Parity violations in electron-nucleon scattering and the SU(2)L ×SU(2)R ×U(1)L+R electroweak symmetry

The SU(2)_L ×SU(2)_R ×U(1)_L+R model of elecroweak interactions is described with the most general gauge couplings g_L, g_Randg_L+R. The case in which neutrino neutral current interactions are identical to the standard SU(2)_L ×U(1)_L+R model is discussed in detail. It is shown that with the weak angle lying in the experimental range sin²θ_w = 0.23 ± 0.015 and 1 < g_L²/g_R² < 3 it is possible to explain the amount of parity violation observed at SLAC and at the same time predict values of the “weak charge” in bismuth to lie in the range admitted by the controversal data from different experiments.     

Models for the weak parity-violating vector meson exchange potential and the circular polarization in n + p → d + γ

We propose three models which lead to a p.v. nucleon-nucleon interaction mediated by charged and neutral vector mesons. Besides the ad hoc hypothesis of octet dominance, we consider two quark models (the Bose quark and colour Fermi quark model), which give a dynamical explanation of the $\text{ΔI =}\text{1}\text{2}$ rule in strangeness changing hyperon decays. They lead to p.v. potentials with different isospin dependence. We also derive the weak NN?_ρ° coupling from a SU(2) × U(1) gauge theory with neutral currents. The circular polarization P_γ of the γ-quanta in the capture of thermal neutrons on protons is calculated for these different models. The Reid hard-core (HC) and soft-core (SC) potentials have been chosen to take into account the strong interaction. Then the naively factorized Cabbibo current-current interaction with charged rho exchange only gives P_γ^HC = ?2.7 × 10^?8 and P_γ^SC = ?2.1 × 10^?8. The strong octet dominance and Bose quark model lead to a vanishing circular polarization |P_γ| ≈ (1–4) × 10^?9. The colour Fermi quark model enhances the circular polarization and gives P_γ ≈ ?5 × 10^?8.     

Perturbation constraint on the Higgs boson mass

It is shown that a systematic perturbation expansion of spontaneously broken gauge theory imposes a constraint on the upper as well as the lower limit of the Higgs boson mass. In the standard SU(2) × U(1) model, the Higgs boson mass is calculated to be between 13 GeV and 500 GeV for the weak mixing angle, θ ≈ 35°.     

η → 3π decay and πη scattering in chiral SU(2) × SU(2) symmetry

The problem of η → 3π decay in chiral SU(2) × SU(2) symmetry is investigated. We argue that the well-known difficulties of the conventional pole model originate from underestimating the role of the η-meson pole graph. This model is shown to be suitable for describing η → 3π decay if the strong ηηππ vertex in the η-pole graph is determined by an SU(2) × SU(2)-invariant interaction. The π^o ? η transition constant g_πη is evaluated from U-spin invariance with the help of a current-mixing model: | g_πη | ≈ 0.05. It turns out that the experimental data on both the decay widths and the energy spectrum can be satisfied by fitting the value of the ηηππ coupling constant as a parameter. As a result, predictions for the s- and p-wave πη scattering lengths are obtained: |a_πη⁰| ≈ 0.2m_π^?1, |a_πη¹| ≈ 0.1m_π^?3.     

Neutronh 11/2 alignments in the triaxial nucleus133La

High spin states have been studied in¹³³La via the¹²²Sn (¹⁵N, 4ny) fusion evaporation reaction. Bands build on low lying h_11/2,g_7/2 and d_5/2 proton states have been identified. At higher spin a h_11/2 neutron alignment is observed. The softness with respect to the triaxial deformation makes the nuclear shape sensitive to the quasiparticle configurations and coexistence between states withy ≈ + 30°,y ≈ ? 30° andy ≦ ? 60° was found. The results have been interpreted using total routhian surface (TRS) model calculations.     

Bare current-quark masses,inelastic reactions and light-cone algebra

Relations connecting the effective bare current-quark masses with asymptotic meson-nucleon and lepton-nucleon scattering are derived by making use of the extended light-cone algebra which includes commutators of pseudoscalar densities. The commutators are relevant to meson-nucleon scattering amplitudes since the pseudoscalar densities act as fields of the (composite) mesons. Assuming pomeron-exchanged Regge behaviour, sufficient analyticity in the meson mass-squared variable is established to obtain finite-mass dispersion and superconvergence relations. Making additionally certain other reasonable assumptions, we are then able to show how these relations yield testable connections among the asymptotic πN and KN total cross sections, the structure functions of the deep inelastic lepton-nucleon scattering (for the scaling variable, ξ →0) and the bare current-quark masses μ_{p, n, λ} that appear essentially as parametrising the breaking of the chiral SU(3) ? SU(3) symmetry. One interesting consequence of our results is at the Llewellyn-Smith inequality on the said structure functions should be experimentally satisfied as a near equality for ξ → 0, if chiral SU(2) ? SU(2) turns out to be a rather good symmetry of nature. Moreover, taking the specific symmetry breaking model of Gell-Mann Oakes and Renner,we find that μ_{p, n} ≈ 35 MeV and μ_λ ≈ 800 MeV.     

Heavy particles and the ϱ parameter in the standard model

A new formalism is presented for the calculation of the contribution δ? to ? = M_w²/M_z²cos²θ_w from heavy particles transforming according to arbitrary representations of SU(2) × U(1). A conjecture for the necessary and sufficient conditions that δ??0 for all values of masses and mixing angles within a particular multiplet is formulated. A number of examples are given (all consistent with the conjecture) and the significance of improved knowledge of ? vis à vis the possible existence of undiscovered heavy particles discussed.     

Gluonium and the 0++ spectrum

We suggest that the σ (broad ππ s-wave states below 1 GeV) and the S¹(0.98) can be interpreted by a mixing between a scalar gluonium and an SU(2) singlet meson with a mixing angle of the order of 14°–19°. The decays of the σ and of the S¹ into a pseudoscalar pair are shown to be dominated by their gluon component. In this way, one expects a universal coupling of the σ and of the S¹ to ππ and KK?. The above scheme is confronted to the ψ-decays and to some scattering data. A radial excitation assignment of the G(1.6) is discussed.     

Cabibbo angle,CP violation and quark masses

By adding suitable discrete flavor symmetries to SU(2)_L ? SU(2)_R ? U(1) left-right symmetric gauge models of weak and electromagnetic interactions, we are able to express all the mixing angles between the quark flavors (u, d, s,c) in terms of the quark masses. This enables us to compute the Cabibbo angle and the CP violating phases using plausible values for the quark masses. The CP violating K ar 2π decay amplitude η_+? (and η₀₀ in the model is then given purely in terms of the parity violating parameter of the model (m_WL⁺/m_WR⁺)².     

Covalent distribution of spin in V2O3:O17 nuclear resonance

O¹⁷ nuclear magnetic resonance has been observed in metallic V₂O₃ with frequency shifts from (?0.10 ± 0.02)-(?0.05 ± 0.02) per cent between 170 and 460°K respectively, a linewidth of 37 ± 5 oe and spin-lattice relaxation rate 1/T₁ ≈ 60 sec^?1 at 296°K. From these quantities, covalency parameters f_s/2S = ? 0.35 × 10^?3 and ?_π/2S ≈ ? 0.07 are calculated. One of the two vanadium 3d electrons in the antiferromagnetic state below the 170°K metal-insulator transition is inferred to lie in a non-magnetic state, while covalent charge transfer augments the spin moment of the other 3d electron to the observed 1.2 μ_B.     

Measurement of the cross sections for reaction π−p → Xo n in the momentum range up to 50 GeVc

The cross sections for the reaction π^?p → X^on, X^o → 2_λ are measured at 32.5 and $\text{48}\text{GeV}\text{c}$ momenta. The cross spectrometer of γ-quanta is used to select events of reaction, whose cross section is only about 0.05 μbarn. The cross section energy dependence has the power form ($\text{≈ p}{}^{\mathrm{?1.11\pm 0.12}}$. conclusion on U(6) symmetry of quark model is made when comparing the differential cross sections at zero angle for the reactions π^?p → X^o and π^?p → η^o. The angle of octet-singlet mixing for pseudo-scalar mesons β = ?(20.6 ± 2.2)° is defined.     

Deviation from tri-bimaximal mixings through flavour twisters in inverted and normal hierarchical neutrino mass models

We explore a novel possibility for lowering the solar mixing angle (θ ₁₂) from tri-bimaximal mixings, without sacrificing the predictions of maximal atmospheric mixing angle (θ ₂₃ = 45°) and zero reactor angle (θ ₁₃ = 0°) in the inverted and normal hierarchical neutrino mass models having 2–3 symmetry. This can be done through the identification of a flavour twister term in the texture of neutrino mass matrix and the variation of such term leads to lowering of solar mixing angle. For the observed ranges of Δm ₂₁² and Δm ₂₃², we calculate the predictions on tan² θ ₁₂ = 0.5, 0.45, 0.35 for different input values of the parameters in the neutrino mass matrix. We also observe a possible transition from inverted hierarchical model having even CP parity (Type-IHA) to inverted hierarchical model having odd CP parity (Type-IHB) in the first two mass eigenvalues, when there is a change in input values of parameters in the same mass matrix. The present work differs from the conventional approaches for the deviations from tri-bimaximal mixing, where the 2–3 symmetry is broken, leading to θ ₂₃ ≠ 45° and θ ₁₃ ≠ 0°.      

Pulsed magnetic field study of Fe2+ in some fluosilicates

Pulsed field experiments up to 450 kOe have been performed on FeSiF_6.6H₂O. We interpret the data: (i) in terms of spin hamiltonian constants: D = 12.3± 0.2 cm^-1 (E = 0.54cm^-1 being known from EPR data); (ii) in terms of axial-crystal-field parameters: $\text{δ}\text{λ}\text{=}\text{orbital trigonal splitting/spin-orbit coupling}\text{= 15 ± 2; λ = -100 ± 7cm}{}^{\mathrm{?1}}$. The magnetic axis is found to deviate from the cristallographie c axis by an angle 1° < θ < 2°. The adiabatic cooling obtained during the pulse is discussed.Similar experiments on Fe_0.15Zn_0.85SiF_6.6H₂O and Fe_0.30Zn_0.70SiF_6.6H₂O single crystals are reported; in both cases we measure $\text{D}\text{g}{}_{\mathrm{\parallel }}\text{= 6.0 ± 0.1cm}{}^{-1}$. Using EPR data, we obtain D = 14.3cm^-1, λ ～ ?75cm^-1, δ ～ 195cm^-1; using Mössbauer data, we obtain D = 15.3cm^-1, λ ～ ?88cm^-1, δ ～ 185cm^-1.     

A novel origin of CP violation

We propose the complex group theoretical Clebsch-Gordan coefficients as a novel origin of CP violation. This is manifest in our model based on SU(5) combined with the double tetrahedral group, T^′. Due to the presence of the doublet representations in T^′, there exist complex CG coefficients, leading to explicit CP violation in the model, while the Yukawa couplings and the vacuum expectation of the scalar fields remain real. The tri-bimaximal neutrino mixing matrix arises from the CG coefficients of T^′. In addition to the prediction for , the model gives rise to a sum rule, , which is a consequence of the Georgi-Jarlskog relations in the charged fermion sector. The leptonic Dirac CP violating phase, δ_?, is predicted to be ∼227^°, which turns out to be the value needed to account for the difference between the experimental best fit value for the solar mixing angle and the TBM prediction. The predicted CP violation measures in the quark sector are also consistent with the current experimental data.     

Efficient laser operation of diode-pumped Pr3+,Mg2+:SrAl12O19

We report on diode-pumped laser operation of Pr³⁺,Mg²⁺:SrAl₁₂O₁₉ at lasing wavelengths of λ _L = 724.4 nm, λ _L = 643.5 nm, and λ _L = 622.8 nm. Furthermore, the laser threshold could be reached in the green spectral range. By pumping the crystal longitudinally from each side with two polarization beam combined InGaN laser diodes, a total pump power of ≈4 W was available. In the deep red spectral range, a maximum output power of 564 mW was achieved with a maximum slope efficiency of 50 % with respect to the absorbed pump power. The maximum possible internal losses were estimated to ≈1 %. Beam quality factors M ² were in the range of 1.2–1.5.     

Transition from strong to weak coupling in SU(N) lattice gauge theories

A possible explanation is proposed for the crossover from strong to weak coupling region in SU(N) lattice gauge theories. We predict the pointswhere the crossover takes place for all SU(N)M: For example, g² ≈ 2.0 for SU(2), g² ≈ 1.0 for SU(3) and lim_N→∞Ng²(SU(N) ≈ 2.0.     

A study of ππ → KK using an experiment on π−p → KS0KS0n at 8.9 GeV/c

We present an analysis of the K_S⁰K_S⁰ system, based on 6380 events, produced in the reactions π^?p → K_S⁰K_S⁰n. Using a one-pion exchange model with absorption we determine the S- and D-wave amplitudes of ππ → $\text{K}\text{K}$. Several A₂ production amplitudes were also included in the fits and we conclude that an unnatural parity exchange amplitudes which does not interfere with pion exchange, seems to present. A branching ratio $\text{Γ(}\text{f}\text{→}\text{K}\text{K}\text{/ Γ(}\text{f}\text{→ ππ) = 0.029 ± 0.006}$ is determined. With this and other new values of branching ratios we have fitted the 2⁺ → 0^?0^? decay rates of the SU(3) relations resulting in (36.2 ± 1)° for the tensor nonet mixing angle.     

Structure-mediated transition in the behavior of elastic and inelastic properties of beach tree bio-carbon

Microstructural characteristics and amplitude dependences of the Young modulus E and of internal friction (logarithmic decrement δ) of bio-carbon matrices prepared from beech tree wood at different carbonization temperatures T _carb ranging from 600 to 1600°C have been studied. The dependences E(T _carb) and δ(T _carb) thus obtained revealed two linear regions of increase of the Young modulus and of decrease of the decrement with increasing carbonization temperature, namely, ΔE ～ AΔT _carb and Δδ ～ BΔT _carb, with A ≈ 13.4 MPa/K and B ≈ ?2.2 × 10^?6 K^?1 for T _carb < 1000°C and A ≈ 2.5 MPa/K and B ≈ ?3.0 × 10^?7 K^?1 for T _carb > 1000°C. The transition observed in the behavior of E(T _carb) and δ(T _carb) at T _carb = 900–1000°C can be assigned to a change of sample microstructure, more specifically, a change in the ratio of the fractions of the amorphous matrix and of the nanocrystalline phase. For T _carb < 1000°C, the elastic properties are governed primarily by the amorphous matrix, whereas for T _carb > 1000°C the nanocrystalline phase plays the dominant part. The structurally induced transition in the behavior of the elastic and microplastic characteristics at a temperature close to 1000°C correlates with the variation of the physical properties, such as electrical conductivity, thermal conductivity, and thermopower, reported in the literature.     

On the sign of the n-p mass difference in gauge models

We examine the sign of the n-p mass difference in some gauge models based on the SU(2) × U(1) × U(1) or SU(2)_L × SU(2)_R × U(1) group, and show that a few specific elements of the neutral-vector-meson mass matrix can determine the sign of Δm|_n?p. We also present an SU(2) × U(1) × U(1) model which can give the correct Δm|_n?p.