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Register a new userOld Wine in a New Bottle: Technidilaton as the 125 GeV Higgs -- Dedicated to the late Professor Yoichiro Nambu
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Koichi Yamawaki
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We show that the Standard Model (SM) Higgs Lagrangian is identical to the nonlinear realization of both the scale and chiral symmetries (scale-invariant nonlinear sigma model), and is further gauge equivalent to the scale-invariant Hidden Local Symmetry (HLS) model having possible new vector bosons as the HLS gauge bosons with scale-invariant mass: SM Higgs is nothing but a (pseudo) dilaton. The effective theory of the walking technicolor has precisely the same type of the scale-invariant nonlinear sigma model, thus further having the scale-invariant HLS gauge bosons (technirhos, etc.). The technidilaton mass M_phi comes from the trace anomaly, which yields M_phi^2 F_phi^2 simeq (2.5)^2 [(8/N_F)(4/N_C)] v^4 via PCDC, in the underlying walking SU(N_C) gauge theory with N_F massless flavors, where F_phi is the decay constant and v=246 GeV. This implies F_phi simeq 5 v for M_phi simeq 125 GeV simeq v/2 in the one-family walking technicolor model (N_F=8, N_C=4), in good agreement with the current LHC Higgs data. In the anti-Veneziano limit, N_C rightarrow infty, with N_C alpha= fixed and N_F/N_C= fixed (gg 1), we have a result: M_phi^2/v^2sim M_phi^2/F_phi^2 sim 1/(N_F N_C) rightarrow 0. Then the technidilaton is a naturally light composite Higgs out of the strongly coupled conformal dynamics, with its couplings even weaker than the SM Higgs.
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The walking technicolor based on the ladder Schwinger-Dyson gap equation is studied, with the scale-invariant coupling being an idealization of the Caswell-Banks-Zaks infrared fixed point in the anti-Veneziano limit, such that $N_C rightarrow infty$ with $N_C cdot alpha(mu^2)=$ fixed and $N_F/N_C=$ fixed ($gg 1$), of the $SU(N_C)$ gauge theory with massless $N_F$ flavors near criticality. We show that the 125 GeV Higgs can be naturally identified with the technidilaton (TD) predicted in the walking technicolor, a pseudo Nambu-Goldstone (NG) boson of the spontaneous symmetry breaking of the approximate scale symmetry. Ladder calculations yield the TD mass $M_phi$ from the trace anomaly as $M_phi^2 F_phi^2= -4 langle theta_mu^mu rangle = - frac{beta(alpha (mu^2))}{alpha(mu^2)}, langle G_{lambda u}^2(mu^2)rangle simeq N_C N_Ffrac{16}{pi^4} m_F^4$, independently of the renormalization point $mu$, where $m_F$ is the dynamical mass of the technifermion, and $F_phi={cal O} (sqrt{N_F N_C}, m_F)$ the TD decay constant. It reads $M_phi^2simeq (frac{v_{rm EW}}{2} cdot frac{5 v_{rm EW}}{F_phi})^2 cdot [frac{8}{N_F}frac{4}{N_C}]$, ($v_{rm EW}=246$ GeV), which implies $F_phisimeq 5 ,v_{rm EW} $ for $M_phi simeq 125, {rm GeV}simeq frac{1}{2} v_{rm EW}$ in the one-family model ($N_C=4, N_F=8$), in good agreement with the current LHC Higgs data. The result reflects a generic scaling $ M_phi^2/v_{rm EW}^2sim M_phi^2/F_phi^2 sim m_F^2 /F_phi^2 sim 1/(N_F N_C) rightarrow 0 $ as a vanishing trace anomaly, namely the TD has a mass vanishing in the anti-Veneziano limit, similarly to $eta^prime$ meson as a pseudo-NG boson of the ordinary QCD with vanishing $U(1)_A$ anomaly in the Veneziano limit ($N_F/N_C ll 1$).
We describe a hybrid framework for electroweak symmetry breaking (EWSB), in which the Higgs mechanism is combined with a Nambu-Jona-Lasinio mechanism. The model introduces an unconstrained scalar (i.e., acts as fundamental but not the SM field) and a strongly coupled doublet of heavy quarks with a mass around 500 GeV, which forms a condensate at a compositeness scale Lambda ~ O(1) TeV. This setup is matched at that scale to a tightly constrained hybrid two Higgs doublet model, where both the composite and unconstrained scalars participate in EWSB. This allows us to get a good candidate for the recently observed 125 GeV scalar which has properties very similar to the Standard Model Higgs. The heavier (mostly composite) CP-even scalar has a mass around 500 GeV, while the pseudoscalar and the charged Higgs particles have masses in the range 200 -300 GeV.
We study four-dimensional gauge theories with arbitrary simple gauge group with $1$-form global center symmetry and $0$-form parity or discrete chiral symmetry. We canonically quantize on $mathbb{T}^3$, in a fixed background field gauging the $1$-form symmetry. We show that the mixed $0$-form/$1$-form t Hooft anomaly results in a central extension of the global-symmetry operator algebra. We determine this algebra in each case and show that the anomaly implies degeneracies in the spectrum of the Hamiltonian at any finite-size torus. We discuss the consistency of these constraints with both older and recent semiclassical calculations in $SU(N)$ theories, with or without adjoint fermions, as well as with their conjectured infrared phases.
The parameter space of the phenomenological MSSM (pMSSM) is explored by means of Markov Chain Monte Charlo (MCMC) methods, taking into account the latest LHC results on the Higgs signal at 125 GeV in addition to relevant low-energy observables and LEP constraints. We use a Bayesian approach to derive posterior densities for the parameters and observables of interests. We find in particular that the Higgs measurements have a significant impact on the parameters mu and tan beta due to radiative corrections to the bottom Yukawa coupling. We show moreover the impact of the most recent dark matter measurements on the probability distributions, and we discuss prospects for the next run of the LHC at 13-14 TeV.
The ATLAS and CMS experiments have recently announced the discovery of a Higgs-like resonance with mass close to 125 GeV. Overall, the data is consistent with a Standard Model (SM)-like Higgs boson. Such a particle may arise in the minimal supersymmetric extension of the SM with average stop masses of the order of the TeV scale and a sizable stop mixing parameter. In this article we discuss properties of the SM-like Higgs production and decay rates induced by the possible presence of light staus and light stops. Light staus can affect the decay rate of the Higgs into di-photons and, in the case of sizable left-right mixing, induce an enhancement in this production channel up to $sim$ 50% of the Standard Model rate. Light stops may induce sizable modifications of the Higgs gluon fusion production rate and correlated modifications to the Higgs diphoton decay. Departures from SM values of the bottom-quark and tau-lepton couplings to the Higgs can be obtained due to Higgs mixing effects triggered by light third generation scalar superpartners. We describe the phenomenological implications of light staus on searches for light stops and non-standard Higgs bosons. Finally, we discuss the current status of the search for light staus produced in association with sneutrinos, in final states containing a $W$ gauge boson and a pair of $tau$s.
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