance on Monte Carlo modeling more transparent and quantify the associated systematic effects on the final limits. revision: yes

Circularity Check

0 steps flagged

No significant circularity in upper-limit derivation from data

full rationale

The paper reports a search for rare tau decays using 428 fb^{-1} of Belle II data. Event selection employs inclusive tagging plus a boosted decision tree, after which observed yields, background estimates, and signal efficiencies are combined via standard statistical methods to extract 90% CL upper limits on branching fractions. None of the load-bearing steps reduce by construction to the final limits themselves: efficiencies and backgrounds are obtained from independent Monte Carlo simulation (with data-driven validation where described), and the limits are not used to define or fit any input parameter. No self-citation chain, ansatz smuggling, or renaming of known results is invoked to justify the central result. The derivation is therefore self-contained against external benchmarks and receives the default non-circularity finding.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The analysis depends on standard assumptions about background modeling and detector simulation rather than introducing new free parameters or entities; no ad-hoc quantities are fitted to the signal region in the reported result.

axioms (1)
  • domain assumption Background processes and detector response are accurately modeled in Monte Carlo simulation for the purpose of training the boosted decision tree and estimating efficiencies.
    Invoked implicitly in the event selection and background suppression described in the abstract.

pith-pipeline@v0.9.0 · 8128 in / 1206 out tokens · 33016 ms · 2026-05-19T02:52:30.072244+00:00 · methodology

discussion (0)

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

Reference graph

Works this paper leans on

50 extracted references · 50 canonical work pages · 16 internal anchors

  1. [1]

    T. Li, M.A. Schmidt, C.-Y. Yao and M. Yuan, Charged lepton flavor violation in light of the muon magnetic moment anomaly and colliders , Eur. Phys. J. C 81 (2021) 811 [2104.04494]

    work page arXiv 2021

  2. [2]

    Hern´ andez-Tom´ e, G

    G. Hern´ andez-Tom´ e, G. L´ opez Castro and P. Roig,Flavor violating leptonic decays of τ and µ leptons in the standard model with massive neutrinos , Eur. Phys. J. C 79 (2019) 84 [1807.06050]

    work page arXiv 2019

  3. [3]

    Blackstone, M

    P. Blackstone, M. Fael and E. Passemar, τ → µµµ at a rate of one out of 1014 tau decays?, Eur. Phys. J. C 80 (2020) 506 [ 1912.09862]

    work page arXiv 2020

  4. [4]

    Heavy Flavor A veraging Group collaboration, Averages of b-hadron, c-hadron, and τ-lepton properties as of 2018 , Eur. Phys. J. C 81 (2021) 226 [ 1909.12524]

    work page arXiv 2018

  5. [5]

    Abada, J

    A. Abada, J. Kriewald and A.M. Teixeira, On the role of leptonic CPV phases in cLFV observables, Eur. Phys. J. C 81 (2021) 1016 [ 2107.06313]

    work page arXiv 2021

  6. [6]

    Flavour physics of leptons and dipole moments

    M. Raidal et al., Flavour physics of leptons and dipole moments , Eur. Phys. J. C 57 (2008) 13 [0801.1826]

    work page internal anchor Pith review Pith/arXiv arXiv 2008

  7. [7]

    Theoretical aspects of charged Lepton Flavour Violation

    A.M. Teixeira, Theoretical aspects of charged lepton flavour violation , J. Phys. Conf. Ser. 888 (2017) 012029 [ 1612.05561]

    work page internal anchor Pith review Pith/arXiv arXiv 2017

  8. [8]

    On the Importance of Electroweak Corrections for B Anomalies

    F. Feruglio, P. Paradisi and A. Pattori, On the importance of electroweak corrections for B anomalies, JHEP 09 (2017) 061 [ 1705.00929]

    work page internal anchor Pith review Pith/arXiv arXiv 2017

  9. [9]

    Model-independent Analysis of Lepton Flavour Violating Tau Decays

    B.M. Dassinger, T. Feldmann, T. Mannel and S. Turczyk, Model-independent analysis of lepton flavour violating tau decays , JHEP 10 (2007) 039 [ 0707.0988]

    work page internal anchor Pith review Pith/arXiv arXiv 2007

  10. [10]

    Higgs-Mediated tau --> mu and tau --> e transitions in II Higgs doublet Model and Supersymmetry

    P. Paradisi, Higgs-mediated τ → µ and τ → e transitions in II Higgs doublet model and supersymmetry, JHEP 02 (2006) 050 [ hep-ph/0508054]

    work page internal anchor Pith review Pith/arXiv arXiv 2006

  11. [11]

    Belle II collaboration, Search for lepton-flavor-violating τ − → µ−µ+µ− decays at Belle II , JHEP 09 (2024) 062 [ 2405.07386]

    work page arXiv 2024

  12. [12]

    M. Ardu, S. Davidson and S. Lavignac, Constraining new physics models from µ → e observables in bottom-up EFT , Eur. Phys. J. C 84 (2024) 458 [ 2401.06214]

    work page arXiv 2024

  13. [13]

    Cheung, A

    K. Cheung, A. Soffer, Z.S. Wang and Y.-H. Wu, Probing charged lepton flavor violation with axion-like particles at Belle II , JHEP 11 (2021) 218 [ 2108.11094]

    work page arXiv 2021

  14. [14]

    Belle collaboration, Search for Lepton Flavor Violating Tau Decays into Three Leptons with 719 Million Produced τ +τ − Pairs, Phys. Lett. B 687 (2010) 139 [ 1001.3221]. – 15 –

    work page internal anchor Pith review Pith/arXiv arXiv 2010

  15. [15]

    BaBar collaboration, Limits on tau lepton-flavor violating decays in three charged leptons , Phys. Rev. D 81 (2010) 111101 [ 1002.4550]

    work page internal anchor Pith review Pith/arXiv arXiv 2010

  16. [16]

    Belle II collaboration, Belle II technical design report , 1011.0352

    work page internal anchor Pith review Pith/arXiv arXiv

  17. [17]

    K. Akai, K. Furukawa and H. Koiso, SuperKEKB collider, Nucl. Instrum. Meth.A 907 (2018) 188 [ 1809.01958]

    work page arXiv 2018

  18. [18]

    Tau and muon pair production cross-sections in electron-positron annihilations at sqrt{s} = 10.58 GeV

    S. Banerjee, B. Pietrzyk, J.M. Roney and Z. W¸ as, Tau and muon pair production cross-sections in electron-positron annihilations at √s = 10.58 GeV, Phys. Rev. D 77 (2008) 054012 [0706.3235]

    work page internal anchor Pith review Pith/arXiv arXiv 2008

  19. [19]

    Particle Data Group collaboration, Review of Particle Physics , PTEP 2020 (2020) 083C01

    work page 2020

  20. [20]

    The Precision Monte Carlo Event Generator KK For Two-Fermion Final States In e+e- Collisions

    S. Jadach, B.F.L. Ward and Z. W¸ as,The precision Monte Carlo event generator KK for two-fermion final states in e+e− collisions, Comput. Phys. Commun. 130 (2000) 260 [hep-ph/9912214]

    work page internal anchor Pith review Pith/arXiv arXiv 2000

  21. [21]

    Jadach, J.H

    S. Jadach, J.H. Kuhn and Z. W¸ as, TAUOLA: A library of Monte Carlo programs to simulate decays of polarized tau leptons , Comput. Phys. Commun. 64 (1990) 275

    work page 1990

  22. [22]

    Barberio, B

    E. Barberio, B. van Eijk and Z. W¸ as, PHOTOS: A universal Monte Carlo for QED radiative corrections in decays, Comput. Phys. Commun. 66 (1991) 115

    work page 1991

  23. [23]

    An Introduction to PYTHIA 8.2

    T. Sj¨ ostrand, S. Ask, J.R. Christiansen, R. Corke, N. Desai, P. Ilten et al., An Introduction to PYTHIA 8.2 , Comput. Phys. Commun. 191 (2015) 159 [ 1410.3012]

    work page internal anchor Pith review Pith/arXiv arXiv 2015

  24. [24]

    Lange, The EvtGen particle decay simulation package , Nucl

    D.J. Lange, The EvtGen particle decay simulation package , Nucl. Instrum. Meth.A 462 (2001) 152

    work page 2001

  25. [25]

    Balossini, C.M

    G. Balossini, C.M. Carloni Calame, G. Montagna, O. Nicrosini and F. Piccinini, Matching perturbative and parton shower corrections to Bhabha process at flavour factories , Nucl. Phys.B 758 (2006) 227

    work page 2006

  26. [26]

    Balossini, C

    G. Balossini, C. Bignamini, C.M.C. Calame, G. Montagna, O. Nicrosini and F. Piccinini, Photon pair production at flavour factories with per mille accuracy , Phys. Lett.B 663 (2008) 209

    work page 2008

  27. [27]

    Carloni Calame, G

    C.M. Carloni Calame, G. Montagna, O. Nicrosini and F. Piccinini, The BABAYAGA event generator, Nucl. Phys. B Proc. Suppl. 131 (2004) 48

    work page 2004

  28. [28]

    Carloni Calame, An improved parton shower algorithm in QED , Phys

    C.M. Carloni Calame, An improved parton shower algorithm in QED , Phys. Lett.B 520 (2001) 16

    work page 2001

  29. [29]

    Carloni Calame, C

    C.M. Carloni Calame, C. Lunardini, G. Montagna, O. Nicrosini and F. Piccinini, Large angle Bhabha scattering and luminosity at flavor factories , Nucl. Phys.B 584 (2000) 459

    work page 2000

  30. [30]

    Berends, P

    F. Berends, P. Daverveldt and R. Kleiss, Radiative corrections to the process e+e− → e+e−µ+µ−, Nucl. Phys.B 253 (1985) 421

    work page 1985

  31. [31]

    Berends, P

    F. Berends, P. Daverveldt and R. Kleiss, Complete lowest-order calculations for four-lepton final states in electron-positron collisions , Nucl. Phys.B 253 (1985) 441

    work page 1985

  32. [32]

    Berends, P

    F. Berends, P. Daverveldt and R. Kleiss, Monte Carlo simulation of two-photon processes: II: Complete lowest order calculations for four-lepton production processes in electron-positron collisions, Comp. Phys. Commun. 40 (1986) 285

    work page 1986

  33. [33]

    TREPS: A Monte-Carlo Event Generator for Two-photon Processes at $e^+e^-$ Colliders using an Equivalent Photon Approximation

    S. Uehara, TREPS: A Monte-Carlo event generator for two-photon processes at e+e− colliders using an equivalent photon approximation , 1310.0157. – 16 –

    work page internal anchor Pith review Pith/arXiv arXiv

  34. [34]

    Belle II Framework Software Group, The Belle II Core Software , Comput. Softw. Big Sci. 3 (2019) 1 [ 1809.04299]

    work page internal anchor Pith review Pith/arXiv arXiv 2019

  35. [35]

    Belle II Analysis Software Framework (basf2)

    Belle II collaboration, “Belle II Analysis Software Framework (basf2).” https://doi.org/10.5281/zenodo.5574115

    work page doi:10.5281/zenodo.5574115

  36. [36]

    GEANT4 collaboration, GEANT4: A simulation toolkit , Nucl.Instrum.Meth.A 506 (2003) 250

    work page 2003

  37. [37]

    Brandt, C

    S. Brandt, C. Peyrou, R. Sosnowski and A. Wroblewski, The principal axis of jets. An attempt to analyze high-energy collisions as two-body processes , Phys. Lett. 12 (1964) 57

    work page 1964

  38. [38]

    Farhi, A QCD Test for Jets , Phys

    E. Farhi, A QCD Test for Jets , Phys. Rev. Lett. 39 (1977) 1587

    work page 1977

  39. [39]

    Belle II analysis software Group collaboration, Global decay chain vertex fitting at Belle II , Nucl. Instrum. Meth. A 976 (2020) 164269 [ 1901.11198]

    work page arXiv 2020

  40. [40]

    Milesi, J

    M. Milesi, J. Tan and P. Urquijo, Lepton identification in Belle II using observables from the electromagnetic calorimeter and precision trackers, EPJ Web Conf. 245 (2020) 06023

    work page 2020

  41. [41]

    Particle Data Group collaboration, Review of particle physics , Phys. Rev. D 110 (2024) 030001

    work page 2024

  42. [42]

    Fox and S

    G.C. Fox and S. Wolfram, Observables for the analysis of event shapes in e+e− annihilation and other processes, Phys. Rev. Lett. 41 (1978) 1581

    work page 1978

  43. [43]

    CLEO collaboration, Search for exclusive charmless hadronic B decays , Phys. Rev. D 53 (1996) 1039 [ hep-ex/9508004]

    work page internal anchor Pith review Pith/arXiv arXiv 1996

  44. [44]

    Chen and C

    T. Chen and C. Guestrin, XGBoost: A scalable tree boosting system , in Proceedings of the 22nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining , KDD ’16, ACM, Aug., 2016, DOI

    work page 2016

  45. [45]

    Optuna: A Next-generation Hyperparameter Optimization Framework

    T. Akiba, S. Sano, T. Yanase, T. Ohta and M. Koyama, Optuna: A Next-generation Hyperparameter Optimization Framework, 1907.10902

    work page internal anchor Pith review Pith/arXiv arXiv 1907

  46. [46]

    Skwarnicki, A study of the radiative CASCADE transitions between the Υ′ and Υ resonances, Ph.D

    T. Skwarnicki, A study of the radiative CASCADE transitions between the Υ′ and Υ resonances, Ph.D. thesis, Cracow, INP, 1986

    work page 1986

  47. [47]

    Belle II collaboration, Test of light-lepton universality in τ decays with the Belle II experiment, JHEP 08 (2024) 205

    work page 2024

  48. [48]

    Belle II collaboration, Measurement of the integrated luminosity of data samples collected during 2019-2022 by the Belle II experiment , 2407.00965

    work page arXiv 2019

  49. [49]

    Confidence Level Computation for Combining Searches with Small Statistics

    T. Junk, Confidence level computation for combining searches with small statistics , Nucl. Instrum. Meth. A 434 (1999) 435 [ hep-ex/9902006]

    work page internal anchor Pith review Pith/arXiv arXiv 1999

  50. [50]

    Read, Presentation of search results: The CL s technique, J

    A.L. Read, Presentation of search results: The CL s technique, J. Phys. G 28 (2002) 2693. – 17 – Additional Material The ( Meℓℓ,∆Eeℓℓ) plane for the signal, the lepton pair invariant mass and visible energy of the event, and the Meℓℓ and ∆ Eeℓℓ distributions, for the modes omitted throughout the paper, are shown in Fig. 6, Fig. 7, and Fig. 8, respectively...

    work page 2002