New physics models facing lepton flavor violating Higgs decays at the percent level

  • Ilja Doršner
  • Svjetlana Fajfer
  • Admir Greljo
  • Jernej F. KamenikEmail author
  • Nejc Košnik
  • Ivan Nišandžić
Open Access
Regular Article - Theoretical Physics


We speculate about the possible interpretations of the recently observed excess in the hτμ decay. We derive a robust lower bound on the Higgs boson coupling strength to a tau and a muon, even in presence of the most general new physics affecting other Higgs properties. Then we reevaluate complementary indirect constraints coming from low energy observables as well as from theoretical considerations. In particular, the tentative signal should lead to τμγ at rates which could be observed at Belle II. In turn we show that, barring fine-tuned cancellations, the effect can only be accommodated within models with an extended scalar sector. These general conclusions are demonstrated using a number of explicit new physics models. Finally we show how, given the hτμ signal, the current and future searches for μ and μe nuclear conversions unambiguously constrain the allowed rates for hτe.


Higgs Physics Rare Decays Beyond Standard Model 


Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


  1. [1]
    ATLAS collaboration, Observation of a new particle in the search for the standard model Higgs boson with the ATLAS detector at the LHC, Phys. Lett. B 716 (2012) 1 [arXiv:1207.7214] [INSPIRE].
  2. [2]
    CMS collaboration, Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC, Phys. Lett. B 716 (2012) 30 [arXiv:1207.7235] [INSPIRE].
  3. [3]
    CMS collaboration, Search for lepton-flavour-violating decays of the Higgs boson, arXiv:1502.07400 [INSPIRE].
  4. [4]
    M.D. Campos et al., Higgsμτ as an indication for S 4 flavor symmetry, arXiv:1408.1652 [INSPIRE].
  5. [5]
    A. Celis, V. Cirigliano and E. Passemar, Disentangling new physics contributions in lepton flavour violating tau decays, arXiv:1409.4439 [INSPIRE].
  6. [6]
    D. Aristizabal Sierra and A. Vicente, Explaining the CMS Higgs flavor violating decay excess, Phys. Rev. D 90 (2014) 115004 [arXiv:1409.7690] [INSPIRE].ADSGoogle Scholar
  7. [7]
    C.-J. Lee and J. Tandean, Lepton-flavored scalar dark matter with minimal flavor violation, JHEP 04 (2015) 174 [arXiv:1410.6803] [INSPIRE].ADSCrossRefGoogle Scholar
  8. [8]
    J. Heeck, M. Holthausen, W. Rodejohann and Y. Shimizu, Higgsμτ in abelian and non-abelian flavor symmetry models, Nucl. Phys. B 896 (2015) 281 [arXiv:1412.3671] [INSPIRE].ADSCrossRefzbMATHGoogle Scholar
  9. [9]
    A. Crivellin, G. D’Ambrosio and J. Heeck, Explaining hμ ± τ , BK * μ + μ and B + μ /BKe + e in a two-Higgs-doublet model with gauged L μL τ, Phys. Rev. Lett. 114 (2015) 151801 [arXiv:1501.00993] [INSPIRE].ADSCrossRefGoogle Scholar
  10. [10]
    L. de Lima, C.S. Machado, R.D. Matheus and L.A.F. do Prado, Higgs flavor violation as a signal to discriminate models, arXiv:1501.06923 [INSPIRE].
  11. [11]
    LHC Higgs Cross Section Working Group collaboration, S. Heinemeyer et al., Handbook of LHC Higgs cross sections: 3. Higgs properties, arXiv:1307.1347 [INSPIRE].
  12. [12]
    CMS collaboration, Search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to bottom quarks, Phys. Rev. D 89 (2014) 012003 [arXiv:1310.3687] [INSPIRE].
  13. [13]
    CMS collaboration, Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs, Phys. Lett. B 736 (2014) 64 [arXiv:1405.3455] [INSPIRE].
  14. [14]
    ATLAS collaboration, Determination of the off-shell Higgs boson signal strength in the high-mass ZZ final state with the ATLAS detector, ATLAS-CONF-2014-042 (2014).
  15. [15]
    C. Englert and M. Spannowsky, Limitations and opportunities of off-shell coupling measurements, Phys. Rev. D 90 (2014) 053003 [arXiv:1405.0285] [INSPIRE].ADSGoogle Scholar
  16. [16]
    A. Azatov, C. Grojean, A. Paul and E. Salvioni, Taming the off-shell Higgs boson, Zh. Eksp. Teor. Fiz. 147 (2015) 410 [arXiv:1406.6338] [INSPIRE].Google Scholar
  17. [17]
    R. Harnik, J. Kopp and J. Zupan, Flavor violating Higgs decays, JHEP 03 (2013) 026 [arXiv:1209.1397] [INSPIRE].ADSCrossRefGoogle Scholar
  18. [18]
    T. Cheng and M. SHer, Mass matrix ansatz and flavor nonconservation in models with multiple Higgs doublets, Phys. Rev. D 35 (1987) 3484 [INSPIRE].ADSGoogle Scholar
  19. [19]
    G.C. Branco et al., Theory and phenomenology of two-Higgs-doublet models, Phys. Rept. 516 (2012) 1 [arXiv:1106.0034] [INSPIRE].ADSCrossRefGoogle Scholar
  20. [20]
    E.E. Jenkins, A.V. Manohar and M. Trott, Renormalization group evolution of the standard model dimension six operators I: formalism and λ dependence, JHEP 10 (2013) 087 [arXiv:1308.2627] [INSPIRE].ADSMathSciNetCrossRefzbMATHGoogle Scholar
  21. [21]
    E.E. Jenkins, A.V. Manohar and M. Trott, Renormalization group evolution of the standard model dimension six operators II: Yukawa dependence, JHEP 01 (2014) 035 [arXiv:1310.4838] [INSPIRE].ADSCrossRefGoogle Scholar
  22. [22]
    A. Goudelis, O. Lebedev and J.-h. Park, Higgs-induced lepton flavor violation, Phys. Lett. B 707 (2012) 369 [arXiv:1111.1715] [INSPIRE].ADSCrossRefGoogle Scholar
  23. [23]
    G. Blankenburg, J. Ellis and G. Isidori, Flavour-changing decays of a 125 GeV Higgs-like particle, Phys. Lett. B 712 (2012) 386 [arXiv:1202.5704] [INSPIRE].ADSCrossRefGoogle Scholar
  24. [24]
    BaBar collaboration, B. Aubert et al., Searches for lepton flavor violation in the decays τ ±e ± γ and τ ±μ ± γ, Phys. Rev. Lett. 104 (2010) 021802 [arXiv:0908.2381] [INSPIRE].
  25. [25]
    T. Aushev et al., Physics at super B factory, arXiv:1002.5012 [INSPIRE].
  26. [26]
    E. Arganda, A.M. Curiel, M.J. Herrero and D. Temes, Lepton flavor violating Higgs boson decays from massive seesaw neutrinos, Phys. Rev. D 71 (2005) 035011 [hep-ph/0407302] [INSPIRE].ADSGoogle Scholar
  27. [27]
    E. Arganda, M.J. Herrero, X. Marcano and C. Weiland, Imprints of massive inverse seesaw model neutrinos in lepton flavor violating Higgs boson decays, Phys. Rev. D 91 (2015) 015001 [arXiv:1405.4300] [INSPIRE].ADSGoogle Scholar
  28. [28]
    R. Kitano, M. Koike and Y. Okada, Detailed calculation of lepton flavor violating muon electron conversion rate for various nuclei, Phys. Rev. D 66 (2002) 096002 [hep-ph/0203110] [INSPIRE].ADSGoogle Scholar
  29. [29]
    SINDRUM II collaboration, W.H. Bertl et al., A search for muon to electron conversion in muonic gold , Eur. Phys. J. C 47 (2006) 337 [INSPIRE].
  30. [30]
    MEG collaboration, J. Adam et al., New constraint on the existence of the μ +e + γ decay, Phys. Rev. Lett. 110 (2013) 201801 [arXiv:1303.0754] [INSPIRE].
  31. [31]
    DeeMe collaboration, M. Aoki et al., An experimental search for muon-electron conversion in nuclear field at sensitivity of 10−14 with a pulsed proton beam, AIP Conf. Proc. 1441 (2012) 599 [INSPIRE].
  32. [32]
    R.K. Kutschke, The Mu2e experiment at Fermilab, arXiv:1112.0242 [INSPIRE].
  33. [33]
    A. Crivellin, A. Kokulu and C. Greub, Flavor-phenomenology of two-Higgs-doublet models with generic Yukawa structure, Phys. Rev. D 87 (2013) 094031 [arXiv:1303.5877] [INSPIRE].ADSGoogle Scholar
  34. [34]
    K.S. Babu and C. Kolda, Higgs mediated τ → 3μ in the supersymmetric seesaw model, Phys. Rev. Lett. 89 (2002) 241802 [hep-ph/0206310] [INSPIRE].ADSCrossRefGoogle Scholar
  35. [35]
    J. Hisano, S. Sugiyama, M. Yamanaka and M.J.S. Yang, Reevaluation of Higgs-mediated μ-e transition in the MSSM, Phys. Lett. B 694 (2011) 380 [arXiv:1005.3648] [INSPIRE].ADSCrossRefGoogle Scholar
  36. [36]
    M. Arana-Catania, E. Arganda and M.J. Herrero, Non-decoupling SUSY in LFV Higgs decays: a window to new physics at the LHC, JHEP 09 (2013) 160 [arXiv:1304.3371] [INSPIRE].ADSCrossRefGoogle Scholar
  37. [37]
    D. Chang, W.S. Hou and W.-Y. Keung, Two loop contributions of flavor changing neutral Higgs bosons to μ, Phys. Rev. D 48 (1993) 217 [hep-ph/9302267] [INSPIRE].ADSGoogle Scholar
  38. [38]
    ATLAS collaboration, Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector, JHEP 04 (2015) 117 [arXiv:1501.04943] [INSPIRE].
  39. [39]
    CMS collaboration, Evidence for the 125 GeV Higgs boson decaying to a pair of τ leptons, JHEP 05 (2014) 104 [arXiv:1401.5041] [INSPIRE].
  40. [40]
    K. Hayasaka et al., Search for lepton flavor violating τ decays into three leptons with 719 million produced τ + τ pairs, Phys. Lett. B 687 (2010) 139 [arXiv:1001.3221] [INSPIRE].ADSCrossRefGoogle Scholar
  41. [41]
    A.M. Baldini et al., MEG upgrade proposal, arXiv:1301.7225 [INSPIRE].
  42. [42]
    Q. Shafi and Z. Tavartkiladze, An improved supersymmetric SU(5), Phys. Lett. B 459 (1999) 563 [hep-ph/9904249] [INSPIRE].ADSMathSciNetCrossRefzbMATHGoogle Scholar
  43. [43]
    M. Malinsky, Quark and lepton masses and mixing in SO(10) with a GUT-scale vector matter, Phys. Rev. D 77 (2008) 055016 [arXiv:0710.0581] [INSPIRE].ADSGoogle Scholar
  44. [44]
    K.S. Babu, B. Bajc and Z. Tavartkiladze, Realistic fermion masses and nucleon decay rates in SUSY SU(5) with vector-like matter, Phys. Rev. D 86 (2012) 075005 [arXiv:1207.6388] [INSPIRE].ADSGoogle Scholar
  45. [45]
    S.M. Barr and H.-Y. Chen, A simple grand unified relation between neutrino mixing and quark mixing, JHEP 11 (2012) 092 [arXiv:1208.6546] [INSPIRE].ADSCrossRefGoogle Scholar
  46. [46]
    S.M. Barr and H.-Y. Chen, Proton decay and the origin of quark and lepton mixing, JHEP 10 (2013) 049 [arXiv:1307.5755] [INSPIRE].ADSCrossRefGoogle Scholar
  47. [47]
    R. Contino, T. Kramer, M. Son and R. Sundrum, Warped/composite phenomenology simplified, JHEP 05 (2007) 074 [hep-ph/0612180] [INSPIRE].ADSCrossRefGoogle Scholar
  48. [48]
    K. Agashe, A.E. Blechman and F. Petriello, Probing the Randall-Sundrum geometric origin of flavor with lepton flavor violation, Phys. Rev. D 74 (2006) 053011 [hep-ph/0606021] [INSPIRE].ADSGoogle Scholar
  49. [49]
    K. Agashe, Relaxing constraints from lepton flavor violation in 5D flavorful theories, Phys. Rev. D 80 (2009) 115020 [arXiv:0902.2400] [INSPIRE].ADSGoogle Scholar
  50. [50]
    M. Redi, Leptons in composite MFV, JHEP 09 (2013) 060 [arXiv:1306.1525] [INSPIRE].ADSCrossRefGoogle Scholar
  51. [51]
    S. Fajfer, A. Greljo, J.F. Kamenik and I. Mustac, Light Higgs and vector-like quarks without prejudice, JHEP 07 (2013) 155 [arXiv:1304.4219] [INSPIRE].ADSCrossRefGoogle Scholar
  52. [52]
    I. Dorsner, S. Fajfer and I. Mustac, Light vector-like fermions in a minimal SU(5) setup, Phys. Rev. D 89 (2014) 115004 [arXiv:1401.6870] [INSPIRE].ADSGoogle Scholar
  53. [53]
    J.F. Kamenik and M. Nemevšek, Lepton flavor violation in type-I + III seesaw, JHEP 11 (2009) 023 [arXiv:0908.3451] [INSPIRE].ADSCrossRefGoogle Scholar
  54. [54]
    A. Falkowski, D.M. Straub and A. Vicente, Vector-like leptons: Higgs decays and collider phenomenology, JHEP 05 (2014) 092 [arXiv:1312.5329] [INSPIRE].ADSCrossRefGoogle Scholar
  55. [55]
    L. Lavoura, General formulae for f(1) → f(2)γ, Eur. Phys. J. C 29 (2003) 191 [hep-ph/0302221] [INSPIRE].ADSCrossRefGoogle Scholar
  56. [56]
    ATLAS collaboration, Search for third generation scalar leptoquarks in pp collisions at \( \sqrt{s}=7 \) TeV with the ATLAS detector, JHEP 06 (2013) 033 [arXiv:1303.0526] [INSPIRE].
  57. [57]
    CMS collaboration, Search for third generation scalar leptoquarks decaying to top quark-τ lepton pairs in pp collisions, CMS-PAS-EXO-13-010 (2013).
  58. [58]
    I. Doršner, S. Fajfer, N. Košnik and I. Nišandžić, Minimally flavored colored scalar in \( \overline{B}\to D\left(*\right)\tau \overline{\nu} \) and the mass matrices constraints, JHEP 11 (2013) 084 [arXiv:1306.6493] [INSPIRE].ADSCrossRefGoogle Scholar
  59. [59]
    F. Boudjema et al., On the presentation of the LHC Higgs results, arXiv:1307.5865 [INSPIRE].
  60. [60]
    ATLAS collaboration, Search for the bb decay of the Standard Model Higgs boson in associated W/ZH production with the ATLAS detector, ATLAS-CONF-2013-079 (2013).
  61. [61]
    ATLAS collaboration, Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC, Phys. Lett. B 726 (2013) 88 [arXiv:1307.1427] [INSPIRE].
  62. [62]
    ATLAS collaboration, Updated coupling measurements of the Higgs boson with the ATLAS detector using up to 25 fb −1 of proton-proton collision data, ATLAS-CONF-2014-009 (2014).
  63. [63]
    ATLAS collaboration, Search for invisible decays of a Higgs boson produced in association with a Z boson in ATLAS, Phys. Rev. Lett. 112 (2014) 201802 [arXiv:1402.3244] [INSPIRE].
  64. [64]
    ATLAS collaboration, Search for Higgs boson decays to a photon and a Z boson in pp collisions at \( \sqrt{s}=7 \) and 8 TeV with the ATLAS detector, Phys. Lett. B 732 (2014) 8 [arXiv:1402.3051] [INSPIRE].
  65. [65]
    ATLAS collaboration, Search for a standard model Higgs boson in Hμμ decays with the ATLAS detector, ATLAS-CONF-2013-010 (2013).
  66. [66]
    CMS collaboration, Higgsbb in the VBF channel, CMS-PAS-HIG-13-011 (2013).
  67. [67]
    CMS collaboration, Search for Higgs boson production in association with a top-quark pair and decaying to bottom quarks or τ leptons, CMS-PAS-HIG-13-019 (2013).
  68. [68]
    CMS collaboration, Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states, JHEP 01 (2014) 096 [arXiv:1312.1129] [INSPIRE].
  69. [69]
    CMS collaboration, Measurement of the properties of a Higgs boson in the four-lepton final state, Phys. Rev. D 89 (2014) 092007 [arXiv:1312.5353] [INSPIRE].
  70. [70]
    CMS collaboration, Updated measurements of the Higgs boson at 125 GeV in the two photon decay channel, CMS-PAS-HIG-13-001 (2013).
  71. [71]
    CMS collaboration, Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes, Eur. Phys. J. C 74 (2014) 2980 [arXiv:1404.1344] [INSPIRE].
  72. [72]
    CMS collaboration, Search for a Higgs boson decaying into a Z and a photon in pp collisions at \( \sqrt{s}=7 \) and 8 TeV, Phys. Lett. B 726 (2013) 587 [arXiv:1307.5515] [INSPIRE].
  73. [73]
    CMS collaboration, Search for the standard model Higgs boson in the dimuon decay channel in pp collisions at \( \sqrt{s}=7 \) and 8 TeV, CMS-PAS-HIG-13-007 (2013).
  74. [74]
    CMS Collaboration, Constraints on the Higgs boson width from off-shell production and decay to ZZllll and llνν, CMS-PAS-HIG-14-002 (2014).

Copyright information

© The Author(s) 2015

Authors and Affiliations

  • Ilja Doršner
    • 1
    • 2
  • Svjetlana Fajfer
    • 2
    • 3
  • Admir Greljo
    • 4
    • 5
  • Jernej F. Kamenik
    • 2
    • 3
    Email author
  • Nejc Košnik
    • 2
    • 3
  • Ivan Nišandžić
    • 6
  1. 1.University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture in Split (FESB)SplitCroatia
  2. 2.Jožef Stefan InstituteLjubljanaSlovenia
  3. 3.Department of Physics, University of LjubljanaLjubljanaSlovenia
  4. 4.Physik-InstitutUniversität ZürichZürichSwitzerland
  5. 5.Department of PhysicsUniversity of SarajevoSarajevoBosnia and Herzegovina
  6. 6.Institut für PhysikTechnische Universität DortmundDortmundGermany

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