Michel parameters for elucidating the neutrinos nature and searching for new physics

Authors

  • Juan Marquez CINVESTAV

DOI:

https://doi.org/10.31349/SuplRevMexFis.4.021105

Keywords:

Electroweak precision physics; sterile or heavy neutrinos

Abstract

We use the most general four-lepton effective interaction Hamiltonian to investigate the impact of massive Dirac and Majorana neutrinos on the leptonic decays of muons and taus. Our analysis encompasses the specific energy and angular distribution of the resulting charged lepton, accounting for both the initial and final polarizations of the charged leptons. Additionally, we identify the emergence of novel generalized Michel parameters and concentrate on the influence of the heavy neutrino masses, which can make significant contributions in cases where new sterile neutrinos exhibit non-negligible mixing. Our analysis reveals that the most promising scenario occurs in the case of τ decays, featuring one heavy neutrino with a mass approximately ranging from 10^2 to 10^3 MeV. In this setting, the discrepancy between the Dirac and Majorana cases could reach an order of magnitude of 10^−4, which is significant enough to be detected in present and future experiments.

References

A. Pich, Precision Tau Physics Prog. Part. Nucl. Phys. 75 (2013) 41, https://doi.org/10.1016/j.ppnp.2013.11.002

A. Pich, Precision tests of the Standard Model (1997), https://doi.org/10.48550/arXiv.hep-ph/9711279

T. P. Gorringe, and D. W. Hertzog, Precision Muon Physics (2015), Prog.Part.Nucl.Phys. 84 (2015) 73, https://doi.org/10.48550/arXiv.1506.01465

J. M. Marquez, G. L. Castro, and P. Roig, Michel parameters in the presence of massive Dirac and Majorana neutrinos. JHEP 11 (2022) 117, https://doi.org/10.1007/JHEP11%282022%29117

L. Michel, Interaction between four half spin particles and the decay of the µ meson, Proc. Phys. Soc. A 63 (1950) 1371, https://doi.org/10.1088/0370-1298/63/5/311

C. Bouchiat and L. Michel, Theory of µ-Meson Decay with the Hypothesis of Nonconservation of Parity, Phys. Rev. 106 (1957) 170, https://doi.org/10.1103/PhysRev. 106.170

Particle Data Group, Review of Particle Physics, PTEP 2022 (2022) 083C01, https://doi.org/10.1093/ptep/ptac097

W. Fetscher, Helicity dependence of the electron-neutrino energy spectrum from the decay of unpolarized muons, Phys. Rev. D 49 (1994) 5945, https://doi.org/10.1103/PhysRevD.49.5945

C. A. Gagliardi, R. E. Tribble, and N. J. Williams, Global analysis of muon decay measurements Phys. Rev. D 72 (2005) 073002, https://doi.org/10.1103/PhysRevD.72.073002

K. Abe et al. (SLD Collaboration), Measurement of the tauneutrino he- licity and the Michel parameters in polarized e +e − collisions, Phys. Rev. Lett. 78 (1997) 4691, https://doi.org/10.1103/PhysRevLett.78.4691

A. Heister et al. (ALEPH Collaboration), Measurement of the Michel parameters and the nu/tau helicity in tau lepton decays, Eur. Phys. J. C 22 (2001) 217, https://doi.org/10.1007/s100520100813

P. Abreu et al., (DELPHI Collaboration), A Study of the Lorentz structure in tau decays, Eur. Phys. J. C 16 (2000) 229, https://doi.org/10.1007/s100520050017

K. Ackerstaff et al., (OPAL Collaboration), Measurement of the Michel parameters in leptonic tau decays, Eur. Phys. J. C 8 (1999) 3, https://doi.org/10.1007/s100529901080

M. Acciarri et al., L3 Collaboration, Measurement of the Michel parameters and the average tau-neutrino helicity from tau decays at LEP, Phys. Lett. B 438 (1998) 405, https://doi.org/10.1016/S0370-2693(98)01082-X

H. Albrecht et al., ARGUS Collaboration, Determination of the Michel parameters rho, xi and delta in tau lepton decays with tau −→ rho neutrino tags, Phys. Lett. B 431 (1998) 179, https://doi.org/10.1016/S0370-2693%2898%2900565-6

J. P. Alexander et al., (CLEO Collaboration), Determination of the Michel parameters and the tau-neutrino helicity in tau decay, Phys. Rev. D 56 (1997) 5320, https://doi.org/10.1103/PhysRevD.56.5320

P. Langacker and D. London, Analysis of Muon Decay With Lepton Number Nonconserving Interactions, Phys. Rev. D 39 (1989) 266, https://doi.org/10.1103/PhysRevD.39.266

R. E. Shrock, Pure Leptonic Decays With Massive Neutrinos And Arbitrary Lorentz Structure, Phys. Lett. B 112 (1982) 382, https://doi.org/10.1016/0370-2693(82)91074-7

A. Denner, H. Eck, O. Hahn, and J. Kublbeck, Feynman rules for fermion number violating interactions, Nucl. Phys. B 387 (1992) 467, https://doi.org/10.1016/0550-3213(92)90169-C

M. Doi, T. Kotani and E. Takasugi, Double Beta Decay and Majorana Neutrinos, Progress of Theoretical Physics Supplement, 83 (1985) 83.1, https://doi.org/10.1143/PTPS.83.1

A. de Gouvea, and A. Kobach, Global Constraints on a Heavy Neutrino Phys. Rev. D 93 (2016) 033005, https://doi.org/10.1103/PhysRevD.93.033005

A. Kobach and S. Dobbs, Heavy Neutrinos and the Kinematics of Tau Decays Phys. Rev. D 91 (2015) 053006, https://doi.org/10.1103/PhysRevD.91.053006

Downloads

Published

2023-09-18

How to Cite

1.
Marquez J. Michel parameters for elucidating the neutrinos nature and searching for new physics. Supl. Rev. Mex. Fis. [Internet]. 2023 Sep. 18 [cited 2024 May 29];4(2):021105 1-6. Available from: https://rmf.smf.mx/ojs/index.php/rmf-s/article/view/7090