Explore the vast range of titles available.

Numerical models indicate that collective animal behavior may emerge from simple local rules of interaction among the individuals. However, very little is known about the nature of such interaction, so that models and theories mostly rely on aprioristic assumptions. By reconstructing the three-dimensional positions of individual birds in airborne flocks of a few thousand members, we show that the interaction does not depend on the metric distance, as most current models and theories assume, but rather on the topological distance. In fact, we discovered that each bird interacts on average with a fixed number of neighbors (six to seven), rather than with all neighbors within a fixed metric distance. We argue that a topological interaction is indispensable to maintain a flock's cohesion against the large density changes caused by external perturbations, typically predation. We support this hypothesis by numerical simulations, showing that a topological interaction grants significantly higher cohesion of the aggregation compared with a standard metric one.

The strong interaction is not well understood at low energies or for interactions with low momentum transfer. Chiral perturbation theory gives testable predictions for the nucleonic generalized polarizabilities, which are fundamental quantities describing the nucleon’s response to an external field. We report a measurement of the proton’s generalized spin polarizabilities extracted with a polarized electron beam and a polarized solid ammonia target in the region where chiral perturbation theory is expected to be valid. The investigated structure function g 2 characterizes the internal spin structure of the proton. From its moments, we extract the longitudinal–transverse spin polarizability δ LT and twist-3 matrix element and polarizability d 2 ¯ . Our results provide discriminating power between existing chiral perturbation theory calculations and will help provide a better understanding of this strong quantum chromodynamics regime. Measurements of the proton’s generalized spin polarizabilities provide discriminating power between effective descriptions of the strong interaction at low energy.

This paper presents the experimental results on the Terapia Oncologica con Protoni-Intensity Modulated Proton Linear Accelerator (TOP-IMPLART) beam that is currently accelerated up to 35 MeV, with a final target of 150 MeV. The TOP-IMPLART project, funded by the Innovation Department of Regione Lazio (Italy), is led by Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) in collaboration with the Italian Institute of Health and the Oncological Hospital Regina Elena-IFO. The accelerator, under construction and test at ENEA-Frascati laboratories, employs a commercial 425 MHz, 7 MeV injector followed by a sequence of 3 GHz accelerating modules consisting of side coupled drift tube linac (SCDTL) structures up to 71 MeV and coupled cavity linac structures for higher energies. The section from 7 to 35 MeV, consisting on four SCDTL modules, is powered by a single 10 MW klystron and has been successfully commissioned. This result demonstrates the feasibility of a “fully linear” proton therapy accelerator operating at a high frequency and paves the way to a new class of machines in the field of cancer treatment.

Microscopic simulations may bring a better understanding of the response of gaseous detectors. Such simulations are computationally demanding, due to the modelling of the low energy processes and to the high segmentation required for the 2D/3D field maps. In MPGD such maps can be much more complex than those of traditional multiwire chambers, due to the heterogeneous materials and more involute geometries, which break the simplifying symmetries featured in the latter. In order to investigate the performance of the triple GEM 2-dimensional tracking chambers being developed for high luminosity experiments with the Super BigBite Spectrometer at Jefferson Laboratory, we have set up a flexible and rather effcient multistep simulation processor based on either ANSYS or GMSH+ELMER for 3D CAD and electrostatic field modelling and then combined to Garfield++. Potential systematic effects from the 3D CAD modellers, the mesh generators and the electrostatic field solvers have been estimated with dedicated simulations; once these effects have been assessed, the results of the multistep approach have been compared to a simplified whole GEM chamber model.

The Intensity Modulated Proton Linear Accelerator for Cancer Therapy (TOP-IMPLART) is under development and construction by ENEA in collaboration with the Italian Institute of Health (ISS) and the Oncological Hospital Regina Elena-IFO with financial support of Regione Lazio. Its peculiar time structure (few microseconds pulse width) and very high peak intensity (≍ 109 proton/pulse) demand for ad hoc dose delivery monitors (DDM). The TOP-IMPLART DDM is based on ionization gas chambers. One segmented chamber prototype uses Micro Pattern Gaseous Detector technology for the 2-dimensional simultaneous x/y readout; the charge collected from each active segment (strips with pad-like shape) is readout by a dedicated gain-adaptable electronics. Two small, highly sensitive, integral ionization chambers, using the same electronics, complement the 2D chamber for the monitor of the single pulse beam charge, down to 1 pC/pulse. While under development and deployment of its accelerating modular cavities, the linear TOP-IMPLART beam is improved thanks also to the continuous monitoring and characterization by these devices, whose responses are periodically compared to calibrated dosimetric detectors such as real-time active microDiamond sensor, passive Alanine pellets, intrinsically stable integral Faraday Cup. Different calibration campaigns have been recently conducted to measure the recombination and dose-rate effects on the above ionization chambers. The outcome of these measurements shows clear electron-ion recombination in the chamber active volume, largely related to the high beam intensity and its small transverse cross section. Those effects can be taken into account and used to correct the actual measurement of the DDM. In this paper, the TOP-IMPLART project and the DDM devices are shortly presented and details of the above experimental studies are discussed.

This work reports on the Monte Carlo optimization studies of detection systems for Molecular Breast Imaging with radionuclides and Bremsstrahlung Imaging in nuclear medicine. Molecular Breast Imaging requires competing performances of the detectors: high efficiency and high spatial resolutions; in this direction, it has been proposed an innovative device which combines images from two different, and somehow complementary, detectors at the opposite sides of the breast. The dual detector design allows for spot compression and improves significantly the performance of the overall system if all components are well tuned, layout and processing carefully optimized; in this direction the Monte Carlo simulation represents a valuable tools. In recent years, Bremsstrahlung Imaging potentiality in internal radiotherapy (with beta-radiopharmaceuticals) has been clearly emerged; Bremsstrahlung Imaging is currently performed with existing detector generally used for single photon radioisotopes. We are evaluating the possibility to adapt an existing compact gamma camera and optimize by Monte Carlo its performance for Bremsstrahlung imaging with photons emitted by the beta- from 90Y.

The high luminosity that will be reached in the new generation of High Energy Particle and Nuclear physics experiments implies large high background rate and large tracker occupancy, representing therefore a new challenge for particle tracking algorithms. For instance, at Jefferson Laboratory (JLab) (VA,USA), one of the most demanding experiment in this respect, performed with a 12 GeV electron beam, is characterized by a luminosity up to 1039cm-2s-1. To this scope, Gaseous Electron Multiplier (GEM) based trackers are under development for a new spectrometer that will operate at these high rates in the Hall A of JLab. Within this context, we developed a new tracking algorithm, based on a multistep approach: (i) all hardware - time and charge - information are exploited to minimize the number of hits to associate; (ii) a dedicated Neural Network (NN) has been designed for a fast and efficient association of the hits measured by the GEM detector; (iii) the measurements of the associated hits are further improved in resolution through the application of Kalman filter and Rauch- Tung-Striebel smoother. The algorithm is shortly presented along with a discussion of the promising first results.

A new proton therapy center is planned to be built in Rome, Italy. The project, named TOP-IMPLART, is developed by three institutions, ENEA (Agenzia Nazionale per le Nuove tecnologie, l’Energia e lo Sviluppo Economico Sostenibile - Italian national agency for new technologies, energy and sustainable economic development), ISS (Istituto Superiore di Sanità, Italian National Institute of Health) and IFO-IRE (Istituto Fisioterapico Ospedaliero - Istituto Regina Elena, Regina Elena, National Cancer Institute in Rome). The project is centered on a medium-energy proton accelerator designed as a sequence of linear accelerators. Two phases of construction are foreseen: the first (funded by the Italian Regione Lazio for 11 M€ spread over four years) with a maximum energy of 150 MeV and the second one up to 230 MeV. The segment up to 150 MeV is under construction and will be tested at the ENEA Research Center in Frascati before the transfer to IFO that is the clinical user. The basic concepts of the design are described here.

[...]CEBAF today, and with an energy upgrade, will continue to operate with several orders of magnitude higher luminosity than what is planned at the Electron-Ion Collider (EIC). Photoproduction cross sections of exotic states could be decisive in understanding the nature of a subset of the pentaquark and tetraquark candidates that contain charm and anti-charm quarks. [...]in Hall B the high-intensity flux of quasi-real photons at high energy will add the extra capability of studying the Q2 evolution of any new state produced. JLab will be able to explore the proton’s gluonic structure by unique precise measurements of the photo and electroproduction cross section near threshold of J/ψ and higher-mass charmonium states, χc and ψ(2S) . [...]with an increase of the polarization figure-of-merit by an order of magnitude, GlueX will be able to measure polarization observables that are critical to disentangle the reaction mechanism and draw conclusions about the mass properties of the proton. [...]JLab has a uniquely fundamental role to play in the EIC era in the realm of precision separation measurements between the longitudinal ( σL ) and transverse ( σT ) photon contributions to the cross section, which are critical for studies of both semi-inclusive and exclusive processes.

A new Large-Acceptance Forward Angle Spectrometer (Super BigBite) is under development at JLab/Hall A for the upcoming experiments in Hall A at Jefferson Lab where a longitudinally polarized electron beam of 11 GeV is now available. This beam, combined with innovative polarized targets will provided luminosity up to 1039/(s·cm2) opening exciting opportunities to investigate unexplored aspects of the inner structure of the nucleon. The tracker of this new apparatus is based on the Gas Electron Multiplier (GEM) technology, which has been chosen to optimize cost/performance, position resolution and to meet the high hit rate (>1 MHz/cm2). The first GEM detector modules, designed and built by the INFN Collaboration JLAB12, were tested at the DESY test beam facility in Hamburg, by using an electron beam with energy ranging from 2.0 to 6.0 GeV. In particular, three 40x50 cm2 GEM chambers were equipped with a new implementation of the APV25 readout chip. Measurements were performed at different impact points and angles between the electron beam and the plane of the GEM chambers, with one large chamber in a solenoid magnetic field up to 500 Gauss. In this paper we present the technical features of the tracker and comment on the presently achieved performance.