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Search Results: 1 - 10 of 464329 matches for " A. Sanchez-Lorente "
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Measurement of the Transverse Beam Spin Asymmetry in Elastic Electron Proton Scattering and the Inelastic Contribution to the Imaginary Part of the Two-Photon Exchange Amplitude
F. E. Maas,K. Aulenbacher,S. Baunack,L. Capozza,J. Diefenbach,B. Gl?ser,Y. Imai,T. Hammel,D. von Harrach,E. -M. Kabub,R. Kothe,J. H. Lee,A. Sanchez-Lorente,E. Schilling,D. Schwaab,G. Stephan,G. Weber,C. Weinrich,I. Altarev,J. Arvieux,M. Elyakoubi,R. Frascaria,R. Kunne,M. Morlet,S. Ong,J. Vandewiele,S. Kowalski,R. Suleiman,S. Taylor
Physics , 2004, DOI: 10.1103/PhysRevLett.94.082001
Abstract: We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A$_\perp$, at two Q$^2$ values of \qsquaredaveragedlow (GeV/c)$^2$ and \qsquaredaveragedhighII (GeV/c)$^2$ and a scattering angle of $30^\circ < \theta_e < 40^\circ$. The measured transverse asymmetries are A$_{\perp}$(Q$^2$ = \qsquaredaveragedlow (GeV/c)$^2$) = (\experimentalasymmetry alulowcorr $\pm$ \statisticalerrorlow$_{\rm stat}$ $\pm$ \combinedsyspolerrorlowalucor$_{\rm sys}$) $\times$ 10$^{-6}$ and A$_{\perp}$(Q$^2$ = \qsquaredaveragedhighII (GeV/c)$^2$) = (\experimentalasymme tryaluhighcorr $\pm$ \statisticalerrorhigh$_{\rm stat}$ $\pm$ \combinedsyspolerrorhighalucor$_{\rm sys}$) $\times$ 10$^{-6}$. The first errors denotes the statistical error and the second the systematic uncertainties. A$_\perp$ arises from the imaginary part of the two-photon exchange amplitude and is zero in the one-photon exchange approximation. From comparison with theoretical estimates of A$_\perp$ we conclude that $\pi$N-intermediate states give a substantial contribution to the imaginary part of the two-photon amplitude. The contribution from the ground state proton to the imaginary part of the two-photon exchange can be neglected. There is no obvious reason why this should be different for the real part of the two-photon amplitude, which enters into the radiative corrections for the Rosenbluth separation measurements of the electric form factor of the proton.
Roadmap for double hypernuclei spectroscopy at PANDA
Pochodzalla J.,Sanchez Lorente A.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100307008
Abstract: Hypernuclear Physics is currently attracting renewed attention. Thanks to the use of stored $ar{p}$ beams, copious production of double Λ hypernuclei is expected at the $ar{P}$anda experiment which will enable high precision γ–spectroscopy of such nuclei for the rst time. In the present work we have studied the population of particle stable, excited states in double hypernuclei after the capture of a Ξ within a statistical decay model. In order to check the feasibility of producing and performing γ–spectroscopy of double hypernuclei at $ar{P}$ANDA, an event generator based on these calculations has been implemented in the $ar{P}$ANDA simulation framework PANDAROOT.
Future use of silicon photomultiplier for KAOS at MAMI and PANDA at FAIR
P. Achenbach,A. Sanchez Lorente,S. Sánchez Majos,J. Pochodzalla
Physics , 2008, DOI: 10.1016/j.nima.2009.05.119
Abstract: A characterisation of scintillating fibres with silicon photomultiplier read-out was performed in view of their possible application in fibre tracking detector systems. Such a concept is being considered for the Kaos spectrometer at the Mainz Microtron MAMI and as a time-of-flight start detector for the hypernuclear physics programme at the PANDA experiment of the FAIR project. Results on particle detection effciency and time resolution are discussed. In summary, the silicon devices are very suitable for the detection of the low light yield from scintillating fibres insofar a trigger scheme is found to cope with the noise rate characteristics.
Detector developments for the hypernuclear programme at PANDA
P. Achenbach,J. Pochodzalla,A. Sanchez Lorente,S. Sánchez Majos
Physics , 2011, DOI: 10.1109/NSSMIC.2008.4774720
Abstract: The technical design of the PANDA experiment at the future FAIR facility next to GSI is progressing. At the proposed anti-proton storage ring the spectroscopy of double Lambda hypernuclei is one of the four main topics which will be addressed by the Collaboration. The hypernuclear experiments require (i) a dedicated internal target, (ii) an active secondary target of alternating silicon and absorber material layers, (iii) high purity germanium (HPGe) detectors, and (iv) a good particle identification system for low momentum kaons. All systems need to operate in the presence of a high magnetic field and a large hadronic background. The status of the detector developments for this programme is summarized.
Hypernuclear Physics at PANDA
P. Achenbach,S. Bleser,J. Pochodzalla,A. Sanchez Lorente,M. Steinen
Physics , 2012, DOI: 10.1007/s10751-012-0571-1
Abstract: Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Anti-proton and Ion Research FAIR at Darmstadt, Germany. A copious production of Xi-hyperons at a dedicated internal target in the stored anti-proton beam is expected, which will enable the high-precision gamma-spectroscopy of double strange systems for the first time. In addition to the general purpose PANDA setup, the hypernuclear experiments require an active secondary target of silicon layers and absorber material as well as high purity germanium (HPGe) crystals as gamma-detectors. The design of the setup and the development of these detectors is progressing: a first HPGe crystal with a new electromechanical cooling system was prepared and the properties of a silicon strip detector as a prototype to be used in the secondary target were studied. Simultaneously to the hardware projects, detailed Monte Carlo simulations were performed to predict the yield of particle stable hypernuclei. With the help of the Monte Carlo a procedure for Lambda-Lambda-hypernuclei identification by the detection and correlation of the weak decay pions was developed.
Effect of Parameters on Geoa/Geob/1 Queues: Theoretical Analysis and Simulation Results  [PDF]
A. Lorente, M. S. Sánchez
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.92011
This paper analyzes a discrete-time Geoa/Geob/1 queuing system with batch arrivals of fixed size a, and batch services of fixed size b. Both arrivals and services occur randomly following a geometric distribution. The steady-state queue length distribution is obtained as the solution of a system of difference equations. Necessary and sufficient conditions are given for the system to be stationary. Besides, the uniqueness of the root of the characteristic polynomial in the interval (0, 1) is proven which is the only root needed for the computation of the theoretical solution with the proposed procedure. The theoretical results are compared with the ones observed in some simulations of the queuing system under different sets of parameters. The agreement of the results encourages the use of simulation for more complex systems. Finally, we explore the effect of parameters on the mean length of the queue as well as on the mean waiting time.
Dinero, precios y capital: una teoría causal
Lorente y Sanchez Bravo Luís
Cuadernos de Economía , 1983,
Abstract: Este trabajo fué presentado el 17 de agosto de 1982 en el Ciclo de Conferencias sobre Neoteorías que tuvo lugar en el Departamento de Economía de la Universidad Nacional. Durante los últimos a os, buena parte de la exploración teórica en economía viene desarrollándose siguiendo dos tendencias, no muy bien definidas, que podríamos llamar sraffiana y kalecklana, en reconocimiento a que esos dos autores plantearon muchas de las ideas que ahora se están discutiendo, criticando y desarrollando o, por 10 menos, generaron buena parte de los nuevas problemas teóricos que hoy se busca resolver.
Production of excited double hypernuclei via Fermi breakup of excited strange systems
Alicia Sanchez Lorente,Alexander Botvina,Josef Pochodzalla
Physics , 2011, DOI: 10.1016/j.physletb.2011.02.002
Abstract: Precise spectroscopy of multi-strange hypernuclei provides a unique chance to explore the hyperon-hyperon interaction. In the present work we explore the production of excited states in double hypernuclei following the micro-canonical break-up of an initially excited double hypernucleus which is created by the absorption and conversion of a stopped $\Xi^{-}$ hyperon. Rather independent on the spectrum of possible excited states in the produced double hypernuclei the formation of excited states dominates in our model. For different initial target nuclei which absorb the $\Xi^-$, different double hypernuclei nuclei dominate. Thus the ability to assign the various observable $\gamma$-transitions in a unique way to a specific double hypernuclei by exploring various light targets as proposed by the {\Panda} collaboration seems possible. We also confront our predictions with the correlated pion spectra measured by the E906 collaboration.
Studies of Hyperons and Antihyperons in Nuclei
Josef Pochodzalla,Alexander Botvina,Alicia Sanchez Lorente
Physics , 2011,
Abstract: Stored antiproton beams at the international FAIR facility will provide unique opportunities to study hyperons as well as antihyperons in nuclear systems. Precise $\gamma$-spectroscopy of multi-strange hypernuclei will serve as a laboratory for the hyperon-hyperon interaction. Exclusive hadron-antihadron pair production close to threshold can measure the potential of a antihadron relative to that of the coincident hadrons. In the present work we explore the production of excited states in double hypernuclei following the micro-canonical break-up of an initially excited double hypernucleus which is created by the absorption and conversion of a stopped $\Xi^{-}$ hyperon. Generally the formation of excited hypernuclear states relative to ground states dominates in this model. For different initial target nuclei which absorb the $\Xi^-$, different double hypernuclei nuclei dominate. We also compare the model predictions with the correlated pion spectra measured by the E906 collaboration. In antiproton nucleus reactions the event-by-event transverse momentum correlations of hadron-antihadron pairs produced close to threshold contain information on the difference between the nuclear potential of the hadron and the associated antihadron. For produced D-meson pairs at 6.7\gevc1 the sensitivity of the transverse momenta correlation will probably be to small to deduce differences between the potentials for D$^+$ and D$^-$ mesons. However, for {\PgX\PagX} pairs produced at 2.9\gevc1 the asymmetry is sufficiently sensitive to predicted differences between the {\PgX} and {\PagX} potentials even if the momentum and density dependence of the the potential are taken into account.
Antihyperon potentials in nuclei via exclusive antiproton-nucleus reactions at FAIR
Alicia Sanchez Lorente,Sebastian Bleser,Marcell Steinen,Josef Pochodzalla
Physics , 2015, DOI: 10.1016/j.physletb.2015.08.025
Abstract: The exclusive production of hyperon-antihyperon pairs close to their production threshold in antiproton - nucleus collisions offers a unique and hitherto unexplored opportunity to elucidate the behaviour of antihyperons in nuclei. For the first time we analyse these reactions in a microscopic transport model using the the Gie\ss en Boltzmann-Uehling-Uhlenbeck transport model. The calculation take the delicate interplay between the strong absorption of antihyperons, their rescattering and refraction at the nuclear surface as well as the Fermi motion of the struck nucleon into account. We find a substantial sensitivity of transverse momentum correlations of coincident $\Lambda\overline{\Lambda}$-pairs to the assumed depth of the $\overline{\Lambda}$-potential. Because of the high cross section for this process and the simplicity of the experimental method our results are highly relevant for future activities at the international Facility for Antiproton and Ion Research (FAIR).
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