Structure of the gauge fields inside baryon

We present the results of lattice calculations of the distributions of the gauge fields inside a baryon constructed from three heavy quarks. It turns out that the chromoelectric flux tube has a Y shape. At nonzero temperature, we observe the breaking of the confining string below the deconfining temperature and the disappearance of the string above the critical temperature.     

Rate of anomalous electroweak baryon and lepton number violation at finite temperature

Using Langer's statistical theory of the decay of metastable states we calculate the rate of the anomalous electroweak baryon and lepton number violating processes in the case that the electroweak phase transition is of second order. Our formulas are valid in a temperature range between M_w and the critical temperature T_c. We get a dissipation of the baryon and lepton number of the order of exp(4.6×10⁹).     

Comments on the possibility of electroweak baryon number violation at high temperatures

Anomalous baryon number violation in the standard electroweak theory was first discussed by 't Hooft, who found it to be suppressed by a large factor exp(−8π²/g²) at zero temperature, due to a large energy barrier separating vacua with different baryon number. One might have expected that in the early Universe or in high-energy collisions, this process would become unsuppressed when the energies involved became comparable to the barrier height. We argue here that in both cases processes violating baryon number are likely to remain suppressed by a least the same zero-temperature factor.     

Indications on the mass of the lightest electroweak baryon

In general, an effective low-energy Lagrangian model of composite electroweak symmetry breaking contains soliton solutions that may be identified with technibaryons. We recall how the masses of such states may be related to the coefficients of fourth-order terms in the effective Lagrangian, and review the qualitative success of this approach for baryons in QCD. We then show how the current theoretical and phenomenological constraints on the corresponding fourth-order coefficients in the electroweak theory could be used to estimate qualitative lower and upper bounds on the lightest electroweak baryon mass. We also discuss how the sensitivity of the LHC experiments could enable these bounds to be improved.     

Thermodynamic generation of the baryon asymmetry

A new technique for generating the baryon asymmetry of the universe is discussed. By using the natural CPT non-invariance of the universe during its early history, we discuss how a baryon asymmetry can develop while baryon violating interactions are still in thermal equilibrium with respect to an effective hamiltonian. Furthermore, both the ground state and fundamental interactions in these theories can be CP conserving.     

Uniqueness of the standard electroweak gauge model

It is proved that the standard SU(2) × U(1) electroweak gauge model is unique against any extension if the effective low-energy neutral-current interaction is to be precisely of the form $\text{(4G}{}_{\mathrm{F}}\text{/}\text{2}\text{) (j}{}_{\mathrm{\mu }}{}^{\mathrm{(3)}}\text{?}\text{sin}{}^2\text{θ}{}_{\mathrm{<mtext>W</mtext>}}\text{j}{}_{\mathrm{\mu }}{}^{\mathrm{<mtext>em</mtext>}}\text{)}{}^2$naturally.     

Perturbative gauge invariance: the electroweak theory

The concept of perturbative gauge invariance formulated exclusively by means of asymptotic fields is generalized to massive gauge fields. Applying it to the electroweak theory leads to a complete fixing of couplings of scalar and ghost fields and of the coupling to leptons, in agreement with the standard theory. The W/Z mass ratio is also determined, as well as the chiral character of the fermions. We start directly with massive gauge fields and leptons and, nevertheless, obtain a theory which satisfies perturbative gauge invariance.     

Dark matter and the baryon asymmetry of the universe

We present a mechanism to generate the baryon asymmetry of the Universe which preserves the net baryon number created in the big bang. If dark matter particles carry baryon number Bx, and sigmaxannih相似文献   

Baryon asymmetry of the universe and the electroweak phase transition

The present baryon asymmetry of the universe has finally been determined at the finite temperature electroweak phase transition. The strength of this transition plays a crucial role. The effective action is presented to higher orders, including wave function correction factors and the fullg ⁴, λ² effective potential. An upper bound for the Higgs massm _H～70 GeV is concluded for the reliability of the perturbative approach. The finite temperature electroweak, phase transition is studied on the lattice and the most important results of Monte-Carlo simulations are collected.     

The electroweak standard model in the axial gauge

We derive the Feynman rules of the standard model in the axial gauge. After this we prove that the fields and do not correspond to physical particles. As a consequence, these fields cannot appear as incoming or outgoing lines in Feynman graphs. We then calculate the contribution of these fields in the case of a particular decay mode of the top quark.Received: 28 January 2004, Revised: 12 February 2004, Published online: 8 April 2004     

Chemical potentials and high temperature phase transitions in electroweak theory

The phenomena of electroweak phase transitions in the early universe depend crucially on the inclusion of the charge corresponding to the spontaneously broken symmetry, which is usually taken as classically conserved. This paper is devoted to the study of the electroweak phase transitions at high temperatures and, correspondingly, to the controversy in the literature concerning the question of the inclusion of the weak neutral charge in the standard model, for the investigation of the phase transition ofW-boson condensation and symmetry restoration in the early universe. Several arguments, general and perturbative, are given against the introduction of the weak neutral charge conservation in the nonsymmetric phase. As a consequence of the above, theW-condensation should occur even at low lepton densities and the symmetry restoration critical curve is independent of the lepton density. The use of different gauges such as the renormalizable and the unitary ones is also discussed.

     

General electroweak mixing models and extended gauge theories

General electroweak mixing schemes containing an arbitrary number of weak bosons and agreeing with the predictions of the standard model for neutrino scattering and polarized electron scattering in the low energy approximation are analyzed using the propagator matrix formalism. The mean charged boson mass is bounded while the mean neutral boson mass is unbounded and determined as a function of the mean charged one. Under a special assumption on the electroweak mixing parameters the four fermion interaction agrees with the one of extended gauge theories and the mean boson masses agree with the boson masses of the standard model.     

Flavour mixing of neutrinos and baryon asymmetry of the universe

We investigate baryogenesis in the ν  MSM, which is the Minimal Standard Model (MSM) extended by three right-handed neutrinos with Majorana masses smaller than the weak scale. In this model the baryon asymmetry of the universe (BAU) is generated via flavour oscillation between right-handed neutrinos. We consider the case when BAU is solely originated from the CP violation in the mixing matrix of active neutrinos. We perform analytical and numerical estimations of the yield of BAU, and show how BAU depends on mixing angles and CP violating phases. It is found that the asymmetry in the inverted hierarchy for neutrino masses receives a suppression factor of about 4% comparing with the normal hierarchy case. It is, however, pointed out that, when θ₁₃=0${\theta }_{13}=0$ and θ₂₃=π/4${\theta }_{23}=\pi /4$, baryogenesis in the normal hierarchy becomes ineffective, and hence the inverted hierarchy case becomes significant to account for the present BAU.