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Počet nalezených dokumentů:
253
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High-resolution Hypernuclear Spectroscopy Electron Scattering at JLab, Hall A
Garibaldi, F.; Cisbani, E.; Cusanno, F.; Frullani, S.; Iodice, M.; Urciuoli, G.M.; De Leo, R.; Lagamba, L.; Marrone, S.; LeRose, J. J.; de Jager, C.W.; Feuerbach, R. J.; Higinbotham, D. W.; Reitz, B.; Acha, A.; Markowitz, P.; Bydžovský, Petr; Sotona, Miloslav; Chang, C. C.; Millener, J.
2010 - anglický
The characteristics of the Jefferson LAB electron beam, together with those of the experimental equipments, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced reactions. Experiment 94-107 started a systematic study on 1p-shell targets, C-12, Be-9 and O-16. We present the results from C-12, O-16 and very preliminary results from Be-9. For C-12 for the first time measurable strength in the core-excited part of the spectrum between the ground state and the p(Lambda) state was shown in B-12(Lambda) for the first time. A high-quality N-16(Lambda) spectrum was produced for the first time with sub-MeV Energy resolution. A very precise B-Lambda value for N-16(Lambda), calibrated against the elementary (e,e'K+) reaction on hydrogen, has also been obtained. Final data on Be-9 will be available soon. The missing energy resolution is the best ever obtained in hypernuclear production experiments.
Klíčová slova:
electromagneti production; Jefferson laboratory; stangeness
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
High-resolution Hypernuclear Spectroscopy Electron Scattering at JLab, Hall A
The characteristics of the Jefferson LAB electron beam, together with those of the experimental equipments, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced ...
QCD factorization at forward rapidities
Nemchik, J.; Šumbera, Michal
2010 - anglický
We analyze several reactions on nuclear targets at forward rapidities and different energies (at smallest experimentally accessible Bjorken x(2) in the target). Nuclear effects are then usually interpreted as a result of shadowing or the Color Glass Condensate. QCD factorization of soft and hard interactions requires the nucleus to be an universal filter for different Fock components of the projectile hadron. We demonstrate, however, that this is not the case in the vicinity of the kinematic limit, Feynman x(F) -> 1, where sharing of energy between the projectile constituents becomes an issue. The rise of suppression with x(F) is confirmed by the E772 and E886 data on the Drell-Yan and heavy quarkonium production. We show that this effect can be treated alternatively as an effective energy loss proportional to initial energy. This leads to a nuclear suppression at any energy, and predicts x(F) scaling of the suppression. We demonstrate also that the same kinematic limit can be approached in transverse momentum when the Cronin enhancement of particle production at medium-high p(T) switches to a suppression at larger p(T) violating thus QCD factorization. Such an unexpected effect seems to be confirmed by the RHIC data for pion production in d+A collisions, and even for direct photons in Au+Au collisions.
Klíčová slova:
suppression; collisions
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
QCD factorization at forward rapidities
We analyze several reactions on nuclear targets at forward rapidities and different energies (at smallest experimentally accessible Bjorken x(2) in the target). Nuclear effects are then usually ...
Spectral flux of the p-Li-7(C) Q-M neutron source measured by proton recoil telescope
Novák, Jan; Bém, Pavel; Fischer, U.; Götz, Miloslav; Honusek, Milan; Simakov, S. P.; Šimečková, Eva; Štefánik, Milan
2010 - anglický
The cyclotron-based fast neutron source at NPI produces mono-energetic neutron fields up to 35 MeV neutron energy using the p + 7Li(carbon backing) reactions. To be applied for activation cross-section measurements, not only the intensity of neutron peak, but also the contribution of low-energy continuum in the spectra must be well determined. Simulations of the spectral flux from present source at a position of irradiated samples were performed using CYRIC TOF-data validated in the present work against LA150h by calculations with the transport Monte Carlo code MCNPX.
Klíčová slova:
MCNPX; TOF; neutron source
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Spectral flux of the p-Li-7(C) Q-M neutron source measured by proton recoil telescope
The cyclotron-based fast neutron source at NPI produces mono-energetic neutron fields up to 35 MeV neutron energy using the p + 7Li(carbon backing) reactions. To be applied for activation ...
Chiral model for (K)over-barN interactions and its pole content
Cieplý, Aleš; Smejkal, J.
2010 - anglický
We use chirally motivated effective meson-baryon potentials to describe the low energy (K) over barN data including the characteristics of kaonic hydrogen. Our results are examined in comparison with other approaches based on the unitarity and dispersion relation for the inverse of the T-matrix. We demonstrate that the movements of the poles generated by the model upon varying the model parameters can serve as a tool to get additional insights on the dynamics of the strongly coupled pi Sigma-(K) over barN system.
Klíčová slova:
chiral Lagrangians; coupled channels; meson-baryon interactions
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Chiral model for (K)over-barN interactions and its pole content
We use chirally motivated effective meson-baryon potentials to describe the low energy (K) over barN data including the characteristics of kaonic hydrogen. Our results are examined in comparison with ...
Indirect measurement of O-17(p,alpha)N-14 cross section at ultra-low energies
Sergi, M. L.; Spitaleri, C.; Coc, A.; Mukhamedzhanov, A.; Burjan, Václav; Cherubini, S.; Crucilla, V.; Gulino, M.; Hammache, F.; Hons, Zdeněk; Irgaziev, B.; Kiss, G. G.; Kroha, Václav; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; de Sereville, N.; Somorjai, E.; Tudisco, S.; Tumino, A.
2010 - anglický
The indirect measurement of O-17(p,alpha)N-14 cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range (E-c.m.= 0-300 keV) relevant for several astrophysics environments, where two resonant levels of F-18 at E-c.m.(R) = 65 keV and E-c.m.(R) = 183 keV play a significant role in the reaction rate determination.
Klíčová slova:
astrophysics; nuclear reaction; reaction rates
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Indirect measurement of O-17(p,alpha)N-14 cross section at ultra-low energies
The indirect measurement of O-17(p,alpha)N-14 cross section was performed by means of the Trojan Horse Method. This approach allowed to investigate the ultra-low energy range (E-c.m.= 0-300 keV) ...
Astrophysical Reaction Rates Obtained By Indirect Techniques
Tribble, R. E.; Al-Abdullah, T.; Alharbi, A.; Aysto, J.; Banu, A.; Burjan, Václav; Carstoiu, F.; Chen, X.; Clark, H. L.; Davidson, T.; Fu, C.; Gagliardi, C. A.; Hardy, J. C.; Iacob, V. E.; Jokinen, J.; Kroha, Václav; Lui, Y. W.; McCleskey, M.; Mukhamedzhanov, A.; Nica, N.; Park, H.; Roeder, B. T.; Saastamoinen, A.; Simmons, E.; Tabacaru, G.; Tokimoto, Y.; Trache, L.; Woods, P. J.; Zhai, Y.
2010 - anglický
ndirect techniques have been used to obtain information about reaction rates for several proton capture reactions that occur on short-lived nuclei. The techniques used to carry out the measurements are reviewed and the results obtained are presented. Also future prospects for further measurements with a new facility, T-REX, are discussed.
Klíčová slova:
nuclear astophysics; explosive nucleosynthesis; proton capture
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Astrophysical Reaction Rates Obtained By Indirect Techniques
ndirect techniques have been used to obtain information about reaction rates for several proton capture reactions that occur on short-lived nuclei. The techniques used to carry out the measurements ...
Indirect Approach To The H-2(d,p)H-3 Reaction Study
Sparta, R.; Pizzone, R. G.; Spitaleri, C.; Aliotta, M.; Burjan, Václav; Cherubini, S.; Crucilla, V.; Gulino, M.; Hons, Zdeněk; Kiss, G. G.; Kroha, Václav; La Cognata, M.; Lamia, L.; McCleskey, M.; Mrázek, Jaromír; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Trache, L.; Tumino, A.
2010 - anglický
In order to understand primordial and stellar nucleosynthesis, we have studied H-2(d,p)H-3 reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The H-2(d,p)H-3 reaction has been studied through the Trojan Horse Method applied to the three-body reaction H-2(He-3,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another H-2(d,p)H-3 THM measurements, where a different spectator particle was employed.
Klíčová slova:
nuclear astrohphysics; Trojan Horse; Big Bang nucleosynthesis
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Indirect Approach To The H-2(d,p)H-3 Reaction Study
In order to understand primordial and stellar nucleosynthesis, we have studied H-2(d,p)H-3 reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan ...
Spectroscopy of Medium-mass Hypernuclear Production
Motoba, T.; Bydžovský, Petr; Sotona, Miloslav; Itonaga, K.; Ogawa, K.; Hashimoto, O.
2010 - anglický
Theoretical hypernuclear photoproduction spectra are demonstrated by choosing typical medium-heavy nuclear targets such as Si-28, Ca-40, and Cr-52. The predictions provide us with interesting opportunities of spectroscopic study beyond p-shell on the dynamical coupling between a hyperon and nuclear core excitations.
Klíčová slova:
hypernuclear photoproduction; DWIA; unnatural parity states
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Spectroscopy of Medium-mass Hypernuclear Production
Theoretical hypernuclear photoproduction spectra are demonstrated by choosing typical medium-heavy nuclear targets such as Si-28, Ca-40, and Cr-52. The predictions provide us with interesting ...
Influence of Plastic Deformation on the Residual Stress Distribution and Fatigue Behaviour of High Strength Steels Welds
Mráz, Ľ.; Karlsson, L.; Hamak, I.; Mikula, Pavol; Vrána, Miroslav
2010 - anglický
The effects of plastic deformation and cyclic loading on residual stress distribution have been studied at welds in high strength 800 MPa steel. Effects of residual stress levels on fatigue life are also presented. Tensile loading was used to induce precisely controlled plastic deformation at weld toes. Residual stress distributions were measured by neutron diffraction. The influence of fatigue loading on the residual stress level was much smaller than that of plastic deformation. A large drop of residual stresses in the vicinity of the welds was recognised after local straining at the level of 2%. Stresses decreased with up to 550 MPa in the region around the weld toe. The effect of local plastic deformation on fatigue properties was also found to be significant. Fatigue strength more than doubled compared to the non-strained as-welded condition.
Klíčová slova:
neutron diffraction; residual stress
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of Plastic Deformation on the Residual Stress Distribution and Fatigue Behaviour of High Strength Steels Welds
The effects of plastic deformation and cyclic loading on residual stress distribution have been studied at welds in high strength 800 MPa steel. Effects of residual stress levels on fatigue life are ...
Geometric Versus Spectral Convergence for the Neumann Laplacian under Exterior Perturbations of the Domain
Arrieta, J. M.; Krejčiřík, David
2010 - anglický
This chapter is concerned with the behavior of the eigenvalues and eigenfunctions of the Laplace operator in bounded domains when the domain undergoes a perturbation. It is well known that if the boundary condition that we are imposing is of Dirichlet type, the kind of perturbations that we may allow in order to obtain the continuity of the spectra is much broader than in the case of a Neumann boundary condition. This is explicitly stated in the pioneer work of Courant and Hilbert [CoHi53], and it has been subsequently clarified in many works, see [BaVy65, Ar97, Da03] and the references therein among others. See also [HeA06] for a general text on different properties of eigenvalues and [HeD05] for a study on the behavior of eigenvalues and in general partial differential equations when the domain is perturbed.
Klíčová slova:
eigenvalues; Laplace operator; Dirichlet condition
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Geometric Versus Spectral Convergence for the Neumann Laplacian under Exterior Perturbations of the Domain
This chapter is concerned with the behavior of the eigenvalues and eigenfunctions of the Laplace operator in bounded domains when the domain undergoes a perturbation. It is well known that if the ...
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