Dissipative Quantum Ising model in a cold atomic spin-boson mixture

Using cold bosonic atoms with two (hyperfine) ground states, we introduce a spin-boson mixture which allows to implement the quantum Ising model in a tunable dissipative environment. The first specie lies in a deep optical lattice with tightly confining wells and forms a spin array; spin-up/down corresponds to occupation by one/no atom at each site. The second specie forms a superfluid reservoir. Different species are coupled coherently via laser transitions and collisions. Whereas the laser coupling mimics a transverse field for the spins, the coupling to the reservoir sound modes induces a ferromagnetic (Ising) coupling as well as dissipation. This gives rise to an order-disorder quantum phase transition where the effect of dissipation can be studied in a controllable manner.Comment: 4 pages, 2 figures, 1 table; Title modified and cosmetic change

On the acoustic diffraction by the edges of benthic shells

Author Posting. © Acoustical Society of America, 2004. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 116 (2004): 239-244, doi:10.1121/1.1675813.Recent laboratory measurements of acoustic backscattering by individual benthic shells have isolated the edge-diffracted echo from echoes due to the surface of the main body of the shell. The data indicate that the echo near broadside incidence is generally the strongest for all orientations and is due principally to the surface of the main body. At angles well away from broadside, the echo levels are lower and are due primarily to the diffraction from the edge of the shell. The decrease in echo levels from broadside incidence to well off broadside is shown to be reasonably consistent with the decrease in acoustic backscattering from normal incidence to well off normal incidence by a shell-covered seafloor. The results suggest the importance of the edge of the shell in off-normal-incidence backscattering by a shell-covered seafloor. Furthermore, when considering bistatic diffraction by edges, there are implications that the edge of the shell (lying on the seafloor) can cause significant scattering in many directions, including at subcritical angles.This research was supported by the U.S. Office of Naval Research (Grant No. N00014-02-1-0095) and the Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA

Abdominal functional electrical stimulation to improve respiratory function after spinal cord injury: a systematic review and meta-analysis

Objectives: Abdominal functional electrical stimulation (abdominal FES) is the application of a train of electrical pulses to the abdominal muscles, causing them to contract. Abdominal FES has been used as a neuroprosthesis to acutely augment respiratory function and as a rehabilitation tool to achieve a chronic increase in respiratory function after abdominal FES training, primarily focusing on patients with spinal cord injury (SCI). This study aimed to review the evidence surrounding the use of abdominal FES to improve respiratory function in both an acute and chronic manner after SCI. Settings: A systematic search was performed on PubMed, with studies included if they applied abdominal FES to improve respiratory function in patients with SCI. Methods: Fourteen studies met the inclusion criteria (10 acute and 4 chronic). Low participant numbers and heterogeneity across studies reduced the power of the meta-analysis. Despite this, abdominal FES was found to cause a significant acute improvement in cough peak flow, whereas forced exhaled volume in 1 s approached significance. A significant chronic increase in unassisted vital capacity, forced vital capacity and peak expiratory flow was found after abdominal FES training compared with baseline. Conclusions: This systematic review suggests that abdominal FES is an effective technique for improving respiratory function in both an acute and chronic manner after SCI. However, further randomised controlled trials, with larger participant numbers and standardised protocols, are needed to fully establish the clinical efficacy of this technique

Improved Measurements of Partial Rate Asymmetry in B -> h h Decays

We report improved measurements of the partial rate asymmetry (Acp) in B -> h h decays with 140fb^-1 of data collected with the Belle detector at the KEKB e+e- collider. Here h stands for a charged or neutral pion or kaon and in total five decay modes are included: K-+ pi+-, K0s pi-+, K-+ pi0, pi-+ pi0 and K0s pi0. The flavor of the last decay mode is determined from the accompanying B meson. Using a data sample 4.7 times larger than that of our previous measurement, we find Acp(K-+ pi+-) -0.088+-0.035+-0.013, 2.4 sigma from zero. Results for other decay modes are also presented.Comment: 9 pages, 1 figur

Measurements of the masses and widths of the Σc(2455)0/++\Sigma_{c}(2455)^{0/++} and Σc(2520)0/++\Sigma_{c}(2520)^{0/++} baryons

We present measurements of the masses and decay widths of the baryonic states $\Sigma_{c}(2455)^{0/++}$ and $\Sigma_{c}(2520)^{0/++}$ using a data sample corresponding to an integrated luminosity of 711 fb$^{-1}$ collected with the Belle detector at the KEKB $e^{+}e^{-}$ asymmetric-energy collider operating at the $\Upsilon(4S)$ resonance. We report the mass differences with respect to the $\Lambda_{c}^{+}$ baryon $M(\Sigma_{c}(2455)^{0})-M(\Lambda_{c}^{+}) = 167.29\pm0.01\pm0.02$ MeV/$c^{2}$, $M(\Sigma_{c}(2455)^{++})-M(\Lambda_{c}^{+}) = 167.51\pm0.01\pm0.02$ MeV/$c^{2}$, $M(\Sigma_{c}(2520)^{0})-M(\Lambda_{c}^{+}) = 231.98\pm0.11\pm0.04$ MeV/$c^{2}$, $M(\Sigma_{c}(2520)^{++})-M(\Lambda_{c}^{+}) = 231.99\pm0.10\pm0.02$ MeV/$c^{2}$, and the decay widths $\Gamma(\Sigma_{c}(2455)^{0}) = 1.76\pm0.04^{+0.09}_{-0.21}$ MeV/$c^{2}$, $\Gamma(\Sigma_{c}(2455)^{++}) = 1.84\pm0.04^{+0.07}_{-0.20}$ MeV/$c^{2}$, $\Gamma(\Sigma_{c}(2520)^{0}) = 15.41\pm0.41^{+0.20}_{-0.32}$ MeV/$c^{2}$, $\Gamma(\Sigma_{c}(2520)^{++}) = 14.77\pm0.25^{+0.18}_{-0.30}$ MeV/$c^{2}$, where the first uncertainties are statistical and the second are systematic. The isospin mass splittings are measured to be $M(\Sigma_{c}(2455)^{++})-M(\Sigma_{c}(2455)^{0})=0.22\pm0.01\pm0.01$ MeV/$c^{2}$ and $M(\Sigma_{c}(2520)^{++})-M(\Sigma_{c}(2520)^{0})=0.01\pm0.15\pm0.03$ MeV/$c^{2}$. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC

Observation of D0→ρ0γD^0\to \rho^0\gamma and search for CPCP violation in radiative charm decays

We report the first observation of the radiative charm decay $D^0 \to \rho^0 \gamma$ and the first search for $CP$ violation in decays $D^0 \to \rho^0 \gamma$, $\phi\gamma$, and $\overline{K}{}^{*0} \gamma$, using a data sample of 943 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The branching fraction is measured to be $\mathcal{B}(D^0 \to \rho^0 \gamma)=(1.77 \pm 0.30 \pm 0.07) \times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. The obtained $CP$ asymmetries, $\mathcal{A}_{CP}(D^0 \to \rho^0 \gamma)=+0.056 \pm 0.152 \pm 0.006$, $\mathcal{A}_{CP}(D^0 \to \phi \gamma)=-0.094 \pm 0.066 \pm 0.001$, and $\mathcal{A}_{CP}(D^0 \to \overline{K}{}^{*0} \gamma)=-0.003 \pm 0.020 \pm 0.000$, are consistent with no $CP$ violation. We also present an improved measurement of the branching fractions $\mathcal{B}(D^0 \to \phi \gamma)=(2.76 \pm 0.19 \pm 0.10) \times 10^{-5}$ and $\mathcal{B}(D^0 \to \overline{K}{}^{*0} \gamma)=(4.66 \pm 0.21 \pm 0.21) \times 10^{-4}$

Study of Excited Ξc\Xi_c States Decaying into Ξc0\Xi_c^0 and Ξc+\Xi_c^+ Baryons

Using a data sample of 980 ${\rm fb}^{-1}$ of $e^+e^-$ annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we report the results of a study of excited $\Xi_c$ states that decay, via the emission of photons and/or charged pions, into $\Xi_c^0$ or $\Xi_c^+$ ground state charmed-strange baryons. We present new measurements of the masses of all members of the $\Xi_c^{\prime}$, $\Xi_c(2645)$, $\Xi_c(2790)$, $\Xi_c(2815)$, and $\Xi_c(2980)$ isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.Comment: Submitted to PR

Search for a massive invisible particle X0X^0 in B+→e+X0B^{+}\to e^{+}X^{0} and B+→μ+X0B^{+}\to \mu^{+}X^{0} decays

We present a search for a non-Standard-Model invisible particle $X^0$ in the mass range $0.1\textrm{-}1.8 \,{\rm GeV}/{c^2}$ in $B^{+}\to e^{+} X^{0}$ and $B^{+}\to \mu^{+} X^{0}$ decays. The results are obtained from a $711~{\rm fb}^{-1}$ data sample that corresponds to $772 \times 10^{6} B\bar{B}$ pairs, collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. One $B$ meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner $B$ meson. We find no evidence of a signal and set upper limits on the order of $10^{-6}$.Comment: 8 pages, 4 figures, 3 table

Search for composite and exotic fermions at LEP 2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio

Observation of D0−Dˉ0D^0-\bar{D}^0 Mixing in e+e−e^+e^- Collisions

We observe $D^0-\bar{D}^0$ mixing in the decay $D^0\rightarrow K^+\pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x'}^2 = (0.09\pm0.22)\times 10^{-3}$ and $y' = (4.6\pm3.4)\times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53\pm0.13)\times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.Comment: 6 pages, 4 figure