Ultraviolet Complete Electroweak Model

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Presentation transcript:

Ultraviolet Complete Electroweak Model J. W. Moffat Perimeter Institute and University of Waterloo 11/19/2018

1. Introduction The problems of the Higgs particle are well known. They include a possible triviality (or non-interacting scalar field) problem related to the occurrence of a Landau pole for scalar fields, the existence of the hierarchy problem that causes the Higgs mass to be unstable and the cosmological constant problem arising from the predicted vacuum energy density being many orders of magnitude greater than the expected observational value. Apart from these theoretical problems, a Higgs particle has not been detected experimentally. A lower bound on the Higgs mass: mH > 114.4 GeV has been established by direct searches at the LEP accelerator. The EW precision data are sensitive to mH through quantum corrections and yield the range : mH = 87+35−26 GeV. Fitting all the data, yields the result mH = 116.4+15.6−1.3 GeV, at the 68% confidence level. 11/19/2018

The ATLAS experiment at CERN. (Courtesy CERN) Copyright © 2006 Interactions.org 11/19/2018

11/19/2018

DESY and Institut für Experimentalphysik der Universität Hamburg Martin Goebel † DESY and Institut für Experimentalphysik der Universität Hamburg 11/19/2018

If 2/fb data at 8 TeV is collected, and expected and planned analyses are implemented, then the median exclusion region covers a range of Higgs boson masses from 114 GeV to well over 500 GeV. ATLAS collaboration. 11/19/2018

The question to be considered is: can we construct a physically consistent EW model containing only the observed particles, namely, 12 quarks and leptons, the charged W boson, the neutral Z boson and the massless photon and gluon? Without the Higgs particle such a model is not renormalizable and the tree graph calculation of WL WL → WL WL longitudinally polarized scattering violates unitarity above an energy of 1-2 TeV. We must construct an EW model that avoids the need for it to be renormalizable and does not violate unitarity. In the following, we will explore an EW model which is rendered ultraviolet (UV) finite by allowing the coupling constants g and g′ associated with the SU(2)L and U(1)Y Feynman vertices, respectively, to possess a running energy dependence. This energy dependence is described by an entire function , which is analytic (holomorphic) in the finite complex p2 plane, and ΛW > 1-2 TeV is an energy scale associated with the EW interactions. This analytic property of the entire function guarantees that no unphysical poles occur in the particle spectrum, preserving the unitarity of the scattering amplitudes. 11/19/2018

Postulate 1: Except for the photon, there is no phase in the universe when the fermion and boson particles have zero mass. Postulate 2: The EW group SUL(2) X UY(1) is not symmetric i.e. it is broken dynamically at all times. Postulate 3: The EW model is based on a finite QFT with nonlocal interactions and there is no Higgs particle associated with a spontaneous symmetry breaking phase in the universe [the EBHGHK mechanism]. 11/19/2018

The EW couplings are chosen so that off the mass-shell thereby ensuring that EW calculations at low-energies agree with experiment. On the other hand, for energies greater than 1 -2 TeV, decreases rapidly enough in Euclidean momentum space guaranteeing the finiteness of radiative loop corrections. A violation of unitarity of scattering amplitudes is avoided for decreasing fast enough as a function of the center-of-mass energy √s for √s > 1 - 2 TeV. In a renormalizable QFT, the coupling constants run with energy as described in the renormalization group flow scenario. The energy dependence of the coupling constants is logarithmic. In our approach, we generalize the standard renormalization group energy dependence, so that the coupling constant energy dependence realizes a QFT finite to all orders of perturbation theory for any Lagrangian based on local quantum fields, including gravity. This allows for a finite quantum gravity theory [arXiv:1008.2482]. 11/19/2018

The model does not contain a fundamental scalar Higgs particle and this removes the hierarchy problem. There is no Landau pole, solving the triviality problem for scalar fields with a quartic self-coupling. Due to the absence of a spontaneous symmetry breaking Higgs mechanism, there is no cosmological constant problem associated with a Higgs particle. 2. Electroweak Model (JWM arXiv:1006.1859) The theory introduced here is based on the local SUC(3) ×SUL(2)×UY (1) Lagrangian that includes leptons and quarks with the color degree of freedom of the strong interaction group SUc(3). For the EW sector 11/19/2018

The quark and lepton fields and the boson fields Waμ and Bμ are local fields that satisfy microcausality. The and are defined by 11/19/2018

To circumvent predicting the existence of a Higgs particle our task is two-fold: 1) We must construct a QFT that is UV complete in perturbation theory and avoids any unitarity violation of scattering amplitudes. 2) We have to invoke a symmetry breaking that is intrinsic to the initial existence of W and Z masses and yields a massless photon. We do not attempt to generate masses of the fermions and bosons as was done by the spontaneous symmetry breaking of the vacuum in the standard Higgs model. To solve the first problem, we invoke a generalized energy dependent coupling at Feynman diagram vertices This allows us to obtain a Poincaré invariant, finite and unitary perturbation theory. 11/19/2018

To solve the second problem of adopting a correct economical breaking of SU(2) XU(1) symmetry, we stipulate that the massive boson Lagrangian takes the form: We do not identify b with the vacuum expectation value in the standard Higgs model. The constant b ~ 246 GeV - the EW energy scale. We do not know the origin of the symmetry breaking mechanism and scale b. To postulate the EW symmetry breaking is no worse than adopting the ad hoc assumption of a scalar field Lagrangian when motivating the Higgs mechanism. 11/19/2018

We circumvent the problem of the lack of renormalizability of our model by damping out divergences with the coupling vertices We We We emphasize that our energy scale parameter ΛW > 1 -2 TeV is not a naive cutoff. The entire function property of the coupling vertices guarantees that the model suffers no violation of unitarity or Poincaré invariance. The relation at the effective tree graph level is satisfied: We do not attempt to explain the origin of the W and Z bosons through e.g., a Higgs field spontaneous symmetry breaking mechanism. Instead, we treat the masses of the W and Z bosons as intrinsic to our EW model by assuming a Proca action. All Feynman loop graphs are finite to all orders. The UEM(1) sector gauge invariance can be satisfied to all orders for the nonlocal interactions . 11/19/2018

3. Unitarity of Scattering Amplitudes The scattering amplitude matrix elements for the process is given in the SM by Higgs In our EW model, the unitarity violation is canceled by the high energy behavior of . 11/19/2018

+ JWM and V. T. Toth, arXiv: 0812.1994 11/19/2018

4. Conclusions By introducing generalized EW coupling constants and , which are energy dependent at Feynman diagram vertices with an energy scale ΛW > 1 TeV, we can obtain a Higgless EW model that is unitary, finite and Poincaré invariant to all orders of perturbation theory, provided that the coupling functions are composed of entire functions of p2 that avoid any unphysical particles that will spoil the unitarity of the scattering amplitudes. All the physical EW fields are local fields that satisfy microcausality, while the interactions are nonlocal. There is no Higgs particle in the particle spectrum and this removes the troublesome aspects of the standard EW model with a spontaneous symmetry breaking. Although the entire function at the Feynman diagram vertices associated with the couplings and is non-local, the vertex operators do not describe propagating particles. Therefore, this nonlocality of the EW interactions does not destroy the physical microscopic causality of our model. The measured masses of the particles, the measured coupling constants e, g and g′ and the energy scale ΛW are the basic constants of the model. The exclusion or detection of the Higgs particle by the Tevatron and the LHC will decide whether a significant revision of the SM is required. 11/19/2018

END 11/19/2018