Ricerc@Sapienza

We discuss the sharp interface limit of the action functional associated with either the Glauber dynamics for Ising systems with Kac potentials or the Glauber+Kawasaki process. The corresponding limiting functionals, for which we provide explicit formulae of the mobility and transport coefficients, describe the large deviation asymptotics with respect to the mean curvature flow.

Active plasma lenses are promising technologies for the focusing of high brightness electron beams due to their radially symmetric focusing and their high field gradients (up to several kT/m). However, in a number of experimental situations, the transverse non-uniformity of the current density flowing in the lens causes beam emittance growth and increases the minimum achievable spot size. To study the physics of the capillary discharge processes employed as active plasma lenses, we developed a 2-D hydrodynamic computational model.

The time-dependent CP asymmetries in B0→π+π- and Bs0→K+K- decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π- and Bs0→π+K- decays.

The first observation of the Bs0→D̄∗0φ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B0→D̄0π+π- and is found to be B(Bs0→D̄∗0φ)=(3.7±0.5±0.3±0.2)×10-5, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B0→D̄0π+π- decay.

Particle Therapy (PT) is a radiation therapy technique in which solid tumors are treated with charged ions and exploits the achievable highly localized dose delivery, allowing to spare healthy tissues and organs at risk. The development of a range monitoring technique to be used on-line, during the treatment, capable to reach millimetric precision is considered one of the important steps towards an optimization of the PT efficacy and of the treatment quality.

Scintillation mechanisms in gases offer the possibility of an optical readout of micropattern gas detectors. This approach takes advantage of the large progress achieved in last years in the performance of the photosensors, opening the way to the realization of high granularity and very sensitive particle trackers. In this paper, the features of a triple-GEM structure filled with a He/CF4 (60/40) mixture and readout by a CMOS sensor are described.

The MOnitor for Neutron Dose in hadrOntherapy (MONDO) project addresses the technical challenges posed by a neutron tracker detector aiming for a high detection efficiency and a good backtracking precision. The project aims to develop a tracking device capable of fully reconstructing the four momen- tum of fast and ultrafast secondary neutrons produced, e.g., in particle therapy (PT) treatments or in other physical processes.

A measurement of the charm-mixing parameter yCP using D0→K+K-, D0→π+π-, and D0→K-π+ decays is reported. The D0 mesons are required to originate from semimuonic decays of B- and B0 mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb-1. The yCP parameter is measured to be (0.57±0.13(stat)±0.09(syst))%, in agreement with, and as precise as, the current world-average value.

The first observation of the decays B(s)0→J/ψpp is reported, using proton-proton collision data corresponding to an integrated luminosity of 5.2 fb-1, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are B(B0→J/ψpp)=[4.51±0.40(stat)±0.44(syst)]×10-7, B(Bs0→J/ψpp)=[3.58±0.19(stat)±0.39(syst)]×10-6. For the Bs0 meson, the result is much higher than the expected value of O(10-9).

A search for charge-parity (CP) violation in D0→K-K+ and D0→π-π+ decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb-1 collected at a center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D∗(2010)+→D0π+ decays or from the charge of the muon in B̄→D0μ-ν̄μX decays. The difference between the CP asymmetries in D0→K-K+ and D0→π-π+ decays is measured to be ΔACP=[-18.2±3.2(stat)±0.9(syst)]×10-4 for π-tagged and ΔACP=[-9±8(stat)±5(syst)]×10-4 for μ-tagged D0 mesons.