| Records |
| Author |
Sekihara, T.; Yamagata-Sekihara, J.; Jido, D.; Kanada-En'yo, Y. |
| Title |
Branching ratios of mesonic and nonmesonic antikaon absorptions in the nuclear medium |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physical Review C |
Abbreviated Journal  |
Phys. Rev. C |
| Volume |
86 |
Issue |
6 |
Pages |
065205 - 17pp |
| Keywords |
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| Abstract |
The branching ratios of K- absorption in nuclear matter are theoretically investigated in order to understand the mechanism of K- absorption into nuclei. For this purpose mesonic and nonmesonic absorption potentials are evaluated as functions of nuclear density, the kaon momentum, and energy from one- and two-body K- self-energy, respectively. By using a chiral unitary approach for the s-wave (K) over bar N amplitude we find that both the mesonic and nonmesonic absorption potentials are dominated by the Lambda(1405) contributions. The fraction of the mesonic and nonmesonic absorptions are evaluated to be respectively about 70% and 30% at the saturation density almost independently of the kaon momentum. We also observe different behavior of the branching ratios to pi(+)Sigma(-) and pi(-)Sigma(+) channels in mesonic absorption due to the interference between Lambda(1405) and the I = 1 nonresonant background, which is consistent with experimental results. The nonmesonic absorption ratios [Lambda p]/[Sigma(0)p] and [Lambda n]/[Sigma(0)n] are about unity while [Sigma(+)n]/[Sigma(0)p] and [Sigma(-) p]/[Sigma(0)n] are about 2 due to the Lambda(1405) dominance in absorption. Taking into account the kaon momenta and energies, the absorption potentials become weaker due to the downward shift of the initial K- N two-body energy, but this does not drastirally change the nonmesonic fraction. The Sigma(1385) contribution in the p-wave (K) over bar N amplitude is examined and found to be very small compared to the Lambda(1405) contribution in slow K- absorption. |
| Address |
[Sekihara, Takayasu] Tokyo Inst Technol, Dept Phys, Tokyo 1528551, Japan |
| Corporate Author |
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Thesis |
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| Publisher |
Amer Physical Soc |
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 |
0556-2813 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000312293900002 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1270 |
| Permanent link to this record |
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| Author |
Steinhardt, T.; Eberth, J.; Skoda, S.; Thelen, O.; Schwengner, R.; Donau, F.; Plettner, C.; Schnare, H.; de Angelis, G.; Napoli, D.R.; Farnea, E.; Gadea, A.; Jungclaus, A.; Lieb, K.P.; Wadsworth, R. |
| Title |
Stabilization of prolate deformation at high spin in Kr-75 |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
| Volume |
86 |
Issue |
6 |
Pages |
064310 - 16pp |
| Keywords |
|
| Abstract |
The neutron-deficient nucleus Kr-75 has been studied in two EUROBALL experiments. The analysis yielded a considerably extended level scheme including two newly observed excited high spin bands. The results are interpreted in the framework of the cranked Nilsson-Strutinsky approach. The calculations compare well to the experimentally established level scheme and predict the nucleus to be mainly prolate or triaxially deformed at high spin. Evidence for an oblate-prolate shape coexistence could not be found at high spin. |
| Address |
[Steinhardt, T.; Eberth, J.; Skoda, S.; Thelen, O.] Univ Cologne, Inst Kernphys, D-50937 Cologne, Germany |
| Corporate Author |
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Thesis |
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| Publisher |
Amer Physical Soc |
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 |
0556-2813 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000312292700001 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1271 |
| Permanent link to this record |
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| Author |
Cabello, J.; Rafecas, M. |
| Title |
Comparison of basis functions for 3D PET reconstruction using a Monte Carlo system matrix |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physics in Medicine and Biology |
Abbreviated Journal |
Phys. Med. Biol. |
| Volume |
57 |
Issue |
7 |
Pages |
1759-1777 |
| Keywords |
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| Abstract |
In emission tomography, iterative statistical methods are accepted as the reconstruction algorithms that achieve the best image quality. The accuracy of these methods relies partly on the quality of the system response matrix (SRM) that characterizes the scanner. The more physical phenomena included in the SRM, the higher the SRM quality, and therefore higher image quality is obtained from the reconstruction process. High-resolution small animal scanners contain as many as 10(3)-10(4) small crystal pairs, while the field of view (FOV) is divided into hundreds of thousands of small voxels. These two characteristics have a significant impact on the number of elements to be calculated in the SRM. Monte Carlo (MC) methods have gained popularity as a way of calculating the SRM, due to the increased accuracy achievable, at the cost of introducing some statistical noise and long simulation times. In the work presented here the SRM is calculated using MC methods exploiting the cylindrical symmetries of the scanner, significantly reducing the simulation time necessary to calculate a high statistical quality SRM and the storage space necessary. The use of cylindrical symmetries makes polar voxels a convenient basis function. Alternatively, spherically symmetric basis functions result in improved noise properties compared to cubic and polar basis functions. The quality of reconstructed images using polar voxels, spherically symmetric basis functions on a polar grid, cubic voxels and post-reconstruction filtered polar and cubic voxels is compared from a noise and spatial resolution perspective. This study demonstrates that polar voxels perform as well as cubic voxels, reducing the simulation time necessary to calculate the SRM and the disk space necessary to store it. Results showed that spherically symmetric functions outperform polar and cubic basis functions in terms of noise properties, at the cost of slightly degraded spatial resolution, larger SRM file size and longer reconstruction times. However, we demonstrate that post-reconstruction smoothing, usually applied in emission imaging to reduce the level of noise, can produce a spatial resolution degradation of similar to 50%, while spherically symmetric basis functions produce a degradation of only similar to 6%, compared to polar and cubic voxels, at the same noise level. Therefore, the image quality trade-off obtained with blobs is higher than that obtained with cubic or polar voxels. |
| Address |
[Cabello, Jorge; Rafecas, Magdalena] Univ Valencia, Inst Fis Corpuscular, CSIC, Valencia, Spain, Email: jorge.cabello@ific.uv.es |
| Corporate Author |
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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 |
0031-9155 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000302121000004 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
no |
| Call Number |
IFIC @ pastor @ |
Serial |
955 |
| Permanent link to this record |
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| Author |
Blume, M.; Navab, N.; Rafecas, M. |
| Title |
Joint image and motion reconstruction for PET using a B-spline motion model |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physics in Medicine and Biology |
Abbreviated Journal |
Phys. Med. Biol. |
| Volume |
57 |
Issue |
24 |
Pages |
22pp |
| Keywords |
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| Abstract |
We present a novel joint image and motion reconstruction method for PET. The method is based on gated data and reconstructs an image together with amotion function. The motion function can be used to transform the reconstructed image to any of the input gates. All available events (from all gates) are used in the reconstruction. The presented method uses a B-spline motion model, together with a novel motion regularization procedure that does not need a regularization parameter (which is usually extremely difficult to adjust). Several image and motion grid levels are used in order to reduce the reconstruction time. In a simulation study, the presented method is compared to a recently proposed joint reconstruction method. While the presented method provides comparable reconstruction quality, it is much easier to use since no regularization parameter has to be chosen. Furthermore, since the B-spline discretization of the motion function depends on fewer parameters than a displacement field, the presented method is considerably faster and consumes less memory than its counterpart. The method is also applied to clinical data, for which a novel purely data-driven gating approach is presented. |
| Address |
[Blume, Moritz; Rafecas, Magdalena] Univ Valencia, CSIC, Inst Fis Corpuscular IFIC, E-46071 Valencia, Spain, Email: moritz.blume@fasterplan.com |
| Corporate Author |
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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 |
0031-9155 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000312106200009 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
1267 |
| Permanent link to this record |
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| Author |
NOMAD Collaboration (Kullenberg, C.T. et al); Cervera-Villanueva, A.; Gomez-Cadenas, J.J. |
| Title |
A search for single photon events in neutrino interactions |
Type |
Journal Article |
| Year |
2012 |
Publication |
Physics Letters B |
Abbreviated Journal |
Phys. Lett. B |
| Volume |
706 |
Issue |
4-5 |
Pages |
268-275 |
| Keywords |
Single photon; Neutrino; Neutral current; Coherent; Pion |
| Abstract |
We present a search for neutrino induced events containing a single, exclusive photon using data from the NOMAD experiment at the CERN SPS where the average energy of the neutrino flux is similar or equal to 25 GeV. The search is motivated by an excess of electron-like events in the 200-475 MeV energy region as reported by the MiniBooNE experiment. In NOMAD, photons are identified via their conversion to e(+)e(-) in an active target embedded in a magnetic field. The background to the single photon signal is dominated by the asymmetric decay of neutral pions produced either in a coherent neutrino-nucleus interaction, or in a neutrino-nucleon neutral current deep inelastic scattering, or in an interaction occurring outside the fiducial volume. All three backgrounds are determined in situ using control data samples prior to opening the 'signal-box'. In the signal region, we observe 155 events with a predicted background of 129.2 +/- 8.5 +/- 3.3. We interpret this as null evidence for excess of single photon events, and set a limit. Assuming that the hypothetical single photon has a momentum distribution similar to that of a photon from the coherent pi(0) decay, the measurement yields an upper limit on single photon events, < 4.0 x 10(-4) per nu(mu) charged current event. Narrowing the search to events where the photon is approximately collinear with the incident neutrino, we observe 78 events with a predicted background of 76.6 +/- 4.9 +/- 1.9 yielding a more stringent upper limit, < 1.6 x 10(-4) per nu(mu) charged current event. |
| Address |
[Kullenberg, C. T.; Mishra, S. R.; Dimmery, D.; Tian, X. C.; Godley, A.; Kim, J. J.; Ling, J.; Petti, R.; Wu, Q.] Univ S Carolina, Columbia, SC 29208 USA, Email: sanjib@sc.edu |
| Corporate Author |
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Thesis |
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| Publisher |
Elsevier Science Bv |
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 |
0370-2693 |
ISBN |
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Medium |
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| Area |
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Expedition |
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Conference |
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| Notes |
WOS:000299756800006 |
Approved |
no |
| Is ISI |
yes |
International Collaboration |
yes |
| Call Number |
IFIC @ pastor @ |
Serial |
886 |
| Permanent link to this record |
