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Author |
Linhart, V.; Burdette, D.; Chessi, E.; Cindro, V.; Clinthorne, N.H.; Cochran, E.; Grosicar, B.; Honscheid, K.; Kagan, H.; Lacasta, C.; Llosa, G.; Mikuz, M.; Stankova, V.; Studen, A.; Weilhammer, P.; Zontar, D. |
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Title |
Spectroscopy study of imaging devices based on silicon Pixel Array Detector coupled to VATAGP7 read-out chips |
Type |
Journal Article |
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Year |
2011 |
Publication |
Journal of Instrumentation |
Abbreviated Journal |
J. Instrum. |
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Volume |
6 |
Issue |
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Pages |
C01092 - 8pp |
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Keywords |
Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA); Compton imaging |
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Abstract |
Spectroscopic and timing response studies have been conducted on a detector module consisting of a silicon Pixel Array Detector bonded on two VATAGP7 read-out chips manufactured by Gamma-Medica Ideas using laboratory gamma sources and the internal calibration facilities (the calibration system of the read-out chips). The performed tests have proven that the chips have (i) non-linear calibration curves which can be approximated by power functions, (ii) capability to measure the energy of photons with energy resolution better than 2 keV (exact range and resolution depend on experimental setup), (iii) the internal calibration facility which provides 6 out of 16 available internal calibration charges within our region of interest (spanning the Compton edge of 511 keV photons). The peaks induced by the internal calibration facility are suitable for a fit of the calibration curves. However, they are not suitable for measurements of equivalent noise charge because their full width at half maximum varies with their amplitude. These facts indicate that the VATAGP7 chips are useful and precise tools for a wide variety of spectroscopic devices. We have also explored time walk of the module and peaking time of the spectroscopy signals provided by the chips. We have observed that (iv) the time walk is caused partly by the peaking time of the signals provided by the fast shaper of the chips and partly by the timing uncertainty related to the varying position of the photon interaction, (v) the peaking time of the spectroscopy signals provided by the chips increases with increasing pulse height. |
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Address |
[Linhart, V.; Lacasta, C.; Llosa, G.; Stankova, V.] UVEG, CSIC, IFIC, Expt Phys Dept,Inst Fis Corpuscular, E-46071 Valencia, Spain, Email: Vladimir.Linhart@ific.uv.es |
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Iop Publishing Ltd |
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English |
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ISSN |
1748-0221 |
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Notes |
ISI:000291345600097 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial |
645 |
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Author |
Pierre Auger Collaboration (Abreu, P. et al); Pastor, S. |
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Title |
The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays |
Type |
Journal Article |
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Year |
2011 |
Publication |
Journal of Instrumentation |
Abbreviated Journal |
J. Instrum. |
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Volume |
6 |
Issue |
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Pages |
P01003 - 16pp |
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Keywords |
Cherenkov detectors; Large detector systems for particle and astroparticle physics; Particle detectors |
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Abstract |
Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found. |
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Address |
[Abreu, P.; Andringa, S.; Assis, P.; Brogueira, P.; Cazon, L.; Conceicao, R.; Goncalves, P.; Pimenta, M.; Santo, C. E.; Santos, E.; Tome, B.] LIP, P-1000 Lisbon, Portugal |
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Iop Publishing Ltd |
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English |
Summary Language |
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Series Volume |
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ISSN |
1748-0221 |
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Notes |
ISI:000291345600003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
646 |
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Author |
Mayoral, C.; Recati, A.; Fabbri, A.; Parentani, R.; Balbinot, R.; Carusotto, I. |
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Title |
Acoustic white holes in flowing atomic Bose-Einstein condensates |
Type |
Journal Article |
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Year |
2011 |
Publication |
New Journal of Physics |
Abbreviated Journal |
New J. Phys. |
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Volume |
13 |
Issue |
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Pages |
025007 - 29pp |
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Abstract |
We study acoustic white holes in a steadily flowing atomic Bose-Einstein condensate. A white hole configuration is obtained when the flow velocity goes from a super-sonic value in the upstream region to a sub-sonic one in the downstream region. The scattering of phonon wavepackets on a white hole horizon is numerically studied in terms of the Gross-Pitaevskii equation of mean-field theory: dynamical stability of the acoustic white hole is found, as well as a signature of a nonlinear back-action of the incident phonon wavepacket onto the horizon. The correlation pattern of density fluctuations is numerically studied by means of the truncated-Wigner method, which includes quantum fluctuations. Signatures of the white hole radiation of correlated phonon pairs by the horizon are characterized; analogies and differences with Hawking radiation from acoustic black holes are discussed. In particular, a short wavelength feature is identified in the density correlation function, whose amplitude steadily grows in time since the formation of the horizon. The numerical observations are quantitatively interpreted by means of an analytical Bogoliubov theory of quantum fluctuations for a white hole configuration within the step-like horizon approximation. |
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Address |
[Recati, Alessio; Carusotto, Iacopo] Univ Trent, INO CNR BEC Ctr, I-38123 Povo, Italy, Email: carusott@science.unitn.it |
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Publisher |
Iop Publishing Ltd |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1367-2630 |
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Notes |
ISI:000287855400003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
556 |
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Author |
Mena, O.; Razzaque, S.; Villaescusa-Navarro, F. |
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Title |
Signatures of photon and axion-like particle mixing in the gamma-ray burst jet |
Type |
Journal Article |
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Year |
2011 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
02 |
Issue |
2 |
Pages |
030 - 16pp |
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Keywords |
axions; magnetic fields; gamma ray bursts theory; gamma ray burst experiments |
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Abstract |
Photons couple to Axion-Like Particles (ALPs) or more generally to any pseudo Nambu-Goldstone boson in the presence of an external electromagnetic field. Mixing between photons and ALPs in the strong magnetic field of a Gamma-Ray Burst (GRB) jet during the prompt emission phase can leave observable imprints on the gamma-ray polarization and spectrum. Mixing in the intergalactic medium is not expected to modify these signatures for ALP mass > 10(-14) eV and/or for < nG magnetic field. We show that the depletion of photons due to conversion to ALPs changes the linear degree of polarization from the values predicted by the synchrotron model of gamma ray emission. We also show that when the magnetic field orientation in the propagation region is perpendicular to the field orientation in the production region, the observed synchrotron spectrum becomes steeper than the theoretical prediction and as detected in a sizable fraction of GRB sample. Detection of the correlated polarization and spectral signatures from these steep-spectrum GRBs by gamma-ray polarimeters can be a very powerful probe to discover ALPs. Measurement of gamma-ray polarization from GRBs in general, with high statistics, can also be useful to search for ALPs. |
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Address |
[Mena, Olga; Villaescusa-Navarro, F.] Univ Valencia, CSIC, IFIC, E-46071 Valencia, Spain, Email: omena@ific.uv.es |
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Publisher |
Iop Publishing Ltd |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Edition |
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ISSN |
1475-7516 |
ISBN |
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Notes |
ISI:000287859800031 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
559 |
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Author |
Borja, E.F.; Freidel, L.; Garay, I.; Livine, E.R. |
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Title |
U(N) tools for loop quantum gravity: the return of the spinor |
Type |
Journal Article |
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Year |
2011 |
Publication |
Classical and Quantum Gravity |
Abbreviated Journal |
Class. Quantum Gravity |
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Volume |
28 |
Issue |
5 |
Pages |
055005 - 28pp |
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Abstract |
We explore the classical setting for the U(N) framework for SU(2) intertwiners for loop quantum gravity and describe the corresponding phase space in terms of spinors with the appropriate constraints. We show how its quantization leads back to the standard Hilbert space of intertwiner states defined as holomorphic functionals. We then explain how to glue these intertwiners states in order to construct spin network states as wavefunctions on the spinor phase space. In particular, we translate the usual loop gravity holonomy observables to our classical framework. Finally, we propose how to derive our phase space structure from an action principle which induces non-trivial dynamics for the spin network states. We conclude by applying explicitly our framework to states living on the simple 2-vertex graph and discuss the properties of the resulting Hamiltonian. |
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Address |
[Borja, Enrique F.; Garay, Inaki] Univ Erlangen Nurnberg, Inst Theoret Phys 3, D-91058 Erlangen, Germany, Email: etera.livine@ens-lyon.fr |
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Thesis |
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Publisher |
Iop Publishing Ltd |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0264-9381 |
ISBN |
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Conference |
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Notes |
ISI:000287308700005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
579 |
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