10 research outputs found
Theory of Single Charge Exchange Heavy Ion Reactions
The theory of heavy ion single charge exchange reactions is reformulated. In
momentum space the reaction amplitude factorizes into a product of projectile
and target transition form factors, folded with the nucleon-nucleon isovector
interaction and a distortion coefficient which accounts for initial and final
state ion-ion elastic interactions. The multipole structure of the transition
form factors is studied in detail for Fermi-type non-spin flip and
Gamow-Teller-type spin flip transitions, also serving to establish the
connection to nuclear beta decay. The reaction kernel is evaluated for central
and rank-2 tensor interactions. Initial and final state elastic ion-ion
interaction are shown to be dominated by the imaginary part of the optical
potential allowing to evaluate the reaction coefficients in the strong
absorption limit, realized by the black disk approximation. In that limit the
distortion coefficient is evaluated in closed form, revealing the relation to
the total reaction cross section and the geometry of the transition form
factors. It is shown that at small momentum transfer distortion effects reduce
to a simple scaling factor, allowing to define reduced forward-angle cross
section which is given by nuclear matrix elements of beta decay-type. The
response function formalism is used to describe nuclear charge changing
transitions. Spectral distributions obtained by a self-consistent HFB and QRPA
approach are discussed for excitations of and ,
respectively, and compared to spectroscopic data. The interplay of nuclear
structure and reaction dynamics is illustrated for the single charge exchange
reaction at MeV
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 “beyond Standard Model” 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
Recent results on heavy-ion induced reactions of interest for neutrinoless double beta decay at INFN-LNS
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 half-life. The methodology of the
experimental campaign presently running at INFN - Laboratori Nazionali
del Sud is reported and the experimental challenges characterizing such
activity are described
A Constrained Analysis of the Ca(O,F)K Direct Charge Exchange Reaction Mechanism at 275 MeV
International audienceThe 40Ca(18O,18F)40K single charge exchange (SCE) reaction is explored at 275 MeV incident energy and analyzed consistently with elastic and inelastic scattering data collected in the same experimental conditions. Fully quantum mechanical SCE calculations of the direct mechanism are performed including microscopic nuclear structure inputs and adopting either a bare optical potential or a coupled channel equivalent polarization potential constrained by elastic and inelastic data. The direct SCE mechanism describes magnitude and shape of the angular distributions rather well, thus suggesting the suppression of sequential multi-nucleon transfer processes
Recent results on heavy-ion induced reactions of interest for neutrinoless double beta decay at INFN-LNS
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 half-life. The methodology of the experimental campaign presently running at INFN - Laboratori Nazionali del Sud is reported andthe experimental challenges characterizing such activity are described