10,096 research outputs found
Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing
The positron-neutrino correlation in the 0^+ \to 0^+ \beta decay of ^{32}Ar
was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of
the narrow proton group following the superallowed decay. Our result is
consistent with the Standard Model prediction; for vanishing Fierz interference
we find a=0.9989 \pm 0.0052 \pm 0.0036. Our result leads to improved
constraints on scalar weak interactions. The positron-neutrino correlation in
^{33}Ar decay was measured in the same experiment; for vanishing Fierz
interference we find a=0.944 \pm 0.002 \pm 0.003. The ^{32}Ar and ^{33}Ar
correlations, in combination with precision measurements of the half-lives,
superallowed branching ratios and beta endpoint energies, will determine the
isospin impurities of the superallowed transitions. These will provide useful
tests of isospin-violation corrections used in deducing |V_{\rm ud}| which
currently indicates non-unitarity of the KM matrix.Comment: 15 pages, 6 figure
Nano granular metallic Fe - oxygen deficient TiO composite films: A room temperature, highly carrier polarized magnetic semiconductor
Nano granular metallic iron (Fe) and titanium dioxide (TiO) were
co-deposited on (100) lanthanum aluminate (LaAlO) substrates in a low
oxygen chamber pressure using a pulsed laser ablation deposition (PLD)
technique. The co-deposition of Fe and TiO resulted in 10 nm
metallic Fe spherical grains suspended within a TiO matrix. The
films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss
at room temperature. Our estimate of the saturation magnetization based on the
size and distribution of the Fe spheres agreed well with the measured value.
The film composite structure was characterized as p-type magnetic semiconductor
at 300 K with a carrier density of the order of . The
hole carriers were excited at the interface between the nano granular Fe and
TiO matrix similar to holes excited in the metal/n-type
semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS)
devices. From the large anomalous Hall effect directly observed in these films
it follows that the holes at the interface were strongly spin polarized.
Structure and magneto transport properties suggested that these PLD films have
potential nano spintronics applications.Comment: 6 pages in Latex including 8 figure
Issues and Opportunities in Exotic Hadrons
The last few years have been witness to a proliferation of new results
concerning heavy exotic hadrons. Experimentally, many new signals have been
discovered that could be pointing towards the existence of tetraquarks,
pentaquarks, and other exotic configurations of quarks and gluons.
Theoretically, advances in lattice field theory techniques place us at the cusp
of understanding complex coupled-channel phenomena, modelling grows more
sophisticated, and effective field theories are being applied to an ever
greater range of situations. It is thus an opportune time to evaluate the
status of the field. In the following, a series of high priority experimental
and theoretical issues concerning heavy exotic hadrons is presented.Comment: White paper from INT workshop, "Modern Exotic Hadrons". References
added. Version to appear in Chinese Physics
Quantum sticking, scattering and transmission of 4He atoms from superfluid 4He surfaces
We develop a microscopic theory of the scattering, transmission, and sticking
of 4He atoms impinging on a superfluid 4He slab at near normal incidence, and
inelastic neutron scattering from the slab. The theory includes coupling
between different modes and allows for inelastic processes. We find a number of
essential aspects that must be observed in a physically meaningful and reliable
theory of atom transmission and scattering; all are connected with
multiparticle scattering, particularly the possibility of energy loss. These
processes are (a) the coupling to low-lying (surface) excitations
(ripplons/third sound) which is manifested in a finite imaginary part of the
self energy, and (b) the reduction of the strength of the excitation in the
maxon/roton region
Non-Hermitian Hamiltonians with real eigenvalues coupled to electric fields: from the time-independent to the time dependent quantum mechanical formulation
We provide a reviewlike introduction into the quantum mechanical formalism
related to non-Hermitian Hamiltonian systems with real eigenvalues. Starting
with the time-independent framework we explain how to determine an appropriate
domain of a non-Hermitian Hamiltonian and pay particular attention to the role
played by PT-symmetry and pseudo-Hermiticity. We discuss the time-evolution of
such systems having in particular the question in mind of how to couple
consistently an electric field to pseudo-Hermitian Hamiltonians. We illustrate
the general formalism with three explicit examples: i) the generalized Swanson
Hamiltonians, which constitute non-Hermitian extensions of anharmonic
oscillators, ii) the spiked harmonic oscillator, which exhibits explicit
supersymmetry and iii) the -x^4-potential, which serves as a toy model for the
quantum field theoretical phi^4-theory.Comment: 14 pages, 3 figures, to appear in Laser Physics, minor typos
correcte
Positron-neutrino correlation in the 0^+ \to 0^+ decay of ^{32}Ar
The positron-neutrino correlation in the decay of
Ar was measured at ISOLDE by analyzing the effect of lepton recoil on
the shape of the narrow proton group following the superallowed decay. Our
result is consistent with the Standard Model prediction. For vanishing Fierz
interference we find , which yields improved
constraints on scalar weak interactions
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