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Search Results: 1 - 10 of 464152 matches for " D. S. Covita "
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Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources
Paul Indelicato,S. Boucard,D. S. Covita,D. Gotta,A. Gruber,A. Hirtl,H. Fuhrmann,E. -O. Le Bigot,S. Schlesser,J. M. F. Dos Santos,L. M. Simons,L. Stingelin,M. Trassinelli,J. Veloso,A. Wasser,J. Zmeskal
Physics , 2006, DOI: 10.1016/j.nima.2007.05.011
Abstract: Radiation from the highly-charged ions contained in the plasma of Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of X-rays. Because the ions have a relatively low kinetic energy ($\approx 1$ eV) transitions can be very narrow, containing only small Doppler broadening. We describe preliminary accurate measurements of two and three-electron ions with Z=16--18. We show how these measurement can test sensitively many-body relativistic calculations or can be used as X-ray standards for precise measurements of X-ray transitions in exotic atoms.
Precision determination of the dpi -> NN transition strength at threshold
Th. Strauch,F. D. Amaro,D. F. Anagnostopoulos,P. Bühler,D. S. Covita,H. Gorke,D. Gotta,A. Gruber,A. Hirtl,P. Indelicato,E. -O. LeBigot,M. Nekipelov,J. M. F. dos Santos,S. Schlesser,Ph. Schmid,L. M. Simons,M. Trassinelli,J. F. C. A. Veloso,J. Zmeskal
Physics , 2010, DOI: 10.1103/PhysRevLett.104.142503
Abstract: An unusual but effective way to determine at threshold the dpi -> NN transition strength is to exploit the hadronic ground-state broadening in pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated by the true absorption channel dpi- -> nn, which is related to s-wave pion production pp -> dpi+ by charge symmetry and detailed balance. Using the exotic atom circumvents the problem of Coulomb corrections to the cross section as necessary in the production experiments. Our dedicated measurement finds (1171+23/-49) meV for the broadening yielding (252+5/-11) \mub.
Pionic deuterium
Th. Strauch,F. D. Amaro,D. Anagnostopoulos,P. Bühler,D. S. Covita,H. Gorke,D. Gotta,A. Gruber,A. Hirtl,P. Indelicato,E. -O. Le Bigot,M. Nekipelov,J. M. F. dos Santos,Ph. Schmid,S. Schlesser,L. M. Simons,M. Trassinelli,J. F. C. A. Veloso,J. Zmeskal
Physics , 2010, DOI: 10.1140/epja/i2011-11088-1
Abstract: The strong interaction shift $\epsilon$ and broadening {\Gamma} in pionic deuterium have been determined in a high statistics study of the {\pi}D(3p - 1s) X-ray transition using a high-resolution crystal spectrometer. The pionic deuterium shift will provide constraints for the pion-nucleon isospin scattering lengths extracted from measurements of shift and broadening in pionic hydrogen. The hadronic broadening is related to pion absorption and production at threshold. The results are \epsilon = (-2356 {\pm} 31)meV (repulsive) and {\Gamma}1s = (1171+23/-49) meV yielding for the complex {\pi}D scattering length a = [-(24.99 {\pm} 0.33) + i (6.22+0.12/-0.26)]x10-3/m{\pi}. From the imaginary part, the threshold parameter for pion production is obtained to be {\alpha} = (251 +5/-11) {\mu}b. This allows, in addition, and by using results from pion absorption in 3He at threshold, the determination of the effective couplings g0 and g1 for s-wave pion absorption on isoscalar and isovector NN pairs.
THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation
L. Arazi,A. Breskin,R. Chechik,M. Cortesi,M. Pitt,A. Rubin,H. Natal da Luz,J. M. F. dos Santos,C. D. R. Azevedo,D. S. Covita,C. A. B. Oliveira,J. F. C. A. Veloso,M. Breidenbach,D. Freytag,G. Haller,R. Herbst,S. Park,A. White,J. Yu,E. Oliveri
Physics , 2011, DOI: 10.1088/1748-0221/7/05/C05011
Abstract: We report on the results of an extensive R&D program aimed at the evaluation of Thick-Gas Electron Multipliers (THGEM) as potential active elements for Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1 cm2 readout pads. The detector is comprised of single- or double-THGEM multipliers coupled to the pad electrode either directly or via a resistive anode. Investigations employing standard discrete electronics and the KPiX readout system have been carried out both under laboratory conditions and with muons and pions at the CERN RD51 test beam. For detectors having a charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM detector reached detection efficiencies above 95%, with pad-hit multiplicity of 1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5 sparks/trigger, depending on the detector structure and gain. Preliminary beam tests with a WELL hole-structure, closed by a resistive anode, yielded discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are presented to reduce charge-spread and pad multiplicity with resistive anodes. The new method showed good prospects for further evaluation of very thin THGEM-based detectors as potential active elements for DHCAL, with competitive performances, simplicity and robustness. Further developments are in course.
Line shape of the muH(3p - 1s) hyperfine transitions
D. S. Covita,D. F. Anagnostopoulos,H. Gorke,D. Gotta,A. Gruber,A. Hirtl,T. Ishiwatari,P. Indelicato,E. -O. LeBigot,M. Nekipelov,J. M. F. dos Santos,Ph. Schmid,L. M. Simons,M. Trassinelli,J. F. C. A. Veloso,J. Zmeskal
Physics , 2008, DOI: 10.1103/PhysRevLett.102.023401
Abstract: The (3p - 1s) X-ray transition to the muonic hydrogen ground state was measured with a high resolution crystal spectrometer. A Doppler effect broadening of the X-ray line was established which could be attributed to different Coulomb de-excitation steps preceding the measured transition. The assumption of a statistical population of the hyperfine levels of the muonic hydrogen ground state was directly confirmed by the experiment and measured values for the hyperfine splitting can be reported. The results allow a decisive test of advanced cascade model calculations and establish a method to extract fundamental strong-interaction parameters from pionic hydrogen experiments.
Planar LAAPDs: Temperature Dependence, Performance, and Application in Low Energy X-ray Spectroscopy
L. Ludhova,F. D. Amaro,A. Antognini,F. Biraben,J. M. R. Cardoso,C. A. N. Conde,D. S. Covita,A. Dax,S. Dhawan,L. M. P. Fernandes,T. W. Hansch,V. W. Hughes,O. Huot,P. Indelicato,L. Julien,P. E. Knowles,F. Kottmann,J. A. M. Lopes,Y. -W. Liu,C. M. B. Monteiro,F. Mulhauser,F. Nez,R. Pohl,P. Rabinowitz,J. M. F. dos Santos,L. A. Schaller,D. Taqqu,J. F. C. A. Veloso
Physics , 2004, DOI: 10.1016/j.nima.2004.11.017
Abstract: An experiment measuring the 2S Lamb shift in muonic hydrogen mup is being performed at the Paul Scherrer Institute, Switzerland. It requires small and compact detectors for 1.9 keV x rays (2P-1S transition) with an energy resolution around 25% at 2 keV, a time resolution better than 100 ns, a large solid angle coverage, and insensitivity to a 5 T magnetic field. We have chosen Large Area Avalanche Photodiodes (LAAPDs) from Radiation Monitoring Devices as x-ray detectors, and they were used during the last data taking period in 2003. For x-ray spectroscopy applications, these LAAPDs have to be cooled in order to suppress the dark current noise, hence, a series of tests were performed to choose the optimal operation temperature. Specifically, the temperature dependence of gain, energy resolution, dark current, excess noise factor, and detector response linearity was studied. Finally, details of the LAAPDs application in the muonic hydrogen experiment as well as their response to alpha particles are presented.
Aprendizagem ao longo da vida: boas práticas e inser??o social
Covita,Horácio Mendes;
Análise Psicológica , 2002,
Abstract: long life learning can be seen as a key element of effective citizenship and employability, becoming a priority for non profit organizations and corporate companies agendas, in searching for a better understanding about new learning contexts and providing solutions near citizens needs and availabilities, recognising those non formal learning contexts as critical players for the emergence and development of skills and competences. in this work we argue and discuss initiatives that can actively promote the organizational and work team best practices identification, transfer and appropriation, as organizational transformation processes, with impacts on productivity, competitiveness and vulnerable people inclusion. we also discuss the knowledge resources centres (krc), as support platforms and devices to citizens, namely training bodies and training professionals, empowered and committed with long life learning and improvement skills projects, with added value when are focused on citizens with specific vulnerabilities.
Experiments towards resolving the proton charge radius puzzle
A. Antognini,K. Schuhmann,F. D. Amaro,P. Amaro,M. Abdou-Ahmed,F. Biraben,T. -L. Chen,D. S. Covita,A. J. Dax,M. Diepold,L. M. P. Fernandes,B. Franke,S. Galtier,A. L. Gouvea,J. G?tzfried,T. Graf,T. W. H?nsch,M. Hildebrandt,P. Indelicato,L. Julien,K. Kirch,A. Knecht,F. Kottmann,J. J. Krauth,Y. -W. Liu,J. Machado,C. M. B. Monteiro,F. Mulhauser,F. Nez,J. P. Santos,J. M. F. dos Santos,C. I. Szabo,D. Taqqu,J. F. C. A. Veloso,A. Voss,B. Weichelt,R. Pohl
Physics , 2015,
Abstract: We review the status of the proton charge radius puzzle. Emphasis is given to the various experiments initiated to resolve the conflict between the muonic hydrogen results and the results from scattering and regular hydrogen spectroscopy.
Improved X-ray detection and particle identification with avalanche photodiodes
Marc Diepold,Luis M. P. Fernandes,Jorge Machado,Pedro Amaro,Marwan Abdou-Ahmed,Fernando D. Amaro,Aldo Antognini,Fran?ois Biraben,Tzu-Ling Chen,Daniel S. Covita,Andreas J. Dax,Beatrice Franke,Sandrine Galtier,Andrea L. Gouvea,Johannes G?tzfried,Thomas Graf,Theodor W. H?nsch,Malte Hildebrandt,Paul Indelicato,Lucile Julien,Klaus Kirch,Andreas Knecht,Franz Kottmann,Julian J. Krauth,Yi-Wei Liu,Cristina M. B. Monteiro,Fran?oise Mulhauser,Boris Naar,Tobias Nebel,Fran?ois Nez,José Paulo Santos,Joaquim M. F. dos Santos,Karsten Schuhmann,Csilla I. Szabo,David Taqqu,Jo?o F. C. A. Veloso,Andreas Voss,Birgit Weichelt,Randolf Pohl
Physics , 2015, DOI: 10.1063/1.4921195
Abstract: Avalanche photodiodes are commonly used as detectors for low energy x-rays. In this work we report on a fitting technique used to account for different detector responses resulting from photo absorption in the various APD layers. The use of this technique results in an improvement of the energy resolution at 8.2 keV by up to a factor of 2, and corrects the timing information by up to 25 ns to account for space dependent electron drift time. In addition, this waveform analysis is used for particle identification, e.g. to distinguish between x-rays and MeV electrons in our experiment.
Lifetime and population of the 2S state in muonic protium and deuterium
Marc Diepold,Fernando D. Amaro,Aldo Antognini,Fran?ois Biraben,Jo?o M. R. Cardoso,Daniel S. Covita,Andreas Dax,Satish Dhawan,Luis M. P. Fernandes,Adolf Giesen,Andrea L. Gouvea,Thomas Graf,Theodor W. H?nsch,Paul Indelicato,Lucile Julien,Cheng-Yang Kao,Paul Knowles,Franz Kottmann,Eric-Olivier Le Bigot,Yi-Wei Liu,José A. M. Lopes,Livia Ludhova,Cristina M. B. Monteiro,Fran?oise Mulhauser,Tobias Nebel,Fran?ois Nez,Paul Rabinowitz,Joaquim M. F. dos Santos,Lukas A. Schaller,Karsten Schuhmann,Catherine Schwob,David Taqqu,Jo?o F. C. A. Veloso,Jan Vogelsang,Randolf Pohl
Physics , 2013, DOI: 10.1103/PhysRevA.88.042520
Abstract: Radiative deexcitation (RD) of the metastable 2S state of muonic protium and deuterium atoms has been observed. In muonic protium, we improve the precision on lifetime and population (formation probability) values for the short-lived {\mu}p(2S) component, and give an upper limit for RD of long-lived {\mu}p(2S) atoms. In muonic deuterium at 1 hPa, 3.1 +-0.3 % of all stopped muons form {\mu}d(2S) atoms. The short-lived 2S component has a population of 1.35 +0.57 -0.33 % and a lifetime of {\tau}_short({\mu}d) = 138 +32 -34 ns. We see evidence for RD of long-lived {\mu}d(2S) with a lifetime of {\tau}_long({\mu}d) = 1.15 +0.75 -0.53 {\mu}s. This is interpreted as formation and decay of excited muonic molecules.
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