32 research outputs found
Coulomb corrections to Fermi beta decay in nuclei
We study the influence of the Coulomb force on the Fermi beta-decays in
nuclei. This work is composed of two main parts. In the first part, we
calculate the Coulomb corrections to super-allowed beta decay. We use the
notion of the isovector monopole state and the self-consistent charge-exchange
Random Phase Approximation to compute the correction. In the second part of
this work, we examine the influence of the anti-analog state on isospin mixing
in the isobaric analog state and the correction to the beta-decay Fermi
transition.Comment: Some numerical mistakes were corrected. The present version matches
the online version published in NP
Dipole resonances and the nuclear Schiff moment
The nuclear Schiff moment creates a mechanism of transfer of the violation of
parity and time-reversal invariance by weak interaction in nuclei into the
atomic electric dipole moment. We point out an additional contribution to the
Schiff moment generated by the mixing of single-particle states through the
low-lying nuclear dipole resonances. An estimate shows that this contribution
is by order of magnitude comparable to single-particle contributions and can be
enhanced if the low-lying resonance has collective nature.Comment: 11 pages, no figure
Octupole deformation instability in atomic nuclei
Recent high-energy heavy-ion collision experiments have revealed that some
atomic nuclei exhibit unusual softness and significant shape fluctuations. In
this Letter, we use the fully self-consistent mean-field theory to identify all
even-even nuclei that are unstable or soft against octupole deformation. All
exceptional cases of enhanced octupole transition strengths in stable even-even
nuclei throughout the nuclide chart are resolved. These results represent a
significant advance in our understanding of the underlying mechanisms of
nuclear octupole deformation and have implications for further experimental and
theoretical studies.Comment: New references [3,4] were added. Thank Prof. Jiangyong Jia for the
discussion
Nuclear Schiff moment and soft vibrational modes
The atomic electric dipole moment (EDM) currently searched by a number of
experimental groups requires that both parity and time-reversal invariance be
violated. According to current theoretical understanding, the EDM is induced by
the nuclear Schiff moment. The enhancement of the Schiff moment by the
combination of static quadrupole and octupole deformation was predicted
earlier. Here we study a further idea of the possible enhancement in the
absence of static deformation but in a nuclear system with soft collective
vibrations of two types. Both analytical approximation and numerical solution
of the simplified problem confirm the presence of the enhancement. We discuss
related aspects of nuclear structure which should be studied beyond mean-field
and random phase approximations.Comment: 14 pages, 4 figure
Super-Radiant Dynamics, Doorways, and Resonances in Nuclei and Other Open Mesoscopic Systems
The phenomenon of super-radiance (Dicke effect, coherent spontaneous
radiation by a gas of atoms coupled through the common radiation field) is well
known in quantum optics. The review discusses similar physics that emerges in
open and marginally stable quantum many-body systems. In the presence of open
decay channels, the intrinsic states are coupled through the continuum. At
sufficiently strong continuum coupling, the spectrum of resonances undergoes
the restructuring with segregation of very broad super-radiant states and
trapping of remaining long-lived compound states. The appropriate formalism
describing this phenomenon is based on the Feshbach projection method and
effective non-Hermitian Hamiltonian. A broader generalization is related to the
idea of doorway states connecting quantum states of different structure. The
method is explained in detail and the examples of applications are given to
nuclear, atomic and particle physics. The interrelation of the collective
dynamics through continuum and possible intrinsic many-body chaos is studied,
including universal mesoscopic conductance fluctuations. The theory serves as a
natural framework for general description of a quantum signal transmission
through an open mesoscopic system.Comment: 85 pages, 10 figure
Recent results on heavy-ion induced reactions of interest for neutrinoless double beta decay at INFN-LNS
Abstract. The possibility to use a special class of heavy-ion induced direct reactions, such as double charge exchange reactions, is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay halflife. The methodology of the experimental campaign presently running at INFN - Laboratori Nazionali del Sud is reported and the experimental challenges characterizing such activity are describe
NURE: An ERC project to study nuclear reactions for neutrinoless double beta decay
Neutrinoless double beta decay (0νββ) is considered the best potential resource to
access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are
their own anti-particles (Majorana particles). Presently, this physics case is one of the most
important research âbeyond Standard Modelâ and might guide the way towards a Grand
Unified Theory of fundamental interactions.
Since the 0νββ decay process involves nuclei, its analysis necessarily implies nuclear structure
issues. In the NURE project, supported by a Starting Grant of the European Research Council
(ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract
information on the 0νββ Nuclear Matrix Elements. In DCE reactions and ββ decay indeed the
initial and final nuclear states are the same and the transition operators have similar structure.
Thus the measurement of the DCE absolute cross-sections can give crucial information on ββ
matrix elements. In a wider view, the NUMEN international collaboration plans a major
upgrade of the INFN-LNS facilities in the next years in order to increase the experimental
production of nuclei of at least two orders of magnitude, thus making feasible a systematic
study of all the cases of interest as candidates for 0νββ
New results from the NUMEN project
NUMEN aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. First evidence about the possibility to get quantitative information about NME from experiments is found for the (18O,18Ne) and (20Ne,20O) reactions. Moreover, to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay, the knowledge of the NME is a crucial aspect. The key tools for this project are the high resolution Superconducting Cyclotron beams and the MAGNEX magnetic spectrometer at INFN Laboratori Nazionali del Sud in Catania (Italy). The measured cross sections are extremely low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest. peerReviewe