Theory of Coexistence of Superconductivity and Ferroelectricity : A Dynamical Symmetry Model

We propose and investigate a model for the coexistence of Superconductivity (SC) and Ferroelectricity (FE) based on the dynamical symmetries $su(2)$ for the pseudo-spin SC sector, $h(4)$ for the displaced oscillator FE sector, and $su(2) \otimes h(4)$ for the composite system. We assume a minimal symmetry-allowed coupling, and simplify the hamiltonian using a double mean field approximation (DMFA). A variational coherent state (VCS) trial wave-function is used for the ground state: the energy, and the relevant order parameters for SC and FE are obtained. For positive sign of the SC-FE coupling coefficient, a non-zero value of either order parameter can suppress the other (FE polarization suppresses SC and vice versa). This gives some support to "Matthias' Conjecture" [1964], that SC and FE tend to be mutually exclusive. For such a Ferroelectric Superconductor we predict: a) the SC gap $\Delta$ (and $T_c$) will increase with increasing applied pressure when pressure quenches FE as in many ferroelectrics, and b) the FE polarization will increase with increaesing magnetic field up to $H_c$. The last result is equivalent to the prediction of a new type of Magneto-Electric Effect in a coexistent SC-FE material. Some discussion will be given of the relation of these results to the cuprate superconductors.Comment: 46 page

Study of the process e + e − → π + π − π 0 η in the c.m. energy range 1394–2005 MeV with the CMD-3 detector

The cross section of the process e+e−→π+π−π0η has been measured using a data sample of 21.8 pb−1 collected with the CMD-3 detector at the VEPP-2000 e+e− collider. 2769±95 signal events have been selected in the center-of-mass energy range 1394–2005 MeV. The production dynamics is dominated by the ω(782)η and ϕ(1020)η intermediate states in the lower energy range, and by the a0(980)ρ(770) intermediate state at higher energies

CMD-3 Overview

The CMD-3 detector is installed at the VEPP-2000 e+e− collider at BINP (Novosibirsk, Russia). It is a general-purpose detector, equipped with a tracking system, two crystal (CSI and BGO) calorimeters, liquid Xe calorimeter, TOF and muon systems. The main goal of experiments at CMD-3 is a study of exclusive modes of e+e−→ hadrons at energies $\sqrt s \le$ GeV. In particular, these results provide an important input for calculation of the hadronic contribution to the muon anomalous magnetic moment. The first round of data taking was performed in 2011–2013, when about 60 1/pb were taken in the center-of-mass (c.m.) energy range from 0.32 to 2.0 GeV. Here we present a survey of results of data analysis. Between 2013 and 2016 the collider and the detector were upgraded. The data taking resumed by the end of 2016. In the first run after the upgrade about 50 1/pb were collected at the energy range between 1.28 and 2.007 GeV. We discuss the upgrade and the first preliminary results from the new data

Study of the process e+e−→KS0KL0 in the center-of-mass energy range 1004–1060 MeV with the CMD-3 detector at the VEPP-2000 e+e− collider

AbstractThe e+e−→KS0KL0 cross section has been measured in the center-of-mass energy range 1004–1060 MeV at 25 energy points using 6.1×105 events with KS0→π+π− decay. The analysis is based on 5.9 pb−1 of an integrated luminosity collected with the CMD-3 detector at the VEPP-2000 e+e− collider. To obtain ϕ(1020) meson parameters the measured cross section is approximated according to the Vector Meson Dominance model as a sum of the ρ,ω,ϕ-like amplitudes and their excitations. This is the most precise measurement of the e+e−→KS0KL0 cross section with a 1.8% systematic uncertainty

Search for the process e+e−→η′(958) with the CMD-3 detector

AbstractA search for the process e+e−→η′(958) in the π+π−η→π+π−γγ final state has been performed with the CMD-3 detector at the VEPP-2000 e+e− collider. Using an integrated luminosity of 2.69 pb−1 collected at the center-of-mass energy Ec.m.=957.68 MeV we set an upper limit for the product of electronic width and branching fractions Γη′(958)→e+e−⋅Bη′(958)→π+π−η⋅Bη→γγ<0.00041 eV at 90% C.L

Preliminary results on CMD-3 measurement of

The CMD-3 detector has been successfully collecting data at the electron-positron collider VEPP-2000 since December 2010. The first scan below 1 GeV for a π+π− measurement was performed in 2013. The collected data sample corresponds to about 18 pb−1 of integrated luminosity in this energy range. Analysis of the e+e−→ π+π− cross section is in progress. Status of this measurement are presented