527 research outputs found
Muon spin relaxation studies of incommensurate magnetism and superconductivity in stage-4 LaCuO and LaSrCuO
This paper reports muon spin relaxation (MuSR) measurements of two single
crystals of the title high-Tc cuprate systems where static incommensurate
magnetism and superconductivity coexist. By zero-field MuSR measurements and
subsequent analyses with simulations, we show that (1) the maximum ordered Cu
moment size (0.36 Bohr magneton) and local spin structure are identical to
those in prototypical stripe spin systems with the 1/8 hole concentration; (2)
the static magnetism is confined to less than a half of the volume of the
sample, and (3) regions with static magnetism form nano-scale islands with the
size comparable to the in-plane superconducting coherence length. By
transverse-field MuSR measurements, we show that Tc of these systems is related
to the superfluid density, in the same way as observed in cuprate systems
without static magnetism. We discuss a heuristic model involving percolation of
these nanoscale islands with static magnetism as a possible picture to
reconcile heterogeneity found by the present MuSR study and long-range spin
correlations found by neutron scattering.Comment: 19 pages, 15 figures, submitted to Phys. Rev. B. E-mail:
[email protected]
The Field Perturbation Theory of the Double Correlated Phase in High Temperature Superconductors
The Double-Correlated phase in HTSC, and its treatment by field perturbation
theory, is established. In particular, we define the ground state, the
quasi-particle excitations, and construct an appropriate field. We also derive
the unperturbed Hamiltonian, and the propagators for the unperturbed state.
Then we discuss the perturbation Hamiltonian, and show that the Hartree diagram
is significant for both the pseudogap and the superconductive order parameter,
and suggest that it yields the major contribution to these parameters.Comment: 23 pages Of MSWord in PDF format, 1 figur
Optimization of Gene Transfer into Neonatal Rat Cardiomyocytes and Unmasking of Cytomegalovirus Promoter Silencing
Measurements of the Sigma_c^0 and Sigma_c^{++} Mass Splittings
Using a high statistics sample of photoproduced charmed particles from the
FOCUS experiment at Fermilab (FNAL-E831), we measure the mass splittings of the
charmed baryons Sigma_c^0 and Sigma_c^{++}. We find M(Sigma_c^0 - Lambda_c^+) =
167.38 +/- 0.21 +/- 0.13 MeV/c^2 and M(Sigma_c^++ - Lambda_c^+) = 167.35 +/-
0.19 +/- 0.12 MeV/c^2 with samples of 362 +/- 36 and 461 +/- 39 events,
respectively. We measure the isospin mass splitting M(Sigma_c^++ - Sigma_c^0)
to be -0.03 +/- 0.28 +/- 0.11 Mev/c^2. The first errors are statistical and the
second are systematic.Comment: 10 pages, 2 figure
Superfluid density of high-Tc cuprate systems: implication on condensation mechanisms, heterogeneity and phase diagram
Extensive muon spin relaxation measurements have been performed to determine
the magnetic field penetration depth in high-Tc cuprate superconductors with
simple hole doping, Zn-doping, overdoping, and formation of static SDW nano
islands. System dependence of (superconducting carrier density /
effective mass) reveals universal correlations between Tc and in
all these cases with / without perturbation. Evidence for spontaneous and
microscopic phase separation was obtained in the cases with strong
perturbation, i.e., Zn-doping. overdoping and SDW nano-islands. The length
scale of this heterogeneity is shown to be comparable to the in-plance
coherence length. We discuss implications of these results on condensation
mechanisms of HTSC systems, resorting to an analogy with He films, on regular
and porous media, reminding essential features of Bose-Einstein, BCS and
Kosterlitz-Thouless condensation/transition in 2-d and 3-d systems, and
comparing models of BE-BCS crossover and phase fluctuations. We propose a new
phase diagram for HTSC systems based on distinction between pair formation and
superconducting phase fluctuations in the pseudogap region and spontaneous
phase separation in the overdoped region. We also remind anomaly in BEDT and
A3C60 systems similar to that in overdoped cuprates, seen in the evolution from
superconducting to metallic ground state.Comment: 21 pages, 18 figures, invited papter presented at the HTSC Workshop,
Williamsburg, Virginia, June 7-8, 2002, to appear in Solid State
Communications (Special Issue edited by A.J. Millis, S. Uchida, Y.J. Uemura):
contact [email protected]
Role of kinase-independent and -dependent functions of FAK in endothelial cell survival and barrier function during embryonic development
Vascular development in mice only requires kinase-independent functions of FAK until E13.5, but kinase activity is needed for embryogenesis to complete
Radiative Decay Modes of the Meson
Using data recorded by the CLEO-II detector at CESR we have searched for four
radiative decay modes of the meson: ,
, , and . We
obtain 90% CL upper limits on the branching ratios of these modes of , , and
respectively.Comment: 15 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
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