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# Tag Archives: Evento scientifico

## Studies of Baryon Resonances with the HADES Spectrometer and Pion Beams @ GSI

The HADES (High Acceptance DiElectron Spectrometer) detector, installed at GSI in Darmstadt, was designed to measure e+epairs (dielectrons) in the 13.5 AGeV energy range. The experimental program of HADES focuses on two main goals. The first one is to measure dielectron emission from a compressed baryonic matter formed in heavy ion collisions and investigate inmedium hadron properties. The second goal is to study dielectron production in elementary proton–proton (pp) and pion–proton (mp) collisions and learn about hadron electromagnetic structure. Both objectives are complementary in a sense that the understanding of the in-medium effects involves also investigations of the dielectron invariant mass spectra in elementary mp,pp reactions. The elementary collisions, especially those with pion beams, also offer a great opportunity to unambiguously fix the description of baryonic resonances and their coupling to the light vector mesons (rho/omega) which plays essential role for the inmedium modifications. Therefore, to understand resonances production mechanisms a systematic energy scan and high precision data are needed. In 2014 a large dataset of m-p scattering have been obtained at four pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c). The data have been included into the multichannel Partial Wave Analysis (PWA) developed by the BonnGatchina group. A combined PWA analysis of all available data provides better understanding of the vector mesonresonance couplings and their impact on the transition formfactors. Recently, a new model of dielectrons productions in the exclusive reaction m N->Ne+e- within an effective field theory approach was proposed. Experimental and theoretical investigations of the reaction ...

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## Highlights in Supergravity:Callan-Coleman-Jackiw 47 years later

We discuss properties of the supercurrent in the superconformal formulation of N=1,4D supergravity. Superconformal matter gives simplified conservation laws as in the case of the CCJ improved energy momentum tensor. This approach is useful to classify curved superspace backgrounds.

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## Measuring propagation speed of Coulomb fields

In planetary systems, the problem arises whether gravity attracting the planets towards the central star has an instantaneous action or propagates with finite velocity. Laplace noticed that, if gravity propagated with finite velocity, planets motion would become unstable due to a torque originating from time lag of the gravitational interactions. Given that equations describing gravitational interaction are formally the same describing electrostatic interactions, we have performed an experiment meant to measure the time/space evolution of the electric field generated by a uniformly moving set of electrons. The results we obtain seem compatible with an electric field rigidly carried by the beam itself.

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## A GENERALIZED SPIN STATISTICS THEOREM

The spin statistics theorem is generalized to show that a state obeys Fermi-Dirac statistics if and only if the state is invariant under the action of SL(n;C). Also a discussion of the experimental evidence and how the theorem relates to spin entanglement and special relativity will be presented.

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## Atomic structure of highly charged ions and exotic atoms: from accurate tests of Quantum Electrodynamics to the measurement of unstable particles masses.

An overview of investigations on unusual atomic systems, such highly charged ions and pionic atoms, is presented. In highly charged ions, where the associated Coulomb field is several order of magnitude higher that of the most powerful available laser, Quantum Electrodynamics (QED) corrections, as the self-energy and the vacuum polarisation, have to be considered to all order of Zα. This is still a challenge for theoretical predictions, which can finely tested by spectroscopy of such systems. In pionic hydrogen and deuterium, high-accuracy X-ray spectroscopy provides important information on the strong interaction force between the pion (formed by an anti-quark and a quark) and the nucleons (proton and/or the neutron, each formed by three quarks). Experimental findings are compared to the more accurate available predictions based on effective field theories. In the case of atomic transitions where the influence of the strong force is negligible and QED predictions are well known, accurate X-ray spectroscopy is used to determine the mass of the negatively charged pion. The new measurement presented here yields an accuracy of 1.3 parts per million improving the accuracy of the value recommended by the Particle Data Group by a factor of about two.

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## EBS Project Overview

The ESRF – the European Synchrotron Radiation Facility – is a user facility in Grenoble, France, and the source of the most intense high-energy (6 GeV) X-rays in the world. It was the very first ‘third-generation’ synchrotron to be built and its light provides opportunities for scientists all over the world in the exploration of materials and living matter ranging from the chemistry and physics of materials to archaeology and cultural heritage, together with structural biology and medical applications, the sciences of the environment and the sciences of information and nanotechnologies. In 2019, the existing storage ring will be removed and a first-of-a-kind new lattice, based on an innovative arrangement of magnets, will be installed in its place, dramatically reducing the equilibrium emittance. This ‘fourth-generation’ synchrotron will produce an X-ray beam 100 times more brilliant and coherent than the ESRF source today, allowing imaging down from the micrometre to the nanometre scale and ‒ in parallel with upgraded beamlines, instrumentation and data infrastructure ‒ providing previously unimaginable opportunities for applications as varied as nanoscopy, science at extreme conditions and structural biology. The ESRF ‒ Extremely Brilliant Source (EBS) project was launched in 2015 and its current status, two years into the project, will be presented, alongside the expected performance of the accelerator, the technical challenges confronted and its future potential fields of applications.

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## Bandi MAECI

Seminario informativo sulle opportunità offerte dai Bandi del MAECI (Ministero degli Affari Esteri e della Cooperazione Internazionale) interverrà la Cons. A.Pastorelli (Direzione Generale per la Promozione del Sistema Paese – MAECI)

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## Autumn Institute: Precision physics to achieve the LHC accuracy goals

Aim of the workshop: The Large Hadron Collider has so far performed extremely well and led in 2012 to the milestone discovery of the Higgs boson; however, no signal of new physics has shown up yet. For the sake of carrying out searches for physics Beyond the Standard Model and reliable estimates of the backgrounds, precise calculations and Monte Carlo generators have been of paramount importance. In this mini-workshop, we shall present novel improvements in the matching of parton showers with exact NLO matrix elements, as well as progresses in the fits of parton distribution functions, including small-x resummation. New strategies to measure the top-quark mass and CP violation in top events at the LHC will also be presented. Speakers: Benjamin Fuks (Université Pierre et Marie Curie, Paris) "Next-to-leading order calculations matched to parton showers for supersymmetry and dark matter" Umberto De Sanctis (Università di Roma Tor Vergata') "Top physics with soft muons in ATLAS" Marco Bonvini (Università di Roma La Sapienza') "Small-x resummation in PDF fits"

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