3,637 research outputs found
Electron-phonon coupling in metals at high electronic temperatures
Electron-phonon coupling, being one of the most important parameters
governing the material evolution after ultrafast energy deposition, yet remains
the most unexplored one. In this work, we applied the dynamical coupling
approach to calculate the nonadiabatic electron-ion energy exchange in
nonequilibrium solids with the electronic temperature high above the atomic
one. It was implemented into the tight-binding molecular dynamics code, and
used to study electron-phonon coupling in various elemental metals. The
developed approach is a universal scheme applicable to electronic temperatures
up to a few electron-Volts, and to arbitrary atomic configuration and dynamics.
We demonstrate that the calculated electron-ion (electron-phonon) coupling
parameter agrees well with the available experimental data in
high-electronic-temperature regime, validating the model. The following
materials are studied here - fcc metals: Al, Ca, Ni, Cu, Sr, Y, Zr, Rh, Pd, Ag,
Ir, Pt, Au, Pb; hcp metals: Mg, Sc, Ti, Co, Zn, Tc, Ru, Cd, Hf, Re, Os; bcc
metals: V, Cr, Fe, Nb, Mo, Ba, Ta, W; diamond cubic lattice metals: Sn;
specific cases of Ga, In, Mn, Te and Se; and additionally semimetal graphite
and semiconductors Si and Ge. For many materials, we provide the first and so
far the only estimation of the electron-phonon coupling at elevated electron
temperatures, which can be used in various models simulating ultrafast energy
deposition in matter. We also discuss the dependence of the coupling parameter
on the atomic mass, temperature and density.Comment: To be submitted for publicatio
Predictions of hadron abundances in pp collisions at the LHC
Based on the statistical hadronization model, we obtain quantitative
predictions for the relative abundances of hadron species in pp collisions at
the LHC. By using the parameters of the model determined at sqrt s = 200 GeV,
and extrapolating the overall normalization from ppbar collisions at the SPS
and Tevatron, we find that the expected rapidity densities are almost
grand-canonical. Therefore, at LHC the ratios between different species become
essentially energy-independent, provided that the hadronization temperature T_H
and the strangeness suppression factor gamma_S retain the stable values
observed in the presently explored range of pp and ppbar collisions.Comment: 4 pages. Final version published in JP
Construction and Expected Performance of the Hadron Blind Detector for the PHENIX Experiment at RHIC
A new Hadron Blind Detector (HBD) for electron identification in high density
hadron environment has been installed in the PHENIX detector at RHIC in the
fall of 2006. The HBD will identify low momentum electron-positron pairs to
reduce the combinatorial background in the mass spectrum, mainly
in the low-mass region below 1 GeV/c. The HBD is a windowless
proximity-focusing Cherenkov detector with a radiator length of 50 cm, a CsI
photocathode and three layers of Gas Electron Multipliers (GEM). The HBD uses
pure CF as a radiator and a detector gas. Construction details and the
expected performance of the detector are described.Comment: QM2006 proceedings, 4 pages 3 figure
In situ imaging of domain structure evolution in labgeo5 single crystals
LaBGeO5 (LBGO) crystals are unique ferroelectric materials for manufacturing highly efficient UV laser sources based on frequency conversion. This is due to their low cut-off wavelength, high nonlinear-optical coefficients, and non-hygroscopicity. Periodical poling requires a deep study of domain kinetics in these crystals. Domain imaging by Cherenkov second harmonic generation microscopy was used to reveal the main processes of domain structure evolution: (1) growth and merging of isolated domains, (2) growth of stripe domains formed on the artificial linear surface defects, and (3) domain shrinkage. In a low field, growth of triangular domains and fast shape recovery after merging were observed, while in a high field, the circular domains grew independently after merging. The revealed essential wall motion anisotropy decreased with the field. The anisotropy led to significant shape transformations during domain shrinkage in low field. The formation of short-lived triangular domains rotated by 180 degrees with respect to the growing isolated domains was observed. The obtained results were explained within the kinetic approach to domain structure evolution based on the analogy between the growth of crystals and ferroelectric domains, taking into account the gradual transition from determined nucleation in low field to the stochastic one in high field. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 19-12-00210Funding: This research was funded by the Russian Science Foundation, grant number 19-12-00210
Experimental investigation of high-energy photon splitting in atomic fields
The new data analysis of the experiment, where the photon splitting in the
atomic fields has been observed for the first time, is presented. This
experiment was performed at the tagged photon beam of the ROKK-1M facility at
the VEPP-4M collider. In the energy region of 120-450 MeV, the statistics of
photons incident on the BGO target was collected. About 400
candidates to the photon splitting events were reconstructed. Within the
attained experimental accuracy, the experimental results are consistent with
the cross section calculated exactly in an atomic field. The predictions
obtained in the Born approximation significantly differ from the experimental
results.Comment: 11 pages, 6 figures, LaTe
Design, Construction, Operation and Performance of a Hadron Blind Detector for the PHENIX Experiment
A Hadron Blind Detector (HBD) has been developed, constructed and
successfully operated within the PHENIX detector at RHIC. The HBD is a
Cherenkov detector operated with pure CF4. It has a 50 cm long radiator
directly coupled in a window- less configuration to a readout element
consisting of a triple GEM stack, with a CsI photocathode evaporated on the top
surface of the top GEM and pad readout at the bottom of the stack. This paper
gives a comprehensive account of the construction, operation and in-beam
performance of the detector.Comment: 51 pages, 39 Figures, submitted to Nuclear Instruments and Method
A Hadron Blind Detector for the PHENIX Experiment
A novel Hadron Blind Detector (HBD) has been developed for an upgrade of the
PHENIX experiment at RHIC. The HBD will allow a precise measurement of
electron-positron pairs from the decay of the light vector mesons and the
low-mass pair continuum in heavy-ion collisions. The detector consists of a 50
cm long radiator filled with pure CF4 and directly coupled in a windowless
configuration to a triple Gas Electron Multiplier (GEM) detector with a CsI
photocathode evaporated on the top face of the first GEM foil.Comment: 4 pages, 3 figures, Quark Matter 2005 conference proceeding
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