147 research outputs found
Some contributions of MAGIC to the physics ofcosmic rays
No full textCosmic ray interactions can be investigated indirectly in γ ray astronomy, with the observation of spectral and morphological features of certain classes of sources. MAGIC is a stereoscopic system of two γ ray telescopes, located at La Palma (Canaries), with access to the energy window between 50 GeV and 30 TeV. Sources of high relevance for the study of very high energy hadronic interactions are active galactic nuclei, as blazars and radio galaxies. MAGIC has detectedabout fifty such extragalactic objects; we will present some where theemission is explained with accelerated hadrons in interaction with ambient photons. We will also mention cosmic ray acceleration in galaxy clusters. Other than that, hadron-hadron interactions are supposed to take place in some supernova remnants in interaction with surrounding molecular clouds; we will show some results, in connection with cosmic rays of galactic origin. Finally, about other possible components, wewill mention the measurement of the diffuse electron and positron spectrum. Trustingly, the close connection between particle physics and astrophysics will contribute in future years to many new interesting observations
Sensitivity of the ANTARES neutrino telescope for secluded dark matter searches
No full textDark matter scenarios starring WIMPs (weakly interacting massive particles) at the GeV-TeV scale have been intensively investigated, among others by neutrino telescopes with indirect searches. So far no WIMP candidate particle has been observed. At the same time, collider experiments are pushing the scale of the needed new physics beyond the TeV range, and such heavy sectors have long been known to provide dark matter candidates in the same mass range. This situation strongly motivates the exploration of DM scenarios with masses at and above 10-100 TeV. 'Secluded' frameworks then emerge as an ideal target for searches of the annihilation products of such heavy Dark Matter: they allow to naturally evade the unitarity bound on the dark matter mass, and at the same time to reliably compute the annihilation spectra of relevance for experiments. These perspectives open a new territory accessible to neutrino telescopes such as ANTARES and KM3NeT. Promising dark matter sources such as the Galactic Centre are in good visibility for these telescopes, that perform an unbinned-likelihood analysis in search for high-energy neutrinos produced in a dark matter pair-annihilation process. Current limits on WIMP pair annihilation cross section encourage the extension at higher energy, where the highest sensitivity is reached. The current status of secluded dark matter searches with ANTARES and the sensitivities achieved are presented
Search for Dark Matter Signatures with ANTARES and KM3NeT
No full textExtraterrestrial messengers can be used as trackers to probe the presence of dark matter particles in our Galaxy. Sizable fluxes of high-energy neutrinos, measurable with neutrino telescopes, are expected from pair annihilation and decay of dark matter in regions where it accumulates to a high density. This is the case for massive celestial bodies such as the Sun and the very large dark matter reservoir at the Galactic Center, which are inside the field of view of neutrino telescopes installed in the Mediterranean Sea. ANTARES was operated for 16 years and was recently decommissioned, and KM3NeT is currently taking its first data with its first detection lines. A search for signatures of Weakly Interacting Massive Particles (WIMPs) has been performed in 14 years of all-flavor neutrino data, yielding competitive upper limits on the strength of WIMP annihilation when targeting the Galactic Center. Limits on the WIMP-nucleon cross section have been set considering the nonobservation of dark-matter-induced neutrinos from the direction of the Sun. Other non-WIMP landscapes, such as the model predicting heavy dark matter candidates, have been tested with dedicated searches in ANTARES data. The current results with the first installed KM3NeT subdetectors are also discussed.Peer reviewe
Pietro Rossano in URSS (1975) e l’Ostpolitik vaticana
No full textThe paper deals with the travel that mgr Piero Rossano, at that time secretary for the Secretariat for non Christians, did in Soviet Union in 1975 with fr. Chiavacci, senator Gozzini, his wife Vilma and an Italian writer, Gino Montesanto. In Montesanto’s archive the author found new information about this travel and about the meetings that Rossano had in Moscow, Zagorsk, Vilnius, Kaunas, Riga and Jurmala. The Italian delegation met representatives of the Moscow Patriarchate, of the Soviet regime, but, above all, met some leaders of the persecuted Catholic Church. The trip must be considered as an important piece of the Catholic Ostpolitik: a pastoral activity that included negotiations with hostile Governments, ecumenical meetings, and brotherly support to Catholic bishops beyond the Iron Curtain
Gamma-ray emission from star-forming complexes observed by MAGIC: The cases of W51 and HESS J1857+026
No full textMassive star-forming regions assemble a large number of young stars with remnants of stellar evolution and a very dense environment. Therefore, particles accelerated in supernova remnants and pulsar wind nebulae encounter optimal conditions for interacting with target material and photon fields, and thus produce gamma-ray emission. However, observations are challenging because multiple phenomena may appear entangled within the resolution of current gamma-ray telescopes. We report on MAGIC observations aimed to understand the nature of the emission from the star-forming region W51 and the unidentified source HESS J1857+026. While gamma-ray emission from W51 is dominated by the interaction of the supernova remnant W51C with dense molecular clouds, HESS J1857+026 is associated to the pulsar wind nebula from PSR J1856+0245. However, an additional source is resolved north of HESSJ1857+026, with sufficient separation to determine that it cannot be powered by the same pulsar. We search for multiwavelength data to determine the origin of the new source
Gamma-ray emission from star-forming complexes observed by MAGIC: The cases of W51 and HESS J1857+026
No full textMassive star-forming regions assemble a large number of young stars with remnants of stellar evolution and a very dense environment. Therefore, particles accelerated in supernova remnants and pulsar wind nebulae encounter optimal conditions for interacting with target material and photon fields, and thus produce gamma-ray emission. However, observations are challenging because multiple phenomena may appear entangled within the resolution of current gamma-ray telescopes. We report on MAGIC observations aimed to understand the nature of the emission from the star-forming region W51 and the unidentified source HESS J1857+026. While gamma-ray emission from W51 is dominated by the interaction of the supernova remnant W51C with dense molecular clouds, HESS J1857+026 is associated to the pulsar wind nebula from PSR J1856+0245. However, an additional source is resolved north of HESSJ1857+026, with sufficient separation to determine that it cannot be powered by the same pulsar. We search for multiwavelength data to determine the origin of the new source
Light-induced atomic desorption in a compact system for ultracold atoms
No full textThis work was supported by the UK EPSRC grant GR/T08272/01 and the Leverhulme Trust Research Project Grant RPG-2013-074. G.S. acknowledges support from a SUPA Advanced Fellowship.In recent years, light-induced atomic desorption (LIAD) of alkali atoms from the inner surface of a vacuum chamber has been employed in cold atom experiments for the purpose of modulating the alkali background vapour. This is beneficial because larger trapped atom samples can be loaded from vapour at higher pressure, after which the pressure is reduced to increase the lifetime of the sample. We present an analysis, based on the case of rubidium atoms adsorbed on pyrex, of various aspects of LIAD that are useful for this application. Firstly, we study the intensity dependence of LIAD by fitting the experimental data with a rate-equation model, from which we extract a correct prediction for the increase in trapped atom number. Following this, we quantify a figure of merit for the utility of LIAD in cold atom experiments and we show how it can be optimised for realistic experimental parameters.Peer reviewe
Astroparticle Physics
No full textTrabalho completo: acesso restrito, p.108–129The air fluorescence detector of the Pierre Auger Observatory is designed to perform calorimetric measurements
of extensive air showers created by cosmic rays of above 1018 eV. To correct these measurements
for the effects introduced by atmospheric fluctuations, the Observatory contains a group of
monitoring instruments to record atmospheric conditions across the detector site, an area exceeding
3000 km2. The atmospheric data are used extensively in the reconstruction of air showers, and are particularly
important for the correct determination of shower energies and the depths of shower maxima.
This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger
Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these
measurements on air shower reconstructions. Between 1018 and 1020 eV, the systematic uncertainties
due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm 2
to 8 g cm 2 in measurements of the shower maximum
Combined search for neutrinos from dark matter self-annihilation in the Galactic Center with ANTARES and IceCube
No full textWe present the results of the first combined dark matter search targeting the Galactic Center using the ANTARES and IceCube neutrino telescopes. For dark matter particles with masses from 50 to 1000 GeV, the sensitivities on the self-annihilation cross section set by ANTARES and IceCube are comparable, making this mass range particularly interesting for a joint analysis. Dark matter self-annihilation through the tau(+)tau(-) , mu(+)mu(-) , b (b) over bar, and W+W- channels is considered for both the Navarro-Frenk-White and Burkert halo profiles. In the combination of 2101.6 days of ANTARES data and 1007 days of IceCube data, no excess over the expected background is observed. Limits on the thermally averaged dark matter annihilation cross section are set. These limits present an improvement of up to a factor of 2 in the studied dark matter mass range with respect to the individual limits published by both collaborations. When considering dark matter particles with a mass of 200 GeV annihilating through the tau(+)tau(-)channel, the value obtained for the limit is 7.44 x 10(-24) cm(3) s(-1 )for the Navarro-Frenk-White halo profile. For the purpose of this joint analysis, the model parameters and the likelihood are unified, providing a benchmark for forthcoming dark matter searches performed by neutrino telescopes
Attualità ed opportunità delle alternative al carcere fra diffidenze e risorse del territorio
No full textIn a period in which the only answer at crime and insecurity of citiziens is prison we wanted to follow historic steps that have carried at the building of prisons (from Middle Ages to XX century) asking us about their actuality and efficiency. In particulary the Authors have examinated an aspect of penal execution that is often forgotten or negletted but, in our opinion, it must be made stronger: alternative measures to prison. We have made a legislative analysis from the Law 354/1975 to the Law Gozzini to understand, with words of its Author, the spirit which carried to the introduction of an alternative street to prison. “Fathers” of this law have understood that if a person is part of the society also when he/she committed a crime – instead of staying in prison doing nothing – there are few possibilities that he/she will break the law again. Even if statistic numbers about alternative measures are positive, people are strongly disinformed about theirs effects. At all levels: from lawer to housewife, from policemen to teacher. And can we allow that with the apology of a low information prison becomes the only possibility to fight crime? As we can see from questionnaires we have handed out, also the distortion of reality on this topic is a known point, but not for this reason must be unchangeable too!In un momento storico in cui l'unica risposta possibile al reato e alla sensazione di insicurezza dei cittadini sembra essere il carcere, gli Autori hanno voluto ripercorrere le fasi storiche che hanno portato alla affermazione degli istituti di pena (dal Medioevo ad oggi), interrogandosi sulla attualità ed (in)efficacia degli stessi. In particolare essi hanno analizzato un aspetto dell'esecuzione penale spesso tralasciato e che, invece, dovrebbe a parer loro essere potenziato: le misure alternative alla detenzione. Un'analisi legislativa per capire lo spirito che generò ed informò l'introduzione di una soluzione alternativa al carcere. La risposta è che non si trattò di uno slancio “buonista”. I “padri” di questa legge avevano compreso che se una persona non viene estromessa dal contesto sociale cui appartiene anche quando ha commesso un reato –anziché essere segregata passivamente in carcere - le possibilità che infranga nuovamente la legge sono quantomeno ridotte. Inoltre, nonostante dati statistici sulla positività delle misure alternative, nella popolazione a tutti i livelli è forte ed allarmante la disinformazione sugli effetti delle stesse: dall'avvocato alla casalinga, dal poliziotto all'insegnante, dallo studente di Giurisprudenza al carabiniere. Come risulta dai questionari che gli Autori hanno somministrato, anche la distorsione della realtà su questo tema è un dato certo. Una corretta azione informativa si impone pertanto quale utile strumento per contribuire allo sviluppo di una adeguata ed opportuna cultura della pena
- …
