We present evidence for $D^0\mathrm{\text{−}}{\overline{D}}^0$ mixing in $D^0\to K^{+}{\pi }^{-}$ decays from $384{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ colliding-beam data recorded near $\sqrt{s}=10.6\mathrm{GeV}$ with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. We find the mixing parameters $x^{\prime 2}=[-0.22\pm 0.30(\mathrm{stat})\pm 0.21(\mathrm{syst})]\times {10}^{-3}$ and $y^{\prime }=[9.7\pm 4.4(\mathrm{stat})\pm 3.1(\mathrm{syst})]\times {10}^{-3}$ and a correlation between them of $-0.95$. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure $R_D$, the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be $[0.303\pm 0.016(\mathrm{stat})\pm 0.010(\mathrm{syst})]\%$. We find no evidence for $CP$ violation.

We observe evidence for $D^0\mathrm{\text{−}}{\overline{D}}^0$ mixing by measuring the difference in the apparent lifetime when a $D^0$ meson decays to the $CP$ eigenstates $K^{+}{K}^{-}$ and ${\pi }^{+}{\pi }^{-}$ and when it decays to the final state $K^{-}{\pi }^{+}$. We find the relative difference of the lifetimes $y_{CP}$ to be $[1.31\pm 0.32(\mathrm{stat})\pm 0.25(\mathrm{syst})]\%$, 3.2 standard deviations from zero. We also search for a $CP$ asymmetry between $D^0$ and ${\overline{D}}^0$ decays; no evidence for $CP$ violation is found. These results are based on $540{\mathrm{fb}}^{-1}$ of data recorded by the Belle detector at the KEKB $e^{+}{e}^{-}$ collider.

An $\alpha$-decay branch of $(1.4\pm 0.4)\times {10}^{-4}$ has been discovered in the decay of ${}^{109}\mathrm{I}$, which predominantly decays via proton emission. The measured $Q_{\alpha }$ value of $3918\pm 21\mathrm{keV}$ allows the indirect determination of the $Q$ value for proton emission from ${}^{105}\mathrm{Sb}$ of $356\pm 22\mathrm{keV}$, which is approximately of 130 keV more bound than previously reported. This result is relevant for the astrophysical rapid proton-capture process, which would terminate in the ${}^{105}\mathrm{Sn}(p,\gamma ){}^{106}\mathrm{Sb}(p,\gamma ){}^{107}\mathrm{Te}(\alpha \mathrm{\text{decay}}){}^{103}\mathrm{Sn}$ cycle at the densities expected in explosive hydrogen burning scenarios, unless unusually strong pairing effects result in a ${}^{103}\mathrm{Sn}(p,\gamma ){}^{104}\mathrm{Sb}(p,\gamma ){}^{105}\mathrm{Te}(\alpha \mathrm{\text{decay}}){}^{101}\mathrm{Sn})$ cycle.

We report a new measurement of the time-dependent $CP$-violating parameters in $B^0\to {\pi }^{+}{\pi }^{-}$ decays with $535\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider operating at the ${\rm Y}(4S)$ resonance. We find $1464\pm 65$ $B^0\to {\pi }^{+}{\pi }^{-}$ events and measure the $CP$-violating parameters ${\mathcal{S}}_{\pi \pi }=-0.61\pm 0.10(\mathrm{stat})\pm 0.04(\mathrm{syst})$ and ${\mathcal{A}}_{\pi \pi }=+0.55\pm 0.08(\mathrm{stat})\pm 0.05(\mathrm{syst})$. We observe large direct $CP$ violation with a significance greater than 5 standard deviations for any ${\mathcal{S}}_{\pi \pi }$ value. Using isospin relations, we measure the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle ${\varphi }_2=(97\pm 11)°$ for the solution consistent with the standard model and exclude the range $11°<{\varphi }_2<79°$ at the 95% confidence level.

It is shown that the Sun can become partially transparent to high energy photons in the presence of a pseudoscalar. In particular, if the axion interpretation of the PVLAS result were true, then up to 2% of GeV energy gamma rays might pass through the Sun, while an even stronger effect is expected for some axion parameters. We discuss the possibilities of observing this effect. Present data are limited to the observation of the solar occultation of 3C 279 by the Energetic Gamma-Ray Experiment Telescope in 1991; 98% C.L. detection of a nonzero flux of gamma rays passing through the Sun is not yet conclusive. Since the same occultation happens every October, future experiments, e.g., the Gamma-Ray Large Area Space Telescope, are expected to have better sensitivity.

Shock wave induced cavitation experiments and atomic force microscopy measurements of flat polyamide and hydrophobized silicon surfaces immersed in water are performed. It is shown that surface nanobubbles, present on these surfaces, do not act as nucleation sites for cavitation bubbles, in contrast to the expectation. This implies that surface nanobubbles are not just stable under ambient conditions but also under enormous reduction of the liquid pressure down to $-6\mathrm{MPa}$. We denote this feature as superstability.

The unusual transport properties of graphene are the direct consequence of a peculiar band structure near the Dirac point. We determine the shape of the $\pi$ bands and their characteristic splitting, and find the transition from two-dimensional to bulk character for 1 to 4 layers of graphene by angle-resolved photoemission. By detailed measurements of the $\pi$ bands we derive the stacking order, layer-dependent electron potential, screening length, and strength of interlayer interaction by comparison with tight binding calculations, yielding a comprehensive description of multilayer graphene’s electronic structure.

Highly dispersed superstructures of a dipolar iridium complex are formed on a Cu(111) surface. We show that the dilute superstructures with density-controlled intermolecular separations are stabilized by the strong and long-range repulsive intermolecular interactions. The repulsive intermolecular interactions are quantitatively evaluated by using low-temperature scanning tunneling microscopy, which are characterized by the surface-enhanced dipole-dipole interactions.

It is generally believed that nature does not provide materials with negative refraction. Here we demonstrate experimentally that such materials do exist at least at GHz frequencies: ferromagnetic metals reveal a negative refraction index close to the frequency of the ferromagnetic resonance. The experimental realization utilizes a colossal magnetoresistance manganite ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_3$ as an example. In this material the negative refractive index can be achieved even at room temperature using external magnetic fields.

We demonstrate the reversible mapping of a coherent state of light with a mean photon number $\overline{n}\simeq 1.1$ to and from the hyperfine states of an atom trapped within the mode of a high-finesse optical cavity. The coherence of the basic processes is verified by mapping the atomic state back onto a field state in a way that depends on the phase of the original coherent state. Our experiment represents an important step toward the realization of cavity QED-based quantum networks, wherein coherent transfer of quantum states enables the distribution of quantum information across the network.

A mesoscopic tiling pattern with 12-fold symmetry has been observed in a three-component polymer system composed of polyisoprene, polystyrene, and poly(2-vinylpyridine) which forms a star-shaped terpolymer, and a polystyrene homopolymer blend. Transmission electron microscopy images reveal a nonperiodic tiling pattern covered with equilateral triangles and squares, their triangle/square number ratio of 2.3 ($\approx 4/\sqrt{3}$), and a microbeam x-ray diffraction pattern shows dodecagonal symmetry. The same kind of quasicrystalline structures have been found for metal alloys ($\sim 0.5\mathrm{nm}$), chalcogenides ($\sim 2\mathrm{nm}$), and liquid crystals ($\sim 10\mathrm{nm}$). The present result ($\sim 50\mathrm{nm}$) confirms the universal nature of dodecagonal quasicrystals over several hierarchical length scales.

We calculate the full phase diagram of spherical charged colloidal particles using Monte Carlo free energy calculations. The system is described using the primitive model, consisting of explicit hard-sphere colloids and point counterions in a uniform dielectric continuum. We show that the gas-liquid critical point becomes metastable with respect to a gas-solid phase separation at colloid charges $Q\ge 20$ times the counterion charge. Approximate free energy calculations with only one and four particles in the fluid and solid phases, respectively, are used to determine the critical line for highly charged colloids up to $Q=2000$. We propose the scaling law $T_c^{*}\sim Q^{1/2}$ for this critical temperature.

We report enhancement of the spin polarization of ${}^{133}\mathrm{Cs}$ nuclei in CsH salt by spin transfer from an optically pumped cesium vapor. The nuclear polarization was 4.0 times the equilibrium polarization at 9.4 T and $137°\mathrm{C}$, with larger enhancements at lower fields. This work is the first demonstration of spin transfer from a polarized alkali vapor to the nuclei of a solid, opening up new possibilities for research in hyperpolarized materials.

We present an experimental investigation on the scaling of resistance in individual single-walled carbon nanotube devices with channel lengths that vary 4 orders of magnitude on the same sample. The electron mean free path is obtained from the linear scaling of resistance with length at various temperatures. The low temperature mean free path is determined by impurity scattering, while at high temperature, the mean free path decreases with increasing temperature, indicating that it is limited by electron-phonon scattering. An unusually long mean free path at room temperature has been experimentally confirmed. Exponentially increasing resistance with length at extremely long length scales suggests anomalous localization effects.

Magnetic transmission x-ray microscopy is used to directly visualize the influence of a spin-polarized current on domain walls in curved permalloy wires. Pulses of nanosecond duration and of high current density up to $1.0\times {10}^{12}\mathrm{A}/{\mathrm{m}}^2$ are used to move and to deform the domain wall. The current pulse drives the wall either undisturbed, i.e., as composite particle through the wire, or causes structural changes of the magnetization. Repetitive pulse measurements reveal the stochastic nature of current-induced domain-wall motion.

The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron $p\overline{p}$ collider. Using a $0.9{\mathrm{fb}}^{-1}$ dataset, we apply a multivariate analysis to separate signal from background and measure $\sigma (p\overline{p}\to tb+X,tqb+X)=4.9\pm 1.4\mathrm{pb}$. The probability to measure a cross section at this value or higher in the absence of a signal is $0.035\%$, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the $Wtb$ coupling and find $0.68<|V_{tb}|\le 1$ at $95\%$ C.L. within the standard model.

The recombination of two split Bose-Einstein condensates on an atom chip is shown to result in heating which depends on the relative phase of the two condensates. This heating reduces the number of condensate atoms between 10% and 40% and provides a robust way to read out the phase of an atom interferometer without the need for ballistic expansion. The heating may be caused by the dissipation of dark solitons created during the merging of the condensates.

Size dependent hole dynamics are measured in colloidal CdSe quantum dots for a specific state-to-state excitonic transition. These experiments show that the hole energy loss rate increases for smaller quantum dots, contradicting known relaxation mechanisms for holes. These experiments reveal a new mechanism for hole relaxation in colloidal quantum dots which circumvents the expected phonon bottleneck for holes. The data are consistent with a nonadiabatic surface channel as the dominant pathway for hole relaxation in colloidal semiconductor quantum dots.

From the fundamental requirement of causality, we derive a rigorous criterion of negative refraction (left handedness). This criterion imposes the lower limits on the electric and magnetic losses in the region of the negative refraction. If these losses are eliminated or significantly reduced by any means, including the compensation by active (gain) media, then the negative refraction will disappear. This theory can be particularly useful in designing new left-handed materials: testing the expected polarizabilities of a medium against this criterion would check the compliance with the causality and verify the design feasibility.

We have performed the first experimental investigation of quantum interference corrections to the conductivity of a bilayer graphene structure. A negative magnetoresistance—a signature of weak localization—is observed at different carrier densities, including the electroneutrality region. It is very different, however, from the weak localization in conventional two-dimensional systems. We show that it is controlled not only by the dephasing time, but also by different elastic processes that break the effective time-reversal symmetry and provide intervalley scattering.