- Physical Review Journals
All JournalsPhysics Magazine

Physical Review D

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Matter unification and lepton flavor violation

Hridoy Debnath* and Pavel Fileviez Pérez†

  • *Contact author: hxd253@case.edu
  • †Contact author: pxf112@case.edu
PDF

Phys. Rev. D 113, 115011 – Published 5 June, 2026

DOI: https://doi.org/10.1103/qgvz-sd3v

Abstract

We explore the idea of quark-lepton unification at low energies. In particular, we discuss the minimal framework for matter unification at the multi-TeV scale, in which neutrino masses are necessarily generated via the inverse seesaw mechanism. To assess the testability of this theory for physics beyond the Standard Model, we analyze current experimental constraints and derive the corresponding lower bound on the symmetry breaking scale. We reexamine the impact of existing limits from lepton number violating meson decays, taking into account the freedom associated with unknown quark-lepton mixing angles. Furthermore, we study the correlation between bounds from meson decays and μ→e conversion. We demonstrate that the upcoming μ→e conversion experiment at Fermilab can play a crucial role in probing quark-lepton unification at the multi-TeV scale.

View figure in article

Physics Subject Headings (PhySH)

Article Text

References (40)

  1. Jogesh C. Pati and Abdus Salam, Is baryon number conserved?, Phys. Rev. Lett. 31, 661 (1973).
  2. Jogesh C. Pati and Abdus Salam, Lepton number as the fourth color, Phys. Rev. D 10, 275 (1974); 11, 703(E) (1975).
  3. Peter Minkowski, μ→eγ at a rate of one out of 109 muon decays?, Phys. Lett. 67B, 421 (1977).
  4. Murray Gell-Mann, Pierre Ramond, and Richard Slansky, Complex spinors and unified theories, Conf. Proc. C 790927, 315 (1979).
  5. Rabindra N. Mohapatra and Goran Senjanovic, Neutrino mass and spontaneous parity nonconservation, Phys. Rev. Lett. 44, 912 (1980).
  6. Tsutomu Yanagida, Horizontal gauge symmetry and masses of neutrinos, Conf. Proc. C 7902131, 95 (1979).
  7. Pavel Fileviez Perez and Mark B. Wise, Low scale quark-lepton unification, Phys. Rev. D 88, 057703 (2013).
  8. Jon Butterworth, Hridoy Debnath, Pavel Fileviez Perez, and Peng Wang, Quark-lepton unification signatures, arXiv:2512.00143.
  9. Pavel Fileviez Pérez, Clara Murgui, Samuel Patrone, Adriano Testa, and Mark B. Wise, Finite naturalness and quark-lepton unification, Phys. Rev. D 109, 015011 (2024).
  10. Pavel Fileviez Perez, Elliot Golias, and Alexis D. Plascencia, Two-Higgs-doublet model and quark-lepton unification, J. High Energy Phys. 08 (2022) 293.
  11. Pavel Fileviez Perez and Clara Murgui, Flavor anomalies and quark-lepton unification, Phys. Rev. D 106, 035033 (2022).
  12. Pavel Fileviez Perez, Elliot Golias, and Alexis D. Plascencia, Probing quark-lepton unification with leptoquark and Higgs boson decays, Phys. Rev. D 105, 075011 (2022).
  13. Pavel Fileviez Perez, Clara Murgui, and Alexis D. Plascencia, Leptoquarks and matter unification: Flavor anomalies and the muon g-2, Phys. Rev. D 104, 035041 (2021).
  14. Thomas Flacke, Jeong Han Kim, Manuel Kunkel, Jun Seung Pi, and Werner Porod, Hunting and identifying coloured resonances in four top events with machine learning, J. High Energy Phys. 02 (2026) 028.
  15. Hedvika Gedeonová and Matěj Hudec, All possible first signals of gauge leptoquark in quark-lepton unification and beyond, Phys. Rev. D 107, 095029 (2023).
  16. Clara Murgui and Mark B. Wise, Scalar leptoquarks, baryon number violation, and Pati-Salam symmetry, Phys. Rev. D 104, 035017 (2021).
  17. G. Valencia and S. Willenbrock, Quark—lepton unification and rare meson decays, Phys. Rev. D 50, 6843 (1994).
  18. A. D. Smirnov, Vector leptoquark mass limits and branching ratios of KL0,B0,Bs→li+lj− decays with account of fermion mixing in leptoquark currents, Mod. Phys. Lett. A 33, 1850019 (2018).
  19. Robert H. Bernstein and Peter S. Cooper, Charged lepton flavor violation: An experimenter’s guide, Phys. Rep. 532, 27 (2013).
  20. Sacha Davidson, Bertrand Echenard, Robert H. Bernstein, Julian Heeck, and David G. Hitlin, Charged lepton flavor violation, arXiv:2209.00142.
  21. Sacha Davidson and Bertrand Echenard, Reach and complementarity of μ→e searches, Eur. Phys. J. C 82, 836 (2022).
  22. Pavel Fileviez Perez et al., On baryon and lepton number violation, arXiv:2208.00010.
  23. L. Bartoszek et al. (Mu2e Collaboration), Mu2e technical design report, 10.2172/1172555 (2014).
  24. R. N. Mohapatra and J. W. F. Valle, Neutrino mass and baryon number nonconservation in superstring models, Phys. Rev. D 34, 1642 (1986).
  25. A. D. Smirnov, The minimal quark—lepton symmetry model and the limit on Z-prime mass, Phys. Lett. B 346, 297 (1995).
  26. K. S. Babu, Sumit Biswas, and Shaikh Saad, TeV scale quark-lepton unification, arXiv:2512.11113.
  27. Georges Aad et al. (ATLAS Collaboration), Search for pair production of third-generation leptoquarks decaying into a bottom quark and a τ-lepton with the ATLAS detector, Eur. Phys. J. C 83, 1075 (2023).
  28. Aram Hayrapetyan et al. (CMS Collaboration), Search for pair production of scalar and vector leptoquarks decaying to muons and bottom quarks in proton-proton collisions at s=13  TeV, Phys. Rev. D 109, 112003 (2024).
  29. A. Hayrapetyan et al. (CMS Collaboration), Search for t-channel scalar and vector leptoquark exchange in the high-mass dimuon and dielectron spectra in proton-proton collisions at s=13  TeV, J. High Energy Phys. 12 (2025) 052.
  30. Armen Tumasyan et al. (CMS Collaboration), Searches for additional Higgs bosons and for vector leptoquarks in ττ final states in proton-proton collisions at s=13  TeV, J. High Energy Phys. 07 (2023) 073.
  31. Andrzej J. Buras, Weak Hamiltonian, CP violation and rare decays, in Les Houches Summer School in Theoretical Physics, Session 68: Probing the Standard Model of Particle Interactions (1998) pp. 281–539, arXiv:hep-ph/9806471.
  32. D. Ambrose et al. (BNL Collaboration), New limit on muon and electron lepton number violation from KL0→μ±e∓ decay, Phys. Rev. Lett. 81, 5734 (1998).
  33. Pavel Fileviez Perez, Tao Han, Tong Li, and Michael J. Ramsey-Musolf, Leptoquarks and neutrino masses at the LHC, Nucl. Phys. B819, 139 (2009).
  34. Ryuichiro Kitano, Masafumi Koike, and Yasuhiro Okada, Detailed calculation of lepton flavor violating muon electron conversion rate for various nuclei, Phys. Rev. D 66, 096002 (2002); 76, 059902(E) (2007).
  35. Andreas Crivellin, Sacha Davidson, Giovanni Marco Pruna, and Adrian Signer, Renormalisation-group improved analysis of μ→e processes in a systematic effective-field-theory approach, J. High Energy Phys. 05 (2017) 117.
  36. Vincenzo Cirigliano, Ryuichiro Kitano, Yasuhiro Okada, and Paula Tuzon, On the model discriminating power of μ→e conversion in nuclei, Phys. Rev. D 80, 013002 (2009).
  37. Martin Hoferichter, J. Ruiz de Elvira, Bastian Kubis, and Ulf-G. Meißner, High-precision determination of the pion-nucleon σ term from Roy-Steiner equations, Phys. Rev. Lett. 115, 092301 (2015).
  38. Parikshit Junnarkar and Andre Walker-Loud, Scalar strange content of the nucleon from lattice QCD, Phys. Rev. D 87, 114510 (2013).
  39. Wilhelm H. Bertl et al. (SINDRUM II Collaboration), A search for muon to electron conversion in muonic gold, Eur. Phys. J. C 47, 337 (2006).
  40. T. Suzuki, David F. Measday, and J. P. Roalsvig, Total nuclear capture rates for negative muons, Phys. Rev. C 35, 2212 (1987).

Outline

Information

Phys. Rev. D 113, 115011– Published 5 June, 2026
  • Received 9 March 2026
  • Accepted 27 April 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation