2,047 research outputs found
Polarized 3 parton production in inclusive DIS at small x
Azimuthal angular correlations between produced hadrons/jets in high energy
collisions are a sensitive probe of the dynamics of QCD at small x. Here we
derive the triple differential cross section for inclusive production of 3
polarized partons in DIS at small x using the spinor helicity formalism. The
target proton or nucleus is described using the Color Glass Condensate (CGC)
formalism. The resulting expressions are used to study azimuthal angular
correlations between produced partons in order to probe the gluon structure of
the target hadron or nucleus. Our analytic expressions can also be used to
calculate the real part of the Next to Leading Order (NLO) corrections to
di-hadron production in DIS by integrating out one of the three final state
partons.Comment: 5 pages, 6 figures; version accepted for publication in Physics
Letters
Broadening of HO rotational lines by collision with He atoms at low temperature
We report pressure broadening coefficients for the 21 electric-dipole
transitions between the eight lowest rotational levels of ortho-HO and
para-HO molecules by collisions with He at temperatures from 20 to 120 K.
These coefficients are derived from recently published experimental
state-to-state rate coefficients for HO:He inelastic collisions, plus an
elastic contribution from close coupling calculations. The resulting
coefficients are compared to the available experimental data. Mostly due to the
elastic contribution, the pressure broadening coefficients differ much from
line to line, and increase markedly at low temperature. The present results are
meant as a guide for future experiments and astrophysical observations.Comment: 2 figures, 2 table
How different Fermi surface maps emerge in photoemission from Bi2212
We report angle-resolved photoemission spectra (ARPES) from the Fermi energy
() over a large area of the () plane using 21.2 eV and 32 eV
photons in two distinct polarizations from an optimally doped single crystal of
BiSrCaCuO (Bi2212), together with extensive
first-principles simulations of the ARPES intensities. The results display a
wide-ranging level of accord between theory and experiment and clarify how
myriad Fermi surface (FS) maps emerge in ARPES under various experimental
conditions. The energy and polarization dependences of the ARPES matrix element
help disentangle primary contributions to the spectrum due to the pristine
lattice from those arising from modulations of the underlying tetragonal
symmetry and provide a route for separating closely placed FS sheets in low
dimensional materials.Comment: submitted to PR
Mixing Effects in the Crystallization of Supercooled Quantum Binary Liquids
By means of Raman spectroscopy of liquid microjets we have investigated the
crystallization process of supercooled quantum liquid mixtures composed of
parahydrogen (pH) diluted with small amounts of up to 5\% of either neon or
orthodeuterium (oD), and of oD diluted with either Ne or pH. We
show that the introduction of Ne impurities affects the crystallization
kinetics in both the pH-Ne and oD-Ne mixtures in terms of a significant
reduction of the crystal growth rate, similarly to what found in our previous
work on supercooled pH-oD liquid mixtures [M. K\"uhnel et {\it al.},
Phys. Rev. B \textbf{89}, 180506(R) (2014)]. Our experimental results, in
combination with path-integral simulations of the supercooled liquid mixtures,
suggest in particular a correlation between the measured growth rates and the
ratio of the effective particle sizes originating from quantum delocalization
effects. We further show that the crystalline structure of the mixture is also
affected to a large extent by the presence of the Ne impurities, which likely
initiate the freezing process through the formation of Ne crystallites.Comment: 19 pages, 7 figures, submitted to J. Chem. Phy
Evaluación del dispositivo Pavement Quality Indicator (PQI) en la determinación de la densidad in situ de mezclas fabricadas con emulsión bituminosa
The Pavement Quality Indicator (PQI) is a non-nuclear gauge used for the on-site density measurement of asphalt pavements without the need to extract core samples. Previous studies of hot asphalt mixes found that PQI density readings were very similar to laboratory density measurements of pavement cores. This paper describes the first stage of a research project whose objective is to analyze PQI density measurements of mixes manufactured with an asphalt emulsion binder. The PQI density variability for such mixes was verified and compared with the results obtained with other on-site methods for measuring pavement density.El equipo Pavement Quality Indicator es un dispositivo para la determinación de densidad in situ en pavimentos asfálticos sin extracción de testigos. Las experiencias con este equipo en mezclas bituminosas en caliente, recogidas en diferentes fuentes bibliográficas, muestran que las densidades medidas in situ con el PQI son muy similares a las obtenidas mediante la extracción de testigos. En este artÃculo se expone la primera etapa de un proyecto de investigación que tiene por objeto analizar los resultados de mediciones efectuadas con PQI en mezclas bituminosas donde se utiliza emulsión asfáltica como ligante. Se comprueba la variabilidad de la densidad obtenida con el equipo para este tipo de mezclas, y se comparan los resultados con otros métodos de medida de densidad in situ
A wide band gap metal-semiconductor-metal nanostructure made entirely from graphene
A blueprint for producing scalable digital graphene electronics has remained
elusive. Current methods to produce semiconducting-metallic graphene networks
all suffer from either stringent lithographic demands that prevent
reproducibility, process-induced disorder in the graphene, or scalability
issues. Using angle resolved photoemission, we have discovered a unique one
dimensional metallic-semiconducting-metallic junction made entirely from
graphene, and produced without chemical functionalization or finite size
patterning. The junction is produced by taking advantage of the inherent,
atomically ordered, substrate-graphene interaction when it is grown on SiC, in
this case when graphene is forced to grow over patterned SiC steps. This
scalable bottomup approach allows us to produce a semiconducting graphene strip
whose width is precisely defined within a few graphene lattice constants, a
level of precision entirely outside modern lithographic limits. The
architecture demonstrated in this work is so robust that variations in the
average electronic band structure of thousands of these patterned ribbons have
little variation over length scales tens of microns long. The semiconducting
graphene has a topologically defined few nanometer wide region with an energy
gap greater than 0.5 eV in an otherwise continuous metallic graphene sheet.
This work demonstrates how the graphene-substrate interaction can be used as a
powerful tool to scalably modify graphene's electronic structure and opens a
new direction in graphene electronics research.Comment: 11 pages, 7 figure
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