1,385 research outputs found
QCD Effects in Cosmology
The cosmological evolution in the radiation dominated regimen is usually
computed by assuming an ideal relativistic thermal bath. In this note, we
discuss the deviation from the non-interaction assumption. In either the
standard model (SM) and the minimal supersymmetric standard model (MSSM), the
main contribution comes from the strong interaction. An understanding of these
effects are important for precision measurements and for the evolution of
scalar modes, where the commented corrections constitute the main source of the
dynamics.Comment: 4 pages, 2 figures. Contributed to CIPANP 2009: Tenth Conference on
the Intersections of Particle and Nuclear Physics, May 26-31, 2009, San
Diego, Californi
Baryons in the Field Correlator Method
The ground and -wave excited states of , and baryons are
studied in the framework of the field correlator method using the running
strong coupling constant in the Coulomb-like part of the three-quark potential.
The string correction for the confinement potential of the orbitally excited
baryons, which is the leading contribution of the proper inertia of the
rotating strings, is estimated.Comment: 6 pages, 2 figures. Talk given at APS April Meeting, Denver,
Colorado, May 2-5, 2009 and at the Tenth Conference on the Intersections of
Particle and Nuclear Physics (CIPANP 2009), San Diego, California, May 26-31,
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Impact of Satellite Sea Surface Salinity Observations on ENSO Predictions from the NASA/GMAO Seasonal Forecast System
We assess the impact of satellite sea surface salinity (SSS) observations on dynamical ENSO forecasts. Assimilation of SSS improves the mixed layer depth (MLD) and modulates the Kelvin waves associated with ENSO. In column 2, the initialization differences between experiments that assimilate SSS minus those withholding SSS assimilation are presented. Column 3 shows examples of forecasts generated for the different phases of ENSO assimilating the different satellite SSS. In general, for all phases of ENSO, SSS assimilation improves forecasts. The far right column compares ensemble means for assimilation of individual and combined SMOS, Aquarius, and SMAP SSS forecasts. Finally, the latest forecasts are presented comparing assimilation versus no- assimilation of satellite SSS for single forecasts over the last year
Extended-soft-core Baryon-Baryon Model II. Hyperon-Nucleon Interaction
The YN results are presented from the Extended-soft-core (ESC) interactions.
They consist of local- and non-local-potentials due to (i) One-boson-exchange
(OBE), with pseudoscalar-, vector-, scalar-, and axial-vector-nonets, (ii)
Diffractive exchanges, (iii) Two-pseudoscalar exchange, and (iv)
Meson-pair-exchange (MPE). This model, called ESC04, describes NN and YN in a
unified way using broken flavor SU(3)-symmetry. Novel ingredients are the
inclusion of (i) the axial-vector-mesons, (ii) a zero in the scalar- and
axial-vector meson form factors. We describe simultaneous fits to the NN- and
YN-data, using four options in the ESC-model. Very good fits were obtained.
G-matrix calculations with these four options are also reported. The obtained
well depths (U_\Lambda, U_\Sigma, U_\Xi) reveal distinct features of ESC04a-d.
The \Lambda\Lambda-interactions are demonstrated to be consistent with the
observed data of_{\Lambda\Lambda}^6He. The possible three-body effects are
investigated by considering phenomenologically the changes of the vector-meson
masses in a nuclear medium.Comment: preprint vesion 66 pages, two-column version 27 pages, 17 figure
Are There Diquarks in the Nucleon?
This work is devoted to the study of diquark correlations inside the nucleon.
We analyze some matrix elements which encode information about the
non-perturbative forces, in different color anti-triplet diquark channels. We
suggest a lattice calculation to check the quark-diquark picture and clarify
the role of instanton-mediated interactions. We study in detail the physical
properties of the 0+ diquark, using the Random Instanton Liquid Model. We find
that instanton forces are sufficiently strong to form a diquark bound-state,
with a mass of ~500 MeV, which is compatible with earlier estimates. We also
compute its electro-magnetic form factor and find that the diquark is a broad
object, with a size comparable with that of the proton.Comment: Final version, accepted for publication on Phys. Rev.
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Physical interpretation of the correlation between multi-angle spectral data and canopy height
Recent empirical studies have shown that multi-angle spectral data can be useful for predicting canopy height, but the physical reason for this correlation was not understood. We follow the concept of canopy spectral invariants, specifically escape probability, to gain insight into the observed correlation. Airborne Multi-Angle Imaging Spectrometer (AirMISR) and airborne Laser Vegetation Imaging Sensor (LVIS) data acquired during a NASA Terrestrial Ecology Program aircraft campaign underlie our analysis. Two multivariate linear regression models were developed to estimate LVIS height measures from 28 AirMISR multi-angle spectral reflectances and from the spectrally invariant escape probability at 7 AirMISR view angles. Both models achieved nearly the same accuracy, suggesting that canopy spectral invariant theory can explain the observed correlation. We hypothesize that the escape probability is sensitive to the aspect ratio (crown diameter to crown height). The multi-angle spectral data alone therefore may not provide enough information to retrieve canopy height globally
A detailed determination of the a priori mixing angles in non-leptonic decays of hyperons
Non-leptonic Decays of Hyperons can provide a detailed determination of the a
priori mixing angles that appear in physical hadrons in the approach in which
non-perturbative flavor and parity violations are present in tiny pieces of the
hadron mass operator. The determination of such angles in these decays will
provide a bench mark to test their necessary universality-like property in
other types of decays. Our main result is that the magnitudes of the a priori
mixing angles can be determined quite accurately
Impact of Satellite Sea Surface Salinity Observations on ENSO Predictions from the GMAO S2S Forecast System
El Nino/Southern Oscillation (ENSO) has far reaching global climatic impacts and so extending useful ENSO forecasts would be of great benefit for society. However, one key variable that has yet to be fully exploited within coupled forecast systems is accurate estimation of near-surface ocean density. Satellite Sea Surface Salinity (SSS), combined with temperature, help to identify ocean density changes and associated mixing near the ocean surface. We assess the impact of satellite SSS observations for improving near-surface dynamics within ocean analyses and how these impact dynamical ENSO forecasts using the NASA GMAO (Global Modeling and Assimilation Office) Sub-seasonal to Seasonal (S2S_v2.1) coupled forecast system (Molod et al. 2018 - i.e. NASA's contribution to the NMME (National Multi-Model Ensemble) project). For all initialization experiments, all available along-track absolute dynamic topography and in situ observations are assimilated using the LETKF ( Local Ensemble Transform Kalman Filter) scheme similar to Penny et al., 2013. A separate reanalysis additionally assimilates Aquarius V5 (September 2011 to June 2015) and SMAP (Soil Moisture Active Passive) V4 (March 2015 to present) along-track data.We highlight the impact of satellite SSS on ocean reanalyses by comparing validation statistics of experiments that assimilate SSS versus our current prediction system that withholds SSS. We find that near-surface validation versus observed statistics for salinity are slightly degraded when assimilating SSS. This is an expected result due to known biases between SSS (measured by the satellite at approximately 1 centimeter) and in situ measurements (typically measured by Argo floats at 3 meters). On the other hand, a very encouraging result is that both temperature, absolute dynamic topography, and mixed layer statistics are improved with SSS assimilation. Previous work has shown that correcting near-surface density structure via gridded SSS assimilation can improve coupled forecasts. Here we present results of coupled forecasts that are initialized from the GMAO S2S reanalyses that assimilates/withholds along-track (L2) SSS. In particular, we contrast forecasts of the overestimated 2014 El Nino, the big 2015 El Nino, and the minor 2016 La Nina. For each of these ENSO scenarios, assimilation of satellite SSS improves the forecast validation. Improved SSS and density upgrades the mixed layer depth leading to more accurate coupled air/sea interaction
Impact of Aquarius and SMAP Sea Surface Salinity Observations on Seasonal Predictions of the 2015 El Nino
We assess the impact of satellite sea surface salinity (SSS) observations on dynamical ENSO forecasts for the big 2015 El Nino event. From March to June 2015, the availability of two overlapping satellite SSS instruments, Aquarius and SMAP (Soil Moisture Active Passive Mission), allows a unique opportunity to compare and contrast forecasts generated with the benefit of these two satellite SSS observation types. Four distinct experiments are presented that include 1) freely evolving model SSS (i.e. no satellite SSS), relaxation to 2) climatological SSS (i.e. WOA13 SSS), 3) Aquarius, and 4) SMAP initialization. Coupled hindcasts are then generated from these initial conditions for March 2015. These forecasts are then validated against observations and evaluated with respect to the observed El Nino development
T-violation in decay in a general two-Higgs doublet model
We calculate the transverse muon polarization in the process
arising from the Yukawa couplings of charged Higgs boson in a general two-Higgs
doublet model where spontaneous violation of CP is presentComment: 6 pages, latex, accepted for publication in Phys. Rev.
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