1,834 research outputs found
Signatures for flow effects in s**(1/2) = 200 GeV proton-proton collisions
A simple model based on relativistic geometry and final-state hadronic
rescattering is used to predict pion source parameters extracted in two-pion
femtoscopy studies of proton-proton collisions at s**(1/2) = 200 GeV. From
studying the momentum and particle multiplicity dependences of these parameters
in the context of this model and assuming a very short hadronization time,
flow-like behavior is seen which resembles the flow behavior commonly observed
in relativistic heavy-ion collisions.Comment: 10 pages, 3 figures, submitted to Physical Revie
Hadron Chemistry at High-PT with Identified Particles
We discuss mechanisms that change the hadron chemistry for high momentum
particles emitted in high energy nuclear collisions. We argue that particle
ratios naturally tend to be different from jets in the vacuum. We show results
of computations in a model that propagates leading particles through a quark
gluon plasma and permits elastic flavor changing processes. We predict less
suppression for kaons compared to pions in central collision. We also discuss
elliptic flow resulting from flavor changing processes.Comment: Report for CIPANP 2009; 4 pages, 4 figures, AIP style files include
The measurement of alpha from the B-factories
Significant progress toward measuring the CKM angle alpha has been made by
the B-factories over the past decade. This work has culminated in a constraint
on alpha with a precision of less than 4 degrees.Comment: Proceedings of the Tenth Conference on the Intersections of Particle
and Nuclear Physics, San Diego, California, May 2009 (4 pages
B+ and Ds+ Decay Constants from Belle and Babar
The Belle and Babar experiments have measured the branching fractions for B+
-> tau+ nu and Ds+ -> mu+ nu decays. From these measurements one can extract
the B+ and Ds+ decay constants, which can be compared to lattice QCD
calculations. For the Ds+ decay constant, there is currently a 2.1 sigma
difference between the calculated value and the measured value.Comment: 10 pages, 8 figures, 1 table, contribution to the Tenth Conference on
the Intersections of Particle and Nuclear Physics (CIPANP 2009), San Diego,
Californi
Fundamental Symmetries of the Early Universe and the Precision Frontier
The search for the next Standard Model of fundamental interactions is being
carried out at two frontiers: the high energy frontier involving the Tevatron
and Large Hadron Collider, and the high precision frontier where the focus is
largely on low energy experiments. I discuss the unique and powerful window on
new physics provided by the precision frontier and its complementarity to the
information we hope to gain from present and future colliders.Comment: Proceedings of CIPANP 2009; 9 pages, 1 figur
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The effect of surface heterogeneity on cloud absorption estimates
This study presents a systematic and quantitative analysis of the effect of inhomogeneous surface albedo on shortwave cloud absorption estimates. We used 3D radiative transfer modeling over a checkerboard surface albedo to calculate cloud absorption. We have found that accounting for surface heterogeneity enhances cloud absorption. However, the enhancement is not sufficient to explain the reported difference between measured and modeled cloud absorption
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Spectrally-invariant behavior of zenith radiance around cloud edges simulated by radiative transfer
In a previous paper, we discovered a surprising spectrally-invariant relationship in shortwave spectrometer observations taken by the Atmospheric Radiation Measurement (ARM) program. The relationship suggests that the shortwave spectrum near cloud edges can be determined by a linear combination of zenith radiance spectra of the cloudy and clear regions. Here, using radiative transfer simulations, we study the sensitivity of this relationship to the properties of aerosols and clouds, to the underlying surface type, and to the finite field-of-view (FOV) of the spectrometer. Overall, the relationship is mostly sensitive to cloud properties and has little sensitivity to other factors. At visible wavelengths, the relationship primarily depends on cloud optical depth regardless of cloud phase function, thermodynamic phase and drop size. At water-absorbing wavelengths, the slope of the relationship depends primarily on cloud optical depth; the intercept, by contrast, depends primarily on cloud absorbing and scattering properties, suggesting a new retrieval method for cloud drop effective radius. These results suggest that the spectrally-invariant relationship can be used to infer cloud properties near cloud edges even with insufficient or no knowledge about spectral surface albedo and aerosol properties
The relevance of positivity in spin physics
Positivity reduces substantially the allowed domain for spin observables. We
briefly recall some methods used to determine these domains and give some
typical examples for exclusive and inclusive spin-dependent reactions.Comment: 7 pages, 3 figures, Talk presented at CIPANP 2009, San Diego
California, USA, May 26-31, 2009 To be published in AIP Conference
Proceeding
Regge-model predictions for K+Sigma photoproduction from the nucleon
We present Regge-model predictions for the p(gamma,K+)Sigma0 and
n(gamma,K+)Sigma- differential cross sections and photon-beam asymmetries in
the resonance region. The reaction amplitude encompasses the exchange of
K+(494) and K*+(892) Regge-trajectories, introducing a mere three free
parameters. These are fitted to the available p(gamma,K+)Sigma0 data beyond the
resonance region. The n(gamma,K+)Sigma- amplitude is obtained from the
p(gamma,K+)Sigma0 one through SU(2) isospin symmetry considerations.Comment: 4 pages, 2 figures; Proceedings Tenth Conference on the Intersections
of Particle and Nuclear Physics, San Diego, 200
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
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