6,238 research outputs found
Fourfold oscillations and anomalous magnetic irreversibility of magnetoresistance in the non-metallic regime of Pr1.85Ce0.15CuO4
Using magnetoresistance measurements as a function of applied magnetic field
and its direction of application, we present sharp angular-dependent
magnetoresistance oscillations for the electron-doped cuprates in their
low-temperature non-metallic regime. The presence of irreversibility in the
magnetoresistance measurements and the related strong anisotropy of the field
dependence for different in-plane magnetic field orientations indicate that
magnetic domains play an important role for the determination of electronic
properties. These domains are likely related to the stripe phase reported
previously in hole-doped cuprates.Comment: 11 pages, 5 figure
Potentiel De DĂ©couverte D'un Boson De Higgs Lourd Avec Le DĂ©tecteur Atlas
One of the main goals of the Large Hadron Collider (LHC) and of the ATLAS detector at CERN is to understand the mechanism that underlies the breaking of electroweak symmetry. To do this, different strategies have been developed to search for the Higgs
Performance of a deterministic source of entangled photonic qubits
We study the possible limitations and sources of decoherence in the scheme
for the deterministic generation of polarization-entangled photons, recently
proposed by Gheri et al. [K. M. Gheri et al., Phys. Rev. A 58, R2627 (1998)],
based on an appropriately driven single atom trapped within an optical cavity.
We consider in particular the effects of laser intensity fluctuations, photon
losses, and atomic motion.Comment: 10 pages, 6 figure
The heavy quark search at the LHC
We explore further the discovery potential for heavy quarks at the LHC, with
emphasis on the and of a sequential fourth family associated with
electroweak symmetry breaking. We consider QCD multijets, ,
and single backgrounds using event generation based on
improved matrix elements and low sensitivity to the modeling of initial state
radiation. We exploit a jet mass technique for the identification of
hadronically decaying 's and 's, to be used in the reconstruction of the
or mass. This along with other aspects of event selection can reduce
backgrounds to very manageable levels. It even allows a search for both
and in the absence of -tagging, of interest for the early running of
the LHC. A heavy quark mass of order 600 GeV is motivated by the connection to
electroweak symmetry breaking, but our analysis is relevant for any new heavy
quarks with weak decay modes.Comment: 12 pages, 7 figure
Ultrastable CO2 Laser Trapping of Lithium Fermions
We demonstrate an ultrastable CO2 laser trap that provides tight confinement
of neutral atoms with negligible optical scattering and minimal laser-noise-
induced heating. Using this method, fermionic 6Li atoms are stored in a 0.4 mK
deep well with a 1/e trap lifetime of 300 sec, consistent with a background
pressure of 10^(-11) Torr. To our knowledge, this is the longest storage time
ever achieved with an all-optical trap, comparable to the best reported
magnetic traps.Comment: 4 pages using REVTeX, 1 eps figur
Cavity cooling of a single atom
All conventional methods to laser-cool atoms rely on repeated cycles of
optical pumping and spontaneous emission of a photon by the atom. Spontaneous
emission in a random direction is the dissipative mechanism required to remove
entropy from the atom. However, alternative cooling methods have been proposed
for a single atom strongly coupled to a high-finesse cavity; the role of
spontaneous emission is replaced by the escape of a photon from the cavity.
Application of such cooling schemes would improve the performance of atom
cavity systems for quantum information processing. Furthermore, as cavity
cooling does not rely on spontaneous emission, it can be applied to systems
that cannot be laser-cooled by conventional methods; these include molecules
(which do not have a closed transition) and collective excitations of Bose
condensates, which are destroyed by randomly directed recoil kicks. Here we
demonstrate cavity cooling of single rubidium atoms stored in an intracavity
dipole trap. The cooling mechanism results in extended storage times and
improved localization of atoms. We estimate that the observed cooling rate is
at least five times larger than that produced by free-space cooling methods,
for comparable excitation of the atom
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