Hyperons Analogous to the Λ(1405)

The low mass of the Λ(1405) hyperon with j ^P =  1/2^?, which is higher than the ground state Λ(1116) mass by 290 MeV, is difficult to understand in quark models. We analyze the hyperon spectrum in the bound state approach of the Skyrme model that successfully describes both the Λ(1116) and the Λ(1405). This model predicts that several hyperon resonances of the same spin but with opposite parity form parity doublets that have a mass difference of around 300 MeV, which is indeed realized in the observed hyperon spectrum. Furthermore, the existence of the ${\Xi(1620)}$ and the ${\Xi(1690)}$ of j ^P  = 1/2^? is predicted by this model. Comments on the Ω baryons and heavy quark baryons are made as well.     

How to Determine the Spin of the ξ(2230)

The possibility for increasing the statistics by summing up the events of decaying into two pseudo scalar mesons from the existing data samples is discussed.     

NH3-induced c(4 × 2) to (2 × 2) transition on the Ge(001) surface by a domino-like dimer flip

Under the conditions of thermodynamic adsorption-desorption equilibrium, the first strongly bound molecular adsorption state of ammonia on Ge(001) saturates at one molecule per Ge reconstruction dimer (1/2 ML). High-resolution electron diffraction studies show that this adsorption is accompanied by a structural transition from c(4 × 2) on the clean surface to a (2 × 2) structure which is already completed for a coverage of about 0.04 ML, far below saturation. We propose a model implying the formation of NH₃ islands locally covered with 1/2 ML and a (2 × 2) periodicity caused by a flip of the dimer tilt direction of every second dimer Beyond the edge of these islands, the dimer flip continues domino-like along the dimer rows over the clean parts of the surface. Elongated (2 × 2) domains about 280–330Å long and 30–65Å wide are formed, depending on coverage.     

Application of the matching procedure to the calculation of phonon dispersion on Ni(100) covered with a C(2×2) overlayer

The equations of motion are worked out for the atoms of a semi-infinite crystal covered with a commensurate adsorbate by using the clean crystal as a basis. This procedure produces a complete set of displacement fields consistent with the relevant space-group symmetry. These equations are solved with help of the matching procedure to give the surface even phonon and resonance dispersion curves in the (010) direction of Ni(1OO) covered with a C(2×2) oxygen overlayer. The consequences of the adsorbate induced folding of the Brillouin zone upon the bulk and surface phonons are analysed. Using symmetry adapted coordinates secures a straightforward identification of the loss features observed by EELS.     

The Application of Raman Spectroscopy to the Study of the Uranyl Mineral Coconinoite Fe2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O

ABSTRACT

Raman spectra of the uranyl-containing mineral coconinoite, Fe₂Al₂(UO₂)₂(PO₄)₄(SO₄)(OH)₂ · 20H₂O, are presented and compared with the mineral's infrared spectra. Bands connected with (UO₂)²⁺, (PO₄)^3?, (SO₄)^2?, (OH)^?, and H₂O stretching and bending vibrations are assigned. Approximate U?O bond lengths in uranyl, (UO₂)²⁺, and O?H…O hydrogen bond lengths are calculated from the wavenumbers of the U?O stretching vibrations and (OH)^? and H₂O stretching vibrations, respectively, and compared with published data for similar natural and synthetic compounds.     

New limit on the half-life of 78Kr with respect to the 2K(2ν)-capture decay mode

The features of data accumulated for 1817 h in an experimental search for the 2K(2ν)-capture mode of ⁷⁸Kr decay are discussed. A new limit on the half-life for this decay is found: T _1/2≥2.3×10²⁰ yr (at a 90% C.L.).     

Spectroscopic Properties of Cu(L-met)2, Cu(DL-met)2, Cu(L-ala)2 and Cu(DL-ala)2˙H2O and Qualitative Explanations to the Magnetism and Relative Ordering of the One-Electron Energy Levels.

Electronic absorption spectra and photoacoustic spectra of four copper(II)-amino acid complexes of formulas Cu(L-met)˙(1). Cu(DL-met)˙(2). Cu(L-ala)x(3) and Cu(DL-ala)˙-H₂O(4)(L-met=L-methioninato;DL-met=DL-methioninato;L-ala=L-alaninato DL-ala=DL-alaninato) were recorded and the results are discussed quantitatively with respect to llgand field theory and the radical wave function of a non-free copper(II) ion. The relationship between the maximum absorption peak in PAS and magnetic properties is also discussed. Lastly, a qualitative explanation on the senquence of splitting energy in going from regular octahedral to strongly elongately and slightly tetragonally distorted octahedral around each copper(II) center is proposed.     

How atoms move in the (1 × 1) to (1 × 2) surface reconstruction of fcc (110) planes

The result of a recent study of atomic steps in the (1 × 1) to (1 × 2) surface reconstruction of Pt and Ir (110) planes using ns pulsed-laser heating can only be understood by highly correlated jumps of atoms within a small [110] atom-row. We argue in favor of a simultaneous jump of the entire small [110] row of atoms, possibly stimulated by surface phonon waves propagating in the direction normal to, and also parallel to, the atom-row direction. Surface reconstruction of fcc (110) planes evolves with long-range atomic diffusion, thus the transition occurs relatively slowly. Reconstruction of fcc (001) planes evolves with short-range atomic movements, and the transition occurs very rapidly.     

Order-disorder transition on Si(001): c(4 × 2) to (2 × 1)

A phase transition between c(4 × 2) and (2 × 1) structures on the clean Si(001) surface has been observed at about 200 K by low energy electron diffraction. From the temperature dependence of the width and intensity of the diffraction spots this transition is concluded to be a second order order-disorder transition. The transition proceeds by a single stage, which is in strong contrast with the case of Ge(001) for which a two-stage transition has been reported.     

Measurement of the decay of the Υ(1S) and Υ(2S) resonances to muon pairs

Using the Crystal Ball detector at thee ⁺ e ^– storage ring DORIS II, we have measured the branching fraction to muon pairsB of the (1S) and (2S) resonances and for the first time the product of the muonic partial width and the branching fraction to electronsB _ee for both resonances. We obtain

Abilities of Antioxidants to Eliminate the Peroxyl Radical Derived from 2,2′-Azobis(2-Amidinopropane) Dihydrochloride (AAPH)

Electron spin resonance (ESR) of 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) spin adducts of free radicals derived from the UV irradiation of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) under rapid scanning condition was examined. The ESR signal obtained was the superposition of two spectra, the spin adduct of the alkoxyl radical [CYPMPO-ORa, Ra = C(CH₃)₂-C(⁺NH₂Cl^?)NH₂] and the peroxyl radical (CYPMPO-OORa). The decay rate of CYPMPO-OORa was 8,400 times that of CYPMPO-ORa. The order of the k _SB/k _ST values (the slope of the Stern–Volmer’s plot) for the peroxyl radical (RaOO·) was l-ascorbic acid > caffeic acid > rutin ~ Trolox ~ (+)-catechin ~ glutathione (reduced), which was almost the same order as that for the alkoxyl radical (RaO·). Though the k _SB/k _ST value of each antioxidant for the peroxyl radical was about half of that for the alkoxyl radical, the ratios of the values of antioxidants to that of trolox (the relative ORAC values) were almost the same between the peroxyl and alkoxyl radicals. The relative oxygen radical absorbance capacity (ORAC) values of polyphenols estimated by the ORAC-ESR assay using both peroxyl and alkoxyl radicals were smaller than those by the ORAC-FL assay.     

Insensitivity of the superconducting gap to variations in the critical temperature of Zn-substituted Bi2Sr2CaCu2O(8+δ) superconductors

The phase diagram of the superconducting high-T(c) cuprates is governed by two energy scales: T*, the temperature below which a gap is opened in the excitation spectrum, and T(c), the superconducting transition temperature. The way these two energy scales are reflected in the low-temperature energy gap is being intensively debated. Using Zn substitution and carefully controlled annealing we prepared a set of samples having the same T* but different T(c)'s, and measured their gap using angle-resolved photoemission spectroscopy (ARPES). We show that T(c) is not related to the gap shape or size, but it controls the size of the coherence peak at the gap edge.     

Spontaneous SU(2) symmetry violation in the SU(2) L × SU(2) R × SU(4) electroweak model

A new approach to electroweak (EW) composite scalars is developed starting from the fundamental gauge interaction on high scale. The latter is assumed to have the group structure SU(2) _L × SU(2) _R × SU(4), where SU(4) is the Pati-Salam color-lepton group. The topological EW vacuum filled by instantons is explicitly constructed and the resulting equations for fermion masses exhibit spontaneous SU(2) flavor symmetry violation with possibility of very large mass ratios.     

What can a heavy U(1)_(B-L) Z' boson do to the muon(g-2)_μ anomaly and to a new Higgs boson mass?

The minimal U(1)_(B-L) extension of the Standard Model(B-L-SM) offers an explanation for neutrino mass generation via a seesaw mechanism;it also offers two new physics states,namely an extra Higgs boson and a new Z' gauge boson.The emergence of a second Higgs particle as well as a new Z' gauge boson,both linked to the breaking of a local U(1)_(B-L) symmetry,makes the B-L-SM rather constrained by direct searches in Large Hadron Collider(LHC) experiments.We investigate the phenomenological status of the B-L-SM by confronting the new physics predictions with the LHC and electroweak precision data.Taking into account the current bounds from direct LHC searches,we demonstrate that the prediction for the muon(g-2)_μ anomaly in the B-L-SM yields at most a contribution of approximately 8.9 × 10~(-12),which represents a tension of 3.28 standard deviations,with the current1σ uncertainty,by means of a Z' boson if its mass is in the range of 6.3 to 6.5 TeV,within the reach of future LHC runs.This means that the B-L-SM,with heavy yet allowed Z' boson mass range,in practice,does not resolve the tension between the observed anomaly in the muon(g-2)_μ and the theoretical prediction in the Standard Model.Such a heavy Z' boson also implies that the minimal value for the new Higgs mass is of the order of 400 GeV.     

From the Group SL(2,?C) to Gyrogroups and Gyrovector Spaces and Hyperbolic Geometry

We show that the algebra of the group SL(2, C) naturally leads to the notion of gyrogroups and gyrovector spaces for dealing with the Lorentz group and its underlying hyperbolic geometry. The superiority of the use of the gyrogroup formalism over the use of the SL(2, C) formalism for dealing with the Lorentz group in some cases is indicated by (i) the validity of gyrogroups and gyrovector spaces in higher dimensions, by (ii) the analogies that they share with groups and vector spaces, and by (iii) the demonstration that gyrovector spaces form the setting for hyperbolic geometry in the same way that vector spaces form the setting for Euclidean geometry. As such, gyrogroups and gyrovector spaces provide powerful tools for the study of relativity physics.     

What can a heavy U(1)B-L Z'boson do to the muon(g-2)u anomaly and to a new Higgs boson mass?

The minimal U(1)B_L extension of the Standard Model(B-L-SM)offers an explanation for neutrino mass generatio n via a seesaw mechanism;it also offers two new physics states,namely an extra Higgs bos on and a new Z'gauge boson.The emerge nee of a second Higgs particle as well as a new Z'gauge boson,both lin ked to the breaking of a local U(1)B_L symmetry,makes the B-L-SM rather constrained by direct searches in Large Hadron Collider(LHC)experiments.We investigate the phenomenological status of the B-L-SM by confr on ting the new physics predictions with the LHC and electroweak precision data.Taking into account the current bounds from direct LHC searches,we demonstrate that the prediction for the muon(g-2)u anomaly in the B-L-SM yields at most a contribution of approximately 8.9×10^-12,which represents a tension of 3.28 standard deviations,with the current 1σuncertainty,by means of a Z'boson if its mass is in the range of 6.3 to 6.5 TeV,within the reach of future LHC runs.This means that the B-L-SM,with heavy yet allowed Z‘bos on mass range,in practice,does not resolve the tension between the observed anomaly in the muon(g-2)u and the theoretical prediction in the Standard Model.Such a heavy Z'boson also implies that the minimal value for the new Higgs mass is of the order of 400 GeV.     

Reevaluation of the hadronic contributions to the muon g−2 and to \alpha (M^{2}_{Z})

We reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass. We include new π ⁺ π ^? cross-section data from KLOE, all available multi-hadron data from BABAR, a reestimation of missing low-energy contributions using results on cross sections and process dynamics from BABAR, a reevaluation of all experimental contributions using the software package HVPTools together with a reanalysis of inter-experiment and inter-channel correlations, and a reevaluation of the continuum contributions from perturbative QCD at four loops. These improvements lead to a decrease in the hadronic contributions with respect to earlier evaluations. For the muon g?2 we find lowest-order hadronic contributions of (692.3±4.2)?10^?10 and (701.5±4.7)?10^?10 for the e ⁺ e ^?-based and τ-based analyses, respectively, and full Standard Model predictions that differ by 3.6σ and 2.4σ from the experimental value. For the e ⁺ e ^?-based five-quark hadronic contribution to $\alpha(M_{Z}^{2})$ we find $\varDelta \alpha_{\mathrm{had}}^{(5)}(M_{Z}^{2}) =(274.9\pm1.0)\cdot10^{-4}$ . The reduced electromagnetic coupling strength at M _Z leads to an increase by 12 GeV in the central value of the Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.     

From the stress response function (back) to the sand pile “dip”

We relate the pressure dip observed at the bottom of a sand pile prepared by successive avalanches to the stress profile obtained on sheared granular layers in response to a localized vertical overload. We show that, within a simple anisotropic elastic analysis, the skewness and the tilt of the response profile caused by shearing provide a qualitative agreement with the sand pile dip effect. We conclude that the texture anisotropy produced by the avalanches is in essence similar to that induced by a simple shearing --albeit tilted by the angle of repose of the pile. This work also shows that this response function technique could be very well adapted to probe the texture of static granular packing.