6,567 research outputs found
Exclusive diffractive processes at HERA within the dipole picture
We present a simultaneous analysis, within an impact parameter dependent
saturated dipole model, of exclusive diffractive vector meson (J/psi, phi and
rho) production, deeply virtual Compton scattering and the total gamma* p cross
section data measured at HERA. Various cross sections measured as a function of
the kinematic variables Q^2, W and t are well described, with little
sensitivity to the details of the vector meson wave functions. We determine the
properties of the gluon density in the proton in both longitudinal and
transverse dimensions, including the impact parameter dependent saturation
scale. The overall success of the description indicates universality of the
emerging gluon distribution and proton shape.Comment: 48 pages, 28 figures, the final version to appear in Physical Review
Modification of Ni - nanotubes by implanting ions C3+
Using PET track-etched membranes with thickness of 12 μm as template, polycrystalline nickel nanotubes with outer diameter of 380 nm and wall thickness 95 nm were synthesized by electrochemical method. A comprehensive study of the structural, morphological and electrical characteristics of irradiated at different conditions Ni nanotubes was carried out. The ability of modification of structural parameters such as lattice parameters and the average size of crystallites and conductivity of Ni nanotubes by irradiated with С3+ ions with energy 1.75 MeV/nucleon and fluence ranging from 1 × 109 to 5 × 1011 cm-2 was shown
Azimuthal Distribution of Quark-Antiquark Jets in DIS Diffractive Dissociation
We investigate the azimuthal distribution of quark-antiquark jets in DIS
diffractive dissociation with large transverse momentum. In this kinematical
region the matrix element is expressed in terms of the gluon structure
function. For the transverse part of the cross section we find a -distribution with the maximum at , i.e.\ the jets
prefer a direction perpendicular to the electron plane. This is in contrast to
boson gluon fusion where the jet cross section for transversely
polarized bosons peaks at and . We discuss the origin of
this striking difference and present numerical results relevant for the
diffractive dissociation at HERA.Comment: 12 pages, latex, 7 figure
Observation and absolute frequency measurements of the 1S0 - 3P0 optical clock transition in ytterbium
We report the direct excitation of the highly forbidden (6s^2) 1S0 - (6s6p)
3P0 optical transition in two odd isotopes of ytterbium. As the excitation
laser frequency is scanned, absorption is detected by monitoring the depletion
from an atomic cloud at ~70 uK in a magneto-optical trap. The measured
frequency in 171Yb (F=1/2) is 518,295,836,593.2 +/- 4.4 kHz. The measured
frequency in 173Yb (F=5/2) is 518,294,576,850.0 +/- 4.4 kHz. Measurements are
made with a femtosecond-laser frequency comb calibrated by the NIST cesium
fountain clock and represent nearly a million-fold reduction in uncertainty.
The natural linewidth of these J=0 to J=0 transitions is calculated to be ~10
mHz, making them well-suited to support a new generation of optical atomic
clocks based on confinement in an optical lattice.Comment: 4 pages, 3 figure
Practice effects in healthy adults: a longitudinal study on frequent repetitive cognitive testing
QCD analysis of the diffractive structure function F_2^{D(3)}
The proton diffractive structure function measured in the H1 and
ZEUS experiments at HERA is analyzed in terms of both Regge phenomenology and
perturbative QCD evolution. A new method determines the values of the Regge
intercepts in ``hard'' diffraction, confirming a higher value of the Pomeron
intercept than for soft physics. The data are well described by a QCD analysis
in which point-like parton distributions, evolving according to the DGLAP
equations, are assigned to the leading and sub-leading Regge exchanges. The
gluon distributions are found to be quite different for H1 and ZEUS. A {\it
global fit} analysis, where a higher twist component is taken from models,
allows us to use data in the whole available range in diffractive mass and
gives a stable answer for the leading twist contribution. We give sets of quark
and gluon parton distributions for the Pomeron, and predictions for the charm
and the longitudinal proton diffractive structure function from the QCD fit. An
extrapolation to the Tevatron range is compared with CDF data on single
diffraction. Conclusions on factorization breaking depend critically whether H1
(strong violation) or ZEUS (compatibility at low ) fits are taken into
account.Comment: 24 page
Attosecond time-scale intra-atomic phase matching of high harmonic generation
Includes bibliographical references (page 5461).Using a model of high-harmonic generation that couples a fully quantum calculation with a semi-classical electron trajectory picture, we show that a new type of phase matching is possible when an atom is driven by an optimal optical waveform. For an optimized laser pulse shape, strong constructive interference is obtained in the frequency domain between emissions from different electron trajectories, thereby selectively enhancing a particular harmonic order. This work demonstrates that coherent control in the strong-field regime is possible by adjusting the peaks of a laser field on an attosecond time scale
Исторические аспекты общества знания на Западе и в СССР
Рецензія на монографію: Осипов Г.В., Кара-Мурза С.Г. Общество знания: История модернизации на Западе и в СССР. — М.: Книжный дом «ЛИБРОКОМ», 2013. — 368 с
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