2,419 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
The broad away side of azimuthal correlations: 3 vs 2 final state particles in high energy nuclear collisions
In high energy heavy ion collisions at RHIC there are important aspects of
the medium induced dynamics, that are still not well understood. In particular,
there is a broadening and even a double hump structure of the away-side peak
appearing in azimuthal correlation studies in Au+Au collisions which is absent
in p+p collisions at the same energies. These features are already present but
suppressed in p+p collisions: 2 to 3 parton processes produce such structures
but are suppressed with respect to 2 to 2 processes. We argue that in A+A
collisions the different geometry for the trajectories of 3 as opposed to 2
particles in the final state, together with the medium induced energy loss
effects on the different cross sections, create a scenario that enhances
processes with 3 particles in the final state, which gives on average this
double hump structure.Comment: Prepared for the 5th International Workshop on High-pT Physics at
LHC, ICN-UNAM, 27 Sep.-1 Oct, 201
Three and two-hadron correlations in \sqrt{s_{NN}}=200 GeV proton-proton and nucleus-nucleus collisions
We compare the azimuthal correlations arising from three and two hadron
production in high energy proton-proton and nucleus-nucleus collisions at
\sqrt{s_{NN}}=200 GeV, using the leading order matrix elements for two-to-three
and two-to-two parton-processes in perturbative QCD. We first compute the two
and three hadron production cross sections in mid-rapidity proton-proton
collisions. Then we consider Au + Au collisions including parton energy loss
using the modified fragmentation function approach. By examining the
geometrical paths the hard partons follow through the medium, we show that the
two away-side partons produced in two-to-three processes have in average a
smaller and a greater path length than the average path length of the away-side
parton in two-to-two processes. Therefore there is a large probability that in
the former processes one of the particles escapes while the other gets
absorbed. This effect leads to an enhancement in the azimuthal correlations of
the two-to-three with respect to the two-to-two parton-processes when comparing
to the same processes in proton-proton collisions since in average the particle
with the shortest path length looses less energy with respect to the away side
particle in two-to-two processes. We argue that this phenomenon may be
responsible for the shape of the away-side in azimuthal correlations observed
in mid-rapidity Au + Au collisions at RHIC.Comment: 4 pages, 2 figure
A study of cyclonic activity in the North Atlantic for the 2005 versus 2020 season
Ponencia presentada en: XII Congreso de la Asociación Española de ClimatologÃa celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.Over the last two decades, the North Atlantic ocean basin has experienced record-breaking hurricane seasons with regards to storm frequency and intensity. This short study examines the ocean and atmospheric characteristics of the two most active hurricane seasons on record, the 2005 and 2020 seasons. Accumulated cyclone energy, sea surface temperature, sea-level pressure and wind shear data in the main development region of the North Atlantic are compared between the two record-breaking seasons. Results of time series analysis show that 2005 was the hurricane season with the highest accumulated cyclone energy index, while 2020 was the 4th highest of 55 seasons analyzed. Results of spatial analysis of sea surface temperature anomalies exhibit that 2005 had a slightly higher average surface temperature than 2020 in the main development region of tropical cyclones, and that 2005 had higher temperatures in the central region of the study area while 2020 had higher surface temperatures in the southern Caribbean region. Comparisons between the sea level pressure anomalies show that 2005 had a slightly lower average pressure than 2020, with 2005 exhibiting lower anomalies in the northern area and 2020 showing anomalous pressure patterns in the eastern part of the main development region. When wind shear anomalies are examined, we found that 2020 had a lower average wind shear than 2005, a factor that could explain why 2020 had a higher number of tropical cyclones. Overall our results suggest that both 2005 and 2020 seasons had similar ideal ocean-atmospheric conditions for higher tropical cyclone activity
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
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