Scales of fermion mass generation and electroweak symmetry breaking

Journal Article · Sun May 01 04:00:00 EDT 2005 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.71.093009· OSTI ID:20709357

Dicus, Duane A ^[1]; Hongjian, He ^[1]

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1. Center for Particle Physics and Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

The scale of mass generation for fermions (including neutrinos) and the scale for electroweak symmetry breaking (EWSB) can be bounded from above by the unitarity of scattering involving longitudinal weak gauge bosons or their corresponding would-be Goldstone bosons. Including the exact n-body phase space we analyze the 2{yields}n (n{>=}2) processes for the fermion-(anti)fermion scattering into multiple gauge boson final states. Contrary to naieve energy power counting, we demonstrate that as n becomes large, the competition between an increasing energy factor and a phase-space suppression leads to a strong new upper bound on the scale of fermion mass generation at a finite value n=n{sub s}, which is independent of the EWSB scale, v=({radical}(2)G{sub F}){sup -1/2}. For quarks, leptons, and Majorana neutrinos, the strongest 2{yields}n limits range from about 3 TeV to 130-170 TeV (with 2 < or approx. s < or approx. 24), depending on the measured fermion masses. Strikingly, given the tiny neutrino masses as constrained by the neutrino oscillations, neutrinoless double-beta decays and astrophysical observations, the unitarity violation of {nu}{sub L}{nu}{sub L}{yields}nW{sub L}{sup a} scattering actually occurs at a scale no higher than {approx}170 TeV. Implications for various mechanisms of neutrino mass generation are analyzed. On the other hand, for the 2{yields}n pure Goldstone boson scattering, we find that the decreasing phase-space factor always dominates over the growing overall energy factor when n becomes large, so that the best unitarity bound on the scale of EWSB remains at n=2.

• OSTI ID: 20709357
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 9 Vol. 71; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
DOUBLE BETA DECAY
GOLDSTONE BOSONS
NEUTRINO OSCILLATION
NEUTRINO-NEUTRINO INTERACTIONS
NEUTRINOS
PHASE SPACE
QUARKS
REST MASS
SCATTERING
STANDARD MODEL
SYMMETRY BREAKING
TEV RANGE
UNITARITY