90,125 research outputs found
Probing the low-x structure of nuclear matter with diffractive hadron production in pA collisions
We argue that hadron production in coherent diffraction of proton on a heavy
nucleus provides a very sensitive probe of the low-x QCD dynamics. This process
probes the BFKL dynamics in proton and the non-linear gluon evolution in
nucleus. We calculate the diffractive hadron production cross sections in the
RHIC and LHC kinematic regions. To study the nuclear effects we introduce the
diffractive nuclear modification factor. We show that unlike the nuclear
modification factor for inclusive hadron production that has a very interesting
dynamics at RHIC but is expected to be almost completely saturated at the LHC,
the nuclear modification factor for diffractive production exhibits a
non-trivial behavior both at RHIC and LHC.Comment: 18 pages, 7 figure
Recent results from BRAHMS
The BRAHMS collaboration ended its data collection program in 2006. We are
now well advanced in the analysis of a comprehensive set of data that spans
systems ranging in mass from p+p to Au+Au and in energy from to 200 GeV. Our analysis has taken two distinct paths: we explore the
rapidity dependence of intermediate and high-transverse-momentum,
identified-particle production, thus helping to characterize the
strongly-interacting quark-gluon plasma (sQGP) formed at RHIC; we also explore
particle yields at lower transverse momentum to develop a systematic
understanding of bulk particle production at RHIC energies.Comment: 8 pages, 5 figures, presented at the 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur,
India, February 4-10, 200
Description of spin transport and precession in spin-orbit coupling systems and a general equation of continuity
By generalizing the usual current density to a matrix with respect to spin
variables, a general equation of continuity satisfied by the density matrix and
current density matrix has been derived. This equation holds in arbitrary
spin-orbit coupling systems as long as its Hamiltonian can be expressed in
terms of a power series in momentum. Thereby, the expressions of the current
density matrix and a torque density matrix are obtained. The current density
matrix completely describes both the usual current and spin current as well;
while the torque density matrix describes the spin precession caused by a total
effective magnetic field, which may include a realistic and an effective one
due to the spin-orbit coupling. In contrast to the conventional definition of
spin current, this expression contains an additional term if the Hamiltonian
includes nonlinear spin-orbit couplings. Moreover, if the degree of the full
Hamiltonian , then the particle current must also be modified in order
to satisfy the local conservation law of number.Comment: 9 page
High-quality Image Restoration from Partial Mixed Adaptive-Random Measurements
A novel framework to construct an efficient sensing (measurement) matrix,
called mixed adaptive-random (MAR) matrix, is introduced for directly acquiring
a compressed image representation. The mixed sampling (sensing) procedure
hybridizes adaptive edge measurements extracted from a low-resolution image
with uniform random measurements predefined for the high-resolution image to be
recovered. The mixed sensing matrix seamlessly captures important information
of an image, and meanwhile approximately satisfies the restricted isometry
property. To recover the high-resolution image from MAR measurements, the total
variation algorithm based on the compressive sensing theory is employed for
solving the Lagrangian regularization problem. Both peak signal-to-noise ratio
and structural similarity results demonstrate the MAR sensing framework shows
much better recovery performance than the completely random sensing one. The
work is particularly helpful for high-performance and lost-cost data
acquisition.Comment: 16 pages, 8 figure
Collective excitation of quantum wires and effect of spin-orbit coupling in the presence of a magnetic field along the wire
The band structure of a quantum wire with the Rashba spin-orbit coupling
develops a pseudogap in the presence of a magnetic field along the wire. In
such a system spin mixing at the Fermi wavevectors and can be
different. We have investigated theoretically the collective mode of this
system, and found that the velocity of this collective excitation depends
sensitively on the strength of the Rashba spin-orbit interaction and magnetic
field. Our result suggests that the strength of the spin-orbit interaction can
be determined from the measurement of the velocity.Comment: RevTeX 4 file, 4pages, 6 eps figures. To appear in Physical Review
HRTEM study of a new non-stoichiometric BaTiO(3-δ) structure
BaTiO3-based multilayer ceramic capacitors (MLCCs) with Ni internal electrodes are co-fired in
reducing atmospheres to avoid oxidation of the electrode. Although dielectric materials are doped by
acceptor, donor and amphoteric dopants to minimize the oxygen vacancy content, there is still a
large concentration of oxygen vacancies that are accommodated in the BaTiO3 active layers. In
general, ABO3 perovskites demonstrates a strong ability to accommodate the oxygen vacancies and
maintain a regular pseudo-cubic structure. Oxygen deficient barium titanate can be transformed to a
hexagonal polymorph (h-BT) at high temperatures1,2. In this paper, we report the new modulated and
long range ordered structures of non-stoichiometric BaTiO3-δ that are observed in the electrically
degraded Ni-BaTiO3 MLCCs at low temperature
Gluon recombination in high parton density QCD: inclusive pion production
We argue that the collinear factorization of the fragmentation functions in
high energy hadron and nuclei collisions breaks down at transverse momenta kT <
Qs/g due to high parton densities in the colliding hadrons and/or nuclei. We
calculate, at next-to-leading order in projectile parton density and to all
orders in target parton density, the double-inclusive cross section for
production of a pair of gluons in the scalar J^(PC)=0^(++) channel. Using the
low energy theorems of QCD we find the inclusive cross section for pi-meson
production.Comment: 24 pages, 5 figure
Gluon multiplicity in coherent diffraction of onium on a heavy nucleus
We derive the cross section for the diffractive gluon production in high
energy onium-nucleus collisions that includes the low-x evolution effects in
the rapidity interval between the onium and the produced gluon and in the
rapidity interval between the gluon and the target nucleus. We analyze our
result in two limiting cases: when the onium size is much smaller than the
saturation scale and when its size is much larger than the saturation scale. In
the later case the gluon multiplicity is very small in the quasi-classical case
and increases when the low-x evolution effects in onium become significant. We
discuss the implications of our result for the RHIC, LHC and EIC phenomenology.Comment: 21 pages, 5 figure
Spin polarization of the quantum Hall state
We report on results of numerical studies of the spin polarization of the
half filled second Landau level, which corresponds to the fractional quantum
Hall state at filling factor . Our studies are performed using both
exact diagonalization and Density Matrix Renormalization Group (DMRG) on the
sphere. We find that for the Coulomb interaction the exact finite-system ground
state is fully polarized, for shifts corresponding to both the Moore-Read
Pfaffian state and its particle-hole conjugate (anti-Pfaffian). This result is
found to be robust against small variations of the interaction. The low-energy
excitation spectrum is consistent with spin-wave excitations of a
fully-magnetized ferromagnet.Comment: Final version published on PR
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