Orthorhombically Mixed s and dx2−y2_{x^2-y^2} Wave Superconductivity and Josephson Tunneling

The effect of orthorhombicity on Josephson tunneling in high T$_c$ superconductors such as YBCO is studied for both single crystals and highly twinned crystals. It is shown that experiments on highly twinned crystals experimentally determine the symmetry of the superconducting twin boundaries (which can be either even or odd with respect to a reflection in the twinning plane). Conversely, Josephson experiments on highly twinned crystals can not experimentally determine whether the superconductivity is predominantly $s$-wave or predominantly $d$-wave. The direct experimental determination of the order-parameter symmetry by Josephson tunneling in YBCO thus comes from the relatively few experiments which have been carried out on untwinned single crystals.Comment: 5 pages, RevTeX file, 1 figure available on request ([email protected]

Mixed symmetry superconductivity in two-dimensional Fermi liquids

We consider a 2D isotropic Fermi liquid with attraction in both $s$ and $d$ channels and examine the possibility of a superconducting state with mixed $s$ and $d$ symmetry of the gap function. We show that both in the weak coupling limit and at strong coupling, a mixed $s+id$ symmetry state is realized in a certain range of interaction. Phase transitions between the mixed and the pure symmetry states are second order. We also show that there is no stable mixed $s+d$ symmetry state at any coupling.Comment: 3 figures attached in uuencoded gzipped file

A Measurement of the Decay Asymmetry Parameters in \Xi_{c}^{0}\to \X^{-}\pi^{+}

Using the CLEO II detector at the Cornell Electron Storage Ring we have measured the $\Xi_c^{0}$ decay asymmetry parameter in the decay $\Xi_c^{0} \to \Xi^{-} \pi^+$. We find $\alpha_{\Xi_c^{0}} \alpha_{\Xi} = 0.26 \pm 0.18{(stat)}^{+0.05}_{-0.04}{(syst)}$, using the world average value of $\alpha_{\Xi} = -0.456 \pm 0.014$ we obtain $\alpha_{\Xi_c^{0}} = -0.56 \pm 0.39{(stat)}^{+0.10}_{-0.09}{(syst)}$. The physically allowed range of a decay asymmetry parameter is $-1<\alpha<+1$. Our result prefers a negative value: $\alpha_{\Xi_c^{0}}$ is $<0.1$ at the 90% CL. The central value occupies the middle of the theoretically expected range but is not yet precise enough to choose between models.Comment: 10 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV

Searches for supersymmetry (SUSY) are presented based on the electroweak pair production of neutralinos and charginos, leading to decay channels with Higgs, Z, and W bosons and undetected lightest SUSY particles (LSPs). The data sample corresponds to an integrated luminosity of about 19.5 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV collected in 2012 with the CMS detector at the LHC. The main emphasis is neutralino pair production in which each neutralino decays either to a Higgs boson (h) and an LSP or to a Z boson and an LSP, leading to hh, hZ, and ZZ states with missing transverse energy (E-T(miss)). A second aspect is chargino-neutralino pair production, leading to hW states with E-T(miss). The decays of a Higgs boson to a bottom-quark pair, to a photon pair, and to final states with leptons are considered in conjunction with hadronic and leptonic decay modes of the Z and W bosons. No evidence is found for supersymmetric particles, and 95% confidence level upper limits are evaluated for the respective pair production cross sections and for neutralino and chargino mass values

On grain size dependence of stress hysteresis in shape memory alloy polycrystals: Role of material internal length scales

In this paper, a multiscale continuum model is proposed to study the effect of grain size on the macroscopic dissipative response of shape memory alloy polycrystals during isothermal thermoelastic phase transition. In the simplest one dimensional (1D) heterogeneous structural hierarchy, a series of non-convex and nonlocal 1D continuum elements are employed to model the microinstability and the macroscopic stress hysteresis of the material under uniaxial quasistatic stretching. Three characteristic length scales (specimen size L, grain size l and intrinsic material length g) of a bulk poly crystal are imbedded in the 1D chain model and their important roles in the macroscopic dissipation are quantified. It is shown that that the specific energy dissipation or the width of the stress hysteresis is governed by two nondimensional ratios N (=L/l) and l̄ = (1/g). For a given specimen size L, the hysteresis decreases rapidly at either very large or small values of l̄. In particular, it vanished when the grain size is reduced to the nano-scale where the grain size and the interface thickness become comparable. The above predictions of the 1D model are reproduced in two-dimensional (2D) nonlocal numerical experiment on the energy dissipation during multiple domain evolution in a heterogeneous strip. The predictions of the 1D and 2D models agree qualitatively well with the recent experimental observations on the stress hysteresis in nano-grained superelastic NiTi polycrystals

Frequency-dependent temperature evolution in NiTi shape memory alloy under cyclic loading

We present a simple analytical model to study the temperature evolution of a superelastic NiTi shape memory alloy (SMA) bar under cyclic tensile loading. By dividing the cycle into five characteristic stages and solving the heat transfer equations for each of the stages, we obtain the analytical expressions of the temperature evolution under the cyclic loading of different frequencies (cycle period t_p) in different convective ambients (characterized by heat transfer time t_h). It is found that, due to latent-heat release/absorption, the specimen's temperature oscillates during the cyclic loading, and the oscillation amplitude (δ_stable) increases with the loading frequency and reaches a saturated value in the high-frequency range (t_p/t_p &lt; 0.1). Moreover, due to the heat accumulated from the intrinsic mechanical dissipation (internal friction), the mean-temperature of the specimen increases with the loading frequency. The temperature rise becomes significant in the high-frequency range. These predictions quantitatively agree well with experiments. © 2010 IOP Publishing Ltd

On the Full-Field Deformation of Single Crystal CuAlNi Shape Memory Alloys—Stress-Induced β1 → γ'1 Martensitic Transformation

Using high sensitivity Moiré interference technology, the full deformation fields about the stress-induced martensitic transformation β1 → γ1' of single crystal CuAlNi shape memory alloys (SMAs) are obtained. A straight and sharp interface between martensite and parent phases and its motion during transformation process are clearly observed. The elastic anisotropic properties of the crystal are also quantitatively characterized by this technique. The results show that there is no deformation incompatibility between the two phases, which is different from that of pseudoelasticity where another stress-induced martensitic transformation β1 → β1' occurs. The present results provide an accurate experimental solution for the phase transformation problem in solids