Gauge theoretical realization of the superweak model of CP violation

It is pointed out that the presence in a gauge theory of vector bosons or left-over Higgs bosons with a weak interaction strength of the order of10^?11G_E and which have CPviolating couplings to the strangeness-changing neutral current, will lead to the superweak model of CP violation. An example of such a theory, based on the gauge group SU (2) ?U(1), is given.     

Polarization amplitudes fore + e − →W + W − ande + e − →ZZ

The main purpose of this work is to study the three weak boson vertex. We give explicit formulae for all polarization amplitudes of the processese ⁺ e ^? →W ⁺ W ^? ande ⁺ e ^? →ZZ, with arbitrary couplings between the various intermediate vector bosons. Using these expressions we discuss possible signatures ofC, P andT violation in the three vector boson coupling, as well as the effects of anomalous magnetic dipole and electric quadrupole moments ofW ^±. The amplitudes for the above processes in any SU(2) × U(1) and SU(2)_L × SU(2)_R × U(1) gauge theory are also given, while the special case of the Weinberg-Salam model is studied in detail.     

Penetration effects in the internal conversion process of the 204 keV transition in205Tl

Penetration effects have been detected in²⁰⁵Tl by measuring theK, L and (M+N+...) internal conversion coefficients of the 204 keV, 3/2⁺→l/2⁺ transition. From the resulting values α _K =0.29±0.04, α _L =0.132±0.006 and α _M+N+...=0.0397±0.0034 the penetration parameter and the mixing ratio have been deduced to be λ=13.1±2.7 andδ ²=1.40±0.46, respectively.     

Onset of chaos in finite interacting Boson systems with F-spin

For m bosons, carrying spin (f = 1 2) degree of freedom, in Ω single particle levels which are doubly degenerate, one-plus two-body Embedded Gaussian Orthogonal random matrix Ensemble which conserves spin (F) [BEGOE(1 + 2)-F] is defined and spectral properties are examined. Using mean field defined by random single particle energies, for fixed-(m,F) BEGOE(1 + 2)-F, density of states being close to Gaussian, we analyze spectral fluctuation properties, like Nearest Neighbour Spacing Distribution (NNSD) and Dyson-Mehta (Δ₃) statistic, as a function of λ- the two-body interaction strength. Numerical calculations are used to demonstrate that for very small value of λ, NNSD and Δ₃ are found close to Poisson form and they move steadily to GOE form as λ increases. Moreover, spin dependence of the transition point λ _C is obtained. It is also verified using periodogram analysis that BEGOE(1 + 2)-F spectra shows 1/f–noise behaviour.     

Structure of even-even actinides in the interacting boson model and the N = 152 subshell closure

We show that a wide range of deformed actinides can be described in terms of an interacting boson model hamiltonian with three parameters, two of them [including the coefficient of the only SU(3) symmetry breaking term] remaining almost constant over the whole region. In addition to ground γ₁ and β₁ spectra, B(E2:0_g⁺ → 2_g⁺) values are well reproduced with no extra adjustable parameters for nuclei with 136⩽N⩽146, while for nuclei beyond N = 146 an effective boson number has to be considered in order to fit the observed in the B(E2:0⁺_g → 2⁺_g) values, which is due to the presensce of a subshell closure at N = 152. The sensitive dependence of the B(E2:0_g⁺→2_g⁺) values on the effective boson numbers is emphasized. β₁ → ground and β₁ → ground transitions are fitted by breaking the SU(3) symmetry of the E2 transition operator.     

Low-energy parity restoration and unification mass scale within maximal symmetries

We investigate the hierarchy of gauge boson masses in the maximal grand unified theory by studying the renormalization group equations for the running coupling constants associated with the symmetry breaking of SU(16)viaSU(12) _q×SU(4) _l×U(1) _|B|?|L| chain. Particular attention is given to the contribution of Higgs scalars to these equations. It is found that the intermediate mass scale M_L, associated with right-handed gauge bosons could be as low as 10 ³ GeV only for sin ²θ _w(M _L) as high as 0.265 with α _s(M _L)=0.13. In this chain of symmetry breaking, we have also examined the lowest unification mass that is allowed by the low-energy data for sin ²θ _w(M _L) and the assumed gauge hierarchy. This has been done in two cases; first for the case where SU(3) ^c is vectorial, second, for the case where SU(3) ^c is axial. In both cases the lowest unification mass scales were found to be 10 ¹³, 10 ¹¹, 10 ⁸ and 10 ⁷ GeV for sin ²θ _w(M _L) = 0.22, 0.24, 0.26,and0.265 respectively with α _s(M _L) = 0.13. The implication of these low unification masses on baryon non-conserving processes is also discussed.     

Complete scissors mode strength in heavy deformed odd-mass nuclei: a case study of 165Ho and 169Tm

The low-energy dipole strength distributions in ¹⁶⁵Ho and ¹⁶⁹Tm have been studied in nuclear resonance fluorescence experiments at the S-DALINAC utilizing a Euroball Cluster detector. In the energy interval between 2.5 and 4.0 MeV, where the scissors mode is expected, 35 ground state transitions could be observed in ¹⁶⁵Ho and 53 in ¹⁶⁹Tm. Assuming M1 character for all these transitions corresponds to ΣB(M1) ↑= 1.54(23), μ_N² and ΣB(M1) ↑= 2.15(63), μ_N² for ¹⁶⁵Ho and ¹⁶⁹Tm, respectively. A statistical analysis is applied to the measured spectra which is capable of reconstructing the complete strength, including contributions of transitions below the observation limit, with the ratio between M1 and E1 excitations and their total strengths taken as an average over the even-mass neighbours. This results in summed M1 transition strengths of ΣB(M1) ↑= 3.54_−0.95^+0.75, μ_N² (¹⁶⁵Ho) and ΣB(M1) ↑= 3.36_−0.57^+1.00μ_N² (¹⁶⁹Tm). The large variations of the summed dipole strength and the fragmentation in other deformed odd-mass nuclei can be reproduced by the same statistical ansatz. The total low-lying M1 strength in heavy deformed odd-mass nuclei is in agreement with the findings in the neighbouring even-mass nuclides as well as with sum-rule predictions.     

Possible structures of the neutral current within a gauge theory framework

We examine a class of gauge theories based on U(1)×SU(2)×G allowing for an arbitrary number of gauge bosons, while retaining the lowq ² four fermion interaction of the standard model. Measurable consequences fore ⁺ e ^?→μ ⁺ μ ^? ande ⁺ e ^?→e ⁺ e ^? at presently available as well as LEP energies are presented. Implications of the recently determined QED cut-offΛ _? ? 100 GeV on gauge boson properties and the anomalous magnetic moment of the muon are pointed out.     

Recent results on intermediate vector boson properties at the CERN super proton synchrotron collider

The properties of a sample of 172 charged intermediate vector bosons decaying in the (ev_e) channel and 16 neutral intermediate vector bosons decaying in the (e⁺e⁻) channel are summarized. Masses, decay widths, decay angular distributions, and production cross sections are given, and a limit is put on the number of light neutrino types N_v ⩽ 10 at 90% CL.     

Electric dipole moment and chromoelectric dipole moment of the top quark inSU(3)C×SU(3)L×U(1)X model

We show that inSU(3) _C ×SU(3) _L ×U(1) _X model, the leading contribution to the electric and chromolelectric dipole moment of the top quark is due to the one-loop diagrams which come from exchanging the charged and neutral Higgs bosons. The dipole moments are typically of the order of 10^?19 e-cm and 10^?19 g-cm respectively, for the values of relative phases of the vev's such that CP violation is maximal. From an experimental point of view, theq ² dependence of dipole moment form factors is given.     

High-resolution (e,e') study of isovector M1 and M2 transitions in the oxygen isotopes: (I). 16O

The M1 and M2 transition strength distribution for ¹⁶O in the excitation energy range from 16 to 20 MeV has been measured in a high-resolution electron scattering experiment. The M1 strength is concentrated in three sharp states at E_x = 16.22, 17.14 and 18.79 MeV (± 0.01 MeV) with B(M1, k)↑ = 0.20 ± 0.02, 0.32 ± 0.03 and 0.13 ± 0.03 μ_N², respectively. An additional strength of 0.35 ± 0.09 μ_N², distributed over eight weakly excited states with excitation energies E_x = 17.4 to 18.0 MeV, brings the total measured M1 strength to B(M1, k)↑ = 1.0 ± 0.1 μ_N². The experimental M2 strength is distributed over states at E_x = 16.82, 17.78, 18.50 and 19.0 MeV (± 0.01 MeV) with B(M2, k)↑ = 19 ± 2, 13 ± 2, 59 ± 7 and 341 ± 51 μ_N² · fm², respectively. Electric transitions were also measured to states at E_x = 16.45 MeV (2⁺, E2), 17.30 MeV (1⁺, E1) and 18.20 MeV (2⁺, E2). Calculations were performed using the modified surface delta interaction in a 2p-2h shell model for the M1 transitions and the random phase approximation for the M2 transitions. The results show the sensitivity of the M1 strength as a measure of ground-state correlations and compare well with results from the ¹⁵N($\text{p}$, γ) reaction.     

A light neutral intermediate vector boson without large e+e−→ μ+μ− asymmetries

An effective SU(2)×U(1)×U(1)' electroweak theory is shown to permit the occurence of a pair of neutral intermediate vector bosons with masses 40 GeV?m_light?70 GeV, m^W.S._Z⁰<m_heavy?100 GeV. Neutrino neutral current interactions are shown to be the same as in the standard electroweak model, and e⁺e^?→μ⁺μ^? forward-backward asymmetries are within experimental bounds for m_light?40 GeV.     

A non-linear Rζ gauge condition for the electroweak SU(2) × U(1) model

A non-linear R_ζ gauge condition is presented and explicitly developed in the framework of the SU(2)×U(1) gauge model. We give the corresponding Feynman rules, which are simpler than in R_ζ gauges, because couplings involving unphysical Higgs and gauge bosons disappear or simplify. The Faddeev-Popov sector is more elegant, the ghosts coupling to neutral gauge bosons like in scalar electrodynamics. Finally, as a practical example, the transition Higgs→γγ is considered and compared with the usual calculation in linear gauges.     

Comments on the symmetry relations in the hyperon radiative decays

We demonstrate that in general Hara's theorem which gives various symmetry relations for the hyperon radiative decays is not valid. The new relations we derive are different from those given by Hara. But for the Σ⁺→P_γ decay, the asymmetry parameter is still zero in the exact SU(3) limit.     

Description of charge-exchange resonances in deformed nuclei

The (p, n) and (n, p) transition strength functions with excitation of the GT resonance, other 1⁺ states, spin-dipole with λ^π=0^- andE1 charge-exchange resonances in deformed nuclei in the regions 156≦A≦168 and 236≦A≦240 are calculated in the RPA. It is shown that the GT resonance has a maximum at 18–20 MeV, and in the region of 5–6 MeV around maximum (60–70)% of strength is concentrated. The spindipole resonance with λ^π=0^-, 1^- and 2^? strength is distributed within 14–33 MeV and theE1 strength within 25–29 MeV. The latter is splitted withΔE equal to 0.6–2 MeV into two peaks withI ^π I=1^-0 and 1^?1. In the region of 4–7 MeV around maximum 73–77% ofE1 strength is concentrated. The total (n,p) transition strength is 10–200 times as small as the total (p, n) transition strength.     

Microscopic mean-field boson approach to the shape transition in Sm isotopes

The phase transition from spherical to deformed shape in nuclei ^146–156Sm is analyzed within the mean-field approximation applied to the Dyson boson image of the shell-model hamiltonian. No quasiparticle transformation is involved in the present approach and the Pauli principle in the physical boson subspace is approximately taken into account. The low-energy spectra, B(E2; 0₁⁺→ 2₁⁺) values and the corresponding transition densities are calculated. The results provide a reasonable explanation of the shape transition in the Sm isotopes. The role of bosons with different angular momenta is investigated and it is found that the g-bosons (J = 4) cannot be neglected in the transitional region. Comparison of the present results with those of other approaches is given as well.     

Shape variables and the shell model

The irreducible representation labelsλ andμ of the SU(3) shell model are related to the shape variablesβ andγ of the collective model by invoking a linear mapping between eigenvalues of invariant operators of the two theories. All but one parameter of the theory is fixed if the shell-model result is required to reproduce the collective-model geometry. And for one special value of the remaining free parameter there is a simple linear relationship between the eigenvalues, λ_α, of the quadrupole matrix of the collective model and the SU(3) representation labels: $$\lambda _1 = ( - \lambda + \mu )/3, \lambda _2 = ( - \lambda + 2\mu + 3)/3, \lambda _3 = (2\lambda + \mu + 3)/3.$$ The correspondence between hamiltonians that describe rotations in each theory is also given. Results are shown for two cases,²⁴Mg and¹⁶⁸Er, to demonstrate that the simplest mapping yields excellent results for both energies and transition rates. For λ and/or μ large, the (β, γ)?(λ,μ) correspondence introduced here reduces to the symplectic shell-model result.     

Four families of composite quarks and leptons

Four families of composite quarks and leptons, two standard and two non-standard, are found in a unique solution SU(3)_HC × SU(6)_L × SU(6)_R of a restricted 't Hooft anomaly-matching program. Testable predictions emerge, such as prohibition of μ → eγ, zero charge asymmetry in e⁺e^? → τ⁺τ^? in contrast to e⁺e^? → μ⁺μ^?, and a rich new hadron spectrum masses around M_W. A minimal set of spectator fermions contains color-singlet objects with fractional quark-like charges.     

The 2+-2+ transition of 879 keV in160Dy investigated by electron-gamma directional correlation

e-γ directional correlation measurements of 2⁺(879 keV)2⁺(87 keV)0⁺ cascade in¹⁶⁰Dy have been made and the magnitude of electric monopole to quadrapole mixing ratio for 879 keV transition was found to beq _k =?0.03(10) for λ=0 (λ-according to Hager-Saltzer definition).