110 research outputs found
Clusters, correlations and transverse momenta
We discuss the short range part of two-particle correlations as it results from the phase space available in cluster decay. In such an approach, certain variables emerge which should be useful to organize the data and extract interesting information. We are in particular concerned with tests of large transverse motion of clusters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22256/1/0000692.pd
Level spacing distribution of pseudointegrable billiard
In this paper, we examine the level spacing distribution of the
rectangular billiard with a single point-like scatterer, which is known as
pseudointegrable. It is shown that the observed is a new type, which is
quite different from the previous conclusion. Even in the strong coupling
limit, the Poisson-like behavior rather than Wigner-like is seen for ,
although the level repulsion still remains in the small region. The
difference from the previous works is analyzed in detail.Comment: 11 pages, REVTeX file, 3 PostScript Figure
A study of the zero modes of the Faddeev-Popov operator in Euclidean Yang-Mills theories in the Landau gauge in d=2,3,4 dimensions
Examples of normalizable zero modes of the Faddeev-Popov operator in SU(2)
Euclidean Yang-Mills theories in the Landau gauge are constructed in d=2,3,4
dimensions.Comment: 18 pages. Text modifications. References added. Version accepted for
publication in the EPJ
Diffractive light quark jet production at hadron colliders in the two-gluon exchange model
Massless quark and antiquark jet production at large transverse momentum in
the coherent diffractive processes at hadron colliders is calculated in the
two-gluon exchange parametrization of the Pomeron model. We use the helicity
amplitude method to calculate the cross section formula. We find that for the
light quark jet production the diffractive process is related to the
differential off-diagonal gluon distribution function in the proton. We
estimate the production rate for this process at the Fermilab Tevatron by
approximating the off-diagonal gluon distribution function by the usual
diagonal gluon distribution in the proton. And we find that the cross sections
for the diffractive light quark jet production and the charm quark jet
production are in the same order of magnitude. We also use the helicity
amplitude method to calculate the diffractive charm jet production at hadron
colliders, by which we reproduce the leading logarithmic approximation result
of this process we previously calculated.Comment: 15 pages, 4 PS figures, Revte
Atmospheric aerosols at the Pierre Auger Observatory and environmental implications
The Pierre Auger Observatory detects the highest energy cosmic rays.
Calorimetric measurements of extensive air showers induced by cosmic rays are
performed with a fluorescence detector. Thus, one of the main challenges is the
atmospheric monitoring, especially for aerosols in suspension in the
atmosphere. Several methods are described which have been developed to measure
the aerosol optical depth profile and aerosol phase function, using lasers and
other light sources as recorded by the fluorescence detector. The origin of
atmospheric aerosols traveling through the Auger site is also presented,
highlighting the effect of surrounding areas to atmospheric properties. In the
aim to extend the Pierre Auger Observatory to an atmospheric research platform,
a discussion about a collaborative project is presented.Comment: Regular Article, 16 pages, 12 figure
Non-gray rotating stellar models and the evolutionary history of the Orion Nebular Cluster
Rotational evolution in the pre-main sequence (PMS) is described with new
sets of PMS evolutionary tracks including rotation, non-gray boundary
conditions (BCs) and either low (LCE) or high convection efficiency (HCE).
Using observational data and our theoretical predictions, we aim at
constraining 1) the differences obtained for the rotational evolution of stars
within the ONC by means of these different sets of models; 2) the initial
angular momentum of low mass stars, by means of their templates in the ONC. We
discuss the reliability of current stellar models for the PMS. While the 2D
radiation hydrodynamic simulations predict HCE in PMS, semi-empirical
calibrations either seem to require that convection is less efficient in PMS
than in the following MS phase or are still contradictory. We derive stellar
masses and ages for the ONC by using both LCE and HCE. The resulting mass
distribution for the bulk of the ONC population is in the range 0.20.3
{\msun} for our non-gray models and in the range 0.10.3{\msun} for models
having gray BCs. In agreement with Herbst et al. (2002) we find that a large
percentage (70%) of low-mass stars (M\simlt 0.5{\msun} for LCE;
M\simlt0.35{\msun} for HCE) in the ONC appears to be fast rotators (P4days).
Three possibilities are open: 1) 70% of the ONC low mass stars lose their
disk at early evolutionary phases; 2)their locking period is shorter; 3) the
period evolution is linked to a different morphology of the magnetic fields of
the two groups of stars. We also estimate the range of initial angular momentum
consistent with the observed periods. The comparisons made indicate that a
second parameter is needed to describe convection in the PMS, possibly related
to the structural effect of a dynamo magnetic field.Comment: 17 pages, 11 figure
Diffractive \jpsi production through Color-Octet mechanism at hadron colliders
We propose the color-octet mechanism combined with the two gluon exchange
model for the diffractive production in hadron collisions. In the
leading logarithmic approximation (LLA) in QCD, we find that the diffractive
production rate is related to the off-diagonal gluon density in the
proton and to the nonperturbative color-octet matrix element of . The
rate is found to be very sensitive to the gluon density at very small values of
(down to ). As a result, this process may provide a wide
window for testing the two-gluon exchange model, and may be particularly useful
in studying the small physics. And it may also be a golden place to test
the color-octet mechanism proposed by solving the surplus
problem at the Tevatron.Comment: 9 pages, 3 Postscript figures, discussions and references added and
main results unchange
Probing helium interfaces with light scattering : from fluid mechanics to statistical physics
We have investigated the formation of helium droplets in two physical
situations. In the first one, droplets are atomised from superfluid or normal
liquid by a fast helium vapour flow. In the second, droplets of normal liquid
are formed inside porous glasses during the process of helium condensation. The
context, aims, and results of these experiments are reviewed, with focus on the
specificity of light scattering by helium. In particular, we discuss how, for
different reasons, the closeness to unity of the index of refraction of helium
allows in both cases to minimise the problem of multiple scattering and obtain
results which it would not be possible to get using other fluids.Comment: 21 page
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