arXiv subjects

Petr Benes

Publications and source records attributed to Petr Benes.

7 recordsLinked to original sources

arXiv2024

Electroweak Monopole-Antimonopole Pair Production at LHC

The monopole production at LHC crucially depends on the monopole production mechanism. We show that, if the monopole production mechanism at LHC is the thermal fluctuation of the Higgs vacuum as the early universe did, it is practically impossible for LHC to produce the monopole, even with the future FCC energy upgrade. This is because the temperature of the p-p fireball is simply too low to produce the monopole. But if the monopole production mechanism is the Drell-Yan and/or Schwinger mechanism, the 14 TeV LHC could produce the monopole in the form of the monopolium of mass around 5,7 TeV even when the monopole mass becomes 11 TeV. Or, it could produce the monopole when the mass is less than 7 TeV. Our result tells that, if the monopole production mechanism at LHC becomes the thermal fluctuation, searching for the remnant monopoles produced in the early universe could be the only way to detect the electroweak monopole. We discuss the physical implications of our result.

hep-ph↗

arXiv2015

Contribution of right-handed neutrinos and standard fermions to W and Z masses

We present expressions of the Pagels--Stokar type for the masses of the W and Z bosons in terms of the quark and lepton self-energies. By introducing a genuine new term in the gauge boson--fermion--anti-fermion vertex we manage to accomplish three main achievements: First, we show that the similar results existing in literature lead, in general, to a non-symmetric gauge boson mass matrix and we fix this flaw. Second, we consider the case of any number of fermion generations with general mixing. Third, we include in our analysis also an arbitrary number of right-handed neutrinos, together with the left-handed and right-handed neutrino Majorana masses (self-energies). On top of that, we give also a correction to the original Pagels--Stokar formula for the pion decay constant in QCD.

hep-ph↗

arXiv2012

Dynamical symmetry breaking in models with strong Yukawa interactions

The primary aim of the thesis is to explore the possibility of spontaneous symmetry breaking by strong Yukawa dynamics. Technically, the symmetry is assumed to be broken by formation of symmetry-breaking parts of both the scalar and the fermion propagators, rather than by the scalar vacuum expectation values. The idea is first introduced on an example of a toy model with the underlying symmetry being an Abelian one and later applied to a realistic model of electroweak interaction. In addition, the thesis also deals with some more general, model-independent issues, applicable not only to the discussed model of strong Yukawa dynamics, but to a wider class of models with dynamical mass generation. First of these issues is the problem of fermion flavor mixing in the presence of fermion self-energies with a general momentum dependence. It is in particular shown how to define the Cabibbo-Kobayashi-Maskawa (CKM) matrix in such models and argued that it can come out in principle non-unitary. Second issue is the problem of calculating the gauge boson masses when the symmetry is broken by fermion self-energies. On top of deriving the formula for the gauge boson mass matrix we also find corrections to the related Pagels-Stokar formula.

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arXiv2011

Masses by gauge flavor dynamics

We gauge the experimentally observed flavor (family) index of chiral lepton and quark fields and argue that the resulting non-vectorial SU(3)_F dynamics completely self-breaks. This breakdown generates fermion masses, which in turn trigger electroweak symmetry breaking (EWSB). Suggested asymptotically free dynamics with an assumed non-perturbative infrared fixed point has just one free parameter and is therefore either right or plainly wrong. Weak point of field theories strongly coupled in the infrared, unfortunately, is that there is no reliable way of computing their spectrum. Because of its rigidity the model provides, however, rather firm theoretically safe experimental predictions without knowing the spectrum: First, anomaly freedom fixes the neutrino sector which contains almost sterile neutrino states. Second, global symmetries of the model, spontaneously broken by fermion masses imply the existence of a fixed pattern of (pseudo-)axions and (pseudo-)majorons. It is gratifying that the predicted both sterile neutrinos and the pseudo-Nambu--Goldstone bosons are the viable candidates for dark matter.

hep-ph↗

arXiv2010

Fermion flavor mixing in models with dynamical mass generation

We present a model-independent method of dealing with fermion flavor mixing in the case when instead of constant, momentum-independent mass matrices one has rather momentum-dependent self-energies. This situation is typical for strongly coupled models of dynamical fermion mass generation. We demonstrate our approach on the example of quark mixing. We show that quark self-energies with a generic momentum dependence lead to an effective Cabibbo-Kobayashi-Maskawa (CKM) matrix, which turns out to be in general non-unitary, in accordance with previous claims of other authors, and to non-trivial flavor changing electromagnetic and neutral currents. We also discuss some conceptual consequences of the momentum-dependent self-energies and show that in such a case the interaction basis and the mass basis are not related by a unitary transformation. In fact, we argue that the latter is merely an effective concept, in a specified sense. While focusing mainly on the fermionic self-energies, we also study the effects of momentum-dependent radiative corrections to the gauge bosons and to the proper vertices. Our approach is based on an application of the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula and for the special case of constant self-energies it gives the same results as the standard approach based on the diagonalization of mass matrices.

hep-ph↗

arXiv2009

Dynamical electroweak symmetry breaking due to strong Yukawa interactions

We present a new mechanism for electroweak symmetry breaking (EWSB) based on a strong Yukawa dynamics. We consider an SU(2)_L x U(1)_Y gauge invariant model endowed with the usual Standard model fermion multiplets and with two massive scalar doublets. We show that, unlike in the Standard model, EWSB is possible even with vanishing vacuum expectation values of the scalars. Such EWSB is achieved dynamically by means of the (presumably strong) Yukawa couplings and manifests itself by the emergence of fermion and gauge boson masses and scalar mass-splittings, which are expressed in a closed form in terms of the fermion and scalar proper self-energies. The `would-be' Nambu--Goldstone bosons are shown to be composites of both the fermions and the scalars. We demonstrate that the simplest version of the model is compatible with basic experimental constraints.

hep-ph↗

arXiv2007

Dynamical breakdown of Abelian gauge chiral symmetry by strong Yukawa interactions

We consider a model with anomaly-free Abelian gauge axial-vector symmetry, which is intended to mimic the standard electroweak gauge chiral SU(2)_L x U(1)_Y theory. Within this model we demonstrate: (1) Strong Yukawa interactions between massless fermion fields and a massive scalar field carrying the axial charge generate dynamically the fermion and boson proper self-energies, which are ultraviolet-finite and chirally noninvariant. (2) Solutions of the underlying Schwinger-Dyson equations found numerically exhibit a huge amplification of the fermion mass ratios as a response to mild changes of the ratios of the Yukawa couplings. (3) The `would-be' Nambu-Goldstone boson is a composite of both the fermion and scalar fields, and it gives rise to the mass of the axial-vector gauge boson. (4) Spontaneous breakdown of the gauge symmetry further manifests by mass splitting of the complex scalar and by new symmetry-breaking vertices, generated at one loop. In particular, we work out in detail the cubic vertex of the Abelian gauge boson.

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