Electroweak Model Research Articles

Thirring's low-energy theorem and its generalizations in the electroweak Standard Model

The radiative corrections to Compton scattering vanish in the low-energy limit in all orders of perturbation theory. This theorem, which is well-known for Abelian gauge theories, is proved in the electroweak Standard Model. Moreover, analogous theorems are derived for photon scattering off other charged particles, in particular W bosons. Since the theorems follow from gauge invariance and on-shell renormalization, their derivation is most conveniently performed in the framework of the background-field method.

Fermion masses in a strong Yukawa coupling model

For strong enough Yukawa coupling the electroweak standard model fermion finds it energetically advantageous to transform itself into a bound state in the hedgehog background of the Higgs field in the semiclassical approximation. By considering that the bound states give the masses for the lepton and quark, it is found that all fermion masses can be described by the strongly Yukawa coupling constants which tend to a unitary constant.

SU(5) monopoles and the dual standard model

We find the spectrum of magnetic monopoles produced in the symmetry breaking SU(5) to [SU(3)\times SU(2)\times U(1)']/Z_6 by constructing classical bound states of the fundamental monopoles. The spectrum of monopoles is found to correspond to the spectrum of one family of standard model fermions and hence, is a starting point for constructing the dual standard model. At this level, however, there is an extra monopole state - the ``diquark'' monopole - with no corresponding standard model fermion. If the SU(3) factor now breaks down to Z_3, the monopoles with non-trivial SU(3) charge get confined by strings in SU(3) singlets. Another outcome of this symmetry breaking is that the diquark monopole becomes unstable (metastable) to fragmentation into fundamental monopoles and the one-one correspondence with the standard model fermions is restored. We discuss the fate of the monopoles if the [SU(2)\times U(1)']/Z_2 factor breaks down to U(1)_Q by a Higgs mechanism as in the electroweak model. Here we find that monopoles that are misaligned with the vacuum get connected by strings even though the electroweak symmetry breaking does not admit topological strings. We discuss the lowest order quantum corrections to the mass spectrum of monopoles.

Radiative corrections toZZ→ZZin the electroweak standard model

The cross section for ZZ{r_arrow}ZZ with arbitrarily polarized Z bosons is calculated within the electroweak standard model including the complete O({alpha}) corrections. We show the numerical importance of the radiative corrections and elaborate its characteristic features. The treatment of the Higgs-boson resonance is discussed in different schemes including the S-matrix-motivated pole scheme and the background-field method. The numerical accuracy of the equivalence theorem is investigated by comparing the cross sections for purely longitudinal Z bosons obtained from the equivalence theorem and from the complete calculation. In this context the full O({alpha}) corrections are also confronted with the enhanced corrections of O({alpha}M{sub H}{sup 2}/s{sub W}{sup 2}M{sub W}{sup 2}), which were frequently used in the literature. {copyright} {ital 1997} {ital The American Physical Society}

Langmuir Wave Generation through a Neutrino Beam Instability

A standard version of a kinetic instability for the generation of Langmuir waves by a beam of electrons is adapted to describe the analogous instability due to a beam of neutrinos. The interaction between a Langmuir wave and a neutrino is treated in the one-loop approximation to lowest order in an expansion in $1/M_W^2$ in the standard electroweak model. It is shown that this kinetic instability is far too weak to occur in a suggested application to the reheating of the plasma behind a stalled shock in a type II supernova (SN). This theory is also used to test the validity of a previous analysis of a reactive neutrino beam instability and various shortcomings of this theory are noted. In particular, it is noted that relativistic plasma effects have a significant effect on the calculated growth rates, and that any theoretical description of neutrino-plasma interactions must be based directly on the electroweak theory. The basic scalings discussed in this paper suggest that a more complete investigation of neutrino-plasma processes should be undertaken to look for an efficient process capable of driving the stalled shock of a type II SN.

HardmtCorrections as a Probe of the Symmetry Breaking Sector

Nondecoupling effects related to a large ${m}_{t}$ affecting nonoblique radiative corrections in vertices $(Z\overline{b}b)$ and boxes ( $B$- $\overline{B}$ mixing and ${\ensuremath{\epsilon}}_{K}$) are sensitive to the mechanism of spontaneous symmetry breaking. In the framework of the effective chiral electroweak standard model there is only one $O({p}^{4})$ operator which modifies the longitudinal part of the ${W}^{+}$ boson without touching the oblique corrections. This operator affects the $Z\overline{b}b$ vertex, the $B$- $\overline{B}$ mixing, and the $\mathrm{CP}$-violating parameter ${\ensuremath{\epsilon}}_{K}$, generating interesting correlations among the hard ${m}_{t}^{4}\mathrm{ln}{m}_{t}^{2}$ corrections to these observables.

Calculation of two-loop top-quark and Higgs-boson corrections in the electroweak Standard Model

A combination of algebraical and numerical techniques for calculating two-loop top-quark and Higgs-boson corrections to electroweak precision observables like Δr or the p-parameter is presented. The renormalization is performed within the on-shell scheme. The results of the calculations are valid for arbitrary values of m t, M H and of the gauge-boson masses. An example is treated where the full result is compared to the result obtained via an expansion up to next-to-leading order in m t. As an application, results for the Higgs-mass dependent top-contributions to Δr are given.

Can long range anomalous neutrino interactions account for the measured tritium beta decay spectrum?

Recent experimental searches for neutrino mass in tritium beta decay yield a negative value for the neutrino ( mass) 2. If this effect is genuine, then it is hard to understand it using conventional particle physics ideas as embodied in (say) the standard electroweak model. We discuss the possibility that there is a hidden anomalous long range interaction of neutrinos that is responsible for this effect and study the phenomenological consistency as well as tests of this idea. We also discuss how such interactions may arise in extensions of the standard model.

A new contribution to the flavour-changing lepton-photon vertex

We show that the correct perturbation theory for mixed fermion states leads to nonvanishing contributions of the dimension-four vertex operators for flavour-changing transitions. Their contributions to the amplitude are of the same order of magnitude as the dimension- five vertex operators. Considerations are valid irrespective of the electroweak model. A complete and correct evaluation of the neutrino lifetime for particular electroweak models could be of greate importance in the theoretical cosmology and astrophysics.

Topological solitons in the Weinberg-Salam theory

We establish the existence of multivortices arising in the self-dual phase of the standard model of Weinberg-Salam, and its two-Higgs-doublet extension, in the unified theory of electromagnetic and weak interactions. For the standard model, we prove the existence of solutions in a periodic lattice domain and study the effect of the gravitational coupling. We find an important connection of these self-dual vortices and the cosmological constant problem: the cosmological constant Λ may be written explictly in terms of several fundamental parameters in electroweak theory and the two-dimensional surface on which the vortices reside becomes noncomplete. We then prove that such a gravitational background leads to the existence of finite-energy vortices on the full plane with a non-Abelian nature. For the extended electroweak model with two Higgs doublets, we solve the self-dual equations completely. For the periodic case, we prove an existence and uniqueness theorem under a necessary and sufficient condition. This result reveals some exact restrictions to the vortex charges. For the problem on the entire plane, we obtain existence, uniqueness, sharp decay estimates, and quantized fluxes.

Meson-lepton interaction in the spinor strong interaction theory

The recently developed spinor strong interaction theory, which successfully accounts for linear confinement and classification of mesons as well as unmixed meson spectra, is applied to semileptonic decays of the π,K, D, andB mesons. These mesons themselves generate massM w for the mediating gauge boson; no Higgs boson is needed. The theory is also applied to purely leptonic interactions. It is shown that the results of the standard electroweak model can be taken over with the Higgs boson replaced by the above mesons. The Cabbibo angle ϑC is given by tan ϑC=(pion mass)/(kaon mass), in agreement with data. The pion decay constantF is essentially a ratio between two large constants introduced to make certain infinite integrals finite.M w is also related to a similar cutoff constant.

Baryogenesis and damping in nonminimal electroweak models

We calculate the baryon asymmetry of the Universe in the standard model of the electroweak theory with CP violation appropriate for simple extensions of the Higgs sector. The propagation of quarks of masses up to about 5 GeV are considered, taking into account the effect of damping rate. We find that the contribution of the b quark can still account for the observed baryon asymmetry to within the theoretical uncertainties of such models.

New limits on the mass of neutral Higgses in general models3

In general electroweak models with weakly coupled (and otherwise arbitrary) Higgs sector there always exists in the spectrum a scalar state with mass controlled by the electroweak scale. A new and simple recipe to compute an analytical tree-level upper bound on the mass of this light scalar is given. We compare this new bound with similar ones existing in the literature and show how to extract extra information on heavier neutral scalars in the spectrum from the interplay of independent bounds. Production of these states at future colliders is addressed and the implications for the decoupling limit in which only one Higgs is expected to remain light are discussed.

An extension of the electroweak model with decoupling at low energy

We present a renormalizable model of electroweak interactions containing an extra SU(2)′ L ⊗ SU(2)′ R symmetry. The masses of the corresponding gauge bosons and of the associated Higgs particles can be made heavy by tuning a convenient vacuum expectation value. According to the way in which the heavy mass limit is taken we obtain a previously considered non-linear model (degenerate BESS) which, in this limit, decouples giving rise to the Higgsless Standard Model (SM). Otherwise we can get a model which decouples giving the full SM. In this paper we argue that in the second limit the decoupling holds true also at the level of radiative corrections. Therefore the model discussed here is not distinguishable from the SM at low energy. Of course the two models differ deeply at higher energies.

Topological incarnations of electroweak defects

A realistic extension of the electroweak model is proposed in which electroweak magnetic monopoles and Z-strings appear as topological defects. The ensuing cosmology is discussed and it is pointed out that electroweak strings and, more generally, light superconducting strings may yield a significant flux of antiprotons in our galaxy.

SUSY models with R-parity violation, longlived charged slepton and quasistable supermatter

We construct two SUSY SU(3) ⊗ SU(2) L ⊗ U(1) electroweak models with superweak R-parity violation. The scale of R-parity violation in one of the models is determined by the Majorana mass of neutrino and it is very small that leads to the existence of longlived ( T ≥ O(10 −4) sec) lightest superparticle. If lightest superparticle is righthanded charged slepton that can be realized within gaugino dominated scenario then the phenomenology of such model differs in a drastic way from the standard SUSY phenomenology, in particular, longlived charged sleptons can form bound states with ordinary matter - quasistable supermatter (SUSY analogs of mu-atoms and muonium). We discuss possible manifestations of the existence of such longlived charged particle at LEP2, TEVATRON and LHC. We also construct SU(3) ⊗ SU(2) L ⊗ SU(2) R ⊗ U(1) model with Majorana mass and superweak R-parity violation

Neutron electric dipole moment in a supersymmetric model with singlet quarks

The neutron electric dipole moment is investigated in a supersymmetric electroweak model admitting SU(2) W singlet and Q = − 1 3 , say D-type, quarks. Significant CP violating phases appear in the coupling between the singlet D-type quarks and the ordinary d-type quarks. Then, through the d- D mixing effects on the squark mass terms the gluino one-loop diagrams provide naturally the contributions ∼ 10 −26 e cm comparable to the current experimental bound on the neutron electric dipole moment. The CP violation in the d- D coupling would also be relevant for the electroweak baryogenesis.

Standard Solar Neutrinos

view Abstract Citations (66) References (102) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Standard Solar Neutrinos Dar, Arnon ; Shaviv, Giora Abstract We describe in detail an improved standard solar model that has been used to calculate the fluxes of standard solar neutrinos. It includes pre-main-sequence evolution, element diffusion, partial ionization effects, and all the possible nuclear reactions between the main elements. It uses updated values for the initial solar element abundances, the solar age, the solar luminosity, the nuclear reaction rates, and the radiative opacities. Neither nuclear equilibrium nor complete ionization are assumed. The calculated solar neutrino fluxes are compared with published results from the four solar neutrino experiments. The calculated 8B solar neutrino flux is consistent, within the theoretical and experimental uncertainties, with the solar neutrino observations at Homestake and Kamiokande. The observations suggest that the 7Be solar neutrino flux is much smaller than that predicted. However, conclusive evidence for the suppression of the 7Be solar neutrino flux will require experiments like BOREXINO and HELLAZ. If the Be solar neutrino flux is suppressed, it still can be due either to standard physics reasons or neutrino properties beyond the standard electroweak model. Only future neutrino experiments, such as SNO, Super-kamiokande, BOREXINO, and HELLAZ, will be able to show that the solar neutrino problem is a consequence of neutrino properties beyond the standard electroweak model. Publication: The Astrophysical Journal Pub Date: September 1996 DOI: 10.1086/177748 Bibcode: 1996ApJ...468..933D Keywords: ELEMENTARY PARTICLES; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; ABUNDANCES; SUN: INTERIOR full text sources ADS |

The phase transition of the two Higgs extension of the standard model

We present the analysis of the phase transition for the two Higgs electroweak model. We have found that for a wide range of parameters the universe first tunnels to a new intermediate phase. This feature not only is very important by itself, but also provides the essential requirements for producing baryon asymmetry with only small explicit CP-violating terms in the two Higgs tree Lagrangian.

Exotic heavy quark contribution in hadron-hadron production of W+W- pairs.

In this paper we study the contribution of new possible heavy quarks to the process $\mathrm{h}\mathrm{a}\mathrm{d}\mathrm{r}\mathrm{o}\mathrm{n}\ensuremath{-}\mathrm{h}\mathrm{a}\mathrm{d}\mathrm{r}\mathrm{o}\mathrm{n}\ensuremath{\rightarrow}{W}^{+}{W}^{\ensuremath{-}}X$. We consider new exotic quarks as proposed in three extended electroweak models: the vector singlet model (VSM), the vector doublet model (VDM), and the fermion---mirror-fermion model (FMFM). We discuss the high energy unitarity behavior for the elementary process and their implications. We present the predictions of the exotic quark contribution for the CERN Large Hadron Collider (LHC). We present some distributions that can separate the standard model contribution from the new exotic quark contribution.