Measurements of $Brightarrow bar{D} D_{s0} ^{*+}(2317)$ decay rates and a search for isospin partners of the $D_{s0}^{*+} (2317)$

We report improved measurements of the product branching fractions ${mathcal B}(B^+rightarrowbar{D}^0 D_{s0}^{*+} (2317))times{mathcal B}( D_{s0} ^{*+}(2317)rightarrow D_s^{+}pi^0) =(8.0^{+1.3}_{-1.2} pm 1.1 pm 0.4)times 10^{-4}$ and ${mathcal B}(B^0rightarrow D^- D_{s0} ^{*+}(2317))times{mathcal B}(D_{s0}^{*+}(2317)rightarrow D_s^{+}pi^0) =(10.2^{+1.3}_{-1.2} pm 1.0 pm 0.4)times 10^{-4}$, where the first errors are statistical, the second are systematic and the third are from $D$ and $D_s$ branching fractions. In addition, we report negative results from a search for hypothesized neutral ($Z^0$) and doubly charged ($Z^{++}$) isospin partners of the $D_{s0}^{*+}(2317)$ and provide upper limits on the product branching fractions ${mathcal B}(B^0 rightarrow D^0 z^0)times{mathcal B}(z^0rightarrow D_s^{+}pi^-)$ and ${mathcal B}(B^+rightarrow D^- z^{++})times{mathcal B}(z^{++}rightarrow D_s^{+}pi^+)$ that are more than an order of magnitude smaller than theoretical expectations for the hypotheses that the $D_{s0} ^{*+}(2317)$ is a member of an isospin triplet. The analysis uses a 711 fb$^{-1}$ data sample containing 772 million $Bbar{B}$ meson pairs collected at the $Upsilon(4S)$ resonance in the Belle detector at the KEKB collider.

Search for neutrinos from annihilation of captured low-mass dark matter particles in the Sun by Super-Kamiokande

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/$c^2$ $sim$ 200-GeV/$c^2$) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent (SD) WIMP-proton cross section for WIMP masses below 200 GeV/$c^2$ (at 10 GeV/$c^2$, 1.49$times 10^{-39}$ cm$^2$ for $chichirightarrow b bar{b}$ and 1.31$times 10^{-40}$ cm$^2$ for $chichirightarrowtau^+tau^-$ annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent (SI) coupling in the few-GeV/$c^2$ mass range.

Parallaxes of Star Forming Regions in the Outer Spiral Arm of the Milky Way

We report parallaxes and proper motions of three water maser sources in high-mass star-forming regions in the Outer Spiral Arm of the Milky Way. The observations were conducted with the Very Long Baseline Array as part of Bar and Spiral Structure Legacy Survey and double the number of such measurements in the literature. The Outer Arm has a pitch angle of 14.9 +/- 2.7 deg and a Galactocentric distance of 14.1 +/- 0.6 kpc toward the Galactic anticenter. The average motion of these sources toward the Galactic center is 10.7 +/- 2.1 km/s and we see no sign of a significant fall in the rotation curve out to 15 kpc from the Galactic center. The three-dimensional locations of these star-forming regions are consistent with a Galactic warp of several hundred parsecs from the plane.

Trigonometric Parallaxes of Star Forming Regions in the Perseus Spiral Arm

We report trigonometric parallaxes and proper motions of water masers for 12 massive star forming regions in the Perseus spiral arm of the Milky Way as part of the Bar and Spiral Structure Legacy (BeSSeL) Survey. Combining our results with 14 parallax measurements in the literature, we estimate a pitch angle of 9.9 +/- 1.5 degrees for a section of the Perseus arm. The three-dimensional Galactic peculiar motions of these sources indicate that on average they are moving toward the Galactic center and slower than the Galactic rotation.

Charge frustration in a triangular triple quantum dot

We experimentally investigate the charge (isospin) frustration induced by a geometrical symmetry in a triangular triple quantum dot. We observe the ground-state charge configurations of six-fold degeneracy, the manifestation of the frustration. The frustration results in omnidirectional charge transport, and it is accompanied by nearby nontrivial triple degenerate states in the charge stability diagram. The findings agree with a capacitive interaction model. We also observe unusual transport by the frustration, which might be related to elastic cotunneling and the interference of trajectories through the dot. This work demonstrates a unique way of studying geometrical frustration in a controllable way.

An Electronic Quantum Eraser

Complementarity, the incomplete nature of a quantum measurement - a core concept in quantum mechanics - stems from the choice of the measurement apparatus. The notion of complementarity is closely related to Heisenbergs uncertainty principle, but the exact relation between the two remains a source of debate. For example, knowledge of a particles position in a double slit interference experiment will quench its wave-like nature and, vice versa, observing the wave property via interference implies lack of knowledge of the particles path. A canonical system for exploring complementarity is the quantum eraser (QE), predominantly studied thus far in photonic systems. A QE is an interference experiment consisting of two stages. First, one of the interfering paths is coupled to a which path (WP) detector - demonstrating loss of interference due to acquisition of WP information. Second, the WP information is being erased by projecting the detectors wavefunction on a particular basis; this renders the WP information inaccessible, thus allowing reconstruction of the interference pattern. In this work, we present a first implementation of a QE in an electronic system. Our system consists of two identical electronic Mach-Zehnder interferometers (MZIs) entangled via Coulomb interactions. Such novel setup has already attracted a considerable theoretical attention. With one MZI serving as a path detector and the other as the system interferometer, the visibility of the Aharonov-Bohm oscillation in the System can be controlled by the Detector. We demonstrate how a continuous change of the measurement basis, followed by post selection (via cross correlation of current fluctuations), allows a smooth transition between keeping and erasing the WP information.

Controlled dephasing of an electron interferometer with a path detector at equilibrium

Controlled dephasing of electrons, via which path detection, involves, in general, coupling a coherent system to a current driven noise source. However, here, we present a case in which a nearly isolated electron puddle at thermal equilibrium strongly affects the coherence of a nearby electronic interferometer. Moreover, for certain average electron occupations of the puddle, the interferometer exhibits complete dephasing. This robust phenomenon stems from the Friedel Sum Rule, which relates a systems occupation with its scattering phases. The interferometer opens a peeping window into physics of the isolated electron puddle, which cannot be accessed otherwise.

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3

We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zig-zag magnetic order. The onset of long-range magnetic order below 15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90 deg Ir-O-Ir bonds required for dominant Kitaev exchange.