DSpace Community:
http://hdl.handle.net/10261/61
20141031T05:12:49Z

Coulomb excitation of Sn104 and the strength of the Sn100 shell closure
http://hdl.handle.net/10261/102994
Title: Coulomb excitation of Sn104 and the strength of the Sn100 shell closure
Authors: Guastalla, G.; Dijulio, D.D.; Górska, M.; Jungclaus, A.; Algora, A.; Domingo Pardo, C.; Winfield, J.S.; Wollersheim, H.J.
Abstract: A measurement of the reduced transition probability for the excitation of the ground state to the first 2+ state in Sn104 has been performed using relativistic Coulomb excitation at GSI. Sn104 is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus Sn100. The value B(E2;0+→2 +)=0.10(4) e2b2 is significantly lower than earlier results for Sn106 and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N=Z=50 shell closure. © 2013 American Physical Society.
20141007T11:13:12Z

Collective nature of lowlying excitations in 70,72 ,74Zn from lifetime measurements using the AGATA spectrometer demonstrator
http://hdl.handle.net/10261/102862
Title: Collective nature of lowlying excitations in 70,72 ,74Zn from lifetime measurements using the AGATA spectrometer demonstrator
Authors: Louchart, C.; Obertelli, A.; Görgen, A.; Korten, W.; Bazzacco, D.; Birkenbach, B.; Bruyneel, B.; Jungclaus, Andrea; ValienteDobón, J.J.; Zielinska, M.
Abstract: Background: Neutronrich 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 nucleonnucleon 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, highpurity 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 205.2+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 stateoftheart microscopic models and call for lifetime measurements beyond the first 2+ state in heavy zinc and nickel isotopes. © 2013 American Physical Society.
20141002T11:18:23Z

The electromagnetic and Proca fields revisited: A unified quantization
http://hdl.handle.net/10261/102540
Title: The electromagnetic and Proca fields revisited: A unified quantization
Authors: Aldaya, Victor; Calixto, Manuel; Navarro, Miguel
Abstract: Quantizing the electromagnetic field with a group formalism faces the difficulty of how to turn the traditional gauge transformation of the vector potential, Aμ(x) → Aμ(x) + ∂μφ(x), into a group law. In this paper, it is shown that the problem can be solved by looking at gauge transformations in a slightly different manner which, in addition, does not require introducing any BRSTlike parameter. This gauge transformation does not appear explicitly in the group law of the symmetry but rather as the trajectories associated with generalized equations of motion generated by vector fields with null Noether invariants. In the new approach the parameters of the local group, U(1)(x, t), acquire dynamical content outside the photon mass shell, a fact which also allows a unified quantization of both the electromagnetic and Proca fields. © World Scientific Publishing Company.
20140926T09:54:22Z

Symmetries and solvable models for evaporating 2D black holes
http://hdl.handle.net/10261/102524
Title: Symmetries and solvable models for evaporating 2D black holes
Authors: Cruz, J.; NavarroSalas, José; Navarro, M.; Talavera, C.F.
Abstract: We study the evaporation process of a 2D black hole in thermal equilibrium when the ingoing radiation is suddenly switched off. We also introduce global symmetries of generic 2D dilaton gravity models which generalize the extra symmetry of the CGHS model. © Elsevier Science B.V
20140926T08:55:48Z

Group quantization on configuration space: Gauge symmetries and linear fields
http://hdl.handle.net/10261/102448
Title: Group quantization on configuration space: Gauge symmetries and linear fields
Authors: Navarro, Miguel; Aldaya, Victor; Calixto, Manuel
Abstract: A new, configurationspace picture of a formalism of group quantization, the GAQ formalism, is presented in the context of a previous algebraic generalization. This presentation serves to make a comprehensive discussion in which other extensions of the formalism, principally to incorporate gauge symmetries, are developed as well. Both images are combined in order to analyze, in a systematic manner and with complete generality, the case of linear fields (Abelian current groups). To illustrate these developments we particularize them for several fields and, in particular, we carry out the quantization of the Abelian ChernSimons models over an arbitrary closed surface in detail. © 1997 American Institute of Physics.
20140925T08:35:09Z

Accidental stability of dark matter
http://hdl.handle.net/10261/101005
Title: Accidental stability of dark matter
Authors: Lavoura, L.; Morisi, Stefano; Valle, José W. F.
Abstract: We propose that dark matter is stable as a consequence of an accidental Z(2) that results from a flavour symmetry group which is the doublecover group of the symmetry group of one of the regular geometric solids. Although modeldependent, the phenomenology resembles that of a generic >inert Higgs> dark matter scheme.
20140822T07:25:48Z

Conformal and nonconformal symmetries in 2D dilaton gravity
http://hdl.handle.net/10261/100780
Title: Conformal and nonconformal symmetries in 2D dilaton gravity
Authors: Cruz, J.; NavarroSalas, José; Navarro, M.; Talavera, C.F.
Abstract: We introduce new extra symmetry transformations for generic 2D dilatongravity models. These symmetries are nonconformal but special linear combinations of them turn out to be the extra (conformal) symmetries of the CGHS model and the model with an exponential potential. We show that one of the nonconformal extra symmetries can be converted into a conformal one by means of adequate field redefinitions involving the metric and the derivatives of the dilaton. Finally, by expressing the PolyakovLiouville effective action in terms of an auxiliary invariant metric, we construct oneloop models which maintain the extra symmetry of the classical action. © 1997 Elsevier Science B.V.
20140811T08:10:46Z

Relativistic field equations from higherorder polarizations of the Poincaré group
http://hdl.handle.net/10261/100745
Title: Relativistic field equations from higherorder polarizations of the Poincaré group
Authors: Navarro, Miguel; Calixto, Manuel; Aldaya, Victor
Abstract: The theory of free relativistic fields is shown to arise in a unified manner from higherorder, configurationspace, irreducible representations of the Poincaré group. A de Sitter subalgebra, in the massive case, and a Poincaré subalgebra, in the massless case, of the enveloping algebra of the Poincaré group are the suitable higherorder polarizations. In particular, a simple grouptheoretic derivation of the Dirac equation is given.
20140807T11:25:38Z

Measurement of the production cross section of prompt J/ψ mesons in association with a W ± boson in pp collisions at √s = 7 TeV with the ATLAS detector
http://hdl.handle.net/10261/96970
Title: Measurement of the production cross section of prompt J/ψ mesons in association with a W ± boson in pp collisions at √s = 7 TeV with the ATLAS detector
Authors: Aad, G.; Cabrera, Susana; CastilloGimenez, V.; Costa, María José; Fassi, F.; Ferrer, Antonio; Fiorini, L.; Fuster, Juan; Garcia, C.; García Navarro, José Enrique; González de la Hoz, Santiago; Hernández Jiménez, Yesenia; Higón, Emilio; Irles Quiles, Adrián; Kaci, Mohamed; Lacasta Llácer, Carlos; Lacuesta, Vicente; March, L.; Marti, S.; Miñano, Mercedes; Mitsou, Vasiliki A.; Moles Valls, Regina; Moreno Llácer, María; Oliver García, Elena; Pedraza, S.; Pérez GarcíaEstañ, María Teresa; Romero, E.; Ros, Eduardo; Salt, José; Sánchez, J.; Sánchez Martínez, Victoria; Soldevila, U.; Torró, Emma; Valero, A.; Valladolid Gallego, Eva; Valls, Juan Antonio; Villaplana Pérez, Miguel; Vos, Marcel; Zwalinski, L.
Abstract: The process pp → W ± J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb−1 of s√ = 7 TeV pp collisions at the LHC, the first observation is made of the production of W ± + prompt J/ψ events in hadronic collisions, using W ± → μν μ and J/ψ → μ + μ −. A yield of 27.4+7.5−6.5 W ± + prompt J/ψ events is observed, with a statistical significance of 5.1σ. The production rate as a ratio to the inclusive W ± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated.
Description: Aad, G. et al.
20140521T07:48:46Z

Measurement of the mass difference between top and antitop quarks in pp collisions at √s = 7 TeV using the ATLAS detector
http://hdl.handle.net/10261/96946
Title: Measurement of the mass difference between top and antitop quarks in pp collisions at √s = 7 TeV using the ATLAS detector
Authors: Aad, G.; Cabrera, Susana; CastilloGimenez, V.; Costa, María José; Fassi, F.; Ferrer, Antonio; Fiorini, L.; Fuster, Juan; Garcia, C.; González de la Hoz, Santiago; Hernández Jiménez, Yesenia; Higón, Emilio; Irles Quiles, Adrián; Kaci, Mohamed; Lacasta, Carlos; Lacuesta, Vicente; March, L.; Martí García, Salvador; Miñano, Mercedes; Mitsou, Vasiliki A.; Moles Valls, Regina; Oliver García, Elena; Pedraza, S.; Pérez GarcíaEstañ, María Teresa; Romero, E.; Ros, Eduardo; Salt, José; Soldevilla, U.; Torró, Emma; Valero, A.; Valladolid Gallego, Eva; Valls, Juan Antonio; Villaplana Pérez, Miguel; Vos, Marcel; Zwalinski, L.
Abstract: A measurement of the mass difference between top and antitop quarks is presented. In a 4.7 fb−1 data sample of proton–proton collisions at View the MathML source recorded with the ATLAS detector at the LHC, events consistent with View the MathML source production and decay into a single charged lepton final state are reconstructed. For each event, the mass difference between the top and antitop quark candidate is calculated. A two b tag requirement is used in order to reduce the background contribution. A maximum likelihood fit to these perevent mass differences yields View the MathML source, consistent with CPT invariance.
Description: Aad, G. et al.
20140520T10:47:01Z