Phase diagram of two-dimensional hard rods from fundamental mixed measure density functional theory

A density functional theory for the bulk phase diagram of two-dimensional orientable hard rods is proposed and tested against Monte Carlo computer simulation data. In detail, an explicit density functional is derived from fundamental mixed measure theory and freely minimized numerically for hard discorectangles. The phase diagram, which involves stable isotropic, nematic, smectic, and crystalline phases, is obtained and shows good agreement with the simulation data. Our functional is valid for a multicomponent mixture of hard particles with arbitrary convex shapes and provides a reliable starting point to explore various inhomogeneous situations of two-dimensional hard rods and their Brownian dynamics

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Elemental fragmentation cross sections for a 16O^{16}O beam of 400 MeV/u kinetic energy interacting with a graphite target using the FOOT ΔE-TOF detectors

International audienceThe study of nuclear fragmentation plays a central role in many important applications: from the study of Particle Therapy (PT) up to radiation protection for space (RPS) missions and the design of shielding for nuclear reactors. The FragmentatiOn Of Target (FOOT) collaboration aims to study the nuclear reactions that describe the interactions with matter of different light ions (like \Hy, \He, \twC, \siO%, \Si, \Ca, \Fe ) of interest for such applications, performing double differential fragmentation cross section measurements in the energy range of interest for PT and RPS. In this manuscript, we present the analysis of the data collected in the interactions of an oxygen ion beam of 400 MeV/nucleon with a graphite target using a partial FOOT setup, at the GSI Helmholtz Center for Heavy Ion Research facility in Darmstadt. During the data taking the magnets, the silicon trackers and the calorimeter foreseen in the final FOOT setup were not yet available, and hence precise measurements of the fragments kinetic energy, momentum and mass were not possible. However, using the FOOT scintillator detectors for the time of flight (TOF) and energy loss ($\Delta E$) measurements together with a drift chamber, used as beam monitor, it was possible to measure the elemental fragmentation cross sections. The reduced detector set-up and the limited available statistics allowed anyway to obtain relevant results, providing statistically significant measurements of cross sections eagerly needed for PT and RPS applications. Whenever possible the obtained results have been compared with existing measurements helping in discriminating between conflicting results in the literature and demonstrating at the same time the proper functioning of the FOOT $\Delta$E-TOF system. Finally, the obtained fragmentation cross sections are compared to the Monte Carlo predictions obtained with the FLUKA software

The Drift Chamber detector of the FOOT experiment: Performance analysis and external calibration

The study that we present is part of the preparation work for the setup of the FOOT (FragmentatiOn Of Target) experiment whose main goal is the measurement of the double differential cross sections of fragments produced in nuclear interactions of particles with energies relevant for particle therapy. The present work is focused on the characterization of the gas-filled drift chamber detector composed of 36 sensitive cells, distributed over two perpendicular views. Each view consists of six consecutive and staggered layers with three cells per layer. We investigated the detector efficiency and we performed an external calibration of the space\u2013time relations at the level of single cells. This information was then used to evaluate the drift chamber resolution. An external tracking system realized with microstrip silicon detectors was adopted to have a track measurement independent on the drift chamber. The characterization was performed with a proton beam at the energies of 228 and 80 MeV. The overall hit detection efficiency of the drift chamber has been found to be 0.929\ub10.008, independent on the proton beam energy. The spatial resolution in the central part of the cell is about 150\ub110\u3bc m and 300\ub110\u3bc m and the corresponding detector angular resolution has been measured to be 1.62\ub10.16 mrad and 2.1\ub10.4 mrad for the higher and lower beam energies, respectively. In addition, the best value on the intrinsic drift chamber resolution has been evaluated to be in the range 60 12100\u3bc m. In the framework of the FOOT experiment, the drift chamber will be adopted in the pre-target region, and will be exploited to measure the projectile direction and position, as well as for the identification of pre-target fragmentation events

Measurement of Ds + production and nuclear modification factor in Pb-Pb collisions at √sNN = 2.76 TeV

The production of prompt D s + mesons was measured for the first time in collisions of heavy nuclei with the ALICE detector at the LHC. The analysis was performed on a data sample of Pb-Pb collisions at a centre-of-mass energy per nucleon pair, sNN−−−√ , of 2.76 TeV in two different centrality classes, namely 0–10% and 20–50%. D s + mesons and their antiparticles were reconstructed at mid-rapidity from their hadronic decay channel D s +  → ϕπ +, with ϕ → K−K+, in the transverse momentum intervals 4 < p T < 12GeV/c and 6 < p T < 12 GeV/c for the 0–10% and 20–50% centrality classes, respectively. The nuclear modification factor R AA was computed by comparing the p T-differential production yields in Pb-Pb collisions to those in proton-proton (pp) collisions at the same energy. This pp reference was obtained using the cross section measured at s√=7 TeV and scaled to s√=2.76 TeV. The R AA of D s + mesons was compared to that of non-strange D mesons in the 10% most central Pb-Pb collisions. At high p T (8 < p T < 12 GeV/c) a suppression of the D s + -meson yield by a factor of about three, compatible within uncertainties with that of non-strange D mesons, is observed. At lower p T (4 < p T < 8 GeV/c) the values of the D s + -meson R AA are larger than those of non-strange D mesons, although compatible within uncertainties. The production ratios D s + /D0 and D s + /D+ were also measured in Pb-Pb collisions and compared to their values in proton-proton collisions