3,073 research outputs found
Measurements of the reaction of antiproton annihilation at rest at three hydrogen target densities
The proton-antiproton annihilation at rest into the final state
was measured for three different target densities: liquid hydrogen, gaseous
hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in
the liquid hydrogen target is smaller than in the low-pressure gas target. The
branching ratios of the channel were calculated on the basis of
simultaneous analysis of the three data samples. The branching ratio for
annihilation into from the protonium state turns out to be
about ten times smaller as compared to the one from the state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters
New data on OZI rule violation in bar{p}p annihilation at rest
The results of a measurement of the ratio R = Y(phi pi+ pi-) / Y(omega pi+
pi-) for antiproton annihilation at rest in a gaseous and in a liquid hydrogen
target are presented. It was found that the value of this ratio increases with
the decreasing of the dipion mass, which demonstrates the difference in the phi
and omega production mechanisms. An indication on the momentum transfer
dependence of the apparent OZI rule violation for phi production from the 3S1
initial state was found.Comment: 11 pages, 3 PostScript figures, submitted to Physics Letter
SR-FTiR microscopy and FTIR imaging in the earth sciences
During the last decades, several books have been devoted to the application
of spectroscopic methods in mineralogy. Several short courses and meetings have
addressed particular aspects of spectroscopy, such as the analysis of hydrous
components in minerals and Earth materials. In these books, complete treatment
of the infrared theory and practical aspects of instrumentation and methods,
along with an exhaustive list of references, can be found. The present chapter
is intended to cover those aspects of infrared spectroscopy that have been
developed in the past decade and are not included in earlier reviews such as
Volume 18 of Reviews in Mineralogy. These new topics involve primarily: (1) the
use of synchrotron radiation (SR), which, although not a routine method, is now
rather extensively applied in infrared studies, in particular those requiring
ultimate spatial and time resolution and the analysis of extremely small
samples (a few tens of micrometers); (2) the development of imaging techniques
also for foreseen time resolved studies of geo-mineralogical processes and
environmental studies.Comment: 36 pages, 24 figures - Reviews in Mineralogy & Geochemistry - Vol. 78
(2013) in pres
Model uncertainties in top-quark physics
The ATLAS and CMS collaborations at the Large Hadron Collider (LHC) are
studying the top quark in pp collisions at 7 and 8 TeV. Due to the large
integrated luminosity, precision measurements of production cross-sections and
properties are often limited by systematic uncertainties. An overview of the
modeling uncertainties for simulated events is given in this report.Comment: Proceedings from the 7th International Workshop on Top Quark Physics,
Cannes, Franc
Giant petrous bone cholesteatoma: combined microscopic surgery and an adjuvant endoscopic approach
Petrous bone cholesteatomas (PBCs) are epidermoid cysts, which have developed in the petrous portion of the temporal bone and may be congenital or acquired. Cholesteatomas arising in this region have a tendency to invade bone and functional structures and the middle and posterior fossae reaching an extensive size. Traditionally, surgery of a giant PBC contemplates lateral transtemporal or middle fossa microscopic surgery; however, in recent years, endoscopic surgical techniques (primary or complementary endoscopic approach) are starting to receive a greater consensus for middle ear and mastoid surgeries. We report the rare case of an 83-year-old Caucasian male affected by a giant cholesteatoma that eroded the labyrinth and the posterior fossa dura and extended to the infralabyrinthine region, going beyond the theca and reaching the first cervical vertebra. The giant cholesteatoma was managed through a combined approach (microscopic and, subsequently, complementary endoscopic approach). In this case report, we illustrate some advantages of this surgical choice
Hölder Continuity and Boundedness Estimates for Nonlinear Fractional Equations in the Heisenberg Group
We extend the celebrate De Giorgi-Nash-Moser theory to a wide class of nonlinear equations driven by nonlocal, possibly degenerate, integro-differential operators, whose model is the fractional p-Laplacian operator on the Heisenberg-Weyl group Hn. Among other results, we prove that the weak solutions to such a class of problems are bounded and Hölder continuous, by also establishing general estimates as fractional Caccioppoli-type estimates with tail and logarithmic-type estimates
Struwe's Global Compactness and energy approximation of the critical Sobolev embedding in the Heisenberg group
We investigate some of the effects of the lack of compactness in the critical
Folland-Stein-Sobolev embedding in very general (possible non-smooth) domains,
by proving via De Giorgi's -convergence techniques that optimal
functions for a natural subcritical approximations of the Sobolev quotient
concentrate energy at one point. In the second part of the paper, we try to
restore the compactness by extending the celebrated Global Compactness result
to the Heisenberg group via a completely different approach with respect to the
original one by Struwe (Math. Z. 1984)
New perspectives on recent trends for Kolmogorov operators
After carrying out an overview on the non Euclidean geometrical setting
suitable for the study of Kolmogorov operators with rough coefficients, we list
some properties of the functional space , mirroring the classical
theory for uniformly elliptic operators. Then we provide the reader with
the proof of a new Sobolev embedding for functions in .
Additionally, after reviewing recent results regarding weak regularity theory,
we discuss some of their recent applications to real life problems arising both
in Physics and in Economics. Finally, we conclude our analysis stating some
recent results regarding the study of nonlinear nonlocal kinetic
Kolmogorov-Fokker-Planck operators
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