arXiv subjects

C. Volpe

Publications and source records attributed to C. Volpe.

34 records · Page 2Linked to original sources

arXiv2006

A Conserved Vector Current test using low energy beta-beams

We discuss the possibility of testing the weak currents and, in particular, the weak magnetism term through the measurement of the electron anti-neutrinos capture by protons at a low energy beta-beam facility. We analyze the sensitivity using both the total number of events and the angular distribution of the positrons emitted in a water Cerenkov detector. We show that the weak magnetism form factor might be determined with better than several percent accuracy using the angular distribution. This offers a new way of testing the Conserved Vector Current hypothesis.

hep-ph↗

arXiv2005

Electroweak Tests at Beta-beams

We explore the possibility of measuring the Weinberg angle from (anti)neutrino-electron scattering using low energy beta beams, a method that produces single flavour neutrino beams from the beta-decay of boosted radioactive ions. We study how the sensitivity of a possible measurement depends on the intensity of the ion beam and on a combination of different Lorentz boosts of the ions.

hep-ph↗

arXiv2005

Does the neutrino magnetic moment have an impact on solar neutrino physics?

Solar neutrino observations coupled with the recent KamLAND data suggest that spin-flavor precession scenario does not play a major role in neutrino propagation in the solar matter. We provide approximate analytical formulas and numerical results to estimate the contribution of the spin-flavor precession, if any, to the electron neutrino survival probability when the magnetic moment and magnetic field combination is small.

hep-ph↗

arXiv2004

Description of Heavy Quark Systems by means of Energy Dependent Potentials

We apply, for the first time, an energy dependent Schrodinger equation to describe static properties of heavy quark systems, i.e. charmonium and bottonium. We show that a good description of the eigenstates and reasonable values for the widths can be obtained. Values of the radii and of the density at the origin are also given. We compare the results to those deduced with a Schrodinger equation implemented with potentials used so far. We note that the energy dependence of the confining potential provides a natural mechanism for the saturation of the spectra. Our results introduce a new class of potentials for the description of heavy quark systems.

hep-ph↗

arXiv2004

Physics potential of beta-beams

Beta-beams is a novel concept for the production of neutrino beams exploiting boosted radioactive ions which decay through beta-decay. Here we describe a project, currently under investigation, where such beams are used to address the issue of CP violation in the lepton sector. We also mention the interest of having low-energy beta-beams. The connection to projects for the production of very intense exotic ion beams, like EURISOL, is emphasized.

hep-ph↗

arXiv2004

Prospects for Detecting a Neutrino Magnetic Moment with a Tritium Source and Beta-beams

We compare the prospects for detecting a neutrino magnetic moment by the measurement of neutrinos from a tritium source, reactors and low-energy beta-beams. In all cases the neutrinos or antineutrinos are detected by scattering of electrons. We find that a large (20 MCurie) tritium source could improve the limit on the neutrino magnetic moment significantly, down to the level of a few $\times 10^{-12}$ while low-energy beta-beams with sufficiently rapid production of ions could improve the limits to the level of a few $\times 10^{-11}$. The latter would require ion production at the rate of at least $10^{15}$ s$^{-1}$.

hep-ph↗

arXiv2003

Short versus long range interactions and the size of two-body weakly bound objects

Very weakly bound systems may manifest intriguing "universal" properties, independent of the specific interaction which keeps the system bound. An interesting example is given by relations between the size of the system and the separation energy, or scaling laws. So far, scaling laws have been investigated for short-range and long-range (repulsive) potentials. We report here on scaling laws for weakly bound two-body systems valid for a larger class of potentials, i.e. short-range potentials having a repulsive core and long-range attractive potentials. We emphasize analogies and differences between the short- and the long-range case. In particular, we show that the emergence of halos is a threshold phenomenon which can arise when the system is bound not only by short-range interactions but also by long-range ones, and this for any value of the orbital angular momentum $\ell$. These results enlarge the image of halo systems we are accustomed to.

nucl-th↗

arXiv2003

On the asymmetry of Gamow-Teller beta-decay rates in mirror nuclei in relation with second-class currents

The theoretical evaluation of major nuclear structure effects on the asymmetry of allowed Gamow-Teller beta-decay rates in light mirror nuclei is presented. The calculations are performed within the shell model, using empirical isospin-nonconserving interaction and realistic Woods-Saxon radial wave functions. The revised treatment of p-shell nuclei is supplemented by systematic calculations for sd-shell nuclei and compared to experimental asymmetries when available. The results are important in connection with the possible existence of second-class currents in the weak interaction.

nucl-th↗

arXiv2003

Charmonium production in relativistic proton-nucleus collisions : What will we learn from the negative x_F region ?

We study the nuclear medium effects on the $c\bar{c}$ time evolution and charmonium production, in a relativistic proton-nucleus collision. In particular, we focus on the fragmentation region of the nucleus where the formation length of the charmonium mesons is shorter than the size of the nucleus. Little is known on the nuclear effects in this region. We use a quantum-mechanical model which includes a realistic potential for the $c\bar{c}$ system and an imaginary potential to describe the collisions of the $c\bar{c}$ with the nucleons. The imaginary potential introduces a transition amplitude among the charmonium states and produces an interference pattern on the charmonium survival probability, which is particulartly important for $ψ'$. Our results on the suppression factors are compared with data from the NA50 and E866/NuSea Collaborations. Predictions are given for the suppression of $J/ψ,~ψ',~χ_c$ as a function of the nuclear mass and in the negative $x_F$ region, where data will be available soon.

hep-ph↗

arXiv2002

What Can Be Learned with a Lead-Based Supernova-Neutrino Detector?

We examine the prospects for using lead as a supernova-neutrino detector by considering the spectrum of electrons produced, and the number of one- and two-neutron events. We show that the electron energy spectrum from charged-current reactions can be used to extract information about the high-temperature component of the neutrino spectrum. Some degree of electron neutrino oscillation is expected in the supernova envelope. We examine the prospects for untangling the signatures of various oscillation scenarios, including, e.g. normal or inverted hierarchies, and different values for the small mixing angle, theta_13.

hep-ph↗

arXiv2001

Charged-current neutrino-208Pb reactions

We present theoretical results on the non flux-averaged $^{208}Pb(ν_{e},e^-)^{208}Bi$ and $^{208}Pb(ν_μ,μ^-)^{208}Bi$ reaction cross sections, obtained within the charge-exchange Random-Phase-Approximation. A detailed knowledge of these cross sections is important in different contexts. In particular, it is necessary to assess the possibility of using lead as a detector in future experiments on supernova neutrinos, such as OMNIS and LAND, and eventually detect neutrino oscillation signals by exploiting the spectroscopic properties of $^{208}Bi$. We discuss the present status on the theoretical predictions of the reaction cross sections.

nucl-th↗

arXiv2001

The size of two-body weakly bound objects : short versus long range potentials

The variation of the size of two-body objects is investigated, as the separation energy approaches zero, with both long range potentials and short range potentials having a repulsive core. It is shown that long range potentials can also give rise to very extended systems. The asymptotic laws derived for states with angular momentum l=1,2 differ from the ones obtained with short range potentials. The sensitivity of the asymptotic laws on the shape and length of short range potentials defined by two and three parameters is studied. These ideas as well as the transition from the short to the long range regime for the l=0 case are illustrated using the Kratzer potential.

nucl-th↗

arXiv2000

Microscopic theories of neutrino-^{12}C reactions

In view of the recent experiments on neutrino oscillations performed by the LSND and KARMEN collaborations as well as of future experiments, we present new theoretical results of the flux averaged $^{12}C(ν_e,e^-)^{12}N$ and $^{12}C(ν_μ,μ^-)^{12}N$ cross sections. The approaches used are charge-exchange RPA, charge-exchange RPA among quasi-particles (QRPA) and the Shell Model. With a large-scale shell model calculation the exclusive cross sections are in nice agreement with the experimental values for both reactions. The inclusive cross section for $ν_μ$ coming from the decay-in-flight of $π^+$ is $15.2 \times 10^{-40} cm^2$ to be compared to the experimental value of $12.4 \pm 0.3 \pm 1.8 \times 10^{-40} cm^2$, while the one due to $ν_{e}$ coming from the decay-at-rest of $μ^+$ is $16.4 \times 10^{-42} cm^2$ which agrees within experimental error bars with the measured values. The shell model prediction for the decay-in-flight neutrino cross section is reduced compared to the RPA one. This is mainly due to the different kind of correlations taken into account in the calculation of the spin modes and partially due to the shell-model configuration basis which is not large enough, as we show using arguments based on sum-rules.

nucl-th↗

arXiv1999

Excitation of multiple giant dipole resonances: from spherical to deformed nuclei

The effect of deformation on the excitation of multiple giant dipole resonances is studied. Analytical expressions are derived in the framework of the interacting boson model for the energies and E1 properties of giant dipole resonances in spherical and deformed nuclei, and a numerical treatment of transitional nuclei is proposed. Coulomb-excitation cross sections are calculated in $^{238}$U and in the samarium isotopes.

nucl-th↗

arXiv1998

Boson expansion methods applied to a two-level model in the study of multiple giant resonances

We apply boson expansion methods to an extended Lipkin-Meshkov-Glick model including anharmonicities in analogy with previous microscopic calculations. We study the effects of different approximations present in these calculations, among which the truncation of the hamiltonian and of the space, in connection with the study of the properties of two-phonon and three-phonon states. By comparing the approximate results on the spectrum with the exact ones we conclude that the approximations made in the microscopic calculations on two-phonon states are well justified. We find also that a good agreement with the exact results for the three-phonon state is obtained by using a bosonic hamiltonian truncated at the fourth order. This result makes us confident that such approximation can be used in realistic calculations, thus allowing a theoretical study of triple excitations of giant resonances.

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arXiv1996

Role of anharmonicities and non-linearities in heavy ion collisions. A microscopic approach

Using a microscopic approach beyond RPA to treat anharmonicities, we mix two-phonon states among themselves and with one-phonon states. We also introduce non-linear terms in the external field. These non-linear terms and the anharmonicities are not taken into account in the "standard" multiphonon picture. Within this framework we calculate Coulomb excitation of 208Pb and 40Ca by a 208Pb nucleus at 641 and 1000MeV/A. We show with different examples the importance of the non-linearities and anharmonicities for the excitation cross section. We find an increase of 10 % for 208Pb and 20 % for 40Ca of the excitation cross section corresponding to the energy region of the double giant dipole resonance with respect to the "standard" calculation. We also find important effects in the low energy region. The predicted cross section in the DGDR region is found to be rather close to the experimental observation.

nucl-th↗