Using dispersion relations, we derive the complete virtual QED contributions to Bhabha scattering due to vacuum polarization effects. We apply our result to hadronic corrections and to heavy lepton and top quark loop insertions. We give the first complete estimate of their net numerical effects for both small and large angle scattering at typical beam energies of meson factories, the CERN Large Electron-Positron Collider, and the International Linear Collider. With a typical amount of 1-3 per mil they are of relevance for precision experiments.

Scanning tunneling spectroscopy has recently discovered a positive correlation between the magnitude of the superconducting gap and positions of dopant oxygen atoms in Bi-based cuprates. We propose a microscopic mechanism that could be responsible for this effect. In particular, we demonstrate that the dopant-induced spatial variation of the atomic levels always enhances the superexchange interaction.

Measurements of the analyzing power for the reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the η meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S₁₁(1535) resonance is predominantly due to the exchange of the η meson between the colliding nucleons.

A novel transport phenomenon is identified that is induced by inertial Brownian particles which move in simple one-dimensional, symmetric periodic potentials under the influence of both a time periodic and a constant, biasing driving force. Within tailored parameter regimes, thermal equilibrium fluctuations induce the phenomenon of absolute negative mobility (ANM), which means that the particle noisily moves backwards against a small constant bias. When no thermal fluctuations act, the transport vanishes identically in these tailored regimes. ANM can also occur in the absence of fluctuations on grounds which are rooted solely in the complex, inertial deterministic dynamics. The experimental verification of this new transport scheme is elucidated for the archetype symmetric physical system: a convenient setup consisting of a resistively and capacitively shunted Josephson junction device.

Combining our results for various O(α_s²) corrections to the weak radiative B-meson decay, we are able to present the first estimate of the branching ratio at the next-to-next-to-leading order in QCD. We find B(...)=(3.15ą0.23)×10^-4 for E_?>1.6 GeV in the B-meson rest frame. The four types of uncertainties: nonperturbative (5%), parametric (3%), higher-order (3%), and m_c-interpolation ambiguity (3%) have been added in quadrature to obtain the total error.

We confirm by explicit computation the conjectured all-orders iteration of planar maximally supersymmetric N=4 Yang-Mills theory in the nontrivial case of five-point two-loop amplitudes. We compute the required unitarity cuts of the integrand and evaluate the resulting integrals numerically using a Mellin-Barnes representation and the automated package of Czakon [Comput. Phys. Commun. 175, 559 (2006)]. This confirmation of the iteration relation provides further evidence suggesting that N=4 gauge theory is solvable.

The charge-disordered three-dimensional uniaxial relaxor ferroelectric Sr_0.61Ba_0.39Nb₂O₆ splits up into metastable polar nanoregions and paraelectric interfaces upon cooling from above T_c. The frozen polar nanoregions are verified by piezoresponse force microscopy, respond domainlike to dynamic light scattering and dielectric excitation, reveal nonergodicity at T>T_c via global aging, and coalesce into polar nanodomains below T_c. Contrastingly, the percolating system of unperturbed interfaces becomes ferroelectric with two-dimensional Ising-model-like critical exponents =0, β=1/8, and ?=7/, as corroborated by ac calorimetry, second harmonic generation, and susceptometry, respectively.

Molecules that only differ by their chirality, so-called enantiomers, often possess different properties with respect to their biological function. Therefore, the separation of enantiomers presents a prominent challenge in molecular biology and has long been a main pursuit of organic chemistry. We suggest a new separation technique for chiral molecules that is based on the transport properties in a microfluidic flow with spatially variable vorticity. Because of their size the thermal fluctuating motion of the molecules must be taken into account. These fluctuations play a decisive role in the proposed separation mechanism.

We observe and explain a universal scaling =const for the electrical resistivity with the inverse magnetic susceptibility ^-1 for the Kondo insulator CeRhSb_1-xSn_x. In the regime where the Kondo gap disappears (x>0.12), the system forms a non-Fermi liquid (NFL), which transforms into a Fermi liquid at higher temperature. The NFL behavior is associated with the presence of a novel quantum critical point (QCP) at the Kondo insulator-correlated metal boundary. The divergent behavior of the resistivity, the susceptibility, and the specific heat has been observed when approaching the QCP from the metallic side and is interpreted as due to the competition between the Kondo and the intersite magnetic correlations.

Creep and relaxation of domain walls under ac electric fields are observed in an ideal model system, periodically poled KTiOPO₄, to occur in different regimes, which are separated by dynamic phase transitions at frequencies f_m(T)=f_m0exp(-E/k_BT), with f_m0=3×10⁹Hz and E=0.6eV. Power law dispersion of the creep susceptibility, 1+(i)^-β, with β0., and large nonlinearity encountered at f<f_m, is contrasted with Cole-Cole-type relaxational dispersion, (1+[i]^1-)^-1, with 0.3, at f>f_m.

In this Letter we present a calculation of the temperature-pressure phase diagram of Si in a range of pressures covering from -5 to 20 GPa and temperatures up to the melting point. The phase boundaries and triple points between the diamond, liquid, β-Sn, and Si₃₄ clathrate phases are reported. We have employed efficient simulation techniques to calculate free energies and to numerically integrate the Clausius-Clapeyron equation, combined with a tight-binding model capable of an accuracy comparable to that of first-principles methods. The resulting phase diagram agrees well with the available experimental data.

The two transverse polarization components P_T1 and P_T2 of the e⁺ from the decay of polarized μ⁺ have been measured as a function of the e⁺ energy. Their energy averaged values areP_T1=(6.3ą7.7ą3.4)×10^-3 and P_T2=(-3.7ą7.7ą3.4)×10^-3. From the energy dependence of P_T1 and P_T2 the decay parameters ,^'' and ^'/A,β^'/A are derived, respectively. Assuming only one additional coupling besides the dominant V-A interaction one gets improved limits on , β^'/A, and the scalar coupling constant g_RR^S:=(-2.1ą7.0ą1.0)×10^-3, β^'/A=(-1.3ą3.5ą0.6)×10^-3, Re{g_RR^S}=(-4.2ą14.0ą2.0)×10^-3, and Im{g_RR^S}=(5.2ą14.0ą2.4)×10^-3.

Infrared absorbance measurements have been carried out on two liquid crystalline organo-siloxane tetrapodes. Results unambiguously show the existence of a biaxial nematic phase below a uniaxial nematic phase. The three components of IR absorbance are used to calculate the various order parameters. On cooling, a weak first-order transition from isotropic to nematic is observed, followed by a second-order phase transition to biaxial nematic where the biaxiality parameters are found to be significantly large. Results are supported by observations from conoscopy and texture. Temperature dependences of the order parameters are well explained by the mean-field model for a biaxial phase.

We present a complete calculation of the contributions to the effective leptonic weak mixing angle, sin ² _eff^lept, generated by closed fermion loops at the two-loop level of the electroweak interactions. This quantity is the source of the most stringent bound on the mass M_H of the standard model Higgs boson. The size of the corrections with respect to known partial results varies between -4×10^-5 and -8×10^-5 for a realistic range of M_H from 100 to 300 GeV. This translates into a shift of the predicted (from sin ² _eff^lept alone) central value of M_H by +19 GeV, to be compared with the shift induced by a recent change in the measured top quark mass which amounts to +36 GeV.

Dielectric spectra of the polyalcohols sorbitol and xylitol were measured under isobaric pressures up to 1.8 GPa. At elevated pressure, the separation between the and β relaxation peaks is larger than at ambient pressure, enabling the β relaxation times to be unambiguously determined. Taking advantage of this, we show that the Arrhenius temperature dependence of the β relaxation time does not persist for temperatures above T_g. This result, consistent with inferences drawn from dielectric relaxation measurements at ambient pressure, is obtained directly, without the usual problematic deconvolution the β and processes.

The transverse polarization of electrons emitted in the β decay of polarized ⁸Li nuclei has been measured. For the time-reversal violating triple correlation parameter we find R=(0.9ą2.2)×10^-3. This result is in agreement with the standard model and yields improved constraints on exotic tensor contributions to the weak interaction. Combined with other experimental results and using a model for the coupling constants, a new limit for the mass of a possible scalar leptoquark, m_LQ>560 GeV/c² (90% C.L.), is obtained.

Broadband dielectric measurements were carried out on di-n-butyl phthalate (DBP) under isothermal conditions at hydrostatic pressures up to 1.6 GPa. A comparison of the dielectric relaxation times with the viscosity revealed that no breakdown of the Einstein-Debye relation is induced by high compression. This absence of any decoupling is attributed to the weak intermolecular cooperativity of DBP and its negligible change with pressure. Because of the latter, the dielectric spectra conform to time-pressure superpositioning.

The last missing correction to the muon lifetime in the standard model at O( ²) coming from gauge and Higgs boson loops is presented. The associated contribution to the parameter r in the on-shell scheme ranges from 6×10^-5 to -4×10^-5 for Higgs boson masses from 100 GeV to 1 TeV. This result translates into a shift of the W boson mass which does not exceed ą1 MeV in the same range and amounts, in particular, to approximately -0.8 MeV for a 115 GeV Higgs boson.

Dielectric loss spectra of four different glass formers revealing either β relaxation or excess wing are presented. We compare the effect of pressure and temperature on the mentioned processes. Our findings suggest that the excess wing and the β relaxation cannot be treated on the same footing.

The occurrence of metallic conductivity in SrTiO₃ single crystals is reported for reduction under low partial pressure of oxygen at 800 °C. This transition is shown to result from the formation of a high concentration of vacancy defects along a network of extended defects within the skin region. A self-healing phenomenon is observed for progressive reduction which causes the concentration of initially introduced defects to decrease in the course of heat treatment and leads to a breakdown of the metallic conductivity as well as a substantial loss of optical subgap absorption.

The differences between neutron and proton density distributions at large nuclear radii in stable nuclei were determined. Two experimental methods were applied: nuclear spectroscopy analysis of the antiproton annihilation residues one mass unit lighter than the target mass and the measurements of strong-interaction effects on antiprotonic x rays. Assuming the validity of two-parameter Fermi neutron and proton distributions at these large radii, the conclusions are that the two experiments are consistent with each other and that for neutron rich nuclei it is mostly the neutron diffuseness which increases and not the half-density radius. The obtained neutron and proton rms radii differences are in agreement with previous results.

A series of measurements have been performed at KVI to obtain the vector analyzing power A_y of the ²H(p),pd) reaction as a function of incident beam energy at energies of 120, 135, 150, and 170 MeV. For all these measurements, a range of _c.m. from 30° to 170° has been covered. The purpose of these investigations is to observe possible spin-dependent effects beyond two-nucleon forces. When compared to the predictions of Faddeev calculations, based on two-nucleon forces only, significant deviations are observed at all energies and at center-of-mass angles between 70° and 130°. The addition of present-day three-nucleon forces does not improve the description of the data, demonstrating the still insufficient understanding of the properties of three-nucleon systems.

We show that the paramagnetic reentrant effect observed in experiments by Mota et al. in mesoscopic cylinders made of a normal metal in proximity with a superconductor, can be caused by paramagnetic persistent currents flowing on the outer shell of the cylinder.

The dynamics of two fragile glass forming liquids was studied as a function of temperature and pressure using dynamic light scattering. On the basis of measured data we evaluated the pressure and temperature scaling of the relaxation. All the isotherms can be superimposed and form a master curve when the reduced relaxation times are plotted versus reduced pressure. The Kohlrausch-Williams-Watts stretching parameter β_KWW is increasing with increasing temperature and decreasing pressure and plotted versus log< _KWW> follows a master curve at all temperatures and pressures studied.

Peripheral fragmentation of a 287 MeV/nucleon beam of the halo nucleus ¹¹Li incident on a carbon target has been studied in a fragment-neutron coincidence experiment. The momentum distribution of the ¹⁰Li fragments gives access to the momentum distribution of the removed neutron in ¹¹Li. From the shape of the distribution, the (1s_1/2)² contribution to the mixture of (1s_1/2)² and (0p_1/2)² components in the ground-state wave function was determined to be (45ą10)%. The angular correlation between the knocked out neutron and the one from the decay of ¹⁰Li shows a skew distribution signaling interference of these two different parity states.

X-ray resonant magnetic scattering has been used to examine the magnetic interactions coupling the rare earth and iron sublattices in the antiferromagnetic compound DyFe₄Al₈. Dramatic differences are observed in the temperature dependencies of the energy profiles at resonance depending on whether the photon energy is tuned to the Dy L₂ or L₃ absorption edge. In particular, for temperatures increasing from 10 K, the resonant scattering intensity at the L₃ edge decreases whereas that at the L₂ edge rises. We suggest a physical model capable of reproducing these phenomena.

We analyze directed transport of overdamped Brownian particles in a 1D spatially periodic potential that are subjected to both zero-mean thermal equilibrium Nyquist noise and zero-mean exponentially correlated dichotomous fluctuations. We show that particles can reverse the direction of average motion upon a variation of noise parameters if two fundamental symmetries, namely, the reflection symmetry of the spatial periodic structure, and the statistical symmetry of dichotomous fluctuations, are broken. There is a critical thermal noise intensity D_c, or equivalently a critical temperature T_c, at which the mean velocity of particles is zero. Below T_c and above T_c particles move in opposite directions. At fixed temperature, there is a region of noise parameters in which particles of different linear size are transported in opposite directions.

A novel mechanism of fluctuation-induced voltage rectification in a Josephson junction is analyzed. A point contact with a defect tunneling incoherently between two states is proposed as a source of nonthermal fluctuations which produce asymmetric dichotomic noise. The dc current-voltage characteristics are calculated, and several transport regimes are identified according to the frequency, amplitude, and asymmetry of the noise. The limiting cases of fast and slow fluctuations are investigated analytically. The loaded dc curves exhibit voltage rectification (nonzero voltage at zero current bias) and pronounced singularities in the differential resistance. The system can be used to measure selected characteristics of the tunneling dynamics.

Peripheral fragmentation of a 240 MeV/nucleon beam of the halo nucleus ⁶He incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus ⁵He is the dominant fragmentation mechanism and that it leads to a spin alignment of ⁵He in a plane perpendicular to the ⁵He momentum vector. This is expected to be a common feature for all neutron halo nuclei.

By evolution of fermion mass matrices of the Fritzsch and the Georgi-Jarlskog forms from the supersymmetric grand unified scale, Dimopoulos, Hall, and Raby obtained predictions for the quark masses and mixings. Using Monte Carlo methods we test these predictions against the latest determinations of the mixings, the CP-violating parameter _K, and the B_d⁰-B--_d⁰ mixing parameter r_d. The acceptable solutions closely specify the quark mixings, but lie at the edges of allowed regions at 90% confidence level.

It is shown that a sufficiently pure mesoscopic metallic ring will exhibit a magnetic phase transition to a low-temperature state with a persistent orbital current in zero external field (to a flux-phase state). The transition temperature and the spontaneous persistent current depend strongly on the geometry of the ring and of the Fermi surface.

In a spectroscopic study of the backward-angle yield from ¹²C+ ²⁴Mg at 3-4 times the Coulomb barrier, we find a strong preference for natural parity transitions in the excitation of close-to-yrast rotational bands. This selectivity is in strong quantitative disagreement with Hauser-Feshbach calculations for a compound-nuclear reaction and provides evidence for the conservation of the dinuclear parentage.