Slow Light amplification in a non-inverted gain medium

We investigate the propagation of a coherent probe light pulse through a three-level atomic medium (in the $\Lambda$--configuration) in the presence of a pump laser under the conditions for gain without inversion. When the carrier frequency of the probe pulse and the pump laser are in a Raman configuration, we show that it is possible to amplify a slow propagating pulse. We also analyze the regime in which the probe pulse is slightly detuned from resonance where we observe anomalous light propagation.Comment: 7 pages, 10 figures. To be published in Europhysics Letter

Observing the intrinsic linewidth of a quantum-cascade laser: beyond the Schawlow-Townes limit

A comprehensive investigation of the frequency-noise spectral density of a free-running mid-infrared quantum-cascade laser is presented for the first time. It provides direct evidence of the leveling of this noise down to a white noise plateau, corresponding to an intrinsic linewidth of a few hundred Hz. The experiment is in agreement with the most recent theory on the fundamental mechanism of line broadening in quantum-cascade lasers, which provides a new insight into the Schawlow-Townes formula and predicts a narrowing beyond the limit set by the radiative lifetime of the upper level.Comment: 4 pages, 4 figure

Incidenza della sclerosi multipla in Toscana: uno studio basato su dati amministrativi

INTRODUZIONE L’Italia è un’area ad elevato rischio di sclerosi multipla (SM) con una prevalenza stimata di 75.000 casi e un’incidenza di 2.000 casi annui. Gli ultimi dati pubblicati sull’incidenza sono 5,5 casi/105 a Padova (2000-09), 6,6 a Genova (1998-2007) e 9,7 in Sardegna (2003-07). In Toscana è presente un registro regionale della SM ma, ad oggi, non è rappresentativo dell’intera popolazione. Una possibile alternativa per studiare l’epidemiologia è attraverso i dati amministrativi. Questi, infatti, coprono l’intera popolazione residente e vengono raccolti di routine in un modo standardizzato ai fini della gestione del servizio sanitario. Il nostro scopo è calcolare l’incidenza della SM in Toscana utilizzando dati amministrativi. METODI Per il calcolo dell’incidenza abbiamo creato il seguente algoritmo: ospedalizzazione in reparto per acuti e con diagnosi primaria di SM, esenzione attiva per SM, e prescrizione di farmaci specifici. I casi incidenti sono stati identificati come quei casi catturati dall’algoritmo non tracciati in precedenza nei flussi amministrativi, e la data della prima traccia è stata considerata quale data di diagnosi della SM. Da questa coorte di soggetti abbiamo selezionato i pazienti con un’età ≤ 55 anni, residenti in Toscana al momento della diagnosi e presenti in anagrafe da almeno 10 anni (o nati in Toscana se età <10). Abbiamo calcolato i tassi grezzi e standardizzati e gli intervalli di confidenza (IC) al 95% per gli anni 2011-2015. RISULTATI Abbiamo identificato, negli anni analizzati, 1.056 nuovi casi con un’incidenza che varia da 5,04/105 nel 2011 a 6,02 casi/105nel 2015 (Tab 1). Nelle donne l’incidenza è circa due volte più alta rispetto agli uomini con un range che va da 6,48 a 7,96/105 nelle donne, e da 3,49 a 3,93/105 negli uomini. CONCLUSIONI L’incidenza calcolata risulta elevata, soprattutto nelle donne, ma comunque in linea ai dati pubblicati in altre Regioni, al di là dei bias metodologici legati all’uso di dati amministrativi

Multi-Parton Interactions at the LHC

We review the recent progress in the theoretical description and experimental observation of multiple parton interactions. Subjects covered include experimental measurements of minimum bias interactions and of the underlying event, models of soft physics implemented in Monte Carlo generators, developments in the theoretical description of multiple parton interactions and phenomenological studies of double parton scattering. This article stems from contributions presented at the Helmholtz Alliance workshop on "Multi-Parton Interactions at the LHC", DESY Hamburg, 13-15 September 2010.Comment: 68 page

Eta photoproduction off the neutron at GRAAL: Evidence for a resonant structure at W=1.67 GeV

New (preliminary) data on eta photoproduction off the neutron are presented. These data reveal a resonant structure at W=1.67 GeV.Comment: 8 pages, 4 figures. Published in Proceedings of Workshop on the Physics of Excited Nucleons NSTAR2004, Grenoble, France, March 24 - 27, pg.19

Eta photoproduction off the neutron at GRAAL

The gamma n -> eta n quasi-free cross section reveals a resonant structure at W ~ 1.675 GeV. This structure may be a manifestation of a baryon resonance. A priori its properties, the possibly narrow width and the strong photocoupling to the neutron, look surprising. This structure may also signal the existence of a narrow state.Comment: To appear in Proceedings of Workshop on the Physics of Excited Nucleons NSTAR2005, 12 - 15 October 2005, Tallahassee, Florida, US

Measurement of eta photoproduction on the proton from threshold to 1500 MeV

Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.Comment: 18 pages, 14 figures, 4 tables Submitted to EPJ

Lowering the Light Speed Isotropy Limit: European Synchrotron Radiation Facility Measurements

The measurement of the Compton edge of the scattered electrons in GRAAL facility in European Synchrotron Radiation Facility (ESRF) in Grenoble with respect to the Cosmic Microwave Background dipole reveals up to 10 sigma variations larger than the statistical errors. We now show that the variations are not due to the frequency variations of the accelerator. The nature of Compton edge variations remains unclear, thus outlining the imperative of dedicated studies of light speed anisotropy

Eta photoproduction on the neutron at GRAAL: Measurement of the differential cross section

In this contribution, we will present our first preliminary measurement of the differential cross section for the reaction gamma+n->eta+n. Comparison of the reactions gamma+p->eta+p for free and bound proton (D2 target) will also be discussed.Comment: 6 pages, 4 figures, Proceedings of the 10th International Symposium on Meson-Nucleon Physics and the Structure of the Nucleon, August 29-September 4 2004, Beijing, Chin