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Precision measurement of the lithium flux in cosmic rays with the AMS-02 detector
Get PDFThe Alpha Magnetic Spectrometer (AMS-02) is a magnetic spectrometer designed for the precision study of cosmic ray (CR) composition and energy spectrum from GeV to TeV. It was installed on May 2011 on the International Space Station and is continuously taking data since then. Using the high acceptance (0.45 m2sr) and long exposure time, AMS-02 is able to measure the flux of numerous CR species and to study their spectral index variation as a function of energy. In particular, lithium nuclei in cosmic rays are produced by the spallation of heavier ions that collide with interstellar nuclei. For this reason, the abundance of lithium in CRs is a useful tool to model the propagation of CRs in the Galaxy. In this contribution the precision measurement of the lithium flux from 1.9 GV to 3 TV, based on 1.9 million events collected by AMS-02 detector in five years is discusse
Implications of Dark Matter bound states
Get PDFWe present generic formulae for computing how bound state formation affects the thermal abundance of Dark Matter with non-Abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2)L. In the latter case bound states raise to 14 TeV the DM mass required to reproduce the cosmological DM abundance. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant in the latter case
THGEM: A fast growing MPGD technology
Get PDFThick-GEMs (THGEMs) are simple and robust gaseous multipliers, derived from the GEM design and proposed for large-scale applications. Classical THGEMs consist of Printed Circuit Boards (PCBs) with a regular pattern of
holes obtained by drilling; they are manufactured by industry in large series and large size; their response for different geometrical parameters and operational conditions has been extensively studied. Different substrates (ceramic, glass, PTFE, etc.) and various production procedures have also been investigated with promising results. Different design options, like highly segmented electrodes, and different architectures, in particular those based on the Thick-WELL design are being actively studied. THGEMs are used as gaseous multipliers and as reflective photocathodes for VUV photons when coated with a CsI layer. THGEM-based Photon Detectors have been successfully implemented in 2016 on COMPASS RICH-1 for a total active area of 1.4 m2. Applications of THGEM (also called LEM) technology in the field of cryogenic detectors, in particular for double-phase large volume Ar ones are proposed. The recently discovered phenomenon of bubble assisted electro-luminescence in liquid Xe opens the way to local dual phase cryogenic detector configurations when using THGEMs. The detection of X-rays and neutrons using THGEM-based devices is a very active field. Promising results have been obtained using THGEMs
for imaging applications
Multivariate Empirical Mode Decomposition analysis of Swarm data
Get PDFThe magnetosphere and the ionosphere of the Earth are populated by different current systems with well-structured spatial patterns. In this paper, by using low-resolution (1 Hz) Swarm A data, we present an application of the Multivariate Empirical Mode Decomposition (MEMD) to the external variations of the geomagnetic field, allowing us to identify magnetospheric and ionospheric current
systems patterns. By using both quiet and disturbed periods, we show that MEMD is able to clearly discern between magnetospheric and ionospheric contributions,
evidencing magnetospheric ring current pattern, field aligned currents, ionospheric Solar quiet (Sq) and equatorial electrojet (EEJ) currents, with well-defined spatial patterns, in addition to which we observe both short- and large-scale contributions
1H HR-MAS NMR reveals the degradation mechanisms of ancient documents
Get PDFWater is highly important in regulating the physico-chemical properties of every biological system it interacts with. In this frame, paper is mainly constituted by an almost equimolar ratio of cellulose and water and the degradation mechanism of ancient documents is linked with the action of hydration water. Indeed, the interaction between water and cellulose within the fibres structure is the cause of breaking of the hydrogen bonds and of the consequent swelling of the cellulose fibres. In this paper, Nuclear Magnetic Resonance (NMR) spectroscopy
results obtained by means of the High-Resolution Magic Angle Spinning (HR-MAS) technique have been shown for modern paper samples made of pure cellulose not aged and artificially aged as well as on ancient paper samples. These results show that water gradually affects the cellulose degradation in aged samples providing fundamental information for industrial applications and for the preservation and restoration of cultural heritage materials based on cellulose such as ancient paper or textiles
Fisici Senza Frontiere: Physics laboratory-based activities for schools
Get PDFThe activities realized in the Physics Education project named Fisici Senza Frontiere are here presented and discussed
Models for B-physics anomalies
Get PDFSeveral different experiments show evidences of Lepton Flavour Universality violation in semi-leptonic B meson decays, both in charged and neutral currents. These anomalies can be interpreted in terms of new short-distance interactions that involve mainly the third generation of fermions. I will first discuss the present status of the anomalies, and their connection to other low- and high-energy observables, in a model-independent way, adopting an Effective Field Theory approach based on a CKM-like flavour structure. I will then extend the analysis to a few simple UV completions with different types of mediator, discussing the main issues that have to be faced in each case. A few models emerge, which look capable of accommodating both charged- and neutral-current anomalies consistently with all the experimental bounds, with associated flavour and high-pT signatures within the reach of present and future experiment
Measurement of the t¯ tγ production cross section in proton-proton collisions at √s =8TeV with the ATLAS detector
Get PDFThe large centre-of-mass energy available at the Large Hadron Collider allows for the copious production of top quark pairs in association with other final state particles at high transverse momenta. The ATLAS experiment measures the cross-section of top quark pair production in association with a photon at 8 TeV. The results are presented for the cross section measurement in a fiducial region and differentially as a function of the transverse momentum and pseudorapidity of the photon
Probing nucleon-nucleon correlations in heavy-ion transfer reactions
Get PDFPair correlations have been investigated in heavy-ion collisions via studies of the transfers of different nucleon pairs. In particular, excitation functions of one- and two-neutron transfer channels have been measured for the closed shell 40Ca + 96Zr and superfluid 60Ni + 116Sn systems from the Coulomb barrier energy to energies far below. By using the unique performance of the magnetic spectrometer PRISMA, in terms of resolution and efficiency, measurements at very low bombarding energies have been performed. The experimental transfer probabilities have been compared with semiclassical microscopic calculations that incorporate nucleonnucleon correlations, together with known structure information of entrance and exit channels nuclei and reaction dynamics. These calculations well reproduce, in the whole energy range, one- and two-neutron transfer channels in shape and magnitude
Extensions of mean-field descriptions in dynamical processes of nucleonic degrees of freedom
Get PDFWe propose new theoretical approaches in order to introduce fluctuations in an Extended-TDHF description. On the one side, a prescription for estimating the dispersions in one-body observables related to small amplitude fluctuations of the statistical kind is proposed. On the other side, the characterization of large amplitude density fluctuations generated by multiparticle correlations is addressed through a stochastic extension yielding Langevin-type fluctuations. Applications to nuclear collisions at incident energies around the Fermi energy are presented