LA RESPONSABILITÀ DELLE AGENZIE DI RATING PER DIFFUSIONE DI GIUDIZI INESATTI SUL MERCATO FINANZIARIO

Since excessive liability can force reputational intermediaries out of the market, it is very important to balance liability restrictions with investor protection. To determine which level of liability the agencies actually face, given the current European regulatory regime, and whether this level could be justified looking at the trade-off between free market dynamics and little regulation of rating services, on one hand, and investor protection, on the other hand, the thesis analyzes two main problems: rating agencies' prospectus liability and the applicability of art. 2055 of the Italian Civil Code. In fact, the extent of liability highly depends on whether the agencies are jointly and severally liable for the misconduct of the issuer, its management, its auditors and other operators of the market

Muon and electron g - 2and proton and cesium weak charges implications on dark Zd models

Theories beyond the standard model involving a sub-GeV-scale vector mediator have been largely studied as a possible explanation of the experimental values of the muon and electron anomalous magnetic moments. Motivated by the recent determination of the anomalous muon magnetic moment performed at Fermilab, we derive the constraints on such a model obtained from the magnetic moment determinations and the measurements of the proton and cesium weak charge, , performed at low-energy transfer. In order to do so, we revisit the determination of the cesium from the atomic parity violation experiment, which depends critically on the value of the average neutron rms radius of , by determining the latter from a practically model-independent extrapolation from the recent average neutron rms radius of performed by the PREX-2 Collaboration. From a combined fit of all the aforementioned experimental results, we obtain rather precise limits on the mass and the kinetic mixing parameter of the boson, namely and , when marginalizing over the mass mixing parameter

Potentialities of a low-energy detector based on 4^4He evaporation to observe atomic effects in coherent neutrino scattering and physics perspectives

We propose an experimental setup to observe coherent elastic neutrino-atom scattering (CE$\nu$AS) using electron antineutrinos from tritium decay and a liquid helium target. In this scattering process with the whole atom, that has not beeen observed so far, the electrons tend to screen the weak charge of the nucleus as seen by the electron antineutrino probe. The interference between the nucleus and the electron cloud produces a sharp dip in the recoil spectrum at atomic recoil energies of about 9 meV, reducing sizeably the number of expected events with respect to the coherent elastic neutrino-nucleus scattering case. We estimate that with a 60 g tritium source surrounded by 500 kg of liquid helium in a cylindrical tank, one could observe the existence of CE$\nu$AS processes at 3$\sigma$ in 5 years of data taking. Keeping the same amount of helium and the same data-taking period, we test the sensitivity to the Weinberg angle and a possible neutrino magnetic moment for three different scenarios: 60 g, 160 g, and 500 g of tritium. In the latter scenario, the Standard Model (SM) value of the Weinberg angle can be measured with a statistical uncertainty of $\sin^2{\vartheta_W^{\mathrm{SM}}}^{+0.015}_{-0.016}$. This would represent the lowest-energy measurement of $\sin^2{\vartheta_W}$, with the advantage of being not affected by the uncertainties on the neutron form factor of the nucleus as the current lowest-energy determination. Finally, we study the sensitivity of this apparatus to a possible electron neutrino magnetic moment and we find that using 60 g of tritium it is possible to set an upper limit of about $7\times10^{-13}\,\mu_B$ at 90% C.L., that is more than one order of magnitude smaller than the current experimental limit.Comment: 9 pages, 7 figures, Fig. 3 corrected, improved discussion on electron form factor (Fig. 1 added) and detector layou

New insights into nuclear physics and weak mixing angle using electroweak probes

Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of Cs-133 and I-127. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of Cs-133 and I-127, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for Cs-133 and I-127. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of Pb-208 performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of Cs-133 and I-127, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction

Tyrosinase Inhibitor Activity of Coumarin-Resveratrol Hybrids

In the present work we report on the contribution of the coumarin moiety to tyrosinase inhibition. Coumarin-resveratrol hybrids 1-8 have been resynthesized to investigate the structure-activity relationships and the IC50 values of these compounds were measured. The results showed that these compounds exhibited tyrosinase inhibitory activity. Compound 3-(3’,4’,5’-trihydroxyphenyl)-6,8-dihydroxycoumarin (8) is the most potent compound (0.27 mM), more so than umbelliferone (0.42 mM), used as reference compound. The kinetic studies revealed that compound 8 caused non-competitive tyrosinase inhibition