Large mass of the littlest Higgs boson

Journal Article · Tue Nov 01 00:00:00 EST 2005 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.72.095019· OSTI ID:20713877

Bazzocchi, F; Fabbrichesi, M; Piai, M ^[1]

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1. INFN, Sezione di Trieste (Italy) and Scuola Internazionale Superiore di Studi Avanzati, via Beirut 4, I-34014 Trieste (Italy)

We study the exact (one-loop) effective potential of the littlest Higgs model and determine the dependence of physical quantities, such as the vacuum expectation value v{sub W} and mass m{sub h} of the Higgs boson, on the fundamental parameters of the Lagrangian--masses, couplings of new states, the fundamental scale f of the sigma model, and the coefficients of operators quadratically sensitive to the cutoff of the theory. On the one hand, we show that it is possible to have the electroweak ground state and a relatively large cutoff {lambda}=4{pi}f with f in the 2 TeV range without requiring unnaturally small coefficients for quadratically divergent quantities, and with only moderate cancellations between the contribution of different sectors to the effective potential of the Higgs. On the other hand, this cannot be achieved while at the same time keeping m{sub h} close to its current lower bound of 114.4 GeV. The natural expectation for m{sub h} is O(f), mainly because of large logarithmically divergent contributions to the effective potential of the top-quark sector. Even a fine-tuning at the level of O(10{sup -2}) in the coefficients of the quadratic divergences is not enough to produce small physical Higgs masses, and the natural expectation is in the 800 GeV range for f{approx}2 TeV. We conclude that the littlest Higgs model is a solution of the little hierarchy problem, in the sense that it stabilizes the electroweak symmetry breaking scale to be a factor of 100 less than the cutoff of the theory, but this requires a quite large physical mass for the Higgs, and hence precision electroweak studies should be redone accordingly. We also study finite temperature corrections. The first order electroweak phase transition is no stronger than in the standard model. A second phase transition (nonrestoration of symmetry at high temperature) depends strongly on the logarithmic terms in the potential.

• OSTI ID: 20713877
• Journal Information: Physical Review. D, Particles Fields, Vol. 72, Issue 9; Other Information: DOI: 10.1103/PhysRevD.72.095019; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AXIOMATIC FIELD THEORY
CORRECTIONS
EXPECTATION VALUE
GEV RANGE
GROUND STATES
HIGGS BOSONS
HIGGS MODEL
INTERMEDIATE BOSONS
LAGRANGIAN FIELD THEORY
LAGRANGIAN FUNCTION
MATHEMATICAL SOLUTIONS
NONLINEAR PROBLEMS
PHASE TRANSFORMATIONS
POTENTIALS
REST MASS
SIGMA MODEL
STANDARD MODEL
SYMMETRY
SYMMETRY BREAKING
T QUARKS
TEV RANGE