2,213 research outputs found
Comparative overview of differential measurements at ATLAS and CMS
The study of the top quark has a central role for both the ATLAS and CMS
experiments. The measurement of the production differential cross
section, in particular, is sensitive to existence of new resonances, it is a
stringent test of perturbative QCD calculations and it is used to improve the
modelling of production. ATLAS and CMS provided a large number of
results during the last years at =7, 8, 13 TeV, in different regions
of the phase space, considering different channels and topology and measuring
the cross section as a function of the kinematic variables of the
system, the top quarks and/or their decay products. Even if the individual
steps are dependent on the specific analysis all the differential cross section
measurements proceed through the same workflow: the event selection, the
background determination, the reconstruction of the system, the
definition of the fiducial phase space, the unfolding applied to remove the
effect of limited acceptance and resolution of the detector and the evaluation
of the systematic uncertainties. In the following I will focus on the
techniques used by ATLAS and CMS to perform some of these steps while
presenting a selection of recent results by the two experiments.Comment: 7 pages, 9 figures, proceedings of a contribution at the 11th
International Workshop on Top Quark Physics (TOP 2018
Constraining scalar resonances with top-quark pair production at the LHC
Constraints on models which predict resonant top-quark pair production at the
LHC are provided via a reinterpretation of the Standard Model (SM) particle
level measurement of the top-anti-top invariant mass distribution,
. We make use of state-of-the-art Monte Carlo event simulation to
perform a direct comparison with measurements of in the
semi-leptonic channels, considering both the boosted and the resolved regime of
the hadronic top decays. A simplified model to describe various scalar
resonances decaying into top-quarks is considered, including CP-even and
CP-odd, color-singlet and color-octet states, and the excluded regions in the
respective parameter spaces are provided.Comment: 34 pages, 17 figure
3D Reconstruction of the Poggio Sommavilla Territory (Sabina Tiberina, Rieti- Italy) A new approach to the knowledge of the archeological evidences
[EN] The area object of this paper is located in the Middle Tiber Valley and comprises a wide stretch of land within the loop of the river Tiber between the municipalities of Magliano Sabina and Ponzano. A study about this region was published in the volume 44 of the Series Forma Italiae, as it has played an important role in the reconstruction of the cultural and historical aspects of the Sabine Tiber Valley in ancient time. Its geological structure has produced a characteristic wavy landscape wich has determined the country life from time to time. Therefore, the 3D reconstruction of this area appears an important aid to the knowledge of the territory shape and its evolution. In fact the 3D model of this area has been developed in order to better understand its geological, hydrographical and anthropological conformation.[ES] El área objeto de este articulo está localizada en el Valle Medio del Tevere y comprende una amplia extensión de tierra dentro del meandro del rio Tevere entre las municipalidades de Magliano Sabina y Ponzano. Un estudio sobre esta región fue publicado en el volumen 44 de la Serie Forma Italiae, y ha jugado un importante papel en la reconstrucción de los aspectos culturales e históricos del Valle Sabina Tiberina en la antigüedad. Su estructura geológica ha producido un paisaje ondulado caracterÃstico el cual ha determinado la vida del paÃs de vez en vez. Por lo tanto, la reconstrucción 3D de esta área parece una importante ayuda para el conocimiento de la forma del territorio y su evolución. De hecho el modelo 3D de esta área ha sido desarrollado con el fin de entender mejor su conformación hidrográfica y antropológica.Verga, F.; Fabbri, F. (2011). 3D Reconstruction of the Poggio Sommavilla Territory (Sabina Tiberina, Rieti- Italy) A new approach to the knowledge of the archeological evidences. Virtual Archaeology Review. 2(3):23-26. https://doi.org/10.4995/var.2011.4578OJS23262
Solar photodegradation of irinotecan in water: optimization and robustness studies by experimental design
Measurement of the differential cross section of ttbar production, using data collected by the ATLAS detector at √s=13 TeV.
The study of the top quark physics covers a large part of the ATLAS experiment physics program and represents an active research field for the theoretical community.
In this thesis, the measurement of the differential cross-sections of top quark pair production in proton proton collisions at a centre of mass energy of √s=13 TeV is presented. The measurement is performed in a fiducial phase-space, as a function of top quark and ttbar system kinematic observables, and the data set corresponds to an integrated luminosity of 3.2 fb^(-1), recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Only events with exactly one electron or muon in the final state are retained and the analysis employs two separate selections and top quark reconstruction techniques, focusing on different regions of the top quark momentum spectra.
The measured spectra are corrected for detector effects and are compared to several theoretical Monte Carlo simulations through χ^2 and p-values calculations.
The measured spectra provide stringent tests of perturbative QCD and can be used to tune the Monte Carlo simulations and re-interpreted to set limits on the existence of processes beyond the standard model.
Finally, new techniques that will improve the sensitivity of future analysis in the region where the top quark is produced with high transverse momentum are presented
Periodic Structural Defects in Graphene Sheets Engineered via Electron Irradiation
Artificially-induced defects in the lattice of graphene are a powerful tool for engineering the properties of the crystal, especially if organized in highly-ordered structures such as periodic arrays. A method to deterministically induce defects in graphene is to irradiate the crystal with low-energy (<20 keV) electrons delivered by a scanning electron microscope. However, the nanometric precision granted by the focused beam can be hindered by the pattern irradiation itself due to the small lateral separation among the elements, which can prevent the generation of sharp features. An accurate analysis of the achievable resolution is thus essential for practical applications. To this end, we investigated patterns generated by low-energy electron irradiation combining atomic force microscopy and micro-Raman spectroscopy measurements. We proved that it is possible to create well-defined periodic patterns with precision of a few tens of nanometers. We found that the defected lines are influenced by electrons back-scattered by the substrate, which limit the achievable resolution. We provided a model that takes into account such substrate effects. The findings of our study allow the design and easily accessible fabrication of graphene devices featuring complex defect engineering, with a remarkable impact on technologies exploiting the increased surface reactivity
Isolating semi-leptonic H → WW∗ decays for Bell inequality tests
We present a method for identifying H→WW∗→ℓνjj events in the presence of large Standard Model backgrounds and illustrate how this decay mode may be applied to the study of Bell-type Inequalities. Our findings reveal the feasibility of complete reconstruction of such Higgs decays and the efficacy of our suggested combination of selection criteria in effectively mitigating the otherwise overwhelming backgrounds. Our approach is based on a combination of bottom and charm tagging, alongside innovative reconstruction techniques. A realistic simulation based on publicly available object identification, reconstruction, and tagging efficiencies from the ATLAS experiment is used to explore the potential sensitivity to violations of the Collins-Gisin-Linden-Massar-Popescu (CGLMP) inequality in existing and expected future data collected at the Large Hadron Collider (LHC). It is found that, the proposed method provides a powerful means of distinguishing the Higgs decay mode from the background, allowing us to achieve an expectation of approximately 3σ significance in detecting violations of these inequalities with 300 fb-1 of data, soon-to-be collected by the LHC
Epoxy resin/TiO2 nanocomposites prepared by the Reactive Suspension Method: Dynamic-mechanical properties and their prediction by theoretical models
Levulinic acid-based bioplasticizers: a facile approach to enhance the thermal and mechanical properties of polyhydroxyalkanoates
PHB has been engineered by incorporating different levulinic acid-based bioplasticizers, which enhance flexibility and thermal processability of the neat biopolymer, while retaining excellent biocompatibility and biodegradability
past present and future ultrasonographic techniques for analyzing ovarian masses
Ultrasonography is today the method of choice for distinguishing between benign and malignant adnexal pathologies. Using pattern recognition several types of tumors can be recognized according to their characteristic appearance on gray-scale imaging. Color Doppler imaging should be used only to perform a semiquantitative color score or evaluate the flow location. International Ovarian Tumor Analysis group had standardized definitions characterizing adnexal masses and suggested the use of 'simple rules' in premenopausal women. Recently, the use of 3D vascular indices has been proposed but its potential use in clinical practice is debated. Also computerized aided diagnosis algorithms showed encouraging results to be confirmed in the future
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