The top quark is the heaviest particle in Standard Model. When it is produced with a large Lorentz boost, its decay products tend to overlap, making the standard reconstruction techniques inefficient; large R jet substructure analysis techniques allow to increase the detection efficiency for these events. Various differential cross section measurements of boosted t-tbar from pp collisions with sqrt(s)=8 TeV are presented: with respect to the mass, to the transverse momentum and the pseudorapidity of the t-tbar system. The results here have been obtained using a sample of 20 fb^-1, recorded by ATLAS during 2012. The events are selected with a cut-based approach in the single lepton plus jets decay channel, where the lepton can be either an electron or a muon. The final background-subtracted distributions are corrected for the distortion introduced by the detector and selection effects using unfolding methods. The measurements are dominated by the systematic uncertainties, and are in agreement with the Standard Model, even if it can be seen a general tendency of the theoretical predictions to overestimate the measured cross section for increasing transverse momentum and mass of the t-tbar system.

Since the discovery of the Higgs boson in 2012, the aim of the correlated physics analyses moved towards the measurement of its properties to verify the consistence with the Standard Model and to study possible signals of physics Beyond Standard Model. In particular, any discrepancy in the Higgs-SM couplings would point to new physics contributions. The ttH channels is a privileged channel for this pourpose, because it depends on a small number of BSM parameters. In this thesis the analysis of the production of a Higgs boson in association with a top and anti-top quark couple and decay into multi-leptonic final states in ATLAS at LHC is described. The analysis is focused on the channel defined by two light leptons of the same sign and no hadronic tau leptons in both Run I and Run II. The analysis is an essential preparatory step for the 2016 data-taking. After introducing the Higgs boson, LHC and the ATLAS experiment, the results of the Run I analysis are presented, which pose a first limit on the deviation of the cross section from the SM. A large part of the thesis is dedicated to the data-driven estimation of the main background of this channel, fake leptons produced in meson decays, using a technique denominated matrix method. This alternative background estimation is explained and applied to the analysis, producing alternative results. In the last part of the thesis, the first stages of the analysis of the 2015 data is shown, in preparation of the 2016 data-taking.

Previous research has identified strength as a key factor for performance in cross-country skiing. The purpose of the present study was to investigate the relationship between upper body strength and performance in swedish junior cross-country skiers. 33 swedish young men and 23 young women age 17,3 ± 1,0 years volunteered to participate in specific tests during a summer training camp were they completed a test battery consisting of bench press and bench pull. The strength variables obtained were correlated with FIS-points (International Ski Federation´s ranking points for distance and sprint performance) used as the performance indicator. Correlations were performed by Spearman´s rank correlation coefficient for all variables. The results showed that FIS-points for sprint correlated significantly with both bench press and bench pull. No significant correlation was found between FIS-points for distance and bench pull. These results may predict performance for cross-country skiers and indicate a justification for increased proportion of strength training.

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In this thesis two related arguments are investigated: - The first stages of the process of massive star formation, investigating the physical conditions and -properties of massive clumps in different evolutionary stages, and their CO depletion; - The influence that high-mass stars have on the nearby material and on the activity of star formation. I characterise the gas and dust temperature, mass and density of a sample of massive clumps, and analyse the variation of these properties from quiescent clumps, without any sign of active star formation, to clumps likely hosting a zero-age main sequence star. I briefly discuss CO depletion and recent observations of several molecular species, tracers of Hot Cores and/or shocked gas, of a subsample of these clumps. The issue of CO depletion is addressed in more detail in a larger sample consisting of the brightest sources in the ATLASGAL survey: using a radiative tranfer code I investigate how the depletion changes from dark clouds to more evolved objects, and compare its evolution to what happens in the low-mass regime. Finally, I derive the physical properties of the molecular gas in the photon-dominated region adjacent to the HII region G353.2+0.9 in the vicinity of Pismis 24, a young, massive cluster, containing some of the most massive and hottest stars known in our Galaxy. I derive the IMF of the cluster and study the star formation activity in its surroundings. Much of the data analysis is done with a Bayesian approach. Therefore, a separate chapter is dedicated to the concepts of Bayesian statistics.

The open clusters (OC) are gravitationally bound systems of a few tens or hundreds of stars. In our Galaxy, the Milky Way, we know about 3000 open clusters, of very different ages in the range of a few millions years to about 9 Gyr. OCs are mainly located in the Galactic thin disc, with distances from the Galactic centre in the range 4-22 kpc and a height scale on the disc of about 200 pc. Their chemical properties trace those of the environment in which they formed and the metallicity is in the range -0.5<[Fe/H]<+0.5 dex. Through photometry and spectroscopy it is possible to study relatively easily the properties of the OCs and estimate their age, distance, and chemistry. For these reasons they are considered primary tracers of the chemical properties and chemical evolution of the Galactic disc. The main subject of this thesis is the comprehensive study of several OCs. The research embraces two different projects: the Bologna Open Cluster Chemical Evolution project (BOCCE) and the Gaia-ESO Survey. The first is a long-term programme, aiming at studying the chemical evolution of the Milky Way disc by means of a homogeneous sample of OCs. The latter is a large public spectroscopy survey, conducted with the high-resolution spectrograph FLAMES@VLT and targeting about 10^5 stars in different part of the Galaxy and 10^4 stars in about 100 OCs. The common ground between the two projects is the study of the properties of the OCs as tracers of the disc's characteristics. The impressive scientific outcome of the Gaia-ESO Survey and the unique framework of homogeneity of the BOCCE project can propose, especially once combined together, a much more accurate description of the properties of the OCs. In turn, this will give fundamental constraints for the interpretation of the properties of the Galactic disc.

The discovery of the Cosmic Microwave Background (CMB) radiation in 1965 is one of the fundamental milestones supporting the Big Bang theory. The CMB is one of the most important source of information in cosmology. The excellent accuracy of the recent CMB data of WMAP and Planck satellites confirmed the validity of the standard cosmological model and set a new challenge for the data analysis processes and their interpretation. In this thesis we deal with several aspects and useful tools of the data analysis. We focus on their optimization in order to have a complete exploitation of the Planck data and contribute to the final published results. The issues investigated are: the change of coordinates of CMB maps using the HEALPix package, the problem of the aliasing effect in the generation of low resolution maps, the comparison of the Angular Power Spectrum (APS) extraction performances of the optimal QML method, implemented in the code called BolPol, and the pseudo-Cl method, implemented in Cromaster. The QML method has been then applied to the Planck data at large angular scales to extract the CMB APS. The same method has been applied also to analyze the TT parity and the Low Variance anomalies in the Planck maps, showing a consistent deviation from the standard cosmological model, the possible origins for this results have been discussed. The Cromaster code instead has been applied to the 408 MHz and 1.42 GHz surveys focusing on the analysis of the APS of selected regions of the synchrotron emission. The new generation of CMB experiments will be dedicated to polarization measurements, for which are necessary high accuracy devices for separating the polarizations. Here a new technology, called Photonic Crystals, is exploited to develop a new polarization splitter device and its performances are compared to the devices used nowadays.

The diameters of traditional dish concentrators can reach several tens of meters, the construction of monolithic mirrors being difficult at these scales: cheap flat reflecting facets mounted on a common frame generally reproduce a paraboloidal surface. When a standard imaging mirror is coupled with a PV dense array, problems arise since the solar image focused is intrinsically circular. Moreover, the corresponding irradiance distribution is bell-shaped in contrast with the requirement of having all the cells under the same illumination. Mismatch losses occur when interconnected cells experience different conditions, in particular in series connections. In this PhD Thesis, we aim at solving these issues by a multidisciplinary approach, exploiting optical concepts and applications developed specifically for astronomical use, where the improvement of the image quality is a very important issue. The strategy we propose is to boost the spot uniformity acting uniquely on the primary reflector and avoiding the big mirrors segmentation into numerous smaller elements that need to be accurately mounted and aligned. In the proposed method, the shape of the mirrors is analytically described by the Zernike polynomials and its optimization is numerically obtained to give a non-imaging optics able to produce a quasi-square spot, spatially uniform and with prescribed concentration level. The freeform primary optics leads to a substantial gain in efficiency without secondary optics. Simple electrical schemes for the receiver are also required. The concept has been investigated theoretically modeling an example of CPV dense array application, including the development of non-optical aspects as the design of the detector and of the supporting mechanics. For the method proposed and the specific CPV system described, a patent application has been filed in Italy with the number TO2014A000016. The patent has been developed thanks to the collaboration between the University of Bologna and INAF (National Institute for Astrophysics).

Compelling evidence of the existence of cosmic neutrinos has been reported by the IceCube collaboration. Some features of this signal could be explained by a Northern/Southern sky asymmetry of the flux. This possible asymmetry would be related to the presence of the bulk our Galaxy in the Southern sky. The ANTARES neutrino telescope, located in the Mediterranean Sea, consists of a three dimensional array of 885 10-inch photomultiplier tubes distributed along twelve vertical lines. Its effective area and its good exposure to the Southern Sky would allow to constrain an enhanced muon neutrino emission from extended sources. An excess of events from the Galactic Plane is searched for. A signal region around the inner Galactic Plane is defined; the background from atmospheric events is estimated looking at data from off-zones for which ANTARES has the same exposure as for the signal region. The ANTARES sensitivity to such a flux has been computed. The results of the analysis after unblinding will be presented.

Con questo lavoro è stata effettuata una misura della differenza $\Delta \mu = \Delta (m / |z|)$ fra il rapporto massa su carica del deutone (d) e dell'anti-deutone (${\rm \overline{d}}$), e del nucleo di ${\rm ^{3}He}$ e di anti-${\rm ^{3}He}$ con l'esperimento ALICE ad LHC in collisioni Pb--Pb a un'energia nel centro di massa per coppia di nucleoni $\sqrt{s_{\rm NN}}=2.76~{\rm TeV}$. Le misure sono pari a ${\Delta \mu}_{\rm{d\bar{d}}}/{\mu}_{\rm{d}} = [0.9 \pm 0.5 (\rm{stat.}) \pm 1.4 (\rm{syst.})] \times 10^{-4}$ e ${\Delta \mu}_{\rm{^{3}He ^{3}\overline{He}}}/{\mu}_{\rm{^{3}He}} = [-1.2 \pm 0.9 (\rm{stat.}) \pm 1.0 (\rm{syst.})] \times 10^{-3}$. Combinando questi risultati con le misure esistenti delle masse dei (anti-)nucleoni, sono state estratte le corrispondenti differenze di energia di legame ${\Delta \varepsilon}_{\rm{d\bar{d}}}/{\varepsilon}_{\rm{d}} = -0.04 \pm 0.05(\rm{stat.}) \pm 0.12(\rm{syst.})$ e ${\Delta \varepsilon}_{\rm{^{3}He ^{3}\overline{He}}}/{\varepsilon}_{\rm{^{3}He}} = 0.24 \pm 0.16(\rm{stat.}) \pm 0.18(\rm{syst.})$. I risultati verificano, con una precisione senza precedenti, l'invarianza CPT nel settore dei nuclei leggeri. / With this work a measurement of the difference $\Delta \mu = \Delta (m / |z|)$ between the mass-over-charge ratio of deuteron (d) and anti-deuteron (${\rm \overline{d}}$), and ${\rm ^{3}He}$ and ${\rm ^{3}\overline{He}}$ nuclei, carried out with the ALICE experiment in Pb--Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}=~2.76~\rm{TeV}$ has been performed. The measurement yields ${\Delta \mu}_{\rm{d\bar{d}}}/{\mu}_{\rm{d}} = [0.9 \pm 0.5 (\rm{stat.}) \pm 1.4 (\rm{syst.})] \times 10^{-4}$ and ${\Delta \mu}_{\rm{^{3}He ^{3}\overline{He}}}/{\mu}_{\rm{^{3}He}} = [-1.2 \pm 0.9 (\rm{stat.}) \pm 1.0 (\rm{syst.})] \times 10^{-3}$. Combining these results with existing measurements of the masses of the (anti-)nucleons, the relative binding energy differences are extracted, ${\Delta \varepsilon}_{\rm{d\bar{d}}}/{\varepsilon}_{\rm{d}} = -0.04 \pm 0.05(\rm{stat.}) \pm 0.12(\rm{syst.})$ and ${\Delta \varepsilon}_{\rm{^{3}He ^{3}\overline{He}}}/{\varepsilon}_{\rm{^{3}He}} = 0.24 \pm 0.16(\rm{stat.}) \pm 0.18(\rm{syst.})$. These results test, to an unprecedented precision, the CPT invariance in the sector of light nuclei.