29 results
Search Results
2. Λp Elastic Scattering in the CLAS Detector.
- Author
-
Price, John W.
- Subjects
NUCLEAR physics ,PARTICLE beams ,PHOTON beams ,LIQUID hydrogen ,NEUTRON stars ,ELASTIC scattering - Abstract
The elastic scattering process Λp → Λp offers insights on multiple problems in nuclear physics. SU(3)
F symmetry implies a close agreement between the Λp and pp scattering cross sections. The Λp elastic scattering cross section can also illuminate the structure of neutron stars. A data-mining project was started using multiple CLAS data sets taken for other purposes with photon beams on a long liquid hydrogen target. A Λ produced in a process such as γp → K+ Λ can interact with a second proton inside the target before either decaying or leaving the target. The good angular acceptance and momentum resolution of CLAS make it well-suited for this type of analysis, even though it was not designed for such a measurement. The scattered Λ can be identified from the π− p invariant mass. The four-vector of the initial Λ is then reconstructed in the process Xp → Λp, which shows a strong peak at the Λ mass with roughly twice the number of events as the existing world data sample. This observation opens up the possibility of other measurements using secondary beams of short-lived particles. This paper will discuss the current status of the analysis, and our plans for future work on this project. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
3. Reliability of the single folding potential to describe the elastic scattering data of the p+43Ca system.
- Author
-
Lee Yen Cheong, Ismail, Atef, Tammam, M., and Yahya, Noorhana
- Subjects
ELASTIC scattering ,NUCLEAR structure ,HEAVY ions ,CALCIUM ions ,SCATTERING cross sections (Physics) - Abstract
The study of the elastic scattering potential on the heavy-ions at various incident energies is a method to investigate the nuclear structures and radii. The cluster structure of the heavy-ions is proposed in order to investigate its reaction potentials. Reaction potentials of the heavy-ions have been a puzzle for many years. In this paper, the cluster structure of the heavy-ions is proposed in order to solve this puzzle. Based on this structure the elastic scattering cross-sections of p+
43 Ca reaction at Ep = 21--65 MeV are calculated and the results are in agreement with the experimental data. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
4. Puzzling out the proton radius puzzle.
- Author
-
Mihovilovič, M., Merkel, H., and Weber, A.
- Subjects
PROTONS ,IRREGULARITIES of distribution (Number theory) ,ELASTIC scattering ,MUONIC atoms ,NUCLEAR physics - Abstract
The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today's nuclear physics: after more than 50 years of research the radius of a basic constituent of matter is still not understood. This paper presents a summary of the best existing proton radius measurements, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. In the last part the upcoming experiments, dedicated to remeasuring the proton radius, are described. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
5. Puzzling out the proton radius puzzle.
- Author
-
Mihovilovič, M., Merkel, H., and Weber, A.
- Subjects
MUONS ,LAMB shift ,ELASTIC scattering ,NUCLEAR physics ,NUCLEAR size (Physics) - Abstract
The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today's nuclear physics: after more than 50 years of research the radius of a basic constituent of matter is still not understood. This paper presents a summary of the best existing proton radius measurements, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. In the last part the upcoming experiments, dedicated to remeasuring the proton radius, are described. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
6. Experimental Methods in the Study of Neutron Scattering at Small Angles.
- Author
-
Dragolici, Cristian A.
- Subjects
NEUTRON scattering ,X-ray scattering ,CONDENSED matter ,ELASTIC scattering ,PARTICLES (Nuclear physics) - Abstract
Small angle scattering (SAS) is the collective name given to the techniques of small angle neutron (SANS) and X-ray (SAXS) scattering. They offer the possibility to analyze particles without disturbing their natural environment. In each of these techniques radiation is elastically scattered by a sample and the resulting scattering pattern is analyzed to provide information about the size, shape and orientation of some component of the sample. Accordingly, a large number of methods and experimental patterns have been developed to ease the investigation of condensed matter by use of these techniques. Some of them are the discussed in this paper. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
7. Analysis of the 12,14Be+12C scattering data within a parallel implementation of 4-parameter model.
- Author
-
Bashashin, Maxim V., Zemlyanaya, Elena V., Kakenov, Meirzhan B., Yermekova, Asel Ye., and Lukyanov, Konstantin V.
- Subjects
BERYLLIUM ,EXOTIC nuclei ,DIFFERENTIAL cross sections ,SCHRODINGER equation ,ELASTIC scattering ,NUMERICAL analysis ,COMPUTER programming - Abstract
The MPI/OpenMP/C++ /Fortran package of computer codes has been developed for high-performance numerical analysis of experimental data on elastic nucleus-nucleus scattering within a microscopic model of optical potential. In the package, a modified DWUCK4 Fortran-code for calculating the physical characteristics of elastic scattering based on a numerical solution of the corresponding Schrödinger equation has been incorporated into the C++ framework, which is responsible for the input-output procedure and a comparison of numerical results with experimental data. MPI-based parallelism allows efficient calculations of the observables depending on a wide range of parameters of real and imaginary parts of the microscopic optical potential. The package has been used to analyze experimental data on differential cross sections of nucleus-nucleus elastic scattering of neutron-rich exotic nuclei
12,14 Be on the target nucleus12 C at energy about 56 MeV/nucleon. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
8. Reactive collisions between electrons and BeT+.
- Author
-
Iacob, F., Pop, N., Mezei, J. Zs., Niyonzima, S., Laporta, V., Chakrabarti, K., and Schneider, I. F.
- Subjects
COLLISIONS (Nuclear physics) ,QUANTUM defect theory ,ELECTRON impact ionization ,IONIZED gases ,ELASTIC scattering ,COLD gases ,HYDROGEN plasmas - Abstract
In order to model and diagnose the low-temperature edge plasmas, a complete database for electron-impact collision processes is required for molecular species containing beryllium and hydrogen. Dominant elementary processes in cold ionized gases are dissociative recombination, elastic collisions, vibrational excitation, vibrational de-excitation and dissociative excitation. In this study, using the stepwise version of the Multichannel Quantum Defect Theory, cross sections and rate coefficients have been obtained for reactions induced on BeT
+ . A set of vibrational resolved rate coefficients for BeT+ cations' reactive collisions with electrons below to the ion dissociation threshold is provided. The incident electron energy range is 10-3 - 2.7 eV and the electron temperature range is 100 - 5000 K. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
9. A Model for Joint Processing of LT and CDB Spectra of Dielectric Nano-sized Powders.
- Author
-
Stepanov, P. S., Selim, F. A., Stepanov, S. V., and Byakov, V. M.
- Subjects
ELASTIC scattering ,POSITRON annihilation ,POWDERS ,DIELECTRICS ,COMPUTER software ,POSITRONIUM - Abstract
A model that allows interpretation of positron annihilation spectra (LT and CDB) in nanodispersed dielectric powders is developed. Model takes into account e
+ capture by vacancy-type defects, formation of e+ surface-bound states, as well as the formation of quasi-free positronium (inside crystallites) which may escape into intergranular space where it becomes thermalized during elastic collisions. The process of annihilation of ortho-Ps is narrowed down to its conversion into the para-state as a result of collisions with oxygen molecules (O2 ) adsorbed on the surface of crystallites. A computer program for lifetime spectra fitting that accounts on the parameters of the above model is developed (with ROOT framework). Combination of the program with our CDB software allows joint processing of the LT and CDB annihilation spectra of nanopowders. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
10. Investigation of the Excited States of 11B in Interactions with Alpha Particles.
- Author
-
Burtebayev, Nassurlla, Janseitov, Daniyar, Kerimkulov, Zhambul, Nassurlla, Marzhan, Mukhamejanov, Yerzhan, and Alimov, Dilshod
- Subjects
EXCITED states ,ALPHA rays ,INELASTIC scattering ,PARTICLE interactions ,ELASTIC scattering - Abstract
The elastic and inelastic scatterings of α-particles were investigated at an energy of 29 MeV with excitation of lowlying states of the
11 B nucleus. As a result of research we obtained new experimental data for the α +11 B inelastic scattering one leading to the 2.12 MeV (1/2− ), 4.44 MeV (5/2− ) and 6.74 MeV (7/2− ) excited states of11 B nucleus. In the framework of Modified diffraction model, the root mean square radii of these excited states are calculated. The theoretical calculations for the concerned excited states were performed using the coupled channel (CC) method. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
11. Boltzmann-Fokker-Planck Kinetic Solver with Adaptive Mesh in Phase Space.
- Author
-
Kolobov, Vladimir, Arslanbekov, Robert, and Levko, Dmitry
- Subjects
PHASE space ,ELECTRON impact ionization ,ELASTIC scattering ,GAS dynamics - Abstract
We describe the implementation of kinetic solvers in 1d2v phase space using adaptive Cartesian mesh. Spherical coordinates in velocity space are used to simplify the Lorentz and Fokker-Planck collisional operators. The key capabilities of the new solvers are illustrated for electron elastic scattering, acceleration, continuous energy loss in collisions, and ionization processes in weakly-ionized plasma. We have also implemented two-stream approach to reduce computational cost for studies of gas breakdown dynamics in the presence of runaway electrons. The benefits and limitations of the nonsplit- phase-space method for kinetic solvers with adaptive mesh in phase space are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
12. Scattering of Elastic Waves by Point-like Obstacle in Two-dimensional Case.
- Author
-
Popov, Igor, Blinova, Irina, Boitsev, Anton, Froehly, Andre, and Neidhardt, Hagen
- Subjects
ELASTIC scattering ,SCATTERING (Physics) ,SYMMETRIC operators ,OPERATOR theory ,S-matrix theory ,ELASTIC waves - Abstract
A model of scattering of elastic wave by point-like scatterer on the plane is suggested. Point-like perturbation is constructed for the Lamé operator in the framework of the theory of self-adjoint extensions of symmetric operators. The eigenvalues of the model operator are found. The scattering matrix is obtained. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
13. New Boundary Integral Equation Formalism for Elastic Wave Scattering.
- Author
-
Schafbuch, Paul J.
- Subjects
ELASTIC waves ,SCATTERING (Physics) ,ELASTIC scattering ,BOUNDARY element methods ,INTEGRAL equations ,FINITE difference method ,SCATTERING (Mathematics) - Abstract
Boundary integral equations methods are inherently advantageous for infinite medium problems such as elastic wave scattering for ultrasonic Nondestructive Testing. The reduction in dimensionality of the problem (e.g., volume to surface) also leads to computational advantages versus finite element or finite difference methods for homogeneous media. However, numerical integration of the strongly singular (1/r²) kernels of the traditional BIE formalism has been a challenge in implementation; although successful functioning codes have long existed. Still, methods to incrementally minimize this difficulty have been the subject of research for three decades. This new BIE method utilizes an analytical representation for the incident plane wave’s stress field and Betti reciprocity to eliminate the strongly singular kernel integration that is required by scatterers with stress-free boundary conditions (such as voids, open cracks, and any nearby free surfaces). An associated weakly singular (1/r) BIE is readily solved instead. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
14. Elastic Scattering Studies of Nuclei Heavier Than A=22 with the Upgraded TAMU-MDM Focal Plane Detector.
- Author
-
Spiridon, Alexandra
- Subjects
ELASTIC scattering ,FOCAL plane arrays sensors ,NUCLEAR reactions ,NUCLEAR astrophysics ,RESEARCH institutes - Abstract
Elastic scattering reactions have been part of a campaign of studies at the Cyclotron Institute from Texas A&M University for more than 30 years. The studied nuclei ranged from
8 Be to22 Ne. In order to study the astrophysically important26 Si (through its mirror26 Mg), it was necessary to perform an upgrade of the focal plane detection system. Several scattering reactions on nuclei heavier than A=22 were measured as tests and the preliminary results are presented here. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
15. Reduction of channel coupling effect on Li isotope elastic scatterings by glue-like behaviour of excess neutron.
- Author
-
Takenori Furumoto, Tadahiro Suhara, and Naoyuki Itagaki
- Subjects
LITHIUM isotopes ,ELASTIC scattering ,NEUTRONS ,CLUSTER theory (Nuclear physics) ,PROTONS - Abstract
The glue-like behavior of valence neutrons has been investigated in the Li isotopes. The
7 Li nucleus is well known to be weakly bound system with the α + t cluster structure. By adding the valence neutrons, the reduction of the root-mean-square (RMS) radius of the proton density for the7 Li,8 Li and,9 Li nuclei is also well known from the viewpoint of the experimental data and theoretical approach. Elastic scattering cross sections of the Li isotopes on the12 C and28 Si targets at E/A~50 MeV are calculated. We find the change of the channel coupling (CC) effect on elastic scatterings of such Li isotopes by the glue-like role of the valence neutrons. Finally, we realize that the valence neutrons stabilize the binding of core parts, and the CC effect related the core excitation is indeed reduced. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
16. The use of the energy flow change theorem in solving the problem of perfectly elastic collision of three mass points.
- Author
-
G., Kolyari I., Kustova, Elena, Leonov, Gennady, Morosov, Nikita, Yushkov, Mikhail, and Mekhonoshina, Mariia
- Subjects
ELASTIC scattering ,SCATTERING (Physics) ,VELOCITY ,IMPACT (Mechanics) ,MASS (Physics) - Abstract
The proposed theoretical model allows for the perfectly elastic collision of three bodies (three mass points) to calculate: 1) the definite value of the three bodies’ projected velocities after the collision with a straight line, along which the bodies moved before the collision; 2) the definite value of the scattering bodies’ velocities on the plane and the definite value of the angles between the bodies’ momenta (or velocities), which the bodies obtain after the collision when moving on the plane. The proposed calculation model of the velocities of the three collided bodies is consistent with the dynamic model of the same bodies’ interaction during the collision, taking into account that the energy flow is conserved for the entire system before and after the collision. It is shown that under the perfectly elastic interaction during the collision of three bodies the energy flow is conserved in addition to the momentum and energy conservation. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
17. Elastic α-12C scattering at Low Energies in the Cluster Effective Field Theory.
- Author
-
Shung-Ichi Ando
- Subjects
CARBON isotopes ,ELASTIC scattering ,RADIATIVE capture ,GROUND state (Quantum mechanics) ,NUCLEAR reactions - Abstract
The elastic α-
12 C scattering at low energies is studied in the cluster effective field theory, in which the ground states of α and12 C are treated as elementary-like fields. We first discuss a construction of an effective field theory for radiative α capture reaction on12 C at the Gamow energy, TG = 0.3 MeV, in the stars and fix some parameters appearing in the theory from the phase shift data of the elastic α-12 C scattering. We then discuss the uncertainties of the present approach when interpolating the scattering amplitudes to TG . [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
18. Atomic Dark Matter with Hyperfine Interactions.
- Author
-
Boddy, Kimberly K., Kaplinghat, Manoj, Kwa, Anna, and Peter, Annika H. G.
- Subjects
DARK matter ,HYDROGEN ,ASTROPHYSICS ,HYPERFINE coupling ,ELASTIC scattering - Abstract
We consider dark matter as an analog of hydrogen in a secluded sector and study its astrophysical implications. The self interactions between dark matter particles include elastic scatterings as well as inelastic processes from hyperfine transitions. We show that for a dark hydrogen mass in the 10-100 GeV range and a dark fine-structure constant larger than 0.01, the self-interaction cross section has the right magnitude and velocity dependence to explain the low dark matter density cores seen in small galaxies while being consistent with all constraints from observations of galaxy clusters. Excitations to the hyperfine state and subsequent decays, however, may cause significant cooling losses and affect the evolution of low-mass halos. We also find minimum halo masses in the range of 10
3.5 -107 M... , which are significantly larger than the typical predictions for weakly interacting dark matter models. This pattern of observables in structure formation is unique to this model, making it possible to determine the viability of hidden-sector hydrogen as a dark matter candidate. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
19. New Results for Ultraperipheral Heavy Ion Collisions.
- Author
-
Szczurek, Antoni, Klusek-Gawenda, Mariola, Lebiedowicz, Piotr, and Schafer, Wolfgang
- Subjects
HEAVY ion collisions ,NUCLEAR cross sections ,LARGE Hadron Collider ,LEPTONS (Nuclear physics) ,ELASTIC scattering - Abstract
We discuss diphoton semi(exclusive) production in ultraperipheral PbPb collisions at energy of ys
NN = 5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary γγ → yy subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution (formally three-loops). We got relatively high cross sections in PbPb collisions. This opens a possibility to study the γγ → γγ (quasi)elastic scattering at the LHC. We find that the cross section for elastic γγ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to ψγγ 15 - 20 GeV. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms. We discuss also first results concerning production of two e+e-pairs in UPCs of heavy ions. We considered only double scattering mechanism. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
20. A General Solution of The Dirac Equation with Superposition of δ-Potentials and Its Application.
- Author
-
Fialka, Siarhei and Kapshai, Valery
- Subjects
SUPERPOSITION principle (Physics) ,ELASTIC scattering ,RELATIVISTIC particles ,DIRAC equation ,PHASE shift (Nuclear physics) ,NUCLEAR cross sections - Abstract
Elastic scattering of relativistic spin 1/2 particle was investigated in the spherically-symmetric case. Based on the phaseshift method, a general solution of the Dirac equation with superposition of N δ-potentials is obtained. The method for approximate solutions of Dirac equation with arbitrary smooth potentials is presented. Scattering cross section dependences on various parameters are investigated. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
21. Fast Computation of High Energy Elastic Collision Scattering Angle for Electric Propulsion Plume Simulation.
- Author
-
Araki, Samuel J.
- Subjects
ELASTIC scattering ,ELECTRIC propulsion ,PLUMES (Fluid dynamics) ,COLLISIONS (Physics) ,COLLOID thrusters ,ELECTRONS - Abstract
In the plumes of Hall thrusters and ion thrusters, high energy ions experience elastic collisions with slow neutral atoms. These collisions involve a process of momentum exchange, altering the initial velocity vectors of the collision pair. In addition to the momentum exchange process, ions and atoms can exchange electrons, resulting in slow charge-exchange ions and fast atoms. In these simulations, it is particularly important to accurately perform computations of ion-atom elastic collisions in determining the plume current profile and assessing the integration of spacecraft components. The existing models are currently capable of accurate calculation but are not fast enough such that the calculation can be a bottleneck of plume simulations. This study investigates methods to accelerate an ion-atom elastic collision calculation that includes both momentum- and charge-exchange processes. The scattering angles are pre-computed through a classical approach with ab initio spin-orbit free potential and are stored in a two-dimensional array as functions of impact parameter and energy. When performing a collision calculation for an ion-atom pair, the scattering angle is computed by a table lookup and multiple linear interpolations, given the relative energy and randomly determined impact parameter. In order to further accelerate the calculations, the number of collision calculations is reduced by properly defining two cut-off cross-sections for the elastic scattering. In the MCC method, the target atom needs to be sampled; however, it is confirmed that initial target atom velocity does not play a significant role in typical electric propulsion plume simulations such that the sampling process is unnecessary. With these implementations, the computational runtime to perform a collision calculation is reduced significantly compared to previous methods, while retaining the accuracy of the high fidelity models. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
22. Extracting integrated and differential cross sections in low energy heavy-ion reactions from backscattering measurements.
- Author
-
Sargsyan, V. V., Adamian, G. G., Antonenko, N. V., Diaz-Torres, A., Gomes, P. R. S., and Lenske, H.
- Subjects
BACKSCATTERING ,ELASTIC scattering ,POTENTIAL scattering ,NUCLEAR excitation ,ENERGY levels (Quantum mechanics) - Abstract
We suggest new methods to extract elastic (quasi-elastic) scattering angular distribution and reaction (capture) cross sections from the experimental elastic (quasi-elastic) backscattering excitation function taken at a single angle. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
23. Systematic Analysis of α Elastic Scattering with the São Paulo Potential.
- Author
-
Charry-Pastran, F. E. and Pinilla, E. C.
- Subjects
ELASTIC scattering ,NUCLEAR optical potentials ,POTENTIAL scattering ,NEUTRON scattering ,SCATTERING length (Nuclear physics) - Abstract
We describe systematically by collision energy and target mass, alpha elastic scattering angular distributions by using the São Paulo potential as the real part of the optical potential. The imaginary part is proportional to the real one by a factor N
i . We find this parameter by fitting the theoretical angular distributions to the experimental cross sections through a χ2 minimization. The Ni and their respective uncertainties, σN , fall in the range 0.4 ≤ Ni i ± σN ≤ 0.8 for all the systems studied. [ABSTRACT FROM AUTHOR]i - Published
- 2016
- Full Text
- View/download PDF
24. Study of Plastic Strain Localization Mechanisms Caused by Nonequilibrium Transitions in Mesodefect Ensembles under High-Speed Loading.
- Author
-
Sokovikov, Mikhail, Chudinov, Vasiliy, Bilalov, Dmitry, Oborin, Vladimir, Uvarov, Sergey, Plekhov, Oleg, and Naimark, Oleg
- Subjects
NON-equilibrium reactions ,SCANNING electron microscopes ,THERMOPLASTIC composites ,THERMODYNAMICS ,ELASTIC scattering - Abstract
The behavior of specimens dynamically loaded during split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in-situ using a high-speed infrared camera CEDIP Silver 450M. The temperature field distribution obtained at different time allowed one to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infrared camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profiler and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
25. Relaxation of Quantum State Population and Volume Viscosity in He/H2 Mixtures.
- Author
-
Bruno, D., Esposito, F., and Giovangigli, V.
- Subjects
QUANTUM states ,VISCOSITY ,GAS mixtures ,FLUID mechanics ,ELASTIC scattering ,THERMODYNAMIC equilibrium - Abstract
A kinetic model for He-H
2 mixtures is studied in a regime where elastic collisions are fast and inelastic collisions are slow. Application of the Chapman-Enskog method yields a state to state fluid model where each quantum state is a separate pseudo species. The relaxation of quantum state population towards thermodynamic equilibrium is investigated as well as the definition of volume viscosity coefficients. The theoretical results are applied to the quantum state population and volume viscosity of molecular hydrogen on the basis of a complete set of cross sections for the He+H2 (v, j) system. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
26. Reconstruction of the "Phase Separation - Ordering" Type and Specific Heat in Carbon Nanotubes.
- Author
-
Ponomarev, Alexander N., Egorushkin, Valery E., Melnikova, Natalia V., and Bobenko, Nadezda G.
- Subjects
PHASE separation ,CARBON nanotubes ,SPECIFIC heat ,LOW temperatures ,PHONONS ,ELASTIC scattering ,HETEROGENEITY ,ELECTRONS - Abstract
The low-temperature behavior of the specific heat in disordered nanotubes strongly depends on structure changes and was not explained by the phonon contribution. Expression for electronic specific heat was carried out taking into account the multiple elastic scattering of electrons on impurities and structural inhomogeneities of short-range order type, it includes dependence on diameter of nanotube, concentration of impurities, parameters of short-range order (structural heterogeneity) and temperature. Anomalous low-temperature behavior of the specific heat of disordered CNT is shown to have electronic nature and may be associated with the electrons that are involved in restructuring. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
27. Λp elastic scattering in the CLAS detector
- Author
-
John W. Price
- Subjects
Physics ,Nuclear physics ,Elastic scattering ,Momentum ,Cross section (physics) ,Neutron star ,Proton ,Scattering ,Invariant mass ,Symmetry (physics) - Abstract
The elastic scattering process Λp → Λp offers insights on multiple problems in nuclear physics. SU(3)F symmetry implies a close agreement between the Λp and pp scattering cross sections. The Λp elastic scattering cross section can also illuminate the structure of neutron stars. A data-mining project was started using multiple CLAS data sets taken for other purposes with photon beams on a long liquid hydrogen target. A Λ produced in a process such as γp → K+ Λ can interact with a second proton inside the target before either decaying or leaving the target. The good angular acceptance and momentum resolution of CLAS make it well-suited for this type of analysis, even though it was not designed for such a measurement. The scattered Λ can be identified from the π− p invariant mass. The four-vector of the initial Λ is then reconstructed in the process Xp → Λp, which shows a strong peak at the Λ mass with roughly twice the number of events as the existing world data sample. This observation opens up the possibility of other measurements using secondary beams of short-lived particles. This paper will discuss the current status of the analysis, and our plans for future work on this project.The elastic scattering process Λp → Λp offers insights on multiple problems in nuclear physics. SU(3)F symmetry implies a close agreement between the Λp and pp scattering cross sections. The Λp elastic scattering cross section can also illuminate the structure of neutron stars. A data-mining project was started using multiple CLAS data sets taken for other purposes with photon beams on a long liquid hydrogen target. A Λ produced in a process such as γp → K+ Λ can interact with a second proton inside the target before either decaying or leaving the target. The good angular acceptance and momentum resolution of CLAS make it well-suited for this type of analysis, even though it was not designed for such a measurement. The scattered Λ can be identified from the π− p invariant mass. The four-vector of the initial Λ is then reconstructed in the process Xp → Λp, which shows a strong peak at the Λ mass with roughly twice the number of events as the existing world data sample. This observation opens up the possibi...
- Published
- 2019
28. Investigation of different C-backings for targets
- Author
-
J. Khuyagbaatar, A. Hübner, Mahananda Dasgupta, Birgit Kindler, J. Steiner, V. Yakusheva, Bettina Lommel, and David Hinde
- Subjects
Elastic scattering ,Carbon deposition ,Yield (engineering) ,Materials science ,chemistry ,Flat surface ,Rough surface ,chemistry.chemical_element ,Deposition (phase transition) ,Composite material ,Carbon ,Layer (electronics) - Abstract
For a special application, carbon-backings with a very flat surface, microscopically as well as macroscopically, were needed as backings for targets of enriched isotopes. However, betaine-sucrose routinely applied at GSI as parting agent for carbon deposition results in a microscopically rough surface which was not perfectly satisfying the experimental requirements. For these targets we investigated the carbon-backing quality in relation to the applied different parting agents and different deposition processes. In this paper we report on the yield, on the structure of the carbon layers and the deposited target layer of 208PbS, 206PbS, and 142NdF3 depending on the parting agent, the thickness and the deposition methods. We report on elastic scattering experiments with a 48Ti-beam demonstrating the influence of the structure of the carbon backing on the experimental results.
- Published
- 2018
29. Puzzling out the proton radius puzzle
- Author
-
Harald Merkel, Adrian Weber, and M. Mihovilovic
- Subjects
Physics ,Elastic scattering ,Hydrogen ,Proton ,QC1-999 ,chemistry.chemical_element ,Radius ,Lamb shift ,Nuclear physics ,chemistry ,Charge radius ,Physics::Atomic Physics ,Atomic physics ,Nuclear Experiment ,Exotic atom - Abstract
The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today’s nuclear physics: after more than 50 years of research the radius of a basic constituent of matter is still not understood. This paper presents a summary of the best existing proton radius measurements, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. In the last part the upcoming experiments, dedicated to remeasuring the proton radius, are described.
- Published
- 2016
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