1,511 research outputs found
Adaptive correction of thermal distortions of multichannel laser radiation
Results of the simulation of multichannel radiation propagation under conditions of thermal blooming are presented. The correction of nonlinear thermal distortion by means of the beam phase and amplitudephase control is considered. The results show the dependence of the correction effectiveness on the number of channels and on the precision of the reference beam phase retrieval. An additional increase in the effectiveness is possible by means of adjustment of amplification in the channels of the optical system, i.e., with the use of amplitude-phase control over the beam wavefront
Threshold of laser destruction of nonlinear GaSe and GaSe:in crystals when exposed to pulsed radiation at a wavelength of 2.1 microns
The aim of this work is to determine the optical breakdown threshold of a single crystal GaSe and GaSe:In when exposed to nanosecond radiation of the two micron range and determining the influence of the energy parameters of the testing radiation on the breakdown threshold. The Ho3+:YAG laser was used as the laser radiation source in this work. Pumping was carried out by a Thule fiber laser.В ст. ошибочно: E. V. Zhuravle
Hole Localization in Underdoped Superconducting Cuprates Near 1/8th Doping
Measurements of thermal conductivity versus temperature over a broad range of
doping in YBaCuO and HgBaCaCuO
(=1,2,3) suggest that small domains of localized holes develop for hole
concentrations near =1/8. The data imply a mechanism for localization that
is intrinsic to the CuO-planes and is enhanced via pinning associated with
oxygen-vacancy clusters.Comment: 4 pages, 4 eps fig.'s, to be published, Phys. Rev.
Influence of post-post processing technology and laser radiation parameters on the optical breakdown threshold of a ZnGeP2 single crystal
The aim of this work is to determine the influence of the parameters of post-growth technological operations and experimental conditions on the threshold of optical breakdown of the surface of ZGP crystals under the action of laser radiation at a wavelength of 2091 nm
Study of below 1 GeV using Integral Equation Approach
The scattering of is studied using the axial
anomaly, elastic unitarity, analyticity and crossing symmetry. Using the
technique to derive the Roy's equation, an integral equation for the P-wave
amplitude is obtained in terms of the strong P-wave pion pion phase shifts. Its
solution is obtained numerically by an iteration procedure using the starting
point as the solution of the integral equation of the Muskelshsvilli-Omnes
type. It is, however, ambiguous and depends sensitively on the second
derivative of the P-wave amplitude at which cannot directly be
measured.Comment: 26 pages, 10 figure
Forward Physics at the LHC; Elastic Scattering
The following effects in the nearly forward ("soft") region of the LHC are
proposed to be investigated: 1) At small |t| the fine structure of the cone
(Pomeron) shouldbe scrutinized: a) a break of the cone near ^2, due to the two-pion threshold, and required by t-channel unitarity, is
expected, and b) possible small-period oscillations between and the dip
region. 2) In measuring the elastic scattering and total cross
section at the LHC, the experimentalists are urged to treat the total cross
section the ratio , the forward slope and the luminosity
as free arameters, and to publish model-independent results on
3) Of extreme interest are the details of the expected diffraction
minimum in the differential cross section. Its position, expected in the
interval GeV at the level of about
GeV GeV, cannot be predicted
unambiguously, and its depth, i.e. the ratio of at the minimum to
that at the subsequent maximum (about GeV, which is about 5 is of
great importance. 4) The expected slow-down with increasing of the
shrinkage of the second cone (beyond the dip-bump), together with the
transition from an exponential to a power decrease in , will be indicative
of the transition from "soft" to "hard" physics. Explicit models are proposed
to help in quantifying this transition. 5) In a number of papers a limiting
behavior, or saturation of the black disc limit (BDL) was predicted. This
controversial phenomenon shows that the BDL may not be the ultimate limit.Comment: pp. 50, figs 16 (typos corrected
First Measurement of pi e -> pi e gamma Pion Virtual Compton Scattering
Pion Virtual Compton Scattering (VCS) via the reaction pi e --> pi e gamma
was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi-
beam incident on target atomic electrons, detecting the incident pi- and the
final state pi-, electron and gamma. Theoretical predictions based on chiral
perturbation theory are incorporated into a Monte Carlo simulation of the
experiment and are compared to the data. The number of reconstructed events (9)
and their distribution with respect to the kinematic variables (for the
kinematic region studied) are in reasonable accord with the predictions. The
corresponding pi- VCS experimental cross section is sigma=38.8+-13 nb, in
agreement with the theoretical expectation sigma=34.7 nb.Comment: 10 pages, 12 figures, 4 tables, 25 references, SELEX home page is
http://fn781a.fnal.gov/, revised July 21, 2002 in response to journal referee
Comment
Search for pentaquark in high statistics measurement of at CLAS
The exclusive reaction was studied in the
photon energy range between 1.6-3.8 GeV searching for evidence of the exotic
baryon . The decay to requires the assignment of
strangeness to any observed resonance. Data were collected with the CLAS
detector at the Thomas Jefferson National Accelerator Facility corresponding to
an integrated luminosity of 70 . No evidence for the
pentaquark was found. Upper limits were set on the production cross section as
function of center-of-mass angle and mass. The 95% CL upper limit on the
total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.Comment: Submitted to Physical Review Letter
Search for an exotic S=-2, Q=-2 baryon resonance at a mass near 1862 MeV in quasi-real photoproduction
A search for an exotic baryon resonance with has been performed
in quasi-real photoproduction on a deuterium target through the decay channel
. No evidence for
a previously reported resonance is found in the invariant mass spectrum. An upper limit for the photoproduction cross
section of 2.1 nb is found at the 90% confidence level. The photoproduction
cross section for the is found to be between 9 and 24 nb
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