Flavor changing neutral currents and a Z′

We consider a non-universal Z′ that affects primarily the third generation fermions as an example of new physics associated with the top-quark. We first discuss constraints on the mass and coupling strength of such a Z′. We then turn our attention to the flavor changing neutral currents (FCNC) present in the model. We discuss the experimental constraints and their implications. We propose an ansatz to understand the smallness of the FCNC in terms of the CKM matrix.     

Decay of Z′ in W+W− and Higgs modes

We show that Z′ → WW and into Higgs mode are valuable probes of the symmetry breaking mechanism in gauge theories. Results are derived for a decay of an arbitrary Z′ from string inspired E₆ theory.     

Z′particles and e~+ e~- → τ~+ μ~-

We analyze the cross section of e + e-→τ + μ-within the frameworks of SM and its Z extension.The theoretical prediction of the SM on the total cross section is suppressed by the tiny neutrino masses.On the other hand,the contributions from Z to the cross section are enhanced drastically because of the tree level FCNC couplings among Z and leptons.     

Z−Z′ mixing and oblique corrections in anSU(3)×U(1) model

We address the effects of the new physics predicted by theSU(3) _l ×U(1) _X model on the precision electroweak measurements. We consider bothZ–Z mixing and one-loop oblique corrections, using a combination of neutral gauge boson mixing parameters and the parametersS andT. At tree level, we obtain strong limits on theZ–Z mixing angle, –0.0006<0.0042 and="> 490$$ " align="middle" border="0"> GeV (both at 90% C.L.). The radiative corrections lead toT>0 if the new Higgs are heavy, which bounds the Higgs masses to be less than a few TeV.S can have either sign depending on the Higgs mass spectrum. Future experiments may soon place strong restrictions on this model, thus making it eminently testable.     

Vibrational Spectroscopic and Theoretical Studies of Urea Derivatives with Biochemical Interest: N,N′-Dimethylurea,N,N,N′,N′-Tetramethylurea,and N,N′-Dimethylpropyleneurea

Abstract

Mid-infrared, far-infrared, and Raman vibrational spectroscopic studies were combined with density functional theory (DFT) calculations and normal coordinate force field analyses for N,N′-dimethylurea (DMU), N,N,N′,N′-tetramethylurea (TMU), and N,N′-dimethylpropyleneurea (DMPU: IUPAC name 1,3-dimethyltetrahydropyrimidin-2(1H)-one). The equilibrium molecular geometry of DMU (all three conformers), TMU, and DMPU and the frequencies, intensities, and depolarization ratios of their fundamental infrared (IR) and Raman vibrational transitions were obtained by DFT calculations. The vibrational spectra were fully analyzed by normal coordinate methods as well. A starting force field for DMPU was obtained by adapting corresponding force constants for DMU and TMU, resulting after refinements in the stretching force constants C=O (7.69, 7.30, 7.68 N·cm^?1), C–N (5.16, 5.55, 5.05 N·cm^?1), and C-Me (5.93, 4.00, 4.22 N·cm^?1) for DMU, TMU, and DMPU, respectively. The dominating conformer of liquid DMU was identified as trans-trans, strong intermolecular hydrogen bonding was verified in solid DMU, and weak dipole–dipole association was found in liquid TMU and in DMPU. Special attention was paid to analyzing the methyl group frequencies, which revealed deviations from local C_3v symmetry. A linear correlation was found between the CH stretching force constants and the inverse of the CH bond lengths (1/r ²). The averaged NH stretching frequencies of gaseous, dissolved, and solid urea and of DMU, with variations for hydrogen bonding of different strength, are linearly correlated to the NH stretching force constants. Characteristic skeletal vibrations were assigned for a broad variety of urea derivatives and also for pyrimidine derivatives, which all contain the N₂C=O entity. The very strong IR bands of C=O stretching (1,676 ± 40 cm^?1) and asymmetric CN₂ stretching (1,478 ± 60 cm^?1), and the very intense Raman feature of symmetric CN₂ stretching or ring breathing (757 ± 80 cm^?1), can be recognized as fingerprint bands also for the pyrimidine derivatives cytosine, thymine, and uracil, which all are nucleobases in DNA and RNA nucleotides.     

Additional Z′-boson and polarization asymmetries in annihilationary creation of a scalar quark pair

The possibility is studied of using the longitudinal and transverse polarization asymmetries as principle variables for detecting creation of scalar quark states in e⁺e^–-annihilation, taking into account the contribution of the superstring Z-boson.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 101–106, April, 1991.The authors thank A. A. Iogansen and I. S. Satsunkevich for stimulating discussion and their interest to this work.     

Probing ZWW couplings through Z0→Wff′

We investigated the possibility of probing the ZWW couplings through the rare decay mode Z⁰→Wff′ of Z⁰. Neglecting masses of the fermions, we computed the combined polarization density matrix of Z and W as a function of the most general ZWW couplings. Integrations over phase space are carried out and the diagonal matrix elements are expressed as quadratic forms of the seven independent couplings. We found that several charge symmetrix polarization channels are particularly sensitive to the CP-violating coupling f₆, which is proportional to the weak magnetic quadrupole moment.     

Identification of E6-generated Z′ from combined charm II,LEP 1, SLC high-precision measurements

We show that a combined analysis of three specific longitudinal polarization asymmetries in electron-positron annihilation on Z₀ resonance, of the mass ratio M_w/M_z and of the neutrino-electron neutral cross-section ratio, which could be measured in the near future at SLC, LEP, ACOL and CHARM II, would lead to a well-defined identification of a single new E₆-generated Z′. In particular, it might be possible to disentangle a superstring-inspired model from other currently considered possibilities down to values of the mixing angle θ_η = 0.02 and, at the same time, to fix the mass ratio ε = M_Z²/M_Z′² with known accuracy.     

3He(e,e′pp) and 3He(e,e′pn) reactions at AmPS and MAMI

This paper reports on measurements of the ³He(e,e′pp) reaction measured at AmPS and the ³He(e,e′pn) reaction measured at MAMI. The measurements were performed in similar kinematics to allow a comparison to be made between the cross sections of the two reactions. Results are shown for both reactions together with a comparison for the ³He(e,e′pp) data with continuum Faddeev calculations.     

Comparative study of Z′ searches in e+e− and e−e− scattering

We consider indirect searches for additional neutral vector bosons in e⁺e⁻ and e⁻e⁻ collisions, and compare these two linear collider modes with similar analysis procedures and assumptions. Discovery limits and resolving power are discussed in a model-independent way.     

Embedding Z′ models in SO(10) GUTs

We embed a theory with Z′ gauge boson (related to an extra U(1) gauge group) into a supersymmetric GUT theory based on SO(10). Two possible sequences of SO(10) breaking via VEVs of appropriate Higgs fields are considered. Gauge coupling unification provides constraints on the low energy values of two additional gauge coupling constants related to Z′ interactions with fermions. Our main purpose is to investigate in detail the freedom in these two values due to different scales of subsequent SO(10) breaking and unknown threshold mass corrections in the gauge RGEs. These corrections are mainly generated by Higgs representations and can be large because of the large dimensions of these representations. To account for many free mass parameters, effective threshold mass corrections have been introduced. Analytic results that show the allowed regions of values of two additional gauge coupling constants have been derived at 1-loop level. For a few points in parameter-space that belong to one of these allowed regions 1-loop running of gauge coupling constants has been compared with more precise running, which is 2-loop for gauge coupling constants and 1-loop for Yukawa coupling constants. 1-loop results have been compared with experimental constraints from electroweak precision tests and from the most recent LHC data.     

Charge-exchange processes in the quasi-elastic (e,e′p) and (e,e′n) reactions

Calculations of charge-exchange processes in the final state of the quasi-elastic (e, e′N) reaction have been performed employing the Lane formalism. The Lane equations were decoupled by means of a transformation to the isospin representation. It is found that charge exchange has a small effect on the (e, e′p) cross section, but may play an appreciable role in the (e, e′n) reaction.     

Z′ in the 3-3-1 model

Phenomenological implications of the Z′ in SU(3) × SU(3) × U(1) extension of the standard model are studied. We find that the current experimental value of R_b puts severe constraints on the Z′ mass in this model. The model improves slightly the fit for large E_T jet cross section observed by CDF.     

Z′和τ的轻子味破坏衰变

许多超出标准模型的新物理预言了非普适规范玻色子Z′的存在.此新粒子可产生许多新的物理现象.本文计算了顶色辅助的人工色(TC2)模型和味普适TC2模型预言的非普适规范玻色子Z′对τ的轻子味破坏衰变过程τ→liγ,τ→liljlk的贡献.结果表明,在整个参数空间内,过程τ→liljlk的分支比比τ→liγ的分支比大.在适当的参数空间内,分支比Br(τ→liljlk)可达到10^－8.因此,在将来的高能实验中有可能探测到此新物理效应.     

Extra Z′-boson in (ν&#x0304;)N-elastic and some quasielastic processes

The contribution of an extra Z′-boson to the elastic ⁽ν&#x0304;⁾p-scattering, π⁰ neutrino-production on nuclei and some diffractive reactions is calculated in the frame of the superstring inspired E₆-model. We give quantitative estimations of this contribution and its dependence on model parameters.     

B →πη（′）, η（′）η（′） decays and NLO contributions in the pQCD approach＊

By employing the perturbative QCD （pQCD） factorization approach, we calculate the full leading and the partial next-to-leading order （NLO） contributions to the seven B →πη（′） and η（′）η（′） decays. For B^＋→ π＋η（′） decays, the pQCD predictions for their decay rates agree very well with the data after the inclusion of the small NLO contributions. For neutral decays, the pQCD predictions are also consistent with the experimental upper limits and can be tested by the LHC experiments. The measured value of dir .Acp^dir（π＋η）= 19±7% can also be accommodated by the pQCD approach.     

Vibrational Spectra of 2,2′-Pyridil and 2,2′-Pyridil-18O and Assignment of Infrared and Raman Bands

Abstract

Vibrational spectra of 2,2′-pyridil and 2,2′-pyridil-¹⁸O in the solid state and in solutions have been measured in the Raman (4000–50 cm^?1) and infrared (4000–100 cm^?1). The assignment of the bands observed is performed using the group vibrational concept and isotopic shifts data of the normal modes. The presence of synand anti-phase vibrations of both pyridyl rings is discussed. The results are compared to the corresponding data for some similar molecules.