A search for the lepton-flavour violating decays τ → eα, τ → μα

Albrecht, H.; Hamacher, T.; Hofmann, Ralf; Kirchhoff, T.; Mankel, R.; Nau, A.; Nowak, S.; Reßing, D.; Schröder, H.; Schulz, H. D.; Walter, Michael; Wurth, R.; Hast, C.; Kapitza, H.; Kolanoski, H.; Kosche, A.; Lange, A.; Lindner, A.; Schieber, M.; Siegmund, Thomas; Spaan, B.; Thurn, H.; Töpfer, D.; Wegener, D.; Eckstein, P.; Frankl, C.; Graf, J.; Śchmidtler, M.; Schramm, Michael; Schubert, K. R.; Schwierz, R.; Waldi, R.; Reim, K.; Wegener, H.; Eckmann, R.; Kuipers, H.; Mai, O.; Mundt, R.; Oest, T.; Reiner, Robert; Schmidt‐Parzefall, W.; Stiewe, J.; Werner, S.; Ehret, K.; Hofmann, W.; Hüpper, A.; Knöpfle, K. T.; Spengler, J.; Kreger, P.; MacFarlane, D. B.; Prentice, J. D.; Saull, P. R. B.; Tzamariúdaki, K.; Water, R. G. Van de; Yoon, T. S.; Schneider, M.; Weseler, S.; Kernel, G.; Križnič, P.; Podobnik, T.; Živko, T.; Balagura, V.; Barsuk, S.; Belyaev, I.; Chistov, R.; Danilov, M.; Eiges, V.; Gershtein, L.; Gershtein, Y.; Golutvin, A.; Igonkina, O.; Korolko, I.; Kostina, G.; Litvintsev, D.; Pakhlov, P.; Semenov, S.; Snizhko, A.; Tichomirov, I.; Zaitsev, Yu.

doi:10.1007/bf01579801

Cited by 62 publications

(70 citation statements)

References 12 publications

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“…Again, however, the uncertainties are dominated by statistical errors. 9 We therefore expect an upper bound on B(τ → µf ) only slightly worse than that on the ef mode.…”

mentioning

confidence: 90%

“…We now compare these bounds to those available in the third generation. The ARGUS collaboration [9] has bounded the branching fractions of τ decays into light bosons and found the limits B(τ − → µ − f ) < 4.6 × 10 −3 (95% CL) and B(τ − → e − f ) < 2.6 × 10 −3 (95% CL). These imply the following constraints on the flavor scale:…”

Section: A Decays To Familonsmentioning

confidence: 99%

“…By fitting the Monte Carlo data to the linear combination of the standard model and familon modes, we find that CLEO can obtain an upper bound on the familon branching fraction of 1.6 × 10 −3 (95% CL). This would already improve the ARGUS bound [9] on τ → ef slightly, leading to a lower bound of F τ e > 7 × 10 6 GeV. Note that in this analysis, only events with the π ± π 0 ν decay of the other τ were used.…”

Section: A Bounds From B Decaysmentioning

confidence: 99%

“…−3 (95% CL) and B(τ − → e − f ) < 2.6×10 −3 (95% CL) [9] therefore do not constrain this scenario. However, if the sensitivity of future experiments is improved by one order of magnitude or more, the predictions of this scenario may be tested, and, if the scenario is correct, exotic τ decays may be seen.…”

mentioning

confidence: 94%

“…In contrast, however, couplings involving the third generation are largely unexplored, although they may have rather rich phenomenological and cosmological implications [8]. Current constraints in the lepton sector are relatively weak, with the best bounds coming from τ → (e, µ)f bounds [9], and there are at present no corresponding bounds reported in the hadronic sector (see, however, Ref. [10]).…”

Section: Introductionmentioning

confidence: 99%

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Third generation familons,Bfactories, and neutrino cosmology

et al. 1998

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We study the physics of spontaneously broken family symmetries acting on the third generation. Massless familons (or Majorons) f associated with such broken symmetries are motivated especially by cosmological scenarios with decaying tau neutrinos. We first note that, in marked contrast with the case for the first two generations, constraints on third generation familon couplings are poor, and are, in fact, non-existent at present in the hadronic sector. We derive new bounds from B 0 -B 0 mixing, B 0 → l + l ′− , b → sνν, and astrophysics. The resulting constraints on familon decay constants are still much weaker than those for the first and second generation. We then discuss the promising prospects for significant improvements from searches for τ → lf , B → (π, K)f , and b → (d, s)f with the current CLEO, ARGUS, and LEP data. Finally, we note that future constraints from CLEO III and the B factories will probe decay constants beyond 10 8 GeV, well within regions of parameter space favored by proposed scenarios in neutrino cosmology.

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“…Again, however, the uncertainties are dominated by statistical errors. 9 We therefore expect an upper bound on B(τ → µf ) only slightly worse than that on the ef mode.…”

mentioning

confidence: 90%

Section: A Decays To Familonsmentioning

confidence: 99%

Section: A Bounds From B Decaysmentioning

confidence: 99%

mentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Third generation familons,Bfactories, and neutrino cosmology

et al. 1998

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Lepton-flavor violating mediators

Galon

Kwa

Tañedo

2017

J. High Energ. Phys.

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We present a framework where dark matter interacts with the Standard Model through a light, spin-0 mediator that couples chirally to pairs of different-flavor leptons. This flavor violating final state weakens bounds on new physics coupled to leptons from terrestrial experiments and cosmic-ray measurements. As an example, we apply this framework to construct a model for the Fermi-LAT excess of GeV γ-rays from the galactic center. We comment on the viability of this portal for self-interacting dark matter explanations of small scale structure anomalies and embeddings in flavor models. Models of this type are shown to be compatible with the muon anomalous magnetic moment anomaly. We review current experimental constraints and identify possible future theoretical and experimental directions.

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Ultralight scalars in leptonic observables

Escribano

Vicente

2021

J. High Energ. Phys.

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Many new physics scenarios contain ultralight scalars, states which are either exactly massless or much lighter than any other massive particle in the model. Axions and majorons constitute well-motivated examples of this type of particle. In this work, we explore the phenomenology of these states in low-energy leptonic observables. After adopting a model independent approach that includes both scalar and pseudoscalar interactions, we briefly discuss the current limits on the diagonal couplings to charged leptons and consider processes in which the ultralight scalar ϕ is directly produced, such as μ → eϕ, or acts as a mediator, as in τ → μμμ. Contributions to the charged leptons magnetic and electric moments are studied as well.

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A search for the lepton-flavour violating decays τ → eα, τ → μα

Cited by 62 publications

References 12 publications

Third generation familons,Bfactories, and neutrino cosmology

Third generation familons,Bfactories, and neutrino cosmology

Lepton-flavor violating mediators

Ultralight scalars in leptonic observables

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