10 research outputs found
Reentrant behavior of superconducting alloys
A dirty BCS superconductor with magnetic impurities is studied. Asymptotic
solution of the thermodynamics of such superconductor with spin and
magnetic impurities, is found. To this end, the system's free energy is bounded from above and below by mean-field type bounds, which are
shown to coalesce almost exactly in the thermodynamic limit, provided the
impurity concentration is sufficiently small. The resulting mean-field
equations for the gap and a parameter , characterizing the
impurity subsystem, are solved and the solution minimizing is found for
various values of magnetic coupling constant and impurity concentration
. The phase diagrams of the system are depicted with five distinct phases:
the normal phase, unperturbed superconducting phase, perturbed superconducting
phase with nonzero gap in the excitation spectrum, perturbed gapless
superconducting phase and impurity phase with completely suppressed
superconductivity. Furthermore, evidence of reentrant superconductivity and
Jaccarino-Peter compensation is found. The credibility of the theory is
verified by testing the dependence of the superconducting transition
temperature on . Very good quantitative agreement with
experimental data is obtained for several alloys: (LaCe)Al,
(LaGd)Al and (LaY)Ce. The theory
presented improves earlier developments in this field.Comment: 15 pages, 8 figures, full length articl
NA61/SHINE facility at the CERN SPS: beams and detector system
NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multi-purpose
experimental facility to study hadron production in hadron-proton,
hadron-nucleus and nucleus-nucleus collisions at the CERN Super Proton
Synchrotron. It recorded the first physics data with hadron beams in 2009 and
with ion beams (secondary 7Be beams) in 2011.
NA61/SHINE has greatly profited from the long development of the CERN proton
and ion sources and the accelerator chain as well as the H2 beamline of the
CERN North Area. The latter has recently been modified to also serve as a
fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous
components of the NA61/SHINE set-up were inherited from its predecessors, in
particular, the last one, the NA49 experiment. Important new detectors and
upgrades of the legacy equipment were introduced by the NA61/SHINE
Collaboration.
This paper describes the state of the NA61/SHINE facility - the beams and the
detector system - before the CERN Long Shutdown I, which started in March 2013
Two-particle correlations in azimuthal angle and pseudorapidity in inelastic p + p interactions at the CERN Super Proton Synchrotron
Results on two-particle ΔηΔϕ correlations in inelastic p + p interactions at 20, 31, 40, 80, and 158 GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the Epos and UrQMD models.ISSN:1434-6044ISSN:1434-605