Measurements of $\mu \to 3e$ Decay with Polarised Muons as a Probe of New Physics

Abstract

Working within the Standard Model effective field theory approach, we examine the possibility to test charged lepton flavour violating (cLFV) new physics (NP) by angular measurements of the outgoing electron and positrons in the polarised ${\mu }^{+}\to e^{+}{e}^{+}{e}^{-}$ decay. This decay is planned to be studied with a sensitivity to the branching ratio of $B_{\mu \to 3e}\sim 10^{-15}$ by the Mu3e experiment at PSI. To illustrate the potential of these measurements, we consider a set of eight effective operators generating the decay at the tree level, including dimension-five dipole operators and dimension-six scalar and vector four-fermion operators of different chiralities. We show that if the polarised ${\mu }^{+}\to e^{+}{e}^{+}{e}^{-}$ decay is observed and is induced by a single operator, data from three angular observables - two P-odd asymmetries and one T-odd asymmetry - can allow to discriminate between all considered operators with the exception of scalar and vector operators of opposite chirality. For these two types of operators, the P-odd asymmetry is maximal in magnitude; they can be distinguished, in principle, by measuring the helicities of the outgoing positrons. The observation of a non-zero T-odd asymmetry would indicate the presence in the decay rate of a dipole and vector operator interference term that is T (CP) violating.

arXiv comment22 pages, 2 figures, 3 tables

References in corpus (33)

• Verifiable Radiative Seesaw Mechanism of Neutrino Mass and Dark Matter
• Oscillating neutrinos and mu --> e, gamma
• Muon Decay and Physics Beyond the Standard Model
• Lepton-Flavor Violation via Right-Handed Neutrino Yukawa Couplings in Supersymmetric Standard Model
• An improved upper limit on the neutrino mass from a direct kinematic method by KATRIN
• Violations of lepton flavour and CP in supersymmetric unified theories
• Flavour-Violating Charged Lepton Decays in Seesaw-Type Models
• From the trees to the forest: a review of radiative neutrino mass models
• Solar and Atmospheric Neutrino Oscillations and Lepton Flavor Violation in Supersymmetric Models with Right-handed Neutrinos
• Minimal Flavor Violation in the Lepton Sector
• The design of the MEG II experiment
• Enhanced lepton flavour violation in the supersymmetric inverse seesaw model
• Muon conversion to electron in nuclei in type-I seesaw models
• COMET Phase-I Technical Design Report
• Mu2e Technical Design Report
• Technical design of the phase I Mu3e experiment
• $\mu \to e\gamma$ and $\tau \to l\gamma$ decays in the fermion triplet seesaw model
• Various definitions of Minimal Flavour Violation for Leptons
• $\mu \to e\gamma$ and $\mu \to 3e$ processes with polarized muons and supersymmetric grand unified theories
• Search for the Lepton Flavour Violating Decay ${\mu }^{+}\to e^{+}\gamma$ with the Full Dataset of the MEG Experiment
• Spin-dependent $\mu \to e$ conversion
• Charged Lepton Flavour Violation in Supersymmetric Low-Scale Seesaw Models
• The Scalar Triplet Contribution to Lepton Flavour Violation and Neutrinoless Double Beta Decay in Left-Right Symmetric Model
• Selecting mu -> e Conversion Targets to distinguish Lepton Flavour-Changing Operators
• A new idea to search for charged lepton flavor violation using a muonic atom
• Revisiting Minimal Lepton Flavour Violation in the Light of Leptonic CP Violation
• CP violation in the $\mu \to 3e$ process and supersymmetric grand unified theory
• Heavy neutral leptons and high-intensity observables
• Science Case for the new High-Intensity Muon Beams HIMB at PSI
• First direct neutrino-mass measurement with sub-eV sensitivity
• Improved analysis for ${\mu }^{-}{e}^{-}\to e^{-}{e}^{-}$ in muonic atoms by photonic interaction
• Improved analyses for ${\mu }^{-}{e}^{-}\to e^{-}{e}^{-}$ in muonic atoms by contact interactions
• Momentum distribution of the electron pair from the charged lepton flavor violating process ${\mu }^{-}{e}^{-}\to e^{-}{e}^{-}$ in muonic atoms with a polarized muon

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