Evidence for muon neutrino oscillation in an accelerator-based experiment

We present results for nu(mu) oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of nu(mu), which we presume have oscillated to nu(tau). The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).     

Structure-based interpretation of the Strouhal-Reynolds number relationship

The wake in the flow past a circular cylinder has posed a long-standing challenge to scientists since the late 19th century. Many aspects of this seemingly simple phenomenon remain unexplained. Of particular interest is the relationship between the dimensionless vortex shedding frequency (the Strouhal number St) and the ratio of inertial to viscous forces in the fluid (the Reynolds number Re). We propose a new St-Re relation based on the observations of the structure of a vortex street in flowing soap films. The measurements suggest a simple two-parameter form St=1/(A+B/Re) that describes laminar vortex shedding remarkably well for bulk fluids as well as for two-dimensional flowing soap films.     

Influence of the dynamic ergodic divertor on the density limit in TEXTOR

A significant influence of the dynamic ergodic divertor (DED) on the density limit in TEXTOR has been found. In Ohmic discharges, where without DED detachment normally arises at the density limit, a MARFE (multifaceted asymmetric radiation from the edge) develops when the DED is operated in a static regime. The threshold of the MARFE onset in the neutral beam heated plasmas is increased by applying 1 kHz ac DED at the high-field side. The theoretical predictions based on the parallel energy balance taking poloidal asymmetries into account agree well with the experimental observation.     

Ultrabroadband beam splitter with matched group-delay dispersion

We present a general design strategy for a broadband thin-film beam splitter with matched group-delay dispersion. By taking the substrate dispersion into account in the coating design, any combination of input and output can show the same dispersion for transmission and reflection. As a specific implementation, an ultrabroadband 50:50 beam splitter from 600 to 1500 nm for femtosecond laser applications was designed, fabricated, and characterized.     

Measurement of the wrong-sign decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi-, and search for CP violation

Using 281 fb-1 of data from the Belle experiment recorded at or near the (4S) resonance, we have measured the rates of the "wrong-sign" decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi- relative to those of the Cabibbo-favored decays D0 --> K- pi+ pi0 and D0 --> K- pi+ pi+ pi-. These wrong-sign decays proceed via a doubly Cabibbo-suppressed amplitude or via D0-D0 mixing; the latter has not yet been observed. We obtain R(WS)(K pi pi0) = [0.229 +/- 0.015(stat)(+0.013)(-0.009)(syst)]% and R(WS)(K3pi) = [0.320 +/- 0.018(stat)(+0.018)(0.013)(syst)]%. The CP asymmetries are measured to be -0.006 +/- 0.053 and -0.018 +/- 0.044 for the K+ pi- pi0 and K+ pi- pi+ pi- final states, respectively.     

Magnetic scattering of spin polarized carriers in (In, Mn)Sb dilute magnetic semiconductor

Magnetoresistance measurements on the magnetic semiconductor (In, Mn)Sb suggest that magnetic scattering in this material is dominated by isolated Mn2+ ions located outside the ferromagnetically ordered regions when the system is below T(c). A model is proposed, based on the p-d exchange between spin-polarized charge carriers and localized Mn2+ ions, which accounts for the observed behavior both below and above the ferromagnetic phase transition. The suggested picture is further verified by high-pressure experiments, in which the degree of magnetic interaction can be varied in a controlled way.     

Polaronic behavior of undoped high-T(c) cuprate superconductors from angle-resolved photoemission spectra

We present angle-resolved photoemission spectroscopy (ARPES) data on undoped La2CuO4, indicating polaronic coupling between bosons and charge carriers. Using a shell model, we calculate the electron-phonon coupling and find that it is strong enough to give self-trapped polarons. We develop an efficient method for calculating ARPES spectra in undoped systems. Using the calculated couplings, we find the width of the phonon sideband in good agreement with experiment. We analyze reasons for the observed dependence of the width on the binding energy.     

Orbital response of evanescent cooper pairs in paramagnetically limited Al films

We report a detailed study of the pairing resonance via tunneling density of states in ultrathin superconducting Al films in supercritical magnetic fields. Particular emphasis is placed on the effects of the perpendicular component of the magnetic field on the resonance energy and magnitude. Though the resonance is broadened and attenuated by H(perpendicular) as expected, its energy is shifted upward linearly with H(perpendicular). Extension of the original theory of the resonance to include strong perpendicular fields shows that at sufficiently large H(perpendicular) the overlap of the broadened resonance tail with the underlying degenerate Fermi sea alters the spectral distribution of the resonance via the exclusion principle. This leads to the shift of the resonance feature to higher energy.     

Localization-dependent photoluminescence spectrum of biexcitons in semiconductor quantum wires

We study exciton and biexciton spectra in disordered semiconductor quantum wires by means of nanophotoluminescence spectroscopy. We demonstrate a close link between the exciton localization length along the wire and the occurrence of a biexciton spectral line. The biexciton signature appears only if the corresponding exciton state extends over more than a few tens of nanometers. We also measure a nonmonotonous variation of the biexciton binding energy with decreasing exciton localization length. This behavior is quantitatively well reproduced by the solution of the single-band Schr?dinger equation of the four-particle problem in a one-dimensional confining potential.     

Turbulence investigations during ergodic divertor operation with induced 2/1 tearing mode

Within the last year of TEXTOR operation a major part of the experiments were dedicated to the interaction of the ergodized plasma edge, induced by the dynamic ergodic divertor (DED), with the core plasma. Systematic experiments are performed in the 3/1 configuration of the DED. Depending on , the DED generates a locked 2/1 mode in the plasma at a critical current in the DED coils. Different diagnostics were used to measure the plasma response in the core and edge. The investigations in this paper are focused on the measurement of density fluctuation and the analysis of the coherent-mode structure outside the q = 2 surface using O-mode poloidal correlation reflectometry. A reduction of the quasi-coherent mode amplitude and frequency is observed, caused by the 2/1 mode together with a decrease of the density scale length. Moreover, the deduced poloidal rotation velocity at the q = 3 surface changes from the electron to the ion diamagnetic drift direction with the onset of the 2/1 island. Also a reduction of the density fluctuations is observed as well as a decrease in the poloidal correlation length. From Ar-injection a delayed inward propagation of the emission maximum is observed for different Ar ionization stages when the 2/1 mode is generated.Similar experiments with a slowly rotating DED show that the steepened density gradients are spatially localized and confirm the hypothesis that the 2/1 mode is responsible for the observations.Presented at the Workshop Electric Fields Structures and Relaxation in Edge Plasmas, Nice, France, October 26–27, 2004.