Resonant CP violation in rare τ ± decays

Saa, J. A. Zamora

doi:10.1007/jhep05(2017)110

Cited by 43 publications

(46 citation statements)

References 32 publications

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“…In the presence of Majorana heavy neutral leptons (a right-handed neutrino, or other sterile fermions), one can have sizeable branching fractions (BRs) for lepton number violating processes, when the Majorana states are produced on-shell [1][2][3][4][5][6][7][8][9][10][11] -the so-called "resonant production" regime. In the case in which a single sterile fermion is present, the branching fractions for the semileptonic decays leading to same-sign and opposite-sign dileptons are predicted to be of the same order.…”

Section: Introductionmentioning

confidence: 99%

Interference effects in LNV and LFV semileptonic decays: the Majorana hypothesis

Abada

Hati

Marcano

et al. 2019

J. High Energ. Phys.

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In the case where the Standard Model is extended by one heavy Majorana fermion, the branching fractions of semileptonic meson decays into same-sign and opposite-sign dileptons are expected to be of the same order. As we discuss here, this need not be the case in extensions by at least two sterile fermions, due to the possible destructive and constructive interferences that might arise. Depending on the CP violating phases, one can have an enhancement of the lepton number violating modes and suppression of the lepton number conserving ones (and vice-versa). We explore for the first time the interference effects in semileptonic decays, and illustrate them for a future observation of kaon decays at NA62. We also argue that a non-observation of a given mode need not be interpreted in terms of reduced active-sterile mixings, but that it could instead be understood in terms of interference effects due to the presence of several sterile states; in particular, for different-flavour final state charged leptons, observing a lepton number conserving process and not a lepton number violating one does not rule out that the mediators are Majorana fermions. arXiv:1904.05367v1 [hep-ph]

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Section: Introductionmentioning

confidence: 99%

Interference effects in LNV and LFV semileptonic decays: the Majorana hypothesis

Abada

Hati

Marcano

et al. 2019

J. High Energ. Phys.

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“…As it is established in the previous article [31], we are interested in studying the LNV processes which are represented by the Feynman diagrams shown in Fig. 1 and from now on, we will focus in the case when = µ.…”

Section: Production Of the Rhnmentioning

confidence: 99%

“…Left Panel: Feynman diagrams for the LNV process τ + → π + π + − . Right Panel: Feynman diagrams for the LNV process τ − → π − π − + The relevant expressions for the aforementioned processes were presented in [26,31] as a function of the distance between production and detection vertices, called L. Therefore, the L dependent effective differential decay width is given by…”

Section: Production Of the Rhnmentioning

confidence: 99%

“…In a previous article [31] we have studied the resonant CP-violation and described the effects of HNOs on it. The study was carry out in the context of Lepton Number Violating (LNV) tau lepton decay (τ ± → π ± π ± µ ∓ ) via two almost degenerate heavy on-shell Majorana neutrinos (M N i ∼ 1GeV) which can oscillate among themselves.…”

Section: Introductionmentioning

confidence: 99%

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Exploring CP-violating heavy neutrino oscillations in rare tau decays at Belle II

Araya

Zamora-Saá

2020

Nuclear Physics B

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In this work, we study the lepton number violating tau decays via two intermediate on-shell Majorana neutrinos N j into two charged pions, and a charged lepton τ ± → π ± N j → π ± π ± ∓ . We consider the scenario where the heavy neutrino masses are within 0.5 GeV ≤ M N ≤ 1.5 GeV. We evaluated the possibility to measure the modulation of the decay width along the detector length for these processes at taus factories, such as Belle II. We study some realistic conditions which could lead to the observation of this phenomenon at futures τ 's factories.

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“…This allows to build upon and update earlier analysis, revising the bounds derived in [10,11,28,30,[37][38][39][40][51][52][53], and obtaining an up-to-date overview of the sterile fermion parameter space (mass and combinations of the active-sterile mixing angles, U α4 U β 4 ). We explore the allowed parameter space in order to identify regimes for which the LNV branching ratios might be within experimental reach, for instance of NA62 (for the light mesons), BES-III for charmed mesons and LHCb (and in the future, Belle II) for B mesons and tau leptons.…”

Section: Jhep02(2018)169mentioning

confidence: 99%

Effective Majorana mass matrix from tau and pseudoscalar meson lepton number violating decays

Abada

Romeri

Lucente

et al. 2018

J. High Energ. Phys.

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An observation of any lepton number violating process will undoubtedly point towards the existence of new physics and indirectly to the clear Majorana nature of the exchanged fermion. In this work, we explore the potential of a minimal extension of the Standard Model via heavy sterile fermions with masses in the [0.1 − 10] GeV range concerning an extensive array of "neutrinoless" meson and tau decay processes. We assume that the Majorana neutrinos are produced on-shell, and focus on three-body decays. We conduct an update on the bounds on the active-sterile mixing elements, |U α4 U β 4 |, taking into account the most recent experimental bounds (and constraints) and new theoretical inputs, as well as the effects of a finite detector, imposing that the heavy neutrino decay within the detector. This allows to establish up-to-date comprehensive constraints on the sterile fermion parameter space. Our results suggest that the branching fractions of several decays are close to current sensitivities (likely within reach of future facilities), some being already in conflict with current data (as is the case of K + → + α + β π − , and τ − → µ + π − π − ). We use these processes to extract constraints on all entries of an enlarged definition of a 3 × 3 "effective" Majorana neutrino mass matrix m αβ ν .

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Resonant CP violation in rare τ ± decays

Cited by 43 publications

References 32 publications

Interference effects in LNV and LFV semileptonic decays: the Majorana hypothesis

Interference effects in LNV and LFV semileptonic decays: the Majorana hypothesis

Exploring CP-violating heavy neutrino oscillations in rare tau decays at Belle II

Effective Majorana mass matrix from tau and pseudoscalar meson lepton number violating decays

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