Phase space and multihadron production in annihilation processes at present energies

With the conjecture that the weak neutral current should have equal status in symmetry as the other weak and electromagnetic currents, we determine it to be a pure axial-vector. This means that the weak interaction of the neutral current is parity conserving. The fundamental interactions of leptons thereby complete the whole scheme of (1 + γ₅)/2, (1 ? γ₅)/2,1 and γ₅.     

Determining theCP-violating phase γ

The weak phase γ is conventionally probed by theB _s→ρ ⁰ mode. The predicted rate is tiny. Even if aB _s→ρ ⁰ K _s rate difference could be established, it would not be clear that sin 2γ had been measured, because amplitudes with other weak phases may contribute significantly. Non-CP eigenstates, such asB _s →D _s ^± K ^?, have a two-fold advantage overB _s→ρ ⁰ K _s. Their rates are orders of magnitude above that forB _s→ρ ⁰ K _s, and they probe theCP-violating phase γ, without any contamination from other weak phases. Detailed time-dependent studies of non-CP eigenstates remove possible final-state phases and extract the weak phase γ.     

The beta-decay asymmetry of the neutron

The beta-decay asymmetry of the free neutron is measured with polarized neutrons and a long solenoidal beta-spectrometer with 4π electron-detection solid angle. The asymmetry parameter corrected for recoil and weak magnetism isA ₀=?0.1146±0.0019, implyingg _A /g _v =1.262±0.005 for the ratio of the axial-vector to the vector weak coupling constants.     

Antiferromagnetic resonance in CuB2O4 single crystal

The frequency-field, temperature, and angular dependences of the antiferromagnetic resonance parameters for the tetragonal CuB₂O₄ single crystal are studied in the frequency range 2.6–80 GHz and at temperatures of 4.2–30 K. The results obtained confirm the fact that, in the high-temperature state in the range 10–21 K, this compound is an easy-plane weak ferromagnet. The temperature dependence of the Dzyaloshinski field is determined. An abrupt change observed in the frequency-field dependence of the magnetic resonance at T=4.2 K and H ⊥ C ₄ indicates the transition to the weak ferromagnetic state induced by the external field H _⊥. The phase diagram for CuB₂O₄ is constructed on the H _⊥-T coordinates. It is demonstrated that, in the low-temperature state, the magnetic moments of copper ions remain in the basal plane, but the weak ferromagnetism is absent.     

Phase diagram and oxygen annealing effect of FeTe1−xSex iron-based superconductor

Phase diagrams of as-grown and O₂-annealed FeTe_1?xSe_x determined from magnetic susceptibility measurement were obtained. For as-grown samples, the antiferromagnetic order was fully suppressed in the range region x≥0.15, and weak superconductivity appeared when x≥0.1. Beginning at x=0.5, weak superconductivity was found to evolve into bulk superconductivity. Interestingly, for O₂-annealed samples, complete suppression of magnetic order and the occurrence of bulk superconductivity were observed when x≥0.1. We found that O₂-annealing induces bulk superconductivity for FeTe_1?xSe_x. Oxygen probably plays a key role in the suppression of the magnetic order and the appearance of bulk superconductivity.     

Electroweak radiative corrections to the e+e− →+− asymmetry

The electromagnetic and purely weak one-loop corrections to e⁺e^? →^+? have been calculated in the SU(2) × U(1) standard model using an on-shell renormalisation scheme with finite Green functions. Thier influence on the forward backward asymmetry A_FB together with soft and hard bremsstrahlung is discussed for PETRA energies. Whereas the electromagnetic corrections to ψ and Z⁰ exchange diminish A_FB, the weak corrections increase A_FB almost compensating the QED correction to Z⁰ exchange. The main weak contribution comes from the Z⁰ self-energy. The other diagrams give only small changes in A_FB.     

Weak correction to the muon magnetic moment in a gauge model

The weak correction, a_μ^w, to the anomalous magnetic moment of the muon is calculated in an SU(2) ? U(1) ? U(1) gauge model of weak and electromagnetic interactions. The R_ξ gauge is used and Ward-Takahashi indentities are utilized eliminating all ξ-dependence before the loop integration is performed. a_μ^w,expt places no constraint on the mass of one of the neutral vector mesons, which may be arbitrarily small.     

Weak annihilation in charm baryon decays — A re-evaluation

We discuss weak decays of charm baryons taking the mode Λ _c ⁺ →Δ⁺⁺ K ^? as the starting point of our analysis. This channel which can occur only due to weak annihilation has been seen at the ISR. Hence we conclude that weak annihilation is very significant for baryons. Further tests of this picture are listed, in particular concerning charm-strange baryons. We argue that τ(D°)~τ(Λ _c ⁺ )<τ(D ⁺) suggests that baryon and meson decays should be treated on an equal footing even when weak annihilation is included. We describe a framework based on evolution equations where this can be done.     

Magnetic and electrical properties of new magnetic phase in Si1−xMnx crystals

We have investigated the magnetic and electrical transport properties of Si_1−xMn_x single crystals grown by the vertical Bridgman method. The alloys with Mn concentrations up to x=0.64 have weak ferromagnetic ordering around T_C∼30 K. However, Si_0.25Mn_0.75 alloys show weak ferromagnetic ordering at 70 K and antiferromagnetic ordering at 104 K, which is confirmed by magnetization and electrical transport studies.     

Weak neutral-current couplings of muons

Inversion of both the charge and the helicity of muon beams is considered as a possibility to determine the weak neutral-current couplings of muons, in particular the right-handed weak charge I^R₃(μ) and sin²θ without using the parton model.     

Implications of the quark-gluon light cone current algebra on neutrino scattering

The explicit canonical structure of the light cone restriction of the commutator of the weak current with its divergence is considered in the interacting quark-gluon model quantized in the finite momentum frame. The implications on neutrino scattering are analyzed. W₄ and W₅ are predicted to scale nontrivially as ν⁻²F₄(ω) and ν⁻²F₅(ω), which provides a simple test of light cone current algebra feasible in the near future. The Σ-term for weak currents is deduced from a casual representation near the light cone, and a correction is also made in the W₅-sum rule obtained by naive infinite momentum techniques.     

Quark contribution to weakNN interaction

The contribution of contact weak interactions of quarks to the longitudinal analyzing powerA _L in the low-energypp-scattering is calculated. The strong interaction between quarks is described by the oscillator potential, and the weak one by the Weinberg-Salam lagrangian. The contribution of the considered mechanism toA _L is approximately — (0.5÷1.0)·10^?7, being responsible for the bulk of the experimental value.     

Reversible magnetization and irreversibility line of tri-layer superconductor Ba2Ca2Cu3O6(O,F)2 with Tc∼108 K

We report magnetization measurements of grain-aligned Ba₂Ca₂Cu₃O₆(O,F)₂ with T_c?108 K. The interlayer distance of the material is the shortest among known tri-layer superconductors. Unexpectedly, the magnetization data show that the coupling strength between CuO₂ layers is rather weak. A direct reflection of the weak coupling is highly suppressed irreversibility line, i.e. a broad reversible region in H-T plane. The decoupling field obtained from the irreversibility line is less than 0.1 T, which is comparable with that of quasi two-dimensional superconductor Bi₂Sr₂CaCu₂O_8+δ. Comparison of data with the Hao-Clem model gives characteristic parameters [ξ_ab(0) and λ_ab(0)] and the critical fields [H_c(0) and H_c2^c(0)]. A large value of penetration depth, λ_ab(0)=240 nm reflects a small carrier concentration in CuO₂ planes, and explains the reason of the weak interlayer coupling.     

Measuring the weak charge of the proton at Jefferson Lab: A search for physics beyond the standard model

The JLab Q _weak Collaboration is designing and constructing an experiment to measure the proton’s weak charge, Q _W ^p , by measuring the parity violating asymmetry in elastic electron-proton scattering at very low momentum transfer. The standard model predicts Q _W ^p = 1 ? 4 sin² θ _w from the running of the weak mixing angle sin² θ _w , corresponding to a 10σ effect in the experiment. The experiment will determine Q _W ^p with 4% combined statistical and systematic uncertainties, which leads to 0.3% uncertainty in sin² θ _w . Installation of the experiment will begin in September 2009.     

A unified model of weak,electromagnetic and strong interactions based on six flavours and “six” colours

A unified model of weak, electromagnetic and strong interactions based on the group SO₆ ? SO₆ ? SO₆ is proposed. The model is anomaly free. Other consequences are: the vector character of colour couplings, a weak mixing angle sin²θ_w = 0.239 and a unification mass 5 orders of magnitude lower than the one required by SU₅.     

Weak radiative decays of baryons

Using recent experimental baryon weak radiative decay data for the fiveB→B′γ decays, we employ the pole model self-consistently to extract the reduced matrix elements 〈B′|H _w|B〉. The resulting pattern is compatible with weak pion decaysB→B′π and also with the quark model.     

Limits to possible scalar-boson mass and coupling from e+e− collisions

Measurements of e⁺e^? → e⁺e^? at 2.8 GeV are reported and interpreted in terms of limits for the mass and coupling of a possible scalar boson of the type introduced in recent renormalizable models of weak interactions. In particular, in the Georgi-Glashow scheme of leptons we find that the scalar boson mass must be larger than 10 GeV for an m_W = 10 GeV (m_W mass of the W-boson) and of 6.5 GeV for m_W = 15 GeV. Alternatively its coupling is extremely weak.     

The weak mixing angle and unification mass in supersymmetric SU(5)

We consider the predictions for the weak mixing angle θ_W and the scale M of unification in a supersymmetric extension of SU(5), with particular emphasis on the sensitivity to the number of Higgs multiplets. In the one-loop approximation, we also calculate the ratio m_b/m_τ. We discuss generally the effects of an intermediate threshold between the weak interaction scale and M and estimate the sensitivity of θ_W and M to the scale of supersymmetry breaking.The evolution of the coupling constants of the supersymmetric SU(3) ? SU(2) ? U(1) effective gauge theory is described and the two-loop corrections to θ_{W and M} are calculated.     

Electronic structure of adsorbed alkali atoms for comparison with UPS data

We have generalised our earlier work calculating the induced density of states in alkali chemisorption to include the valence np level in addition to the s level. This allows the theory to take account of the possibility of sp hybridization. Hybridization is said to be weak is the sp level separation ΔE_sP exceeds twice the width of the s or p_z resonance. In the converse case hybridization is strong and the induced density of states no longer reflects distinguishable s and p_z resonances. We argue that ΔE_sP for the chemisorbed alkali exceeds considerably that for the free alkali atom. In the case of Na on r_s = 2 jellium (considered typical of the smaller alkali on r_s = 2?3 substrates) hybridization is strong for the atomic value of ΔE_sp but weak when a somewhat larger value is taken, making the conclusions a little indefinite. For Cs on Cu(111), we find a clear situation of weak hybridization with the atomic ΔE_sP and a fortiori with a more realistic value. There should thus be a well defined 6s resonance in this system. Our estimate of the width of the 6s resonance is in good agreement with photoemission data.     

Magnetic properties of TmxDy1−xFeO3 single crystals

The magnetic behaviour of Tm_xDy_1?xFeO₃ (x = 0.3; 0.5; 0.7; 1.0) single crystals in the temperature range 90-4.2° K were investigated. The transition from the weak ferromagnetic to antiferromagnetic state was observed at about 9° K for Tm_0.3Dy_0.7FeO₃ single crystal. The reorientation of weak ferromagnetic moment from c- to a-axis was observed for Tm_0.7Dy_0.3FeO₃ single crystal at 35–65° K. The magnetic structure change of iron and rare-earth ions took place when external magnetic field was applied. The thulium and disprosium ion interaction does not essentially influence on the single crystal magnetic properties of the substituted compounds in a low temperature range.