Search results for "Isospin"
showing 10 items of 264 documents
Evolution of collectivity in the78Ni region: Coulomb excitation of74Ni at intermediate energies.
2014
The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neu…
Electroweak penguins in isospin-violating Bs decays
2011
¯Bs ! φ π 0 and ¯ Bs ! φ ρ 0 , which are dominated by EW penguins. Our results extend the analysis in [1] and have recently been published in [2]. Here we give a brief overview of the outcome. We show that in presence of a new EW penguin amplitude the two Bs branching ratios can be enhanced by an order of magnitude without violating any constraints from other hadronic B decays. This makes them very interesting modes for LHCb and Super B factories. We perform both a model-independent analysis and a study within realistic New Physics (NP) models such as a modified- Z 0 -penguin scenario, a model with an additional Z 0 boson and the MSSM, including a fit to B ! πK data and the relevant experim…
Theρ(ω)/B*(B) system and bound states in the unitary local Hidden Gauge approach
2016
In this work, we study systems composed of a ρ/ω and B* meson pair. We find three bound states in isospin, spin-parity channels (1/2, 0+ ), (1/2, 1+ ) and (1/2, 2+ ). The state with J = 2 can be a good candidate for the B * 2 (5747). We also study the ρB system, and a bound state with mass 5728 MeV and width around 20 MeV is obtained, which can be identified with the B 1 (5721) resonance. In the case of I = 3/2, one obtains repulsion and thus, no exotic (molecular) mesons in this sector are generated in the approach.
Linear response of homogeneous nuclear matter with energy density functionals
2014
Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions…
Generalized Nutbrown representation of the vector vertex function and the magnetic moment of the chargedρmeson
1975
A former representation of the vector vertex function, due to Nutbrown, is generalized. It is shown how this resolves an apparent contradiction between the effective-Lagrangian and hard-meson techniques. Further possible applications are discussed. (AIP)
Symmetries in mirror nuclei $^{31}$S and $^{31}$P
2018
Excited states in mirror nuclei 31S and 31P were populated in the 1n and 1p exit channels, respectively, of the reaction 20Ne + 12C. The beam of 20Ne, with an energy of 33 MeV, was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident pairs and Doppler-shift attenuation lifetime measurements in 31S and 31P were performed using the multidetector array GASP in conjunction with the EUCLIDES charged particle detector. A comparison of the determined B(E1) strengths of the analog mirror 7/2- → 5/2+ transitions indicates the presence of a violation of isospin symmetry.
Isospin Mixing Within the Symmetry Restored Density Functional Theory and Beyond
2013
We present results of systematic calculations of the isospin-symmetry-breaking corrections to the superallowed I=$0+,T=1 --> I=0+,T=1 beta-decays, based on the self-consistent isospin- and angular-momentum-projected nuclear density functional theory (DFT). We discuss theoretical uncertainties of the formalism related to the basis truncation, parametrization of the underlying energy density functional, and ambiguities related to determination of Slater determinants in odd-odd nuclei. A generalization of the double-projected DFT model towards a no core shell-model-like configuration-mixing approach is formulated and implemented. We also discuss new opportunities in charge-symmetry- and cha…
Mean-Field Calculation Based on Proton-Neutron Mixed Energy Density Functionals
2015
We have performed calculations based on the Skyrme energy density functional (EDF) that includes arbitrary mixing between protons and neutrons. In this framework, single-particle states are generalized as mixtures of proton and neutron components. The model assumes that the Skyrme EDF is invariant under the rotation in isospin space and the Coulomb force is the only source of the isospin symmetry breaking. To control the isospin of the system, we employ the isocranking method, which is analogous to the standard cranking approach used for describing high-spin states. Here, we present results of the isocranking calculations performed for the isobaric analog states in A = 40 and A = 54 nuclei.
Isospin breaking effects in the X(3872) resonance
2009
In this paper we study the effects of isospin breaking in the dynamical generation of the X(3872) state. We also calculate the ratio of the branching fractions of the $X$ decaying into $J/\psi$ with two and three pions, which has been measured experimentally to be close to unity. Together with the X(3872), of positive C-parity, we predict the existence of a negative C-parity state and we comment on which decay channel is more promising to observe this state.
SU(3)-breaking corrections to the hyperon vector couplingf1(0)in covariant baryon chiral perturbation theory
2009
This work was partially supported by the MEC Grant No. FIS2006-03438 and the European Community- Research Infrastructure Integrating Activity Study of Strongly Interacting Matter (Hadron-Physics2, Grant Agreement 227431) under the Seventh Framework Programme of EU. L. S. G. acknowledges support from the MICINN in the Program ‘‘Juan de la Cierva.’’ J. M. C. acknowledges the same institution for an FPU grant.