Search results for "scattering [WIMP nucleon]"
showing 10 items of 187 documents
Complex, energy-independent, local potential reproducing an absorptive phase shift and a bound state
1994
The triton binding energy, and the partly real and partly complex neutron-deuteron doublet channel elastic scattering phase shifts, calculated by means of the exact three-body theory, are used as input in the fixed-[ital l] inverse scattering theory of Marchenko. The local potentials obtained hereby are independent of energy, and complex. Their strong imaginary part reflects the strong absorption in the doublet channel arising from the opening of the deuteron breakup channel. For total orbital angular momentum [ital l] different from zero the potentials are unique, reproducing the input phase shift in the whole energy region. For [ital l]=0 where there exists, in addition, a bound state we …
η−3Nproblem with separable interactions
2002
The $\eta$-3N-interaction is studied within the four-body Faddeev-Yakubovsky theory adopting purely separable forms for the two- and three-body subamplitudes, limiting the basic two-body interactions to s-waves only. The corresponding separable approximation for the integral kernels is obtained by using the Hilbert-Schmidt procedure. Results are presented for the $\eta$-$^3$H scattering amplitude and for the total elastic cross section for energies below the triton break-up threshold.
Microwave characterization and modeling of packaged HEMTs by a direct extraction procedure at cryogenic temperatures
2004
In the present work we employ a direct extraction procedure to determine small signal equivalent circuit of microwave GaAs FETs by means of scattering (S-) parameter measurements down to cryogenic temperatures. The direct extraction procedure was tested on packaged AlGaAs/InGaAs HEMTs and good agreement between the simulated and measured S-parameters was obtained at different bias and temperature conditions. We employed a properly designed cryogenic set-up operating in our laboratory that allows to perform DC and RF characterization down to 30 K.
Self-assembled silver nanoparticles for plasmon-enhanced solar cell back reflectors: correlation between structural and optical properties
2013
The spectra of localized surface plasmon resonances (LSPRs) in self-assembled silver nanoparticles (NPs), prepared by solid-state dewetting of thin films, are discussed in terms of their structural properties. We summarize the dependences of size and shape of NPs on the fabrication conditions with a proposed structural-phase diagram. It was found that the surface coverage distribution and the mean surface coverage (SC) size were the most appropriate statistical parameters to describe the correlation between the morphology and the optical properties of the nanostructures. The results are interpreted with theoretical predictions based on Mie theory. The broadband scattering efficiency of LSPR…
Characterization of semicrystalline random copolymers by small-angle neutron scattering
1979
A new method is introduced to determine the degree of partitioning of noncrystallizable comonomer units (B units) between the two phases of a semicrystalline random copolymer. The method is based on the comparison of the intensities of small-angle neutron and x-ray scattering (SANS and SAXS, respectively). By this technique two quantities can be evaluated: the difference Δρ of the mass densities between the crystalline and the disordered regions, and the concentration fluctuations of the B units in the two phases. It is found that SANS is very sensitive to the presence of small amounts of B units if their scattering length is sufficiently different from that of the A units. This will be the…
Phonons of hexagonal BN under pressure: Effects of isotopic composition
2021
Raman scattering experiments on isotopically enriched hexagonal boron nitride have been performed under pressure up to 11 GPa at room temperature. The sublinear increase of the Raman-active E2g mode frequencies has been characterized. The pressure behavior has been analyzed by means of a bond-stiffness–bond-length scaling parameter γ which takes into consideration the vast differences in a- and c-axis compressibilities. The interlayer shear mode exhibits a γ parameter similar to that of graphite, and the mode frequency in isotopically pure samples separates faster at low pressures as a result of van der Waals interactions. Because of the extremely low a-axis compressibility, the intralayer …
TEMPERATURE DEPENDENT NOISY MODELS OF PSEUDOMORPHIC HEMTs
1994
From a complete characterization in terms of noise and scattering parameters carried out at room temperature in the 8–16 GHz frequency range, the noisy small‐signal model of a pseudomotphic HEMT series has been extracted. The transistor scattering parameters have been subsequently measured at lower temperatures (down to −50 °C) by placing the device text fixture in a thermo‐controlled chamber. The model effectiveness has then been tested by determining the circuit element values at the different temperatures and by observing the model noise performance.
Fixed angle inverse scattering in the presence of a Riemannian metric
2020
We consider a fixed angle inverse scattering problem in the presence of a known Riemannian metric. First, assuming a no caustics condition, we study the direct problem by utilizing the progressing wave expansion. Under a symmetry assumption on the metric, we obtain uniqueness and stability results in the inverse scattering problem for a potential with data generated by two incident waves from opposite directions. Further, similar results are given using one measurement provided the potential also satisfies a symmetry assumption. This work extends the results of [23,24] from the Euclidean case to certain Riemannian metrics.
12C + 12C large angle elastic scattering at 240 MeV
2010
Abstract The measurement of the differential cross sections of the 12C + 12C and the 13C + 12C elastic scattering are carried out at the 12C energy 240 MeV and the 13C energy 250 MeV to solve some interpretation problem of the 12C + 12C scattering data. Is it possible that the 1st Airy minimum in 12C + 12C scattering data is missing? Our analysis shows that the positions of the 1st Airy minima obtained in former measurements are confirmed.
Second-order approximations to laser-assisted charged-particle scattering.
1990
Multiphoton free-free transitions within a full second-order treatment of the scattering potential are considered with two specific aims: (i) to test some widely used approximations against exact calculations; (ii) to present differential cross sections for the laser-assisted positron scattering, in the regime of intermediate field intensities (up to ${10}^{13}$ W/${\mathrm{cm}}^{2}$). In the case of a field linearly polarized along the incident particle momentum, the results clearly discriminate among the approximations, setting interesting limitations to each of them as functions of the scattering potential features and of the field parameters. Each approach shows good performance for par…