Attraction and repulsion of spiral waves by inhomogeneity of conduction anisotropy-a model of spiral wave interaction with electrical remodeling of heart tissue

Various forms of heart disease are associated with remodeling of the heart muscle, which results in a perturbation of cell-to-cell electrical coupling. These perturbations may alter the trajectory of spiral wave drift in the heart muscle. We investigate the effect of spatially extended inhomogeneity of transverse cell coupling on the spiral wave trajectory using a simple active media model. The spiral wave was either attracted or repelled from the center of inhomogeneity as a function of cell excitability and gradient of the cell coupling. High levels of excitability resulted in an attraction of the wave to the center of inhomogeneity, whereas low levels resulted in an escape and termination of the spiral wave. The spiral wave drift velocity was related to the gradient of the coupling and the initial position of the wave. In a diseased heart, a region of altered transverse coupling corresponds with local gap junction remodeling that may be responsible for stabilization-destabilization of spiral waves and hence reflect potentially important targets in the treatment of heart arrhythmias.Pawel Kuklik, Prashanthan Sanders, Lukasz Szumowski, Jan J. Żebrowsk

Observation of the Cabibbo-suppressed decay Xi(+)(c) -> pK(-)pi(+)

We report the first observation of the Cabibbo-suppressed charm baryon decay Xi(c)(+) --> pK(-)pi(+) We observe 150 +/- 22 +/- 5 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Sigma(-) beam. The branching fractions of the decay relative to the Cabibbo-favored Xi(c)(+) --> Sigma(+)K(-)pi(+) and Xi(c)(+) --> Xi(-)pi(+)pi(+) are measured to be B(Xi(c)(+) --> pK(-)pi(+))/B(Xi(c)(+) --> Sigma(+)K(-)pi(+)) = 0.22 +/- 0.06 +/- 0.03 and B(Xi(c)(+) --> pK(-)pi(+))/B(Xi(c)(+) --> Xi(-)pi(+)pi(+)) = 0.20 +/- 0.04 +/- 0.02, respectively

Charm hadroproduction results from Selex

The SELEX experiment (E781) is 5-stage magnetic spectrometer for a high statistics study of hadroproduction of charm baryons out to large x(F) using 650 Gev Sigma (-), pi (-) and p beams. The main features of the spectrometer are: a high precision silicon vertex system, powerful particle identification provided by TRD and RICH, forward Lambda (s) decay spectrometer and 3-stage lead glass photon detector. An experiment overview and spectrometer features are shown. Reconstructed charm states and results on Lambda (c), D+ particles and antiparticles produced by Sigma (-), pi (-) and p beams at x(F) > 0.3 and asymmetry for Lambda (c) are presented

Radiative decay width of the a(2)(1320)(-) meson

Coherent pi (+)pi (-)pi (-) production in the interactions of a beam of 600GeV pi (-) mesons with C, Cu and Pb nuclei has been studied with the SELEX facility (Experiment E781 at Fermilab). The a(2)(1320) meson signal has been detected in the Coulomb (low q(2)) region. The Primakoff formalism used to extract radiative decay width of this meson yields Gamma = 284 +/- 25 +/- 25 keV, which is the most precise measurement to date. (C) 2001 Elsevier Science B.V. All rights reserved

Upper limit on the decay Sigma(1385)(-) -> Sigma(-)gamma and cross section for gamma Sigma(-) -> Lambda pi(-)

Coherent Lambdapi(-) production on Pb of 600 GeV Sigma(-) hyperons has been studied with the SELEX facility at Fermilab. Using the Primakoff formalism, we set a 90% CL upper limit on the radiative decay width Gamma[Sigma(1385)(-) --> Sigma(-) gamma] Lambdapi(-) at roots approximate to 1.385 GeV to be 56 +/- 16 mub. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved

Production asymmetry of D-s from 600 GeV/c Sigma(-) and pi(-) beam

The production of D-S(-) relative to D-S(+) as a function of x(F) with 600 GeV/c Sigma(-) beam is measured in the interval 0.15 < x(F) < 0.7 by the SELEX (E781) experiment at Fermilab. The integrated charge asymmetries with 600 GeV/c Sigma(-) beam (0.53 +/- 0.06) and pi(-) beam (0.06 +/- 0.11) are also compared. The results show the Sigma(-) beam fragments play a role in the production of D-S(-), as suggested by the leading quark model. (C) 2003 Elsevier Science B.V. All rights reserved