A supersymmetric extension of the Weinberg-Salam model

By use of Slavnov's procedure, a supersymmetric extension of the Weinberg-Salam model of lepton interactions is obtained. At low energies (E ? m_W), that model is approached very closely. In addition, we get four heavy leptons (m?m_W) and a number of heavy scalars, plus a normally unobservable new neutrino.     

Associated production of heavy Higgs boson with top quarks

Associated production of a heavy Higgs boson (m_H > 100 GeV) with top quarks at Juratron energies is studied. It is natural to differentiate between the “light” (2m_t < m_H < 2m_W) and “heavy” (m_H > 2m_W) Higgs search. It is assumed that the mass value of the top quarks is in the interval m_t ≈ 30–80 GeV. m_W is the W-boson mass. If m_H < 2m_W a dangerous background is given by the QCD production of four top quarks. We have calculated the cross sections for both the Higgs production and the background reaction. The disappointing result found is that the background is overwhelmingly large. However the Higgs search in this mass region is not hopeless. The associated production of the Higgs boson with a W-boson may have a clear experimental signature, its background given by the reaction $\text{p}\text{+}\text{p}\text{→}\text{W}\text{+}\text{t}\text{+}\text{t}$ might be suppressed. The difficulty with this mechanism is that the rate is rather low. If m_H > 2m_W the background is different and its contribution is expected to be small. The associated production of a Higgs boson with a pair of top quarks might be a useful method in the Higgs search in this case.     

Physical null zones and radiation representation

General conditions for reconstructing physical null radiation zones in single photon tree amplitudes are given. The systematic analysis has been carried out using invariant quantities. For arbitrary values of masses and charges these zones are always smaller than in the massless and equal charges case. As an application the radiative W boson decay into heavy quarks is studied. This process turns out be a rather sensitive test of the current quark masses m_q(M_W²), as well as of the $\text{q}$qW, q$\text{q}$γ and W⁺W^?γ vertices. This is to the presence of a null line in the photon phase space with a location which strongly depends on m_q. A recently proposed radiation representation for single photon tree amplitudes is analyzed. Explicit examples are given for a number of cases including fermion and vector boson lines.     

Role of heavy fermions and heavy Higgs scalars in the electroweak correction to the MW − MZ relation

The role of heavy fermions and heavy Higgs-scalars in the M_W ? M_Z relation resulting from the one-loop-corrected μ decay width Γ⁽¹⁾ and its experimental data Γ^exp is studied in the framework of the standard electroweak theory. Exact and approximate formulae are both given for these heavy particle effects. The quadratic dependence of Γ⁽¹⁾ on large fermion mass m_heavy gives a positive contribution to the calculation of M_W from Γ⁽¹⁾ = Γ^exp for a given M_Z, and cancels the light fermion contributions of the form ～ αln(m_light/M_W) at the value of m_heavy ～ 200 GeV. On the other hand, the Higgs mass dependence of the calculation is, at best, logarithmic, and does not produce visible effects. Applications for deriving constraints for the top-quark mass (or heavier fermion mass) are discussed, and a concrete example is given of the relation between experimental uncertainties in measurements of M_W,Z and the corresponding allowed region for m_t.     

Distribution of electromagnetic transition amplitudes

In this paper the distribution of electromagnetic transition amplitudes 〈W′∥O∥W〉 is described in terms of fluctuations about a gaussian secular variation (as a function of initial and final energies) according to the Porter-Thomas assumption. Explicit formulas are derived both for the case (i) that∑ _w ′¦〈W′∥O∥W〉¦² is replaced by its local average and (ii) that∑ _W ′¦〈W′∥O∥W〉¦² is treated as a stochastic variable showing a χ _d ² -distribution. The resulting distribution function appears to possess a monomial tail. Comparisons with shell-model results are made.     

Search for the right-handed boson W R and heavy neutrino

The SU _c (3) ? SU _L(2) ? SU _R(2) ? U(1) left-right symmetric gauge model has been briefly reviewed. The possibility of the detection of signals from the production of the W _R boson in pp-collisions at the Large Hadron Collider has been discussed. Constraints on the masses of the W _R-boson and heavy neutrino obtained by analyzing the recent experimental data from the Compact Muon Solenoid detector with the total energy of collisions E _tot = 8 TeV have been reviewed.     

Distinctive signatures for new particles in e+ e− annihilation and z-decay

New particles and new interactions reveal themselves most clearly where standard model contributions are negligibly small. A prominent example with this advantage is the one-lepton inclusive longitudinal structure function (W_L) in e⁺ e^? annihilation and Z-decay. We discuss general features of this approach and present structure functions for two types of new particles (heavy charged fermion, e.g. new sequential lepton or top quark; and supersymmetric scalar lepton, i.e. slepton), along with the (small) standard model “background”. The x-dependence of W_L provides a distinct signature of the identity of the new particle. Extensions of this approach are discussed.     

How to compare the SU(5) value of sin2θw with experiments?

We establish the relation between κsin²θ_w to be found from neutral-current experiments and sin²θ_w(Q) for Q=M_W predicted by grand unified theories. We then calculate sin²θ_W(M_W) in the minimal SU(5) model taking the M_W as well as M_x threshold effects into account. We find that these two threshold effects on sin²θ_W(M_W) cancel with each other and sin²θ_W(M_W)=0.211± 0.005.     

Enhancement of CP-violating phenomena at tree level due to heavy quark propagator singularities

We discuss new interesting CP-violating phenomena in scattering processes resulting from heavy quarks with masses larger than the W-mass (m _q >M _W ). Such a situation is connected with a singularity in the heavy quark propagator which, properly regularized, gives rise to measurable CP-odd effects. The observability of these CP-odd signals in the most representative Kobayashi-Maskawa (KM) models (like fourth generation model, left-right symmetric model and two Higgs doublet model) is investigated. We find that the necessary conditions for measurable CP-asymmetries imply the enlargement of the Standard Model (SM) in the generations of quarks. In addition a significant mixing between the fourth and the other generations is required.     

Heavy neutrino mixing and single production at linear collider

We study the single production of heavy neutrinos via the processes e⁻e⁺ → νN and e⁻γ → W⁻N at future linear colliders. As a base of our considerations we take a wide class of models, both with vanishing and non-vanishing left-handed Majorana neutrino mass matrix m_L. We perform a model independent analyses of the existing experimental data and find connections between the characteristic of heavy neutrinos (masses, mixings, CP eigenvalues) and the m_L parameters. We show that with the present experimental constraints heavy neutrino masses almost up to the collision energy can be tested in the future experiments.     

Universal behavior in the scattering of heavy, weakly interacting dark matter on nuclear targets

Particles that are heavy compared to the electroweak scale (M?mW), and that are charged under electroweak SU(2) gauge interactions display universal properties such as a characteristic fine structure in the mass spectrum induced by electroweak symmetry breaking, and an approximately universal cross section for scattering on nuclear targets. The heavy particle effective theory framework is developed to compute these properties. As illustration, the spin independent cross section for low-velocity scattering on a nucleon is evaluated in the limit M?mW, including complete leading-order matching onto quark and gluon operators, renormalization analysis, and systematic treatment of perturbative and hadronic-input uncertainties.     

Second upper-bound on the three-phonon resistivity in Ge

Contributions of different allowed three-phonon resistances in Ge have been presented in the second upper-bound W^>₁. It is found that the deviation of W^>₁ from W^>₀, the first upper-bound, is markable. As a matter of fact W^>₁ is shown to be less than W^>₀ by about 14% at 100°K and about 5% at 300°K.     

Non-leptonic weak decay rate of explicitly flavored heavy mesons

It is argued quantitatively that a large difference between the D⁰ and D⁺ lifetimes is mainly due to non-perturbative long-distance effects. The total non-leptonic weak decay rates are related to the soft limit of short-distance processes. Scaling laws for the decay rates of heavy mesons with respect to mass are inferred from the QCD analysis of the soft limit of fragmentation. It is found that the decay rates are not determined by the disconnected spectator diagrams alone even in the limit of the heavy quark mass M going to infinity (< M_W), since the leading term after the QCD correction scales like M⁵ exp √clog M. Some numerical discussion is made for the decay of B mesons and T mesons.     

Response times for a storage electrooptic effect in liquid crystals

By the optical storage effect in large pitch cholesterics, a relation of the type t_W (U_W-U_th)^-2 is established between the writing time t_W and the writing voltage U_W, revealing the existence of a threshold voltage U_th. Interpretations are given for the different erasure times observed at two selected scattering angles.     

Double parton scattering contribution toW+jets

We investigate the double parton scattering production ofW ^±+jets in proton colliders. At high energies an observable signal is expected from double parton collisions when events with small transverse momentumW together with two jets balancing inp _T are selected. Double parton scattering is also a potentially serious background to several rare processes whose signal is aW ⁺+W ^?(→ev+jets) final state. A simplep _T ^W cut seems to be sufficient to separate the genuineW-pair events from the double scattering background.     

Electrochromic colour centres in amorphous tungsten trioxide thin films

Amorphous tungsten trioxide films, investigated by the Raman scattering method, are shown to be composed of a spatial network of tightly bound (WO₆)_n·mH₂O clusters with a large number of terminal oxygen W=O and W-O-W bonds between clusters. The injected electrons in an amorphous tungsten trioxide film are localized in the tungsten 5d orbitals in an axially distorted octahedron, as is shown by ESR analysis. The optical absorption of a coloured amorphous tungsten trioxide film, as has previously been proposed, can be satisfactorily described by an intervalence charge-transfer transition between localized W⁵⁺ and W⁶⁺ states.     

On the role of the higgs mechanism in present electroweak precision tests

Based on the observablesM _W, Γ _l ,s _W ^?2 (M _Z ² ), we evaluate the parameters Δx, Δy and ε at one-loop level within an electroweak massive vector-boson theory, which does not employ the Higgs mechanism. The theoretical results are consistent with the experimental ones on Δx, Δy, ε. The theoretical prediction for Δy coincides with the standard-model one (apart from numerically irrelevant terms which vanish forM _H→∞). Nonrenormalizability only affects Δx and ε, which differ from the standard-model results by the replacement logM _H→log Λ for a heavy Higgs mass,M _H (where Λ denotes an effective UV cut-off).     

Estimation of W0/WT ratio for cloud-to-ground lightnings

The aim of this paper was to obtain the quantitative estimation of the W₀/W_T (initial electric energy/atmospheric parameter of a surrounding medium) ratio for CG lightnings initiated with a stepped leader process. The results of analytical and numerical models show that the W₀/W_T ratio for CG lightnings spans the range of approximately two orders of magnitude 20 ≤ W₀/W_T ≤ 2000. The results also suggest that CG lightnings differ significantly from small-scale discharges in the laboratories: the thundercloud CG lightnings occur at considerably lower initial electric energy, higher atmospheric parameter of the surrounding medium or a combination of both.     

Griffiths phase and the magnetic and transport properties of doped manganites

A phenomenological model is proposed to describe the magnetic and magnetoresistance properties of ferromagnetic manganites. This model is based on the methods used to describe hysteretic systems, takes into account phase separation effects, and assumes the transition of ferromagnetic manganites into the Griffiths phase at above the Curie temperature. This formalism makes it possible to describe the conducting properties of the systems in the temperature range from low temperatures to the Griffiths temperature (T _G). This approach is used to qualitatively explain the experimental laws of the behavior of ferromagnetic manganites using the temperature and field dependences of the electrical resistivity and magnetization, the hysteretic properties, and the magnetoresistive effect (MRE) and to classify manganites in the magnitude of the MRE. The parameter that is responsible for the response of a system to thermal effects is the ratio of the maximum energy barrier separating various states of a system at zero temperature W _A (0) to thermal fluctuation energy W _Cfl at T _G. The W _A (0)/W _Cfl ratio is found to determine the temperature range of the Griffiths phase. The relation between the magnitudes of the MRE and parameter W _A (0)/W _Cfl for a certain system is revealed. The behavior of the magnetization and electrical resistivity of manganites in the Griffiths phase is discussed.