Moving Quarks Help Solve Proton Spin Puzzle
The famous proton spin problem, which began with data from the European
Muon Collaboration 20 years ago, keeps producing new surprises. It was
thought that the spin of the proton would come from its quarks, but the
EMC found that the quarks' combined spin didn't account for all of the
proton's spin. Researchers began investigating other spin sources, such as
the gluons that hold the quarks together and spin generated by the
movement of the quarks, called orbital angular momentum. This Letter
explains that within the successful model recently proposed by Myhrer and
Thomas, more than half of the spin of the proton is actually carried as
orbital angular momentum by its quarks. Even more fascinating, it is
shown, as a model independent consequence of QCD evolution, that whereas
the orbital angular momentum of up quarks is much larger than that of down
quarks at low resolution, this reverses at higher resolution. The
resulting high-resolution values are in surprisingly good agreement with
state-of-the-art lattice QCD calculations, as well as with recent studies
of Generalized Parton Distributions conducted at Hermes and JLab.
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LQ11129B
Charge and spin pairing instabilities in nanoclusters
Scientists have been trying to explain the unique superconducting, ferromagnetic, ferroelectric properties in inhomogeneous cuprates, manganites and multiferroics for many decades. However, not much progress has been reached based on studies of long range electron correlations appropriate for large homogeneous systems. In contrast, we propose exact microscopic analyses of local correlations in nanoclusters (triangles, tetrahedrons, octahedrons) that give important clues for understanding the origin of pseudogaps and inhomogeneities in respective frustrated (triangular, pyrochlore, perovskite) bulk structures. This bottom-up approach allows to unravel the details which depend on the local cluster geometry, electron interaction and temperature e.g. to investigate many body physics and spatial inhomogeneities in high Tc cuprates, manganites and multiferroics. For the first time we show that electrons' charge and spin in nanoscale undergo spin-charge separation instabilities and various types of pairings. The exact phase diagrams that we obtain provide novel insight into electron condensation, magnetism, ferroelectricity and display a number of inhomogeneous, coherent and incoherent nanophases seen recently by scanning tunneling microscopy in numerous nanomaterials, assembled nanoclusters, ultra-cold fermionic atoms.
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BP10522
Observation of the Josephson effect in thin films YBa2Cu3O7 samples
We have observed for the the first time the Josephson modulation of the
maximum superconducting current flowing in YBa2Cu3O7 films with
non-nanometric dimensions. Josephson effect is the transport of
superconducting electrons from a superconductor to a neighboring one
across a non-superconducting barrier. A well-known manifestation of this
effect is the modulation of the maximum current flowing across the barrier
by a magnetic field. Since the discovery of the high temperature
superconductor YBa2Cu3O7, many authors have pointed out that this oxide
includes boundary planes between crystalline domains that could behave as
Josephson barriers. However, the magnetic modulation of the barrier
current had never been observed, except in samples with nanometric
dimensions and in films including artificial grain boundaries. In this
paper we establish the experimental conditions required for the
observation of the effect in thin film YBa2Cu3O7 strips with
non-nanometric dimensions and we report the modulation of the maximum
supercurrent by a low magnetic field observed in two samples.
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LP11484
Alpha Particle Condensation in Nuclei
An atomic nucleus can have a gas-like structure composed of alpha particles.
The alpha particle, helium nucleus, is a tightly bound quartet containing two protons and two neutrons. A clump of alpha particles interacting weakly with each other is bound as a gaseous nuclear state.
The most amazing is that they can be condensed into a single quantum orbit,
reflecting Bose statistics of them with spin zero, as might be called
``Bose-Einstein condensation'', which is analogous to the ultra-cold atomic
gas condensation. A characteristic aspect inherent to the nuclear system is
that the phenomenon can only be observed in excited states not in the ground
states, because in the ground states with higher density all of the alpha
particles dissolve into nucleons in pieces, i.e. into liquid of nucleons. Ever since the possibility of occurrence of the novel structure was suggested by some of the present authors, a lot of theoretical and experimental efforts have been devoted to
revealing presence of the structure. The Hoyle state in 12C, which plays a special role in carbon production in stars, now becomes convincing to be of the dilute three alpha particle condensate.
We investigate quite a wide energy
region in 16O theoretically for finding the quantum condensate with a
gas-like structure of four alpha particles (see figure), and give strong evidence of the existence. This exotic state is obtained together with the
other well-known quantum states, and its candidate for experimental
observation is also mentioned. The present discovery is of a great
significance in convincing the existence in heavier nuclei and in
establishing the new aspect in nuclear physics.
