A. Molinari

The role of two particle-two hole excitations in the spin-isospin nuclear response

Abstract We investigate the role of the 2 p -2 h states in the spin-isospin nuclear response function. This is done in the frame of a microscopic approach which includes the meson exchange currents and the nucleon-nucleon correlation. We first test our theory on the transverse response in the inclusive deep inclastic electron scattering, where we achieve a satisfactory agreement with the data for values of the momentum transfer ranging from 1 to 2 fm −1 . We next explore the p -wave pion-nucleus absorptive optical potential. We find that a strong (∼3) Lorentz-Lorenz-Ericson-Ericson quenching factor is needed to reproduce in our framework the phenomenological optical potential deduced from π-mesic atom data. We also examine the real photon absorption cross section accounting rather satisfactorily for its behaviour, in particular for the Pauli blocking at small frequencies. Finally, we elucidate the conditions for the existence of a connection between the magnetic photon absorption and the p -wave pion absorption in nuclei.

Heavy-flavour spectra in high-energy nucleus-nucleus collisions

The propagation of the heavy quarks produced in relativistic nucleus–nucleus collisions at RHIC and LHC is studied within the framework of Langevin dynamics in the background of an expanding deconfined medium described by ideal and viscous hydrodynamics. The transport coefficients entering into the relativistic Langevin equation are evaluated by matching the hard-thermal-loop result for soft collisions with a perturbative QCD calculation for hard scatterings. The heavy-quark spectra thus obtained are employed to compute the differential cross sections, the nuclear modification factors RAA and the elliptic-flow coefficients v2 of electrons from heavy-flavor decay.

Using electron scattering superscaling to predict charge-changing neutrino cross sections in nuclei

Superscaling analyses of few-GeV inclusive electron scattering from nuclei are extended to include not only quasielastic processes, but also the region where {delta} excitation dominates. With reasonable assumptions about the basic nuclear scaling function extracted from data and information from other studies of the relative roles played by correlation and meson-exchange-current effects, it is shown that the residual strength in the resonance region can be accounted for through an extended scaling analysis. One observes scaling upon assuming that the elementary cross section by which one divides the residual to obtain a new scaling function is dominated by the N{yields}{delta} transition and employing a new scaling variable suited to the resonance region. This yields a good representation of the electromagnetic response in both the quasielastic and {delta} regions. The scaling approach is then inverted and predictions are made for charge-changing neutrino reactions at energies of a few GeV, with focus placed on nuclei that are relevant to neutrino oscillation measurements. For this, a relativistic treatment of the required weak interaction vector and axial-vector currents for both quasielastic and {delta}-excitation processes is presented.

Heavy flavors in AA collisions: production, transport and final spectra

A multi-step setup for heavy-flavor studies in high-energy nucleus-nucleus (AA) collisions—addressing within a comprehensive framework the initial

Inclusive charge longitudinal response in finite nuclei

Q\overline{Q}

Gauge and Lorentz invariant one pion exchange currents in electron scattering from a relativistic Fermi gas

production, the propagation in the hot medium until decoupling and the final hadronization and decays—is presented. The initial hard production of

Parity-violating quasielastic electron scattering☆

Q\overline{Q}

Monopole states in 40Ca

pairs is simulated using the POWHEG pQCD event generator, interfaced with the PYTHIA parton shower. Outcomes of the calculations are compared to experimental data in pp collisions and are used as a validated benchmark for the study of medium effects. In the AA case, the propagation of the heavy quarks in the medium is described in a framework provided by the relativistic Langevin equation. For the latter, different choices of transport coefficients are explored (either provided by a perturbative calculation or extracted from lattice-QCD simulations) and the corresponding numerical results are compared to experimental data from RHIC and the LHC. In particular, outcomes for the nuclear modification factor RAA and for the elliptic flow v2 of D/B mesons, heavy-flavor electrons and non-prompt J/ψ’s are displayed.

Rotational motion at large angular momentum in even-even deformed nuclei

Abstract The experimental dynamic and static longitudinal structure factors of 12 C, 40 Ca and 56 Fe are investigated with a semiclassical RPA theory. The ph interaction is linked at zero momentum to the nuclear compression modulus and symmetry energy. Its momentum evolution is handled phenomenologically, as well as the position-dependent nucleon effective mass. Quite reasonable values of these quantities allow a satisfactory account of the experimental data over a wide range of momentum transfers in all the three nuclei. In order to achieve this result the proton root mean square radius has to be increased of about 13% in 12 C, 23% in 40 Ca and 21% in 56 Fe.

Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC

Abstract A consistent analysis of relativistic pionic correlations and meson-exchange currents for electroweak quasielastic electron scattering from nuclei is carried out. Fully relativistic one-pion-exchange electromagnetic operators are developed for use in one-particle emission electronuclear reactions within the context of the relativistic Fermi gas model. Then the exchange and pionic correlation currents are set up fully respecting the gauge invariance of the theory. Emphasis is placed on the self-energy current which, being infinite, needs to be renormalized. This is achieved starting in the Hartree–Fock framework and then expanding the Hartree–Fock current to first order in the square of the pion coupling constant to obtain a truly gauge invariant, one-pion-exchange current. The model is applied to the calculation of the parity-conserving and parity-violating inclusive responses of nuclei. Interestingly, in the pionic correlations terms exist which arise uniquely from relativity, although their impact on the responses is found to be modest.