Article

A precision constraint on multi-Higgs-doublet models

Journal of Physics G Nuclear and Particle Physics (Impact Factor: 2.78). 12/2007; 35(7). DOI: 10.1088/0954-3899/35/7/075001
Source: arXiv

ABSTRACT

We derive a general expression for Delta rho (or, equivalently, for the oblique parameter T) in the SU(2) x U(1) electroweak model with an arbitrary number of scalar SU(2) doublets, with hypercharge +-1/2, and an arbitrary number of scalar SU(2) singlets. The experimental bound on Delta rho constitutes a strong constraint on the masses and mixings of the scalar particles in that model.

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    • "The impact of a second Higgs doublet in the so-called electroweak precision tests (EWPT), encoded in the Peskin-Takeuchi parameters S, T , and U [33], has been studied in the literature to a great extent (see for instance refs. [34] [35] [36]). These are radiative corrections to the gauge boson two point functions, known as oblique corrections. "
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    ABSTRACT: We study the constraints that electroweak precision data can impose, after the discovery of the Higgs boson by the LHC, on neutrinophilic two-Higgs-doublet models which comprise one extra $SU(2)\times U(1)$ doublet and a new symmetry, namely a spontaneously broken $\mathbb{Z}_2$ or a softly broken global $U(1)$. In these models the extra Higgs doublet, via its very small vacuum expectation value, is the sole responsible for neutrino masses. We find that the model with a $\mathbb{Z}_2$ symmetry is basically ruled out by electroweak precision data, even if the model is slightly extended to include extra right-handed neutrinos, due to the presence of a very light scalar. While the other model is still perfectly viable, the parameter space is considerably constrained by current data, specially by the $T$ parameter. In particular, the new charged and neutral scalars must have very similar masses.
    Full-text · Article · Jul 2015 · Journal of High Energy Physics
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    • "• The oblique T -parameter can restrict the splitting between the heavy scalar masses. In the 2HDM alignment limit, the expression for the new physics contribution to the T -parameter can be expressed as [31] [32] "
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    ABSTRACT: We study the conditions required to make the 2HDM scalar potential stable up to the Planck scale. The lightest CP-even scalar is assumed to have been found at the LHC and the alignment limit is imposed in view of the LHC Higgs data. We find that ensuring stability up to scales 10 10 GeV necessitates the introduction of a soft breaking parameter in the theory. Even then, some interesting correlations between the nonstandard masses and the soft breaking parameter need to be satisfied. Consequently, a 2HDM becomes completely determined by only two nonstandard parameters, namely, tan β and a mass parameter, m0, with tan β 3. These observations make a 2HDM, in the stable alignment limit, more predictive than ever.
    Full-text · Article · Mar 2015
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    • "• The oblique T -parameter can restrict the splitting between the heavy scalar masses. In the 2HDM alignment limit, the expression for the new physics contribution to the T -parameter can be expressed as [31] [32] "
    [Show abstract] [Hide abstract]
    ABSTRACT: We study the conditions required to make the 2HDM scalar potential stable up to the Planck scale. The lightest CP-even scalar is assumed to have been found at the LHC and the {\em alignment limit} is imposed in view of the LHC Higgs data. We find that ensuring stability up to scales $\gtrsim 10^{10}$~GeV necessitates the introduction of a soft breaking parameter in the theory. Even then, some interesting correlations between the nonstandard masses and the soft breaking parameter need to be satisfied. Consequently, a 2HDM becomes completely determined by only two nonstandard parameters, namely, $\tb$ and a mass parameter, $m_0$, with $\tb \gtrsim 3$. These observations make a 2HDM, in the {\em stable alignment limit}, more predictive than ever.
    Full-text · Article · Mar 2015 · Physical review D: Particles and fields
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