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Author |
Stefanis, N.G.; Bakulev, A.P.; Mikhailov, S.V.; Pimikov, A.V. |
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Title |
Can we understand an auxetic pion-photon transition form factor within QCD? |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
87 |
Issue |
9 |
Pages |
094025 - 13pp |
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Keywords |
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Abstract |
A state-of-the-art analysis of the pion-photon transition form factor is presented based on an improved theoretical calculation that includes the effect of a finite virtuality of the quasireal photon in the method of light-cone sum rules. We carry out a detailed statistical analysis of the existing experimental data using this method and by employing pion distribution amplitudes with up to three Gegenbauer coefficients a(2), a(4), a(6). Allowing for an error range in the coefficient a(6) approximate to 0, the theoretical predictions for gamma*gamma -> pi(0) obtained with nonlocal QCD sum rules are found to be in good agreement with all data that support a scaling behavior of the transition form factor at higher Q(2), like those of the Belle Collaboration. The data on gamma*gamma -> eta/eta' from CLEO and BABAR are also reproduced, while there is a strong conflict with the auxetic trend of the BABAR data above 10 GeV2. The broader implications of these findings are discussed. |
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Address |
Ruhr Univ Bochum, Inst Theoret Phys 2, D-44780 Bochum, Germany, Email: stefanis@tp2.ruhr-uni-bochum.de; |
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Publisher |
Amer Physical Soc |
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English |
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ISSN |
1550-7998 |
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Conference |
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Notes |
WOS:000319283700001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1459 |
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Permanent link to this record |
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Author |
Garzon, E.J.; Xie, J.J.; Oset, E. |
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Title |
Case in favor of the N*(1700)(3/2(-)) |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
87 |
Issue |
5 |
Pages |
055204 - 12pp |
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Keywords |
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Abstract |
Using an interaction extracted from the local hidden-gauge Lagrangians, which brings together vector and pseudoscalar mesons, and the coupled channels rho N (s wave), pi N (d wave), pi Delta (s wave), and pi Delta (d wave), we look in the region ofv root s = 1400-1850 MeV and find two resonances dynamically generated by the interaction of these channels, which are naturally associated to N*(1520)(3/2(-)) and N*(1700)(3/2(-)). N*(1700)(3/2(-)) appears neatly as a pole in the complex plane. The free parameters of the theory are chosen to fit the pi N (d-wave) data. Both the real and imaginary parts of the pi N amplitude vanish in our approach in the vicinity of this resonance, which is similar to what happens in experimental determinations and which makes this signal very weak in this channel. This feature could explain why this resonance does not show up in some experimental analyses, but the situation is analogous to that of the f(0)(980) resonance, the second scalar meson after sigma[f(0)(500)] in the pi pi(d-wave) amplitude. The unitary coupled channel approach followed here, in connectionwith the experimental data, leads automatically to a pole in the 1700-MeV region and makes this second 3/2-resonance unavoidable. |
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Address |
Univ Valencia, CSIC, Inst Invest Paterna, Ctr Mixto,Dept Fis Teor, Valencia 46071, Spain |
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Amer Physical Soc |
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English |
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ISSN |
0556-2813 |
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Notes |
WOS:000319058200003 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1455 |
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Author |
ATLAS Collaboration (Aad, G. et al); Cabrera Urban, S.; Castillo Gimenez, V.; Costa, M.J.; Fassi, F.; Ferrer, A.; Fiorini, L.; Fuster, J.; Garcia, C.; Garcia Navarro, J.E.; Gonzalez de la Hoz, S.; Hernandez Jimenez, Y.; Higon-Rodriguez, E.; Irles Quiles, A.; Kaci, M.; Lacasta, C.; Lacuesta, V.R.; March, L.; Marti-Garcia, S.; Miñano, M.; Mitsou, V.A.; Moles-Valls, R.; Moreno Llacer, M.; Oliver Garcia, E.; Pedraza Lopez, S.; Perez Garcia-Estañ, M.T.; Romero Adam, E.; Ros, E.; Salt, J.; Sanchez Martinez, V.; Solans, C.A.; Soldevila, U.; Sanchez, J.; Torro Pastor, E.; Valero, A.; Valladolid Gallego, E.; Valls Ferrer, J.A.; Villaplana Perez, M.; Vos, M. |
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Title |
Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of Instrumentation |
Abbreviated Journal |
J. Instrum. |
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Volume |
8 |
Issue |
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Pages |
P07004 - 72pp |
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Keywords |
Pattern recognition, cluster finding, calibration and fitting methods; Performance of High Energy Physics Detectors; Accelerator modelling and simulations (multi-particle dynamics; single-particle dynamics); Analysis and statistical methods |
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Abstract |
This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Trigger-rate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are exploited to develop dedicated background tagging tools. These tools, based on observables in the Pixel detector, the muon spectrometer and the calorimeters, are described in detail and their efficiencies are evaluated. Finally an example of an application of these techniques to a monojet analysis is given, which demonstrates the importance of such event cleaning techniques for some new physics searches. |
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Address |
[Jackson, P.; Soni, N.] Univ Adelaide, Sch Chem & Phys, Adelaide, SA, Australia |
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Publisher |
Iop Publishing Ltd |
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English |
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ISSN |
1748-0221 |
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Notes |
WOS:000322572900015 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1557 |
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Permanent link to this record |
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Author |
Goel, N.; Domingo-Pardo, C.; Habermann, T.; Ameil, F.; Engert, T.; Gerl, J.; Kojouharov, I.; Maruhn, J.; Pietralla, N.; Schaffner, H. |
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Title |
Characterisation of a symmetric AGATA detector using the gamma-ray imaging scanning technique |
Type |
Journal Article |
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Year |
2013 |
Publication |
Nuclear Instruments & Methods in Physics Research A |
Abbreviated Journal |
Nucl. Instrum. Methods Phys. Res. A |
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Volume |
700 |
Issue |
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Pages |
10-21 |
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Keywords |
AGATA; Pulse shape comparison (PSC); Pulse shape analysis (PSA) |
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Abstract |
The imaging scanning technique for the characterisation of large volume, highly segmented, HPGe detectors is demonstrated by comparing the measured spatial response of a symmetric AGATA crystal versus the theoretical calculations obtained with the Multi-Geometry Simulation (MGS) code. The signal rise-times measured as a function of the gamma-ray interaction positions, in both coaxial and planar regions of the detection volume, are presented and confronted with the expected behaviour obtained via MGS. The transition in charge carrier transport behaviour as a function of the depth is studied for the region of the complex electric field. In general, a fairly good agreement between theory and experiment is obtained. Only systematic deviations between simulation and measurement are observed in the critical front part of the AGATA detector. They may be ascribed to a non-linear impurity concentration profile of the germanium crystal. |
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Address |
[Goel, N.; Domingo-Pardo, C.; Habermann, T.; Ameil, F.; Engert, T.; Gerl, J.; Kojouharov, I.; Schaffner, H.] GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany, Email: n.goel@gsi.de |
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Publisher |
Elsevier Science Bv |
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English |
Summary Language |
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Edition |
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ISSN |
0168-9002 |
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Notes |
WOS:000312811400003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1283 |
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Permanent link to this record |
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Author |
Alvarez-Ruso, L.; Nieves, J.; Ruiz Simo, I.; Valverde, M.; Vicente Vacas, M.J. |
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Title |
Charged kaon production by coherent scattering of neutrinos and antineutrinos on nuclei |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
87 |
Issue |
1 |
Pages |
015503 - 11pp |
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Keywords |
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Abstract |
With the aim of achieving a better and more complete understanding of neutrino interactions with nuclear targets, the coherent production of charged kaons induced by neutrinos and antineutrinos is investigated in the energy range of some of the current neutrino experiments. We follow a microscopic approach which, at the nucleon level, incorporates the most important mechanisms allowed by the chiral-symmetry-breaking pattern of QCD. The distortion of the outgoing K ((K) over bar) is taken into account by solving the Klein-Gordon equation with realistic optical potentials. Angular and momentum distributions, as well as the energy and nuclear dependence of the total cross section, are studied. |
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Address |
[Alvarez-Ruso, L.] Univ Coimbra, Dept Fis, Ctr Fis Computac, P-3000 Coimbra, Portugal |
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Publisher |
Amer Physical Soc |
Place of Publication |
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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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Conference |
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Notes |
WOS:000314335800004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1321 |
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Permanent link to this record |
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Author |
Rafi Alam, M.; Ruiz Simo, I.; Sajjad Athar, M.; Vicente Vacas, M.J. |
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Title |
Charged lepton induced one kaon production off the nucleon |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
87 |
Issue |
5 |
Pages |
053008 - 7pp |
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Keywords |
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Abstract |
We study single kaon production off the nucleon induced by electrons (positrons) i.e., e(-) (e(+)) + N -> v(e) ((v) over bar (e)) + (K) over bar (K) + N' at low energies. The possibility of observing these processes with the high luminosity beams available at TJNAF and Mainz is discussed, taking into account that the strangeness conserving electromagnetic reactions have a higher energy threshold for (K) over bar (K) production. The calculations are done using a microscopic model that starts from the SU(3) chiral Lagrangians and includes background terms and the resonant mechanisms associated to the lowest lying resonance Sigma*(1385) |
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Address |
[Alam, M. Rafi; Athar, M. Sajjad] Aligarh Muslim Univ, Dept Phys, Aligarh 202002, Uttar Pradesh, India |
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Publisher |
Amer Physical Soc |
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English |
Summary Language |
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Series Editor |
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Series Volume |
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Series Issue |
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ISSN |
1550-7998 |
ISBN |
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Conference |
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Notes |
WOS:000316387200002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1381 |
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Permanent link to this record |
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Author |
Dehnadi, B.; Hoang, A.H.; Mateu, V.; Zebarjad, S.M. |
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Title |
Charm mass determination from QCD charmonium sum rules at order alpha(3)(s) |
Type |
Journal Article |
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Year |
2013 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
09 |
Issue |
9 |
Pages |
103 - 56pp |
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Keywords |
Sum Rules; QCD |
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Abstract |
We determine the (MS) over bar charm quark mass from a charmonium QCD sum rules analysis. On the theoretical side we use input from perturbation theory at O (alpha(3)(s)). Improvements with respect to previous O (alpha(3)(s)) analyses include (1) an account of all available e(+)e(-) hadronic cross section data and (2) a thorough analysis of perturbative uncertainties. Using a data clustering method to combine hadronic cross section data sets from di ff erent measurements we demonstrate that using all available experimental data up to c. m. energies of 10 : 538 GeV allows for determinations of experimental moments and their correlations with small errors and that there is no need to rely on theoretical input above the charmonium resonances. We also show that good convergence properties of the perturbative series for the theoretical sum rule moments need to be considered with some care when extracting the charm mass and demonstrate how to set up a suitable set of scale variations to obtain a proper estimate of the perturbative uncertainty. As the fi nal outcome of our analysis we obtain (m(c)) over bar((m(c)) over bar) = 1 : 282 +/- (0.009)(stat) +/- (0.009)(syst) +/- (0.019)(pert) +/- (0.010)(alpha s) +/- (0.002)(< GG >) GeV. The perturbative error is an order of magnitude larger than the one obtained in previous O (alpha(3)(s)) sum rule analyses. |
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Address |
[Dehnadi, Bahman; Zebarjad, S. Mohammad] Shiraz Univ, Dept Phys, Shiraz 71454, Iran, Email: bahman.dehnadi@univie.ac.at; |
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Thesis |
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Publisher |
Springer |
Place of Publication |
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English |
Summary Language |
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Edition |
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ISSN |
1029-8479 |
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Conference |
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Notes |
WOS:000324653800001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1626 |
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Permanent link to this record |
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Author |
AGATA Collaboration (Louchart, C. et al); Gadea, A.; Huyuk, T. |
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Title |
Collective nature of low-lying excitations in 70,72,74Zn from lifetime measurements using the AGATA spectrometer demonstrator |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
87 |
Issue |
5 |
Pages |
054302 - 10pp |
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Keywords |
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Abstract |
Background: Neutron-rich nuclei with protons in the fp shell show an onset of collectivity around N=40. Spectroscopic information is required to understand the underlying mechanism and to determine the relevant terms of the nucleon-nucleon interaction that are responsible for the evolution of the shell structure in this mass region. Methods: We report on the lifetime measurement of the first 2+ and 4+ states in 70,72,74Zn and the first 6+ state in 72Zn using the recoil distance Doppler shift method. The experiment was carried out at the INFN Laboratory of Legnaro with the AGATA demonstrator, first phase of the Advanced Gamma Tracking Array of highly segmented, high-purity germanium detectors coupled to the PRISMA magnetic spectrometer. The excited states of the nuclei of interest were populated in the deep inelastic scattering of a 76Ge beam impinging on a 238U target. Results: The maximum of collectivity along the chain of Zn isotopes is observed for 72Zn at N=42. An unexpectedly long lifetime of 20−5.2+1.8 ps was measured for the 4+ state in 74Zn. Conclusions: Our results lead to small values of the B(E2;41+→21+)/B(E2;21+→01+) ratio for 72,74Zn, suggesting a significant noncollective contribution to these excitations. These experimental results are not reproduced by state-of-the-art microscopic models and call for lifetime measurements beyond the first 2+ state in heavy zinc and nickel isotopes. |
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Notes |
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Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1638 |
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Permanent link to this record |
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Author |
Perez-Ramos, R.; Mathieu, V. |
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Title |
Collimation of energy in medium-modified QCD jets |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physics Letters B |
Abbreviated Journal |
Phys. Lett. B |
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Volume |
718 |
Issue |
4-5 |
Pages |
1421-1424 |
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Keywords |
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Abstract |
The collimation of energy inside medium-modified jets is investigated in the leading logarithmic approximation of QCD. The Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations are slightly modified by introducing splitting functions enhanced in the infrared sector. As compared to elementary collisions in the vacuum, the angular distribution of the jet energy is found to broaden in QCD media. |
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Address |
[Perez-Ramos, Redamy] Univ Jyvaskyla, Dept Phys, FI-40014 Jyvaskyla, Finland, Email: redamy.perez@uv.es; |
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Publisher |
Elsevier Science Bv |
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English |
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ISSN |
0370-2693 |
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Conference |
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Notes |
WOS:000314554300034 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1388 |
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Permanent link to this record |
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Author |
Albaladejo, M.; Oset, E. |
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Title |
Combined analysis of the pn -> d pi(+)pi(-) and pn -> pn pi(+)pi(-) cross sections and implications for the interpretation of the pn -> d pi(+)pi(-) data |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review C |
Abbreviated Journal |
Phys. Rev. C |
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Volume |
88 |
Issue |
1 |
Pages |
014006 - 6pp |
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Keywords |
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Abstract |
We use recent data that show a narrow peak around root s = 2.37 GeV in the pn -> d pi(+)pi(-) cross section, with about double strength at the peak than in the analogous pn -> d pi(0)pi(0) reaction, and, assuming that it is due to the excitation of a dibaryon resonance, we evaluate the cross section for the pn -> pn pi(+)pi(-) reaction, with the final pn unbound but with the same quantum numbers as the deuteron. We use accurate techniques to determine the final state interaction in the case of the pn forming a deuteron or a positive energy state, which allow us to get the pn -> pn pi(+)pi(-) cross section with pn in I = 0 and S = 1, that turns out to be quite close or saturates the experimental pn -> pn pi(+)pi(-) total cross section around root s = 2.37 GeV, depending on the angular momentum assumed. This poses problems to the assumption of the dibaryon hypothesis, which could be rendered more restrictive with future precise data on the pn -> pn pi(+)pi(-) reaction. |
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Address |
[Albaladejo, M.] Ctr Mixto Univ Valencia CSIC, Dept Fis Teor, Valencia 46071, Spain |
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Publisher |
Amer Physical Soc |
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English |
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Series Issue |
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Edition |
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ISSN |
0556-2813 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000322531400001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
1521 |
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Permanent link to this record |