2,327 research outputs found
Monte Carlo simulation of single spin asymmetries in pion-proton collisions
We present Monte Carlo simulations of both the Sivers and the Boer-Mulders
effects in the polarized Drell-Yan
process at the center-of-mass energy GeV reachable at
COMPASS with pion beams of energy 100 GeV. For the Sivers effect, we adopt two
different parametrizations for the Sivers function to explore the statistical
accuracy required to extract unambiguous information on this parton density. In
particular, we verify the possibility of checking its predicted sign change
between Semi-Inclusive Deep-Inelastic Scattering (SIDIS) and Drell-Yan
processes, a crucial test of nonperturbative QCD. For the Boer-Mulders effect,
because of the lack of parametrizations we can make only guesses. The goal is
to explore the possibility of extracting information on the transversity
distribution, the missing piece necessary to complete the knowledge of the
nucleon spin structure at leading twist, and the Boer-Mulders function, which
is related to the long-standing problem of the violation of the Lam-Tung sum
rule in the unpolarized Drell-Yan cross section.Comment: RevTeX, 13 pages, 7 figures included in .eps forma
BCS - BEC crossover and quantum hydrodynamics in p-wave superfluids with a symmetry of the A1 - phase
We solve the Leggett equations for the BCS - BEC crossover in the three
dimension resonance p-wave superfluid with the symmetry of the A1 - phase. We
calculate the sound velocity, the normal density, and the specific heat for the
BCS-domain (\mu > 0), BEC-domain (\mu < 0), and close to important point \mu =
0 in 100% polarized case. We find the indications of quantum phase - transition
close to the point \mu(T = 0) = 0. Deep in the BCS and BEC-domains the
crossover ideas of Leggett and Nozieres, Schmitt-Rink work pretty well. We
discuss the spectrum of orbital waves, the paradox of intrinsic angular
momentum and complicated problem of chiral anomaly in the BCS A1 - phase at T =
0. We present two different approaches to a chiral anomaly: one based on
supersymmetric hydrodynamics, another one on the formal analogy with the Dirac
equation in quantum electrodynamics. We evaluate the damping of nodal fermions
due to different decay processes in superclean case at T = 0 and find that we
are in a ballistic regime \omega\tau >> 1. We propose to use aerogel or
nonmagnetic impurities to reach hydrodynamic regime \omega\tau<< 1 at T = 0. We
discuss the concept of the spectral flow and exact cancellations between
time-derivatives of anomalous and quasiparticle currents in the equation for
the total linear momentum conservation. We propose to derive and solve the
kinetic equation for the nodal quasiparticles both in the hydrodynamic and in
the ballistic regimes to demonstrate this cancellation explicitly. We briefly
discuss the role of the other residual interactions different from damping and
invite experimentalists to measure the spectrum and damping of orbital waves in
A-phase of 3He at low temperatures.Comment: 14 pages, 10 figure
How Could the Proton Transversity be Measured
The perspectives of two new nonstandard methods of transversal quark
polarization measurement are considered: the jet handedness and the so-called
"Collins effect" due to spin dependent T-odd fragmentation function responsible
for the left-right asymmetry in fragmenting of transversally polarized quarks.
Recent experimental indications in favor of these effects are observed: 1.The
correlation of the T-odd one-particle fragmentation functions found by DELPHI
in -jet decay. Integrated over the fraction of longitudinal and
transversal momenta, this correlation is of 1.6% order, which means order of
13% for the analyzing power. 2.A rather large () handedness
transversal to the production plane observed in the diffractive production of
() triples from nuclei by the --beam.
It shows a clear dynamic origin and resembles the single spin asymmetry
behavior.
All this makes us hope to use these effects in polarized DIS experiments for
transversity measurement. The first estimation of transversity was done by
using the azimuthal asymmetry in semi-inclusive DIS recently measured by HERMES
and SMC.Comment: 8 pages, Latex, czjphys2.sty. Talk at Int. Workshop "PRAHA-SPIN99",
Prague 6-11 Sept 1999. To appear in Czech.J.Phys Supp
Sivers effect in Drell Yan at RHIC
On the basis of a fit to the Sivers effect in deep-inelastic scattering, we
make predictions for single-spin asymmetries in the Drell-Yan process at RHIC.Comment: 10 pages, 7 figures, 1 table. v2: References and comments added,
minor correction
Old and new parton distribution and fragmentation functions
A short review of problems with parton distribution functions in nucleons,
non-polarized and polarized, is given. The main part is devoted to the
transversity distribution its possible measurement and its first experimental
probe via spin asymmetry in semi-inclusive DIS. It is argued that the proton
transversity distribution could be successfully measured in future DIS
experiments with {\it longitudinally} polarized target.Comment: 9 pages, latex, czjphys2.sty, 4 eps figures. Submitted at 35-th
Rancontre de Moriond, March 2000 and at Praha-SPIN-2000, July 2000. To be
published in Czechoslovak J. Phys. (Suppl) 51 (2001
Star complexes and stellar populations in NGC 6822 - Comparison with the Magellanic Clouds
The star complexes (large scale star forming regions) of NGC 6822 were traced
and mapped and their size distribution was compared with the size distribution
of star complexes in the Magellanic Clouds (MCs). Furthermore, the spatial
distributions of different age stellar populations were compared with each
other. The star complexes of NGC 6822 were determined by using the isopleths,
based on star counts, of the young stars of the galaxy, using a statistical
cutoff limit in density. In order to map them and determine their geometrical
properties, an ellipse was fitted to every distinct region satisfying this
minimum limit. The Kolmogorov-Smirnov statistical test was used to study
possible patterns in their size distribution. Isopleths were also used to study
the stellar populations of NGC 6822. The star complexes of NGC 6822 were
detected and a list of their positions and sizes was produced. Indications of
hierarchical star formation, in terms of spatial distribution, time evolution
and preferable sizes were found in NGC 6822 and the MCs. The spatial
distribution of the various age stellar populations has indicated traces of an
interaction in NGC 6822, dated before 350 +/- 50 Myr.Comment: 10 pages, 7 figures, accepted by A&A; minor typeface correction
The Role of Inflation in Soviet History: Prices, Living Standards, and Political Change
This thesis discusses the interaction between inflation, living standards, and political change in Soviet/Russian history. It traces the establishment and evolution of the Soviet monetary system, inflationary episodes, and their consequences. The goal of this study is to show how inflation affects the lives of ordinary people and how it has contributed to larger changes in Soviet history. Sources include economic statistics and analysis from articles and monographs, as well as first-hand accounts from interviews and newspapers. The results show that inflation was a factor in both the rise and the fall of the Soviet Union. Russia\u27s first hyperinflation (1917-1923) nearly destroyed the economy, and the Bolsheviks were forced to stabilize prices. The Soviet system of price controls prevented inflation, but it also created persistent shortages of food and consumer goods. Mikhail Gorbachev tried to alleviate these problems, but his efforts resulted instead in Russia\u27s second hyperinflation (1992-1993)
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