The Higgs boson mass from precision electroweak data

We present a new global fit to precision electroweak data, including new low- and high-energy data and analyzing the radiative corrections arising from the minimal symmetry breaking sectors of the Standard Model (SM) and its supersymmetric extension (MSSM). It is shown that present data favor a Higgs mass of ${cal O}(M_Z)$: $$M_{H}=76 {+ 152 ?op -50}{? GeV}.$$ We confront our analysis with (meta) stability and perturbative bounds on the SM Higgs mass, and the theoretical upper bound on the MSSM Higgs mass. Present data do not discriminate significantly between the SM and MSSM Higgs mass ranges. We comment in passing on the sensitivity of the Higgs mass determination to the values of $←pha (M_Z)$ and ${←pha_s} (M_Z)$.     

Strange particle production by antineutrinos

Cross sections are presented for antineutrino production of Λ, Σ⁰ and K⁰ in strangeness changing reactions. Associated production reactions (ΔS = 0) have been observed in the charged and the neutral current channels. For the elastic reaction $\text{v}\text{p}\text{→ μ}{}^{\mathrm{+}}\text{Λ}$, estimates have been made of the axial transition form factor.     

A new approach to the charged current induced weak one-pion production

The weak one-pion production mechanism is analyzed in terms of resonant and non-resonant contributions coming from the πN invariant-mass region extended from threshold to 1.6 GeV/c². Together with the P₃₃, contributing to the $\text{I =}\text{3}\text{2}$ amplitude, the first $\text{I =}\text{1}\text{2}$ resonances (S₁₁, P₁₁, D₁₃) are also added to the background treated in the Born approximation. Form factors are explicitly extracted from PCAC and from existing fits to electroproduction data, so that the “free” parameters are essentially reduced to the axial masses of the resonances. In the calculation of the cross sections the resonance-background interference is explicitly worked out and its important rôle is stressed. The emerging picture is compared with the available data, which are in this way extensively reviewed, at low, intermediate and high energy. Good agreement is found, and in particular the experimentally observed increasing $\text{I =}\text{1}\text{2}$ contribution is justified by the model in terms of an increasing rôle of the 1.4 ? M_Nπ ? 1.6 GeV/c² invariant-mass region.     

Spatial harmonics modelling of planar periodic segmented waveguides

A theoretical approach based on Bloch theorem and spatial harmonics has been used to investigate the propagation characteristics in planar periodic segmented waveguides. This analytical method allows to evaluate the field distribution, the effective index and the propagation losses of these structures, taking into account both the propagating and the counterpropagating field components, thus evidencing all the phenomena which can take place in: Bragg reflections, leaky waves, etc. Results for TE fields are presented and compared with those obtained using a paraxial 2D FD-BPM method and a Padé based one, showing that no more than (1, 1) order approximants are needed to provide good estimates of the device characteristics.     

Structure of the hadronic neutral current and parameters of the standard model from an analysis of the neutrino-induced deep-inelastic scattering

An updated and refined analysis of the structure of the hadronic neutral current in the neutrino-induced deep-inelastic scattering is reported. Starting from a careful treatment of the most recent neutrino charged current data, a reparametrization of the nucleon structure functions is performed including all effects such as QCD evolution, longitudinal structure function, quark mixing, slow rescaling, radiative corrections, and so on. The errors induced by the theoretical approach on the final estimate are conveniently introduced together with their correlations. Starting from all available experimental data concerning both isoscalar and non-isoscalar targer (43 independent experimental results are included in the analysis), through an analytic procedure the four squared chiral couplings are derived: the modelindependent analysis leads to $$\begin{gathered} u_L^2 = 0.1197 \pm 0.0116( \pm 0.0008), \hfill \\ d_L^2 = 0.1785 \pm 0.0119( \pm 0.0035), \hfill \\ u_R^2 = 0.0257 \pm 0.0081( \pm 0.0014), \hfill \\ d_R^2 = 0.0052 \pm 0.0078( \pm 0.0030), \hfill \\ \end{gathered} $$ where the first error comes from the experimental errors affecting the different measurements (with quadratic addition of statistical and systematic errors) and the second one is the theoretical error induced by the uncertainties in the parametrization. A comparison with the standard model is then performed. If ρ=1 is 0.0029 (±0.0024) is obtained for fixedc-quark mass. If the assumption ρ=1 is relaxed, the simultaneous estimate of both parameters leads to sin² θ _W =0.2346±0.0105(±0.0079) and ρ=1.0036±0.0099 (±0.0064). A comparison with the case in which radiative corrections are not included is also considered. Furthermore, constraints on the masses of the charm and top are derived. By using the slow rescaling to describe the threshold effect induced bym _c within the minimal standard model,m _c =1.54±0.33, is obtained. In an analogous way, starting from the effects induced by them _t -dependent terms in the radiative corrections, the upper limitm _t <267 (291) GeV (with and without the inclusion of the uncertainties due to the parametrization) at 90% C.L. is found.