9,261 research outputs found
Novel Quark Fragmentation Functions and the Nucleon's Transversity Distribution
We define twist-two and twist-three quark fragmentation functions in Quantum
Chromodynamics (QCD) and study their physical implications. Using this
formalism we show how the nucleon's transversity distribution can be measured
in single pion inclusive electroproduction.Comment: 10 pages, uses PHYZZX macro package, 2 PostScript figures (added
using FIGURES). MIT-CTP-215
Thermal Properties of a Simulated Lunar Material in Air and in Vacuum
Thermal properties of simulated lunar material in air and in vacuu
Metals Production Requirements for Rapid Photovoltaics Deployment
If global photovoltaics (PV) deployment grows rapidly, the required input
materials need to be supplied at an increasing rate. In this paper, we quantify
the effect of PV deployment levels on the scale of metals production. For
example, we find that if cadmium telluride {copper indium gallium diselenide}
PV accounts for more than 3% {10%} of electricity generation by 2030, the
required growth rates for the production of indium and tellurium would exceed
historically-observed production growth rates for a large set of metals. In
contrast, even if crystalline silicon PV supplies all electricity in 2030, the
required silicon production growth rate would fall within the historical range.
More generally, this paper highlights possible constraints to the rate of
scaling up metals production for some PV technologies, and outlines an approach
to assessing projected metals growth requirements against an ensemble of past
growth rates from across the metals production sector. The framework developed
in this paper may be useful for evaluating the scalability of a wide range of
materials and devices, to inform technology development in the laboratory, as
well as public and private research investment
The Theory of the Nucleon Spin
I discuss two topics of current interest in the study of the spin structure
of the nucleon. First, I discuss whether there is a sum rule for the components
of the nucleon's angular moments. Second, I discuss the measurement of the
nucleon's transversity distribution in light of recent results reported by the
HERMES collaboration at DESY.Comment: 15 pages, 8 figures, LaTeX using rspublic.cls and BoxedEPS macros; as
submitted to Phil Trans A of the Royal Society for forthcoming volume: The
Quark Structure of Matter; email correspondence to [email protected]
Double-Spin Transverse Asymmetries in Drell-Yan Processes
We calculate the double-spin transverse asymmetries for the Drell-Yan lepton
pair production in p-p and p-anti p collisions. We assume the transverse and
the longitudinal polarization densities to be equal at a very small scale, as
it is suggested by confinement model results. Using a global fit for the
longitudinal distributions, we find transverse asymmetries of order of 10^-2 at
most, in the accessible kinematic regions.Comment: 8 pages, REVTeX, 6 figures included as file figures.tar.g
CMB Likelihood Functions for Beginners and Experts
Although the broad outlines of the appropriate pipeline for cosmological
likelihood analysis with CMB data has been known for several years, only
recently have we had to contend with the full, large-scale, computationally
challenging problem involving both highly-correlated noise and extremely large
datasets (). In this talk we concentrate on the beginning and end of
this process. First, we discuss estimating the noise covariance from the data
itself in a rigorous and unbiased way; this is essentially an iterated
minimum-variance mapmaking approach. We also discuss the unbiased determination
of cosmological parameters from estimates of the power spectrum or experimental
bandpowers.Comment: Long-delayed submission. In AIP Conference Proceedings "3K Cosmology"
held in Rome, Oct 5-10, 1998, edited by Luciano Maiani, Francesco Melchiorri
and Nicola Vittorio, 343-347, New York, American Institute of Physics 199
Perturbative fragmentation of vector colored particle into bound states with a heavy antiquark
The fragmentation function of vector particle into possible bound S-wave
states with a heavy antiquark is calculated in the leading order of
perturbative QCD for the high energy processes at large transverse momenta with
the different behaviour of anomalous chromomagnetic moment. One-loop equations
are derived for the evolution of fragmentation function moments, which is
caused by the emission of hard gluons by the vector particle. The integrated
probabilities of fragmentation are given. The distribution of bound state over
the transverse momentum with respect to the axis of fragmentation is calculated
in the scaling limit.Comment: 10 pages, Latex file + 4 ps-figure
Implications of the Babinet Principle for Casimir Interactions
We formulate the Babinet Principle (BP) as a relation between the scattering
amplitudes for electromagnetic waves, and combine it with multiple scattering
techniques to derive new properties of Casimir forces. We show that the Casimir
force exerted by a planar conductor or dielectric on a self- complementary
perforated planar mirror is approximately half that on a uniform mirror
independent of the distance between them. The BP suggests that Casimir edge
effects are anomalously small, supporting results obtained earlier in special
cases. Finally, we illustrate how the BP can be used to estimate Casimir forces
between perforated planar mirrors
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